Molecular Docking, Antibacterial and Antioxidant Activities of Compounds Isolated from Ethiopian Plants

This study evaluated the antibacterial and antioxidant activities of the constituents of L. tomentosa and S. longipedunculata. The in-silico molecular docking analysis of the isolated compounds was also reported herein for the first time. The GC-MS analysis of the essential oil of L. tomentosa led to the identification of eleven components with 2,5-dimethoxy-p-cymene identified as the principal constituent (59.39%). Lauric acid (1), β-stigmasterol (2), chrysophanol (3), and emodin (4) were isolated from L. tomentosa using silica gel column chromatography. Likewise, 9H-xanthene-3,5-diol (5), 1,7-dihydroxy-4-methoxyxanthone (6), and oleic acid (7) were isolated from S. longipedunculata. The structures of the isolated compounds were elucidated using UV-Vis, IR, and NMR spectroscopic methods. Compounds 3 and 4 are new to the genus Laggera, while 5 and 6 are new to the species S. longipedunculata. Compounds 3-6 inhibited DPPH radical by 86, 92, 88, and 90%, respectively. Compounds 5 and 6 inhibited 79.2 and 81.9% peroxide formation, respectively. The antioxidant activities displayed by compounds 4-6 suggest their use as a natural antioxidant. Compounds 4 and 6 inhibited the growth of bacteria by 18.00±0.10 and 16.06±0.22 mm, respectively. Compounds 3, 4, and 6 showed binding affinities of −10.4, −10.4, and −9.9 kcal/mol against Staphylococcus aureus DNA Gyrase, respectively, while 4 showed −10.4 kcal/mol against human topoisomerase IIβ. Therefore, the present study results showed that emodin and 1,7-dihydroxy-4-methoxyxanthone might be considered lead compounds for further development as antibacterial and anti-cancer agents. The findings also substantiate the traditional use of these plants against bacteria.