Bauhinia guianensis is a typical plant in the Amazon region belonging to the family Leguminosea, used by local populations for the treatment of infectious and renal diseases. Previous work on the plant B. guianensis led to the isolation of substances with anti-inflammatory and analgesic activities. Thus, compounds isolated from B. guianensis with antimicrobial activities had not been identified. Given that there is a possibility of biological activity reported for a given plant being found in the endophytic fungi, we decided to isolate endophytic fungi from B. guianensis and test their antimicrobial activities. The alkaloids known as fumigaclavine C and pseurotin A were isolated by column chromatography and identified by 1D and 2D NMR techniques and mass spectrometry. The alkaloids are first reported as broad-spectrum antibacterial agents with good activity.

BACKGROUND Since the World Health Organization (WHO) declared Coronavirus disease 2019 (COVID-19) to be a pandemic infection, important severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) non-structural proteins (nsp) have been analysed as promising targets in virtual screening approaches. Among these proteins, 3-chymotrypsin-like cysteine protease (3CLpro), also named main protease, and the RNA-dependent RNA polymerase (RdRp), have been identified as fundamental targets due to its importance in the viral replication stages. OBJECTIVES To investigate, in silico, two of the most abundant flavonoid glycosides from Dysphania ambrosioides; a medicinal plant found in many regions of the world, along with some of the putative derivatives of these flavonoid glycosides in the human organism as potential inhibitors of the SARS-CoV-2 3CLpro and RdRp. METHODS Using a molecular docking approach, the interactions and the binding affinity with SARS-CoV-2 3CLpro and RdRp were predicted for quercetin-3-O-rutinoside (rutin), kaempferol-3-O-rutinoside (nicotiflorin) and some of their glucuronide and sulfate derivatives. FINDINGS Docking analysis, based on the crystal structure of 3CLpro and RdRp, indicated rutin, nicotiflorin, and their glucuronide and sulfate derivatives as potential inhibitors for both proteins. Also, the importance of the hydrogen bond and π-based interactions was evidenced for the presumed active sites. MAIN CONCLUSIONS Overall, these results suggest that both flavonoid glycosides and their putative human metabolites can play a key role as inhibitors of the SARS-CoV-2 3CLpro and RdRp. Obviously, further researches, mainly in vitro and in vivo experiments, are necessary to certify the docking results reported here, as well as the adequate application of these substances. Furthermore, it is necessary to investigate the risks of D. ambrosioides as a phytomedicine for use against COVID-19.