In silico studies on phytochemicals of Pimpinella anisum L. (Apiaceae) as potential inhibitors of SARS-CoV-2 3C-like protease

Objectives. As of October 13 2020, the current pandemic (COVID-19) caused by the coronavirus SARS-CoV-2 has resulted in 38,167,109 infections and 1,087,118 deaths and has practically affected nearly all countries of the world. One of the characteristics of this virus-induced disease is severe respiratory distress, hence the name Severe Acute Respiratory Syndrome Coronavirus. So far there has been no discovery of therapeutics in the form of vaccines and drugs, which can control this virus. Pimpinella anisum (anise in English) is used in the three major traditional medicinal systems of India (Ayurveda, Siddha and Unani) to control respiratory distress. It was of interest to evaluate some of the phytochemicals reported in anise for their binding and possible inhibition of the main protease or 3C-like protease of SARS-CoV-2, which plays an indispensable part in replication of the virus. Methods. Binding studies were carried out in silico using AutoDock Vina program to carry out molecular docking of the phytochemicals to 3C-like protease.  Results. Of the eleven phytochemicals studied, five compounds, namely cyanidin, malvidin, peonidin, petunidin and pelargonidin demonstrated high binding energy values to the protease (more than -7.5 kcal/mol). These five compounds were followed by isorhamnetin with a binding energy of -7.4 kcal/mol. The compounds bound at or close to the catalytic site of the protease, indicating that they can possibly inhibit the proteolytic activity. Conclusions. Several phytochemicals from Pimpinella anisum merits further studies both in vitro and in vivo to evaluate their ability to inhibit SARS-CoV-2 and their use as therapeutics.