Abstract
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.