2. Academic Validation
  3. Polymethoxyflavone from Citrus depressa as an inhibitor against various variants of SARS-CoV-2 spike protein

Polymethoxyflavone from Citrus depressa as an inhibitor against various variants of SARS-CoV-2 spike protein

  • J Ethnopharmacol. 2024 Feb 10:320:117412. doi: 10.1016/j.jep.2023.117412.
Ta-Wei Liu 1,  Su-Jung Hsu 2,  Yves S Y Hsieh 3,  Hui-Kang Liu 4,  Ching-Kuo Lee 5
Affiliations

Affiliations

  • 1 School of Pharmacy, College of Pharmacy, Taipei Medical University, Taipei, 11042, Taiwan. Electronic address: [email protected].
  • 2 School of Pharmacy, College of Pharmacy, Taipei Medical University, Taipei, 11042, Taiwan. Electronic address: [email protected].
  • 3 School of Pharmacy, College of Pharmacy, Taipei Medical University, Taipei, 11042, Taiwan; Graduate Institute of Pharmacognosy, College of Pharmacy, Taipei Medical University, Taipei, 11042, Taiwan; Division of Glycoscience, Department of Chemistry, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, AlbaNova University Centre, Stockholm, SE106 91, Sweden. Electronic address: [email protected].
  • 4 National Research Institute of Chinese Medicine (NRICM), Ministry of Health and Welfare, Taipei City, Taiwan; Ph. D. Program in the Clinical Drug Development of Herbal Medicine, Taipei Medical University, Taipei, Taiwan. Electronic address: [email protected].
  • 5 School of Pharmacy, College of Pharmacy, Taipei Medical University, Taipei, 11042, Taiwan; Graduate Institute of Pharmacognosy, College of Pharmacy, Taipei Medical University, Taipei, 11042, Taiwan; Ph. D. Program in the Clinical Drug Development of Herbal Medicine, Taipei Medical University, Taipei, Taiwan. Electronic address: [email protected].
PMID: 37995824 DOI: 10.1016/j.jep.2023.117412
Abstract

Ethnopharmacological relevance: In traditional Taiwanese medicine, Citrus depressa Hayata serves as the raw material of Chen-Pi which has been widely used to treat respiratory ailments. Scientific investigations have validated the attributes of C. depressa, elucidating its valuable properties, including antioxidative, anti-inflammatory, Anticancer, neuroprotion, hepatoprotection, and hypolipidemic effects.

Aim of the study: This study aims to isolate a universal inhibitor of the SARS-CoV-2 spike protein from C. depressa and confirm the mechanism by which these inhibitors disrupt the binding of the spike protein to hACE2.

Materials and methods: The whole fruit of C. depressa was subjected to ethanol extraction, following by partitioning to obtain water, butanol, and ethyl acetate fractions. To identify the inhibitory components in citrus fruits, we performed both the SPR assay and the SARS-CoV-2 pseudo-virus assays. Subsequently, we employed a bioassay-guided approach to efficiently isolate and characterize the bioactive constituents that hindered the interaction between the SARS-CoV-2 spike protein and hACE2, using a combination of MPLC and Semi-preparative HPLC for compound isolation. ELISA based spike protein binding assay evaluate the inhibitory activities of the extract and potential constituents against multiple spike protein variants. To further shed LIGHT on the inhibitory mechanism, candidate inhibitors were validated through the SPR assay and molecular docking.

Results: The crude extract and ethyl acetate layer derived from C. depressa showed significant inhibitory activity on SARS-CoV-2 Omicron BA.4/5, with IC50 of 77.4 μg/mL and 100 μg/mL, respectively. Ten potential compounds from C. depressa have been identified with inhibitory activity against various SARS-CoV-2 Spike Proteins. 2'-hydroxy-4,4',5',6'-tetramethoxychalcone (CD3) and 5-hydroxy-3',4',6,7,8-pentamethoxyflavone (Cd8) also showed good inhibitory activity to the spike protein, with KD of 0.79 μM and 37.3 nM, respectively. These findings are in line with prior study, indicating CD3 and Cd8 can bind to key amino acid residue, disrupting the formation of the spike protein and h-ACE2 complex.

Conclusion: This study presents the initial evidence showcasing the inhibitory effect of polymethoxyflavones (PMFs) on the spike protein of SARS-CoV-2. Moreover, the inhibitory activity of C. depressa extracts indicates their potential to prevent infections of different SARS-CoV-2 variants.

Keywords

ACE-2; Citrus depress; Polymethoxyflavone; SARS-CoV-2; Spike protein.

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