LC-MS/MS quantification method

Metabolomics is the large-scale study of cellular metabolic complement, with proven utility in both basic and applied studies of plants, microorganisms, and mammals. As an important tool for the study of complex biological systems, metabolomics monitors the complex molecular networks that exist in the natural flow of information from genes to mRNA and proteins to organisms. The metabolome is composed of biomolecules that most closely resemble the phenotype of an organism, and changes in its composition can easily lead to the production of diseases. Therefore, metabolomics has received much attention in drug target discovery, drug response and translational research of disease mechanisms. Mass spectrometry-based metabolomics methods can simultaneously detect and quantify thousands of metabolite signatures, thereby characterizing the pathophysiological mechanisms of various biomedical symptoms.

MCE can provide 667 mass spectrometry human endogenous metabolites that can be used for metabolite identification and quantification, functional cell detection and phenotypic screening of mass spectrometry.

Mongolian medicine refers to drugs used for disease prevention and treatment under the guidance of Mongolian medical theory. Originating from the vast grasslands and desert regions of northern China, Mongolian medicine developed under specific natural conditions and a nomadic lifestyle, forming a unique theoretical system and treatment methods. It emphasizes the balance between the human body and the natural environment and has demonstrated distinct efficacy in treating digestive system diseases, rheumatism, skin diseases, and various chronic conditions. For example, Mongolian medicine often uses Chinese red date for palpitations and angina pectoris, sea buckthorn to relieve coughs, reduce phlegm, promote blood circulation, and remove blood stasis, and scabious to clear lung heat and treat liver heat diseases. The application of these characteristic Mongolian medicines embodies the profound wisdom of Mongolian medical practice.

With the advancement of modern technology, research on Mongolian medicine continues to deepen. Systematic studies on the chemical composition and pharmacological effects of Mongolian medicines can provide new ideas and methods for modern drug development.

MCE has collected 2,383 characteristic natural products derived from Mongolian medicines, with 400+ plant sources of Mongolian medicine.

Chemotherapy is one of the most common treatments for cancer. It can be used alone for some types of cancer or in combination with other treatments such as radiation or surgery. Chemotherapy drugs usually target cells at different phases of the cell cycle and inhibit tumor proliferation and avoid cancer cell invasion and metastasis. It is a cancer treatment method that kills cancer cells with drugs.

Chemotherapeutic agents can be classified into alkylating agents, antimetabolites, antimicrotubular agents, antibiotics, etc. according to the mechanism of action. MCE offers a unique collection of 157 chemotherapy drugs, which is a useful tool for cancer treatment research.

Unlike the 20 natural amino acids commonly found within living organisms, non-natural amino acids are synthesized through chemical or biosynthetic methods, thereby being endowed with unique chemical properties or biological activities. In drug development, these amino acids can be utilized to design novel pharmaceutical molecules that may exhibit superior pharmacological characteristics, such as increased selectivity, improved pharmacokinetic profiles, or reduced toxicity. In biomedical research, uon-natural amino acids can act as biological markers or probes for investigating biological processes like cell signaling, protein conformation, and protein-protein interactions. In addition, non-natural amino acids can also be used in the field of agriculture to develop new pesticides, plant growth regulators and so on.

Human metabolism is an integral part of cellular function that reflects individual differences in health, disease, diet, and lifestyle. Many health conditions such as obesity, diabetes, hypertension, heart disease, and cancer are associated with abnormal metabolic states. In the pathological state of the human body, metabolic pathways are significantly altered, resulting in aberrant levels of intermediates or end-products that can be viewed as potential diagnostic biomarkers or even therapeutic targets. Therefore, detection, identification and quantification of human metabolites are very important for drug metabolism research in drug development.

MCE offers a unique collection of 6,744 human metabolites, including endogenous metabolites and exogenous metabolites, covering multiple structure types, such as lipids, amino acids, nucleic acids, carbohydrates, organic acids, biogenic amines, vitamins,. MCE Human Metabolites Library is a helpful tool for studying the relationship between diseases and metabolism.

The TCA cycle (tricarboxylic acid cycle)—is also known as the Krebs cycle or the citric acid cycle (CAC). The TCA cycle is a series of chemical reactions that release stored energy through the oxidation of acetyl-CoA in carbohydrates, fats, and proteins.

For decades, the TCA cycle has been considered as the central pathway for cell oxidative phosphorylation to produce energy and biosynthesis. Research shows that TCA cycle is associated with many diseases, especially cancer. In colon carcinoma, liver cancer and other cancers, there are mutations that lead to the imbalance of TCA cycle metabolites, indicating that TCA cycle may be related to the occurrence of cancer. Understanding the role and molecular mechanism of TCA cycle in inhibiting or promoting cancer progression will promote the development of new metabolite-based cancer treatment methods in the future.

MCE supplies a unique collection of 26 key intermediates of the TCA cycle, which can be utilized for TCA-related research and metabolomics identification studies.

Cancer is a multi-step process which involves initiation, promotion and progression. Chemical carcinogens can alter any of these processes to induce their carcinogenic effects. People are continuously exposed exogenously to varying amounts of chemicals that have been shown to have carcinogenic or mutagenic properties in experimental systems. Exposure can occur exogenously when these agents are present in food, air or water, and also endogenously when they are products of metabolism or pathophysiologic states such as inflammation. The administration of chemical carcinogens is one of the most commonly used methods to induce tumors in several organs in laboratory animals in order to study oncologic diseases of humans. MCE offers a unique collection of 144 chemical carcinogens which have been identified with carcinogenic activity either in humans or in animal models. MCE Tumorigenesis-Related Compound Library is a powerful tool for studying oncologic diseases of humans. Standard opration based on safety data sheet will not cause harm to the body.

The TCA cycle (tricarboxylic acid cycle)—is also known as the Krebs cycle or the citric acid cycle (CAC). The TCA cycle is a series of chemical reactions that release stored energy through the oxidation of acetyl-CoA in carbohydrates, fats, and proteins.

For decades, the TCA cycle has been considered as the central pathway for cell oxidative phosphorylation to produce energy and biosynthesis. Research shows that TCA cycle is associated with many diseases, especially cancer. In colon carcinoma, liver cancer and other cancers, there are mutations that lead to the imbalance of TCA cycle metabolites, indicating that TCA cycle may be related to the occurrence of cancer. Understanding the role and molecular mechanism of TCA cycle in inhibiting or promoting cancer progression will promote the development of new metabolite-based cancer treatment methods in the future.

MCE supplies a unique collection of 73 compounds related to the TCA cycle. MCE TCA Cycle Compound Library is a useful tool for the TCA cycle related research and anti-cancer drug development.

Rare diseases are an important public-health issue and a challenge for the medical community. Most rare diseases are genetic disorders, which are often severely disabling, substantially affect life expectancy, and impair physical and mental abilities. Currently, there are about 7,000 identified rare diseases, together affecting 10% of the population. However, fewer than 6% of all rare diseases have an approved treatment option, highlighting their tremendous unmet needs in drug development. The process of repurposing drugs for new indications, compared with the development of novel orphan drugs, is a time-saving and cost-efficient method resulting in higher success rates, which can therefore drastically reduce the risk of drug development for rare diseases.

MCE carefully collects a unique of 1,886 compounds studied in preclinical, clinical trials or approved used in rare diseases treatment. MCE rare diseases drug library is a useful tool for the research of rare diseases. All compounds can provide corresponding indications for rare diseases.

Miao medicine is an important part of Chinese medicine, which carries the profound cultural heritage and rich life wisdom of the Hmongb people. Miao people live in a concentrated community in the mountainous area of the southwest border of China, which has a unique natural environment. Complex and diverse geology, lush natural vegetation, rich animal and plant species, a large number of mineral resources which provide a wide range of species sources for miao ethnicity medicine. On the other hand, due to the characteristics of the living environment of the Hmongb people, Miao medicine has demonstrated its unique therapeutic effect in the treatment of some endemic diseases, infectious diseases, insect, snake and beast bites, rheumatism and other diseases. With the development of modern science and technology, the research and application of seedling medicine are also deepening. Through the systematic study of the chemical composition and pharmacological action of the seedling medicine, it can provide a new idea and method for modern medicine.

MCE included 1,641 natural products from traditional miao ethnicity medicine, including animal, plant and mineral sources.

An emerging drug design method is based on the secondary binding site effect, where small molecule drugs are designed to bind to secondary binding sites on target biomolecules rather than primary orthomorphic sites. Successful potential drugs (known as allosteric modulators) will be able to bind to allosteric sites and remotely alter (or modify) the conformation of the main orthosteric binding sites of biological targets. Allosteric modulators (AMs) are ligands of proteins that act through binding sites different from natural (orthosteric) ligand sites. AMs are relatively small, more lipophilic, and more rigid compounds. The binding efficacy of AMs with their targets is often slightly lower. AMs are divided into positive AMs (PAMs) and negative AMs (NAMs). AMs are ideal drug targets because they can fine-tune receptor activity while preserving the spatial and temporal signal transduction characteristics of endogenous ligands, resulting in fewer targeted side effects, improved subtype selectivity, and better promotion of biased signal transduction than normal ligands.

MCE designs a unique collection of 250 small allosteric modulators. It is a good tool to be used for research on metabolize, cancer and other diseases.

Ovarian cancer is the most common cause of death in female genital malignancies, with the highest mortality rate in female genital malignancies. It is characterized by difficulty in detection in the early stage of the disease, high recurrence rate and poor prognosis. In fact, ovarian cancer includes many pathologic types. It is usually divided into epithelial ovarian cancer, malignant germ cell tumors and sex cord stromal tumors, of which epithelial ovarian cancer is the most dominant form. Clinical treatment of ovarian cancer prioritizes surgery combined with paclitaxel chemotherapy. However, due to the spread and drug resistance of tumor cells, the recurrence of ovarian cancer is high. In this case, combined with traditional methods, the development of new therapeutic agents can help to improve the treatment effect of ovarian cancer.

MCE designs a unique collection of 2,854 compounds with definite or potential anti-ovarian cancer activity, which mainly targeting the main targets of ovarian cancer such as PARP, ATM/ATR, VEGFR and HIF/HIF Prolyl-Hydroxylase, etc. It is an essential tool for development and research of anti-ovarian compounds.

Heat-clearing and detoxification is a specific treatment method in the research of traditional Chinese medicine (TCM), which is clinically used to treat infectious diseases with remarkable effect. Over the past decades, the research of heat-clearing and detoxification treatment has been one of the most active fields of combining traditional Chinese and western medicines, and has made remarkable achievements. Nowadays, the application field of heat-clearing and detoxification traditional Chinese medicine is not only limited to antibacterial and antiviral, but also has made progress in the research fields of anti-inflammatory reaction, anti-endotoxin, anti-peroxidative damage, anti-inflammatory cytokines, enhancement of immune function, protection of cellular organelles, and maintenance of calcium homeostasis. In addition to this, clearing heat and removing toxins has also made significant research progress in non-infectious diseases, for example, in tumors, cardiovascular diseases, renal diseases, blood diseases, geriatrics, and diabetes, all of which have shown good curative effect.

MCE can supply 1,272 monomer component from more than a hundred sources of heat-clearing and detoxification TCM, which can be used in TCM studies, drug development and mechanism-based studies.

Techniques for reprogramming somatic cells create new opportunities for drug screening, disease modeling, artificial organ development, and cell therapy. The development of reprogramming techniques has grown exponentially since Yamanaka reprogrammed somatic cells to become induced pluripotent stem cells (iPSCs) using four transcription factors, OCT4, SOX2, KLF4, and c-MYC in 2006. Despite the development of efficient reprogramming methods, most methods are inappropriate for clinical applications because they carry the risk of integrating exogenous genetic factors or use oncogenes. Alternative approaches, such as those based on miRNA, non-viral genes, non-integrative vectors, and small molecules, have been studied as possible solutions to the problems. Among these alternatives, small molecules are attractive options for clinical applications. Reprogramming using small molecules is inexpensive and easy to control in a concentration- and time-dependent manner. It offers a high level of cell permeability, ease of synthesis and standardization, and it is appropriate for mass-producing cells.

MCE Reprogramming Compound Library contains a unique collection of 3,129 compounds that act on reprogramming signaling pathways. These compounds are potential stimulators for reprogramming. This library is a useful tool for researching reprogramming and regenerative medicine.

Stem cells, which are found in all multi-cellular organisms, can divide and differentiate into diverse special cell types and can self-renew to produce more stem cells. To be useful in therapy, stem cells must be converted into desired cell types as necessary which is called induced differentiation or directed differentiation. Understanding and using signaling pathways for differentiation is an important method in successful regenerative medicine. Small molecules or growth factors induce the conversion of stem cells into appropriate progenitor cells, which will later give rise to the desired cell type. There is a variety of signal molecules and molecular families that may affect the establishment of germ layers in vivo, such as fibroblast growth factors (FGFs); the wnt family or superfamily of transforming growth factors β (TGFβ) and bone morphogenetic proteins (BMP). Unfortunately, for now, a high cost of recombinant factors is likely to limit their use on a larger scale in medicine. The more promising technique focuses on the use of small molecules. These small molecules can be used for either activating or deactivating specific signaling pathways. They enhance reprogramming efficiency by creating cells that are compatible with the desired type of tissue. It is a cheaper and non-immunogenic method.

MCE Differentiation Inducing Compound Library contains a unique collection of 2,439 compounds that act on signaling pathways for differentiation. These compounds are potential stimulators for induced differentiation. This library is a useful tool for researching directed differentiation and regenerative medicine.

ASINEX has elaborated a library of diverse macrocycles using an effective tool box of synthetic methods. The resulting scaffolds are novel, tremendously diverse, medchem-relevant, macrocyclic frameworks.

Macrocyles tend to be larger than traditional screening molecules which make them perfect discovery tools for targets with shallow or extended binding sites. At the same time, their unique character based on restricted flexibility and ability to form intra-molecular hydrogen bonds allows for design approaches effectively optimizing properties such asaqueous solubility and membrane permeability. Many of these macrocycles have been tested for aqueous and DMSO solubility with cut-offs applied at 10 mM in DMSO and 50 µM in PBS (pH 7.4) followed by PAMPA permeability assay.

Accumulating evidence has revealed that intestinal microbiota play an important role in human health and disease, including cardiovascular diseases, inflammatory bowel disease, diabetes, obesity, cancer, and depression, etc. Changes in the composition of gut microbiota associated with disease, referred to as dysbiosis, have been linked to pathologies. Indeed, the gut microbiome functions like an endocrine organ, generating bioactive metabolites which play important roles in human metabolism, health, and disease. Gut microbiome has become a novel therapeutic target for many diseases. Analysis and identification of gut microbial metabolite will contribute to the development of therapeutic methods.

In order to meet the need of gut microbiome research, MCE carefully selected a unique collection of 476 gut microbial metabolites. MCE gut microbial metabolite library is a powerful tool for gut microbiome research and gut microbiome -related drug discovery.

Metabolomics, positioned as the systemic characterization of small-molecule metabolites within biological systems, has emerged as an indispensable analytical platform in both fundamental research and translational applications across plant sciences, microbial biotechnology, and biomedical investigations. Functioning as a critical component in multi-omics integration, this discipline deciphers the intricate molecular networks operating downstream of genomic, transcriptomic, and proteomic regulation, thereby capturing the dynamic biochemical phenotype closest to organismal functionality. The metabolome, comprising endogenous compounds with molecular weights typically below 1500 Da, serves as the functional readout of cellular processes and environmental interactions, where perturbations in metabolic networks are frequently implicated in disease pathogenesis. Such unique attributes have propelled metabolomics into a pivotal role in pharmacological research, particularly in target deconvolution, pharmacodynamic assessment, and mechanistic elucidation of pathological processes.

MCE can provide 5,955 mass spectrometry human metabolites that can be used for metabolite identification and quantification, functional cell detection and phenotypic screening of mass spectrometry.

Antitussive and antiasthmatic method is a type of treatment strategy in traditional Chinese medicine, mainly used to alleviate symptoms such as coughing and asthma. These symptoms may be caused by various factors, such as: Bronchial asthma, chronic obstructive pulmonary disease, asthmatic bronchitis, cough-induced asthma, and others. Based on existing research in traditional Chinese medicine, many types of Chinese medicinal herbs showed antitussive and antiasthmatic effects. For example: Ardisiae Japonicae Herba, Ginkgo Semen, Amygdalus Communis Vas, Farfarae Flos, Viticis Cannabifoliae Fructus, Eriobotryae Folium etc. Therefore, the active ingredients derived from these traditional Chinese medicine have high medicinal value and have the potential to be developed into drugs for related diseases.

MCE can provide 862 active ingredients that can be obtained from traditional Chinese medicine with antitussive and antiasthmatic functions, which can be applied to drug development and research on disease mechanisms.

Macrocyclic compounds (≥12-atom cyclic small molecules/peptides) have unique physicochemical properties. They form preorganized conformations with high binding affinity/selectivity, target traditional small-molecule-inaccessible proteins, and bridge small-molecule drugs and biological agents. As key protein phosphorylation enzymes, kinases are linked to tumors, COPD, etc., and are critical therapeutic targets. Traditional small-molecule kinase inhibitors lack selectivity, causing off-target toxicity, low bioavailability, and acquired resistance. Macrocycles’ semi-rigid structure restricts conformations, boosts binding selectivity, optimizes pharmacokinetics, and makes macrocyclization a core kinase inhibitor optimization strategy.

Thousands of bioactive macrocycles were curated from ChEMBL. Via Transformer, macrocyclization was converted into a chemical language translation task, enabling end-to-end macrocycle generation from linear precursors with simplified inputs. Macformer achieves efficient, automated linear molecule macrocyclization via deep learning; generated macrocycles have diversity, novelty, biocompatibility, and cover broader chemical space.

MCE collected thousands of marketed/clinical kinase inhibitors, using their fragments for macrocyclization to generate derivatives. After evaluating synthetic accessibility and physicochemical properties, a million-scale virtual macrocyclic library was built for kinase-related virtual and AI-driven screening.

Macrocyclic compounds (≥12-atom cyclic small molecules/peptides) have unique physicochemical properties. They form preorganized conformations with high binding affinity/selectivity, target traditional small-molecule-inaccessible proteins, and bridge small-molecule drugs and biological agents. As key protein phosphorylation enzymes, kinases are linked to tumors, COPD, etc., and are critical therapeutic targets. Traditional small-molecule kinase inhibitors lack selectivity, causing off-target toxicity, low bioavailability, and acquired resistance. Macrocycles’ semi-rigid structure restricts conformations, boosts binding selectivity, optimizes pharmacokinetics, and makes macrocyclization a core kinase inhibitor optimization strategy.

Thousands of bioactive macrocycles were curated from ChEMBL. Via Transformer, macrocyclization was converted into a chemical language translation task, enabling end-to-end macrocycle generation from linear precursors with simplified inputs. Macformer achieves efficient, automated linear molecule macrocyclization via deep learning; generated macrocycles have diversity, novelty, biocompatibility, and cover broader chemical space.

MCE collected thousands of marketed/clinical kinase inhibitors, using their fragments for macrocyclization to generate derivatives. After evaluating synthetic accessibility and physicochemical properties, a million-scale virtual macrocyclic library was built for kinase-related virtual and AI-driven screening.

Environmental pollution refers to the process where human activities release harmful chemicals or energy (such as industrial waste, pesticides, and plastic particles) into the natural environment at a rate that exceeds the ecosystem's capacity for self-purification, leading to deterioration in the composition or state of the atmosphere, water bodies, and soil. Environmental pollution is not only a direct threat to biodiversity but also ultimately impacts human health through the bioaccumulation effect of the food chain. Therefore, the accurate identification and dynamic monitoring of pollutants constitute the scientific cornerstone for formulating environmental policies, assessing ecological risks, and promoting green chemistry transformation.

MCE features a collection of 869 environmental pollutants, covering categories such as air pollutants, water pollutants, and pesticides, for research in the field of environmental chemistry.

KRAS (Kirsten Rat Sarcoma Viral Oncogene Homolog) is one of the most important oncogenic driver genes in oncology, with high mutation frequencies in pancreatic cancer, non‑small cell lung cancer, and colorectal cancer. For a long time, KRAS was considered "undruggable" due to the lack of suitable small‑molecule binding pockets on its protein surface. In recent years, with the discovery of the switch‑II pocket and the successful approval of KRAS G12C inhibitors, KRAS‑targeted research has achieved groundbreaking progress, which has also spurred a wave of development targeting non‑G12C mutants such as G12D and G12V, as well as upstream and downstream regulatory factors including SOS1 and SHP2.

MCE KRAS Targeted Compound Library contains 32 small‑molecule compounds targeting the KRAS, serving as high‑quality research tools for mechanistic studies of KRAS‑mutant tumors, combination therapy development, resistance mechanism exploration, and high‑throughput drug screening, thereby providing robust support for KRAS‑targeted drug discovery.

Built on druggable heterocyclic backbones with tunable electrophilic warheads (halogens, cyano groups), our electrophilic heterocyclic fragment library targets non-conserved cysteine/lysine residues and screens covalent ligands through an electrophile-first workflow. It generates high-quality dual-functional fragments for KRAS, BTK and other popular targets, supporting MS and DEL high-throughput screening to accelerate covalent drug lead discovery.

MCE Electrophilic Heterocyclic Fragment Library Built on druggable heterocyclic backbones with tunable electrophilic warheads (halogens, cyano groups), our electrophilic heterocyclic fragment library targets non-conserved cysteine/lysine residues and screens covalent ligands through an electrophile-first workflow. It generates high-quality dual-functional fragments for KRAS, BTK and other popular targets, supporting MS and DEL high-throughput screening to accelerate covalent drug lead discovery.

Cell death is a core biological process that maintains homeostasis in multicellular organisms, playing a dual role in life activities. On one hand, cell death participates in physiological processes such as cell renewal and damage repair through precise regulation; on the other hand, it actively eliminates damaged, infected, or cancerous cells, thereby blocking pathological progression and preserving organism health. Cell death not only ensures the normal development and growth regulation of organisms but is also closely associated with the occurrence and development of various diseases. Numerous studies have shown that specific types of programmed cell death play critical roles in disease progression, providing an important theoretical basis for developing novel therapeutic strategies by regulating cell death pathways.

MCE offers 23 types of commonly used cell death inhibitors, such as apoptosis, ferroptosis, pyroptosis, and cuproptosis, suitable for use as positive controls in the study of novel cell death mechanisms.

Amino acids are indispensable building blocks for life activities and are widely involved in key biological processes such as cell signal transduction, energy metabolism, gene expression regulation, and neurotransmitter synthesis. As components of proteins, 20 kinds of amino acids make up over one million kinds of proteins in the human body. These amino acids can be classified into nine types of "essential amino acids" that the human body cannot synthesize on its own and must obtain from food, as well as eleven types of "non-essential amino acids" that the human body can synthesize on its own.

MCE offers 20 kinds of amino acids provided which can be applied in research fields such as the study of amino acid metabolic processes, metabolite identification, food/cosmetic ingredient research, and the development of nutritional supplements.

In drug discovery and development (R&D) area, target binding and druggability optimization are core processes. Among these attributes, high solubility is critical for a compound to achieve druggability, as it directly impacts the progress of drug R&D. Superior solubility ensures the rapid dissolution and uniform distribution of drug molecules in vivo, thereby enhancing bioavailability and effectively mitigating issues such as suboptimal efficacy, increased dosage requirements, or exacerbated toxic and side effects arising from insufficient solubility.

From the perspective of medicinal chemistry, high-solubility drug fragments serve as high-quality "molecular building blocks". Based on these fragments, lead compounds with potential druggability can be rapidly screened out, which significantly shortens the drug R&D cycle and reduces R&D costs. Meanwhile, the high-solubility drug fragment library can provide diverse options for drug development in different therapeutic areas, offer solutions for the solubility defects of existing clinical drugs, and facilitate the development of novel, highly effective targeted drugs with higher bioavailability and better safety profiles.

MCE has collected and compiled 2,526 experimentally validated small-molecule fragments with high solubility. These fragments can be directly used for drug molecular design, providing high-quality pre-validated solubility fragments that significantly improve the efficiency of lead compound screening and accelerate the progress of drug R&D.

Plant hormones are natural signaling molecules synthesized by plants themselves, serving as crucial chemical messengers that exert physiological effects on plants at extremely low concentrations. They coordinate cellular growth, division, differentiation, and organ formation, helping plants adapt to environmental changes. Major categories include abscisic acid, auxins, gibberellins, cytokinins, ethylene, and brassinosteroids, among others.

MCE has included 45 plant hormones, which can be used for identification in plant metabolomics and related botanical research.

Cysteine proteases (CPs), a key enzyme family regulating physiological metabolism and mediating pathological processes (e.g., abnormal bone resorption, tumour invasion, and pathogen infection), represent a core therapeutic target for disease intervention via the development of specific inhibitors. Currently reported CP covalent inhibitors encompass diverse structural types, including epoxides, aziridine, and activated double bonds (vinyl sulphones, α,β-unsaturated ketones), providing clear structural references for the development of novel CP covalent inhibitors.

This compound library contains multiple warheads that specifically target cysteine proteases, serving as a powerful tool for the efficient discovery of novel covalent inhibitors against this enzyme family.

Flavors and fragrances serve as indispensable enhancing elements in modern industries, playing multidimensional roles in the fields of food, cosmetics, and pharmaceutical development. In the food industry, flavors and fragrances are not only used to compensate for flavor loss during processing but also to create novel sensory experiences and enhance product appeal. Natural flavors such as vanilla and citrus oils impart rich, layered aromas to foods, while synthetic flavors can precisely replicate specific tastes, meeting the demands of standardized production and extending the flavor stability of food products. In the cosmetics sector, flavors and fragrances are key to emotional design. They enhance product recognition and elevate the pleasure of use through pleasant scents. In pharmaceutical development, the application of flavors and fragrances focuses on improving compliance. Especially in formulations such as oral liquids and chewable tablets, the addition of mint, fruit, and other flavoring components effectively masks the bitter or irritating taste of medications, increasing patient acceptance. Additionally, some natural flavors may themselves possess auxiliary therapeutic benefits.

MCE contains 496 kinds of flavors and fragrances, which can be used in fields such as food, cosmetics and drug development.

Unnatural amino acids (UAAs), also referred to as non-canonical amino acids (ncAAs) or non-proteinogenic amino acids, are a class of amino acids that are distinct from the 20 standard natural amino acids. They can be obtained through chemical synthesis, biosynthesis, and other approaches, with structural diversity far exceeding that of natural amino acids. UAAs are mainly including naturally occurring non-canonical amino acids, chemically synthesized amino acids, and biosynthetic amino acids, which provide a molecular basis for protein function design.

UAAs exhibit significant value in multiple fields. They can optimize the pharmacokinetic properties of peptide drugs and peptidomimetics, modify enzyme functions and endow them with new biological activities, thereby overcoming the limitations of traditional peptide drugs and expanding the chemical space . Meanwhile, UAAs can serve as molecular probes to analyze protein-protein interactions and investigate the regulatory mechanisms of protein functions.

MCE has compiled a UAAs Fragment Library comprising nearly a thousand unnatural amino acid fragments with extensive coverage of chemical space and enhanced structural diversity. This compound library can be widely applied in peptide synthesis, drug design, and protein engineering.

Proteolysis-targeting chimera (PROTAC) has been developed to be a useful technology for targeted protein degradation. PROTACs consist of a ligand for E3 ligase (E3 ligase binder), a linker and a ligand (mostly small-molecule inhibitor) for protein of interest（target binder）. Upon binding to the target protein, the PROTACs can recruit E3 for target protein ubiquitination, which is subjected to proteasome-mediated degradation.

Although there are more than 600 E3 ubiquitin ligases, only several with small molecule ligands have been used for designing PROTACs, including Skp1-Cullin-F box complex containing Hrt1 (SCF), Von Hippel-Lindau tumor suppressor (VHL), Cereblon (CRBN), inhibitor of apoptosis proteins (IAPs), and mouse double minute 2 homolog (MDM2).

MCE carefully prepared a unique collection of 177 ligands for E3 ligase, which have been reported to be used in PROTAC design. MCE E3 ligase ligand library is a useful tool for PROTAC development.

Cyclic peptides are polypeptide chains taking cyclic ring structure, which exhibit diverse biological activities, such as antibacterial activity, immunosuppressive activity and anti-tumor activity. Cyclic peptides, with the features of good binding affinity, target selectivity and low toxicity, show great success as therapeutics. Multiple cyclic peptides are currently in clinical use, for examples, gramicidin and tyrocidine with bactericidal activity, cyclosporin A with immunosuppressive activity, and vancomycin with antibacterial activity. Furthermore, cyclic peptides usually have the sufficient size and a balanced conformational flexibility/rigidity for binding to flat protein-protein interaction (PPI) interfaces, which have potential to develop PPI drugs.

MCE offers a unique collection of 96 cyclic peptides, all of which have good bioactivities. MCE Cyclic Peptide Library is a powerful tool for drug discovery and PPI inhibitor screening.

Chinese Baijiu is one of the oldest alcoholic beverages in the world, with a history of over 2,000 years. It can be classified into 12 aroma types based on its fragrance and flavor characteristics. The specific flavor profile of Baijiu is determined by the composition and concentration of certain compounds. These trace compounds, present in low concentrations yet rich in esters, alcohols, acids, lactones, aldehydes, ketones, acetals, alkenes, and others, significantly influence the flavor of Baijiu. Additionally, some active components in Baijiu possess antioxidant properties, and moderate consumption may help reduce the risk of cardiovascular diseases, dementia, and insulin resistance. Therefore, studying the chemical composition of Baijiu is crucial for promoting its fermentation process and enhancing its flavor and quality.

MCE has compiled included 669 Chinese Baijiu components, which can be used for drug development, Baijiu fermentation, and research related to Baijiu flavor and aroma.

Cysteine proteases (CPs), a key enzyme family regulating physiological metabolism and mediating pathological processes (such as abnormal bone resorption, tumour invasion, and pathogen infection), represent a core therapeutic target for developing specific inhibitors in disease intervention. Currently reported CP inhibitors primarily achieve their inhibitory function by precisely binding to CP active pockets (e.g., S1-S4 non-primed regions or S1'-S2' primed regions) and forming covalent/non-covalent interactions with the active site cysteine residues, providing clear structural references for the development of novel inhibitors.

This compound library, designed based on the core strategy of "similarity-based known active structures", contains over 200 cysteine protease inhibitors. Leveraging AI-driven molecular screening technology, it retains the critical pharmacological and shape features of reported CP inhibitors, serving as a specialized tool for efficiently discovering novel cysteine protease inhibitors.

In the progression of various diseases, metabolic reprogramming has emerged as a key hallmark. Lactate, as an important metabolic signaling molecule, is widely involved in tumorigenesis, immune regulation, and inflammatory responses. Particularly within the tumor microenvironment, the abnormal accumulation of lactate not only affects cellular energy metabolism but also promotes disease progression by modulating immune cell functions and mediating protein lactylation, thereby participating in epigenetic regulation and signaling networks. Therefore, systematic investigation of lactate metabolic pathways and their associated metabolites is of great significance for understanding disease mechanisms and developing novel therapeutic strategies.

The MCE lactic acid metabolite compound library contains 63 compounds and is constructed around key metabolic pathways involving lactate production, transport, and utilization. This library systematically includes core intermediates from glycolysis, the tricarboxylic acid (TCA) cycle, and the lactate cycle. Focusing on disease-associated metabolic reprogramming, it is suitable for research in oncology, inflammation, and metabolic disorders. The library can be used to elucidate the roles of lactate in tumor microenvironment regulation, immune evasion, and epigenetic modifications (such as protein lactylation). In addition, it provides high-quality small-molecule resources for drug screening, facilitating the discovery of potential modulators targeting key enzymes (such as LDH) or transporters (such as MCTs) involved in lactate metabolism.

Proteolysis-targeting chimera (PROTAC) has been developed to be a useful technology for targeted protein degradation. PROTACs consist of a ligand for E3 ligase (E3 ligase binder), a linker and a ligand (mostly small-molecule inhibitor) for protein of interest（target binder）. Upon binding to the target protein, the PROTACs can recruit E3 for target protein ubiquitination, which is subjected to proteasome-mediated degradation. Therefore, PROTACs execute their functions by degrading the target proteins rather than inhibiting them, which has a great superiority in overcoming resistance caused by target mutation or overexpression. To date, PROTAC technology has been applied to a variety of targets, including AR, ER, BTK, BET, and BCR-ABL to overcome resistance.

MCE carefully prepared a unique collection of 96 ligands for target proteins, which have been reported to be used in PROTAC design. MCE Target Protein Ligand Library is a useful tool for PROTAC development.

The discovery of hit molecule is a cornerstone of drug development. Among the diverse tools available, DNA-encoded libraries have emerged a revolutionary platform for high-throughput screening. Compared with traditional HTS, DEL features shorter screening processes, lower costs, simpler assays, and larger library capacities.

DEL Construction utilizes split-and-pool synthesis, a combinatorial chemistry approach that involves iterative splitting, reaction, and pooling. This strategy enables rapid, exponential assembly of fragments in minimal steps without the need for individual compound synthesis andassoicicated isolation or purification steps, thus greatly reducing overall costs. The technology enables simultaneous affinity screeningof massive compound collections to target proteins in a single step. By coupling chemical structures with unique DNA barcodes, each compound is tagged with a distinct DNA sequence for convenient tracking and decoding.DELs readily enable the construction and efficient screening of libraries containing millions to billions of compounds. As a result, DEL screening combines the dual advantages of high efficiency and low cost, making DEL a transformative technology in modern drug discovery.

The DEL kit consists of 50 independent libraries with a total scale of 100 billion compounds. It is constructed through stepwise combinatorial chemistry strategies involving 2-, 3-, and 4-round synthesis. By employing diverse scaffolds and flexible linking strategies, it encompasses various ring systems, linear frameworks, and heterocyclic structures. Screening can be achieved solely through affinity, independent of target-specific activity detection methods. This library is suitable for DEL screening against a wide range of targets.

Protein lactylation, an emerging post-translational modification identified in recent years, plays a critical role in linking cellular metabolic reprogramming, epigenetic regulation, and signaling networks. Based on a systematic framework encompassing lactate metabolism, lactylation, and downstream signaling pathways, this compound library comprehensively targets multiple regulatory layers, including histone modification enzymes (such as p300 and HDACs), key glycolytic enzymes (such as PKM2, LDHA, and GAPDH), transcriptional regulators (such as STAT3, HMGB1, and p53), as well as central signaling pathway nodes including HIF-1α, NF-κB, and PI3K-AKT-mTOR. This integrated design enables a comprehensive representation of the regulatory roles of lactylation across the “metabolism–epigenetics–signaling” axis.

MCE has assembled a collection of 5,946 known bioactive compounds and potential functional molecules, making this library suitable for a wide range of applications, including high-throughput drug screening, inhibitor identification, and mechanistic studies. It can be used to systematically evaluate the functional roles of lactylation in biological processes such as tumor metabolism, immune regulation, and inflammatory responses, and to efficiently identify small-molecule candidates with regulatory potential, thereby facilitating the development of innovative therapeutics targeting the interplay between metabolism and epigenetic regulation.

MCE-18 stands for Medicinal Chemistry Evolution 2018, which was first published in Journal of Medicinal Chemistry in 2019 for assessing molecular novelty and three-dimensional complexity. Developed based on Clarivate global pharmaceutical patent database, this descriptor was constructed via big-data analysis covering 28,161 patented lead compounds, 1,370 approved drugs and nearly 30,000 preclinical-to-phase III drug candidates from 23 top pharmaceutical companies worldwide between 1950 and 2018, followed by structural clustering and removal of redundant outdated scaffolds for data denoising. Its scoring system integrates five core structural features including aromatic ring (AR), aliphatic heterocycle (NAR), chiral center (CHIRAL), spiro atom (SPIRO), cyclic and acyclic sp³ carbon ratio together with a quadratic topological correction factor. Breaking the limitations of the single Fsp³ parameter, MCE-18 effectively distinguishes conventional flat aromatic scaffolds from modern 3D-enriched novel chemotypes, overcoming typical drawbacks of traditional compound libraries such as scaffold redundancy, low screening hit rates and poor compatibility with allosteric and PPI-related difficult targets.

This library contains over 37,000 structurally diverse compounds with favorable overall drug-likeness, suitable for high-throughput screening against canonical targets including kinases, GPCRs and proteases as well as challenging allosteric and PPI targets. Compounds comply with the developmental trend of modern novel drug discovery, supporting routine primary screening as well as early hit identification of allosteric modulators and PPI inhibitors, serving as an efficient screening resource for early-stage innovative drug discovery.

CRBN, namely cereblon, is the substrate recognition subunit of the E3 ubiquitin ligase complex in the ubiquitin-proteasome system. A CRBN ligand library refers to a collection of numerous fragments that can specifically bind to the CRBN protein.

These ligands are mostly designed based on validated CRBN-binding warheads and modified through AI-driven molecular generation optimization systems. They not only include classic lenalidomide-derived structures but also cover novel non-lenalidomide scaffolds. After drug-likeness filtering, these ligands exhibit structural diversity and favorable druggable properties. They can be further optimized and modified to facilitate the development of novel molecular glue degraders, accelerate the discovery of molecular glues that induce interactions between CRBN and new substrate proteins, and enable the exploration of novel CRBN substrates for identifying previously unknown CRBN-binding proteins.

MCE compiles 121 fragments that can specifically bind to the CRBN protein, with molecular weights ranging from 200 to 500. Compounds developed based on the library ligands target multiple disease targets such as cancer and autoimmune diseases, further advancing the development of Molecular Glues and PROTACs therapeutic agents.

Animal disease models are used in a variety of settings in basic research, such as studies on mechanisms of disease progression and evaluation new drugs. Animal models can be broadly classified into five categories: 1) experimental, 2) spontaneous, 3) negative, 4) orphan, 5) genetically engineered. Experimental models, which are induced artificially in the laboratory, are most common. Some small molecular compounds are usually used as inducers for animal models, such as Ceruletide for inflammatory model, Azoxymethane for tumor model. These inducers are useful tool in building animal models.

MCE offers a unique collection of 51 animal model inducers, involving inflammatory model, tumor model, nervous disease model, etc. MCE Animal Disease Model library is a powerful tool for the establishment of animal disease models.

Peptides are a group of biologically active substances that are involved in various cellular functions of organisms. Peptides are often used in functional analysis, vaccine research and especially in the field of drug research and development. At present, more than 80 peptide drugs have reached the market for a wide range of diseases, including diabetes, cancer, osteoporosis, multiple sclerosis, HIV infection and chronic pain.

MedChemExpress (MCE) offers a comprehensive collection of 2,537 peptides, including bioactive peptides, amino acid derivatives, and blocking peptides. MCE Peptide Library can be used for peptide library screening, peptide drug discovery, vaccine development, target verification, structural activity research, etc.

A drug metabolite is a byproduct of the body breaking down, or “metabolizing” a drug into a different substance. Most drugs undergo chemical alteration by various bodily systems as a way to create compounds that are more easily excreted from the body. Drugs can be metabolized by oxidation, reduction, hydrolysis, hydration, conjugation, condensation, or isomerization. Drug metabolism can produce metabolites with physicochemical and pharmacological properties that differ substantially from those of the parent drug, and consequently have important implications for both drug safety and efficacy.

MCE offers a unique collection of 423 drug metabolites which is a useful tool for drug safety and efficacy study and drug repurposing.

G protein-coupled receptors (GPCRs) are membrane proteins in humans and one of the most important targets in drug discovery. Approximately 35% of launched drugs are targeted GPCRs, making them a crucial class of targets in drug discovery.

The orthosteric site of a GPCR is its endogenous ligand’s (such as neurotransmitters or hormones) binding site. This site plays a central role in signal transduction. Small molecules binding to this site typically contain a protonatable amino group, enabling the formation of salt bridges or hydrogen bonds with acidic residues in the binding pocket. In contrast, the allosteric site does not directly initiate signaling but modulates the signal intensity of the GPCR by altering or stabilizing the conformation of the orthosteric site. Small molecules binding to the allosteric site often contain multiple aromatic rings to occupy hydrophobic pockets and achieve their functional effects.

MCE has collected over 7,116 reported bioactive molecules targeting GPCRs, covering Class A, B, and C GPCRs. These small molecules were subjected to AI representation to extract 2D and 3D features. Subsequently, we do screening by AI score based on similarity to identify molecules in diversity library highly similar to the reported bioactive molecules in both 2D and 3D, with a threshold greater than 0.7. Further screening based on cLogP was applied to select molecules with good lipophilicity, which facilitates the binding of small molecules to GPCRs. This diversity library can be widely applied to the discovery of compounds targeting GPCR proteins.

Orthosteric sites are highly conserved, leading to poor subtype selectivity, off-target toxicity and drug resistance in traditional drugs. By contrast, allosteric sites show low conservation, high hydrophobicity, weak polarity, confined geometry and dynamic cryptic properties, granting modulators high selectivity, functional tunability and safety. Thus, allosteric therapy has become a major focus in drug discovery.

MCE curated nearly 1,000 clinical-stage allosteric modulators, analyzed PDB complex structures to identify key pharmacophores and privileged scaffolds, then designed and filtered compounds using rational “scaffold derivation + physicochemical screening” with strict property criteria. The resulting compounds show high rigidity and shape complementarity to shallow, dynamic, hydrophobic allosteric pockets.

This library comprises 4,315 diverse, lead-like compounds ideal for allosteric drug discovery and target screening, covering kinases, GPCRs and more. All are analogs of clinical-stage molecules with similarity > 0.6, combining high druggability and allosteric binding potential to support efficient early-stage R&D.