The naturally-derived alkaloids as a potential treatment for COVID-19: A scoping review.

Coronavirus disease 2019 (COVID-19) is caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), which has a high mortality rate and transmissibility. In this context, medicinal plants have attracted attention due to the wide availability and variety of therapeutic compounds, such as alkaloids, a vast class with several proven pharmacological effects, like the antiviral and anti-inflammatory activities. Therefore, this scoping review aimed to summarize the current knowledge of the potential applicability of alkaloids for treating COVID-19. A systematic search was performed on PubMed and Scopus, from database inception to August 2021. Among the 63 eligible studies, 65.07% were in silico model, 20.63% in vitro and 14.28% clinical trials and observational studies. According to the in silico assessments, the alkaloids 10-hydroxyusambarensine, cryptospirolepine, crambescidin 826, deoxynortryptoquivaline, ergotamine, michellamine B, nigellidine, norboldine and quinadoline B showed higher binding energy with more than two target proteins. The remaining studies showed potential use of berberine, cephaeline, emetine, homoharringtonine, lycorine, narciclasine, quinine, papaverine and colchicine. The possible ability of alkaloids to inhibit protein targets and to reduce inflammatory markers show the potential for development of new treatment strategies against COVID-19. However, more high quality analyses/reviews in this field are necessary to firmly establish the effectiveness/safety of the alkaloids here described.

Dimeric glycosylated flavan-3-ol and antimicrobial in vitro evaluation of Trichilia catigua extracts.

Trichilia catigua is a tree known as "catuaba", widely distributed in Brazil. Studies carried out with T. catigua barks suggest that plant has antidepressant, antidiabetic, antimicrobial, antioxidant, antiviral, and preventive against brain damage. The aim of this work was to isolate and characterise compounds from the semipurified fraction of T. catigua barks, and to conduct microbiological screening against bacteria and fungi. The crude extract (CE) of "catuaba" was produced by turbo extraction with acetone-water, and later, partitioned to yield ethyl-acetate (EAF) and aqueous (AqF) fractions. From AqF the new catechin-3-O-α-L-rhamnoside-(4α→8)-epicatechin was isolated, identified, and described here for the first time. Regarding antimicrobial activity, the extracts presented impressive results, mainly for Vancomycin Resistant Enterococcus faecium (VREfm) with MIC of 156.5 µg/mL. The results suggest that extract of T. catigua could potentially be used as an adjuvant to treatment and is a promising candidate for the development of new antimicrobial drugs.