Alkaloids

Serotonin (5-Hydroxytryptamine) hydrochloride is a monoamine neurotransmitter in the CNS and an endogenous 5-HT receptor agonist, with blood-brain barrier permeability. Serotonin hydrochloride is also a catechol O-methyltransferase (COMT) inhibitor with a K_i of 44 μM.

Cyclopamine is a Hedgehog (Hh) pathway antagonist with an IC₅₀ of 46 nM in the Hh cell assay. Cyclopamine is also a selective Smo inhibitor.

Homoharringtonine (Omacetaxine mepesuccinate;HHT) is a cytotoxic alkaloid with antitumor properties which acts by inhibiting translation elongation.

Bicuculline ((+)-Bicuculline) is A competing neurotransmitter GABA_A receptor antagonist (IC₅₀=2 μM). Bicuculline also blocks Ca²⁺ activating potassium (SK) channels and subsequently blocks slow post-hyperpolarization (slow AHP). Bicuculline has anticonvulsant activity. Bicuculline can be used to induce seizures in mice.

Letrozole (CGS 20267) is a potent, selective, reversible and orally active non-steroidal inhibitor of aromatase, with an IC₅₀ of 11.5 nM. Letrozole selective inhibits estrogen biosynthesis, and can be used for the research of breast cancer.

Ergothioneine is an imidazole-2-thione derivative with orally active histidine betaine. Ergothioneine is a specific inhibitor of p38-MAPK and Akt, which plays a protective role in cell apoptosis induced by stress. Ergothioneine has antioxidant activity.

Norepinephrine (Levarterenol; L-Noradrenaline) hydrochloride is a potent adrenergic receptor (AR) agonist. Norepinephrine activates α₁, α₂, β₁ receptors.

Atropine (Tropine tropate) is a competitive muscarinic acetylcholine receptor (mAChR) antagonist with IC₅₀ values of 0.39 and 0.71 nM for Human mAChR M₄ and Chicken mAChR M₄, respectively. Atropine inhibits ACh-induced relaxations in human pulmonary veins. Atropine can be used for research of anti-myopia and bradycardia.

Irinotecan hydrochloride ((+)-Irinotecan hydrochloride) is a topoisomerase I inhibitor mainly used to treat colon cancer and rectal cancer.

Vinblastine sulfate is a cytotoxic alkaloid used against various cancer types. Vinblastine sulfate inhibits the formation of microtubule and suppresses nAChR with an IC₅₀ of 8.9 μM.

Kynurenic acid, an endogenous tryptophan metabolite, is a broad-spectrum antagonist targeting NMDA, glutamate, α7 nicotinic acetylcholine receptor. Kynurenic acid is also an agonist of GPR35/CXCR8.

Vinorelbine (ditartrate) is an anti-mitotic agent which inhibits the proliferation of Hela cells with IC₅₀ of 1.25 nM.

6PPD-Q (6PPD-Quinone) is an environmental pollutant that can be detected in human urine and is widely present in the environment. 6PPD-Q targets and binds to CNR2, CNR1, AA2AR, LCAT, and TRPA1, with CNR2 exhibiting the highest binding affinity, potentially acting as a CNR2 receptor agonist to activate cannabinoid receptors. 6PPD-Q induces intestinal inflammation and barrier damage by disrupting mitochondrial function, reducing neuronal glycolysis metabolites and TCA cycle intermediates, and exacerbating α-synuclein (α-syn) aggregation. 6PPD-Q is applicable in research on environmental toxicology, neurodegenerative diseases, and inflammation-related disorders.

Halofuginone (RU-19110), a Febrifugine derivative, is a competitive prolyl-tRNA synthetase inhibitor with a K_i of 18.3 nM. Halofuginone is a specific inhibitor of type-I collagen synthesis and attenuates osteoarthritis (OA) by inhibition of TGF-β activity. Halofuginone is also a potent pulmonary vasodilator by activating Kv channels and blocking voltage-gated, receptor-operated and store-operated Ca²⁺ channels. Halofuginone has anti-malaria, anti-inflammatory, anti-cancer, anti-fibrosis effects.

C16-Ceramide (d18:1/16:0) is a natural small molecule activating p53 through the direct and selective binding.

(R)-(-)-Phenylephrine hydrochloride is a selective α₁-adrenoceptor agonist with pK_is of 5.86, 4.87 and 4.70 for α_1D, α_1B and α_1A receptors respectively.

Indole-3-pyruvic acid is an orally active ketone analog of tryptophan, and is an aryl hydrocarbon receptor (AHR) agonist. Indole-3-pyruvic acid inhibits p38/MAPK phosphorylation, regulates the tryptophan metabolic pathway, and also possesses protective activities against skin photodamage, as well as anti-inflammatory and anti-anxiety bioactivities in the gut. Indole-3-pyruvic acid can downregulate the expression of IL-1β, IL-6, Cox-2, and Bax to alleviate UVB-induced keratinocyte toxicity. Indole-3-pyruvic acid can activate AHR to promote Tr1 cell differentiation, increase IL-10, and inhibit Th1 cytokine production. Indole-3-pyruvic acid can alter the levels of kynurenine metabolites in the brain, mediating central nervous system-related effects. Indole-3-pyruvic acid can be used in research on skin lesions, colitis, and anxiety.

Harmine is a natural dual-specificity tyrosine phosphorylation-regulated kinase (DYRK) inhibitor with anticancer and anti-inflammatory activities. Harmine has a high affinity of 5-HT_2A serotonin receptor, with an K_i of 397 nM.

(E/Z)-4-Hydroxytamoxifen (Afimoxifene) is a racemic compound of (Z)-4-Hydroxytamoxifen and (E)-4-Hydroxytamoxifen isomers. (E/Z)-4-Hydroxytamoxifen is a selective estrogen receptor modulator with mixed estrogenic and antiestrogenic activity, which is also an active metabolite of Tamoxifen (HY-13757A). (E/Z)-4-Hydroxytamoxifen is an agonist of the G protein-coupled estrogen receptor (GPER) with relatively low affinity (100-1000 nM). (E/Z)-4-Hydroxytamoxifen is promising for research of cyclical mastalgia, such as breast pain, tenderness, and nodularity.

Coelenterazine is a luminescent enzyme substrate for apoaequorin and Renilla luciferase. Renilla luciferase and substrate coelenterazine has been used as the bioluminescence donor in bioluminescence resonance energy transfer (BRET) to detect protein-protein interactions. Coelenterazine is a superoxide anion-sensitive chemiluminescent probe and it can also be used in chemiluminescent detection of peroxynitrite (Ex/Em = 429/466 nm).