Flavonoids, phenols, antioxidant, and antimicrobial activities in various extracts from Tossa jute leave (Corchorus olitorus L.)

Tossa jute (Corchorus olitorius L.) is one of the Tunisian plants, traditionally used as a medicinal herb. The purpose of this study was to analyze the antioxidant and antibacterial activities, and phenolic profiles of C. olitorius L extracts. The effects of various solvents (ethanol, 50/50 ethanol/water and water) on the phenolic profile of C. olitorius leaf and their corresponding biological activity were studied. The results showed that ethanol appeared the most effective solvent for polyphenols and flavonoids’ extraction, as confirmed by the LC–MS analysis. In fact, the ethanolic extract (EE) showed the highest content of phenolic acid and flavonoid compounds. The major identified compounds were quinic acid, 4-O-caffeoylquinic acid, 3,4-di-O-caffeoyquinic acid, protocatchuic acid, caffeic acid, quercetin, and cirsiliol. Also, other phenolic compounds such as p-coumaric acid, trans-Ferulic acid, rosmarinic acid, naringenin, naringin, apegenin-7-O-glucoside, cirsilineol, and cirsiliol were detected in this extract. Results indicated that EE extraction exhibited higher antioxidant activities than the ethanol/aqueous extract (EAE) and aqueous extract (AE), in dose-dependent manner (p < 0.05). At EE concentration of 500 μg/mL, the antioxidant activities were about 91.65 ± 0.15% against 1,1-diphenyl-2-picryl hydrazyl radical (DPPH) radicals, 70.24 ± 0.19% against lipid peroxidation and 86.19 ± 0.85% against β-carotene bleaching. The EE ferric reducing power (FRAP) reached a high absorbance of 2.0 ± 0.14 and displayed a protection role of DNA, at the same concentration. Antimicrobial test showed also that increasing concentrations of phenolic extracts increased the clear diameter zone around the tested bacteria and that EE exhibited the best antibacterial activity against Staphylocaccus aureus, Micrococcus luteus, Bacillus cereus, Escherichia coli, Klebsiella pneumoniae, Salmonella enterica, Salmonella typhi, and Enterobacter sp. The overall data suggested that EE might be used as a natural antioxidant and antimicrobial for functional foods.