Antiradical, antibacterial activities and <i>in silico</i> molecular docking of ethyl-<i>β-D</i>-fructofuranoside from hydro-ethanolic crude extract of <i>Erythrina excelsa</i> stem bark

The aim of the present study was to isolate and characterize compounds responsible of the antiradical and antibacterial activities in the hydro-ethanolic crude extract of <i>Erythrina excelsa</i> stem bark. Chemical investigation of this polar extract resulted in the isolation of a fructose derivative identified as ethyl-<i>β-D</i>-fructofuranoside (<b>3</b>) and an alkaloid designated <i>L</i>-(+)-Abrine (<b>4</b>); two compounds isolated here for the first time from the genus <i>Erythrina</i>, along with a mixture of sitosterol 3-<i>O-β-D</i>-glucopyranoside (<b>2</b>) and stigmasterol 3-<i>O-β-D</i>-glucopyranoside (<b>1</b>). Their structures were determined using spectroscopic methods (IR, 1 &amp; 2D NMR) as well as HR-ESI-MS and literature data. The hydro-ethanolic extract and compound <b>3</b> were tested for antibacterial activity on <i>Escherichia coli</i>, <i>Salmonella typhi</i>, <i>Salmonella typhimurium</i> and <i>Salmonella enterica</i>, and for antioxidant activity using free radical scavenging (DPPH) and Ferric Reducing Ability Power (FRAP). Compound <b>3</b> showed good antiradical potential (IC₅₀ 21.11 ± 0.53 μg/mL) and moderate antibacterial activity against all the tested bacteria with MIC of 200 μg/mL. For the FRAP method, hydro-ethanolic extract showed weak activity with value of 425 mg GAE/g, while Ethyl-<i>β-D</i>-fructofuranoside (<b>3</b>) exhibited a very good reducing power (40 mg GAE/g). Ethyl-<i>β-D</i>-fructofuranoside (<b>3</b>) could, therefore, be responsible for the antiradical activity of the hydro-ethanolic crude extract.