Antibacterial and Antioxidant Compounds from Root Extracts of Gloriosa superba Linn: A Combined Experimental and Computational Study

Abstract

Throughout history, medicinal plants have globally served as remedies for various ailments, and diseases. The roots of Gloriosa superba are traditionally used to treat antitumor, antimicrobial, and anti-inflammatory diseases. In this study, the roots of G. superba (320 g) were 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 combined chloroform and methanol extracts gave 4-methoxy caffeic acid heptyl ester (1), desmosterol (2), 3-hydroxymethyl phenol (3), 3-Hydroxy-5-methoxy-benzoic acid (4), sucrose (5) and rutinose (6). In vitro antibacterial study revealed promising zone of inhibition value by chloroform extract against Klebsiella pneumoniae (13±0.00 mm) compared to gentamicin (15.86±4.67 mm). Desmosterol (2), 3-hydroxymethyl phenol (3), and 3-Hydroxy-5-methoxy-benzoic acid (4) displayed promising zone of inhibition against K. pneumonia (12.33±0.58, 11.33±1.53 and 11.33±1.15 mm, respectively) at 1000 μg/mL compared to gentamycin (15.86±4.67 mm at 100 μg/mL). Promising inhibition zone values were also displayed by desmosterol (2) and 3-Hydroxy-5-methoxy-benzoic acid (4) against Pseudomonas aeruginosa (14±1.00 and 14±1.73 mm, respectively) compared to gentamycin (25±2.52 mm).Chloroform extract displayed 95.14% DPPH radical scavenging value compared to ascorbic acid (96.11%) at 200 μg/mL. Compounds 2 and 4 displayed binding affinities of -7.8 and -6.5 Kcal/mol, respectively, against PqsA protein of P. aeruginosa, compared to amoxicillin (-7.3 kcal/mol). Therefore, the in vitro antibacterial and radical scavenging activity results suggest the potential uses of the root extracts of G. superba as promising antibacterial agents and free radical scavengers.