Phytochemical Investigation, Biological Evaluation, And In Silico Molecular Docking Studies Of Compounds Isolated From The Root Extracts Of Gloriosa Superba Linn.

Abstract

Since ancient times, medicinal plants have been used around the world to treat a wide range of ailments, diseases, and wounds. They are part of the socio-cultural legacy of different countries, evidenced by the ethnobotanical information showed in their pharmacopeias. The roots of G. superba are commonly used as an antitumor, antimicrobial, abortifacient, anthelmintic, and anti inflammatory agent. In this study the roots of G. superba (320 g) was successively extracted with n-hexane, chloroform, and methanol to afford 530 mg (0.17%), 2.89 g (0.90%), and 17.78 g (5.56%) yields, respectively. Silica gel column chromatographic separation of the chloroform and methanol extracts afforded one caffeic acid derivative (48), desmosterol (49), two phenolic derivatives (50, 51) and two disaccharides (52, 53). All compounds reported herein for the first time from the species. The structures of isolated compounds were characterized using NMR spectroscopic techniques (1H NMR, 13C NMR, and DEPT-135). The crude extracts and isolated compounds were evaluated for their in vitro antibacterial activities using the disc diffusion method against six bacterial strains. Promising inhibition zone values were observed by chloroform extract against K. pneumoniae (13±0.00 mm), S. typhimurium (13±1.00 mm), and S. aureus (12.33±0.58 mm) compared to gentamicin (15.86±4.67 mm, 28.86±2.34 mm, and 25.43±2.15 mm, respectively). Compounds 49 and 51 showed significant activities against P. aeruginosa with a mean inhibition zone of 14±1.00 mm and 14±1.73 mm, respectively, compared to gentamycin (25±2.52 mm). Compound 49 also displayed promising inhibition against S. typhimurium with a mean inhibition zone value of 15±0.00 mm. The results from DPPH activity demonstrated chloroform and methanol extracts inhibited the DPPH radical by 95.14 % and 72.98 % whereas compound 49 displayed 35.69 % inhibition. The drug-likeness analysis showed that compounds 48, 49, and 51 to satisfy Lipinski’s rule of five with zero violations. Compounds 48 and 49 showed binding affinities of -6.3 and -6.7 against E. coli and DNA gyrase B, respectively, while 49 showed -7.8 kcal/mol against PqsA, compared to amoxicillin (-6.1 kcal/mol and -7.3 kcal/mol, respectively). Therefore, the in vitro antibacterial and radical scavenging activity tests of the molecular docking analysis could suggest the potential use of the extracts of G. superba and compounds 48, 49 and 51 as promising antibacterial agents and the extracts as promising free radical scavengers.