Inhibition of the SARS-CoV-2 3CLpro main protease by plant polyphenols

The abundance of polyphenols in edible plants makes them an important component of human nutrition. Considering the ongoing COVID-19 pandemic, a number of studies have investigated polyphenols as bioactive constituents. We applied in-silico molecular docking as well as molecular dynamics supported by in-vitro assays to determine the inhibitory potential of various plant polyphenols against an important SARS-CoV-2 therapeutic target, the protease 3CL^pro. Of the polyphenols in initial in-vitro screening, quercetin, ellagic acid, curcumin, epigallocatechin gallate and resveratrol showed IC₅₀ values of 11.8 µM to 23.4 µM. In-silico molecular dynamics simulations indicated stable interactions with the 3CL^pro active site over 100 ns production runs. Moreover, surface plasmon resonance spectroscopy was used to measure the binding of polyphenols to 3CL^pro in real time. Therefore, we provide evidence for inhibition of SARS-CoV-2 3CL^pro by natural plant polyphenols, and suggest further research into the development of these novel 3CL^pro inhibitors or biochemical probes.

In vitro inhibition of human CYP2E1 and CYP3A by quercetin and myricetin in hepatic microsomes is not gender dependent

This is the first in vitro study to investigate gender-related differences in the regulation of human cytochrome P450 by the flavonoids. Activities of CYP2E1 and CYP3A were measured in the presence of quercetin, myricetin, or isorhamnetin in hepatic microsomal pools from male and female donors. Hydroxylation of p-nitrophenol (PNPH) was measured to determine CYP2E1 activity, and O-dealkylation of 7-benzyloxy-4-trifluoromethylcoumarin (BFC) was measured to determine CYP3A activity. Quercetin, but not myricetin or isorhamnetin, competitively inhibited PNPH activity in human recombinant cDNA-expressed CYP2E1 with the Ki=52.1±6.31μM. In the human microsomes, slight inhibition of PNPH activity by quercetin was not considered as physiologically relevant. Quercetin inhibited BFC activity in human recombinant cDNA-expressed CYP3A4 competitively with the Ki=15.4±1.52μM, and myricetin - noncompetitively with the Ki=74.6±7.99μM. The degree of inhibition by quercetin was similar between genders. Myricetin showed somewhat stronger inhibition in female pools, but the Ki values were higher than physiologically relevant concentrations. Isorhamnetin did not affect either PNPH or BFC activity. We concluded that observed inhibition of CYP2E1 and CYP3A by some flavonols were not gender-dependent.

Belamcanda chinensis (L.) DC-An ethnopharmacological, phytochemical and pharmacological review

ETHNOPHARMACOLOGICAL RELEVANCE

Belamcanda chinensis (L.) DC is the sole species in the genus Belamcanda Adans. (Iridaceae), found mainly in Northeast Asia. Bombus chinensis has long been used in traditional Chinese medicine for its multiple therapeutic uses in the form of antipyretic agents, antidote, expectorant, antiphlogistic and analgesic.

AIM OF THE REVIEW

This manuscript comprehensively summarizes the various studies published in recent years on the botany, ethnopharmacology, phytochemistry, biological activity and toxicology of B. chinensis. We hope to provide a foundation for future studies on the mechanism of action and development of better therapeutic agents based on B. chinensis.

MATERIAL AND METHODS

All information available on B. chinensis was collected using electronic search engines, such as PubMed, SciFinder Scholar, CNKI, TPL (www.theplantlist.org), Google Scholar and Web of Science.

RESULTS

The analysis shown that ethno-medical uses of B. chinensis have been recorded in China, Japan and Korea since a long time. Based on a phytochemical investigation, this plant contains flavonoids, terpenoids, quinones, phenolic compounds, ketones, organic acids, etc. Crude extracts and pure compounds isolated from B. chinensis exhibited various biological effects.

CONCLUSIONS

In light of its long traditional use and the modern phytochemical and pharmacological studies summarized here, B. chinensis is known to be a promising medicinal plant with the isolated extracts and chemical components showing a wide range of biological activities. Thus, it is imperative that the necessary programs and value assessment of B. chinensis be established for further studies. It is also important that the synergistic or antagonistic effects of this traditional herbal medicine are investigated in depth to identify more bioactive components by bioactivity-guided isolation strategies, and to illustrate the mechanisms of action targeting on ethnomedical uses. Future clinical studies can also focus on the main therapeutic aspects, toxicity and adverse effects of B. chinensis.