A Diterpenoid Taxoquinone from Metasequoia glyptostroboides with Pharmacological Potential

Background: The ubiquitin-proteasome pathway plays an important role in selective protein degradation and regulates multiple cellular processes, including cell cycle progression, proliferation and apoptosis. Cancer cells are more sensitive to the pro-apoptotic effects of proteasome inhibition than normal cells, hence, proteasome inhibitors can be used as novel anticancer drugs. Further, influenzacommonly known as “flu” is a contagious respiratory disease caused by sub-type of influenza A virus H1N1 which has resulted in enormous medical attention world-wide. Natural products are well known for their pharmacological potential in anticancer and antiviral therapies. Methods: In this study, an abietane-type diterpenoid, taxoquinone, isolated from Metasequoia glyptostroboides, was assessed for the first time for its therapeutic efficacy as a potential inhibitor of influenza A (H1N1) virus and 20S proteasomeusing cytopathic reduction assay and proteasome inhibition assay, respectively. Results: The taxoquinonedisplayed its anticancer effect in terms its ability to inhibit 20S human proteasome with IC50 value of 8.2 ± 2.4 µg/µL. Moreover, taxoquinone (500 µg/mL) displayed significant antiviral effect against H1N1 influenza virus in cytopathic reduction assay on MDCK cell line. Conclusion: These finding confirm pharmaceutical potential of taxoquinone as a novel therapeutic agent.