The isolation, characterization and activity testing of two previously undescribed flavonoid glycosides and other constituents from the stem bark of Olax latifolia (Olacaceae)

Modern chromatographic techniques were used to isolate and characterize two previously undescribed epimeric flavonoids, Latifolioside A (1a) and Latifolioside B (1b), from the acetone fraction of the stem bark crude extract of Olax latifolia (Olacaceae) . These two flavonoids were found together with two dihydromyricetin glycosides, (2R,3S) 4′- O -methyl dihydromyricetin-3- O -α-ʟ-rhamnopyranoside (2a) and (2R,3R) 4′- O -methyl dihydromyricetin-3- O -α-ʟ-rhamnopyranoside (2b), which were previously described as an inseparable racemic mixture. Furthermore, four known compounds (3-6) also were isolated. The crude extract, fractions as well as the isolated compounds were assayed for their antibacterial and antioxidant activities. The crude extract and the acetone fraction showed significant antibacterial activity against Staphylococcus aureus isolate strain O74 with the minimum inhibitory concentration (MIC) in the range of 34.37-81.25 μg/mL. Compound 2b demonstrated the highest level of antibacterial activity against the six strains tested, with MIC values between 0.156 and 20 μg/mL. The antioxidant activity of the compounds was low, highlighting the importance of free hydroxyl groups. The cytotoxicity of the crude extract and acetone fraction was evaluated on one cell line of the African green monkey normal kidney Vero cells (ATCC CRL 1586). Their cytotoxic concentration (CC 50 ) values were greater than 500 μg/mL demonstrating that both extracts were non cytotoxic.