Phytochemical Investigation, Antioxidant and Antimycobacterial Activities of Schkuhria pinnata (Lam) Thell Extracts Against Mycobacterium smegmatis

Abstract

The focus of this study was to evaluate the antioxidants and antimycobacterial activities of extracts of Schkuhria pinnata. Serial exhaustive extraction procedure was employed using solvents of varying polarity to obtain the desired extracts. Thin layer chromatography and standard chemical tests were used to analyze phytochemicals constituents. Free radical scavenging 2,2-diphenyl-1-picrylhydrazyl (DPPH) methods were used to detect the presence of antioxidant compounds. Antimycobacterial activity was evaluated using microdilution and bioautography assays. A variety of secondary metabolites such as flavonoids, tannins, and alkaloids were detected in the extract. Ethyl acetate and acetone extracts had high antioxidant activity on chromatograms eluted in ethyl acetate/methanol/water while methanol extract at various concentrations had the best scavenging activity. The minimum inhibitory concentration (MIC) values ranged from 0.02 to 2.50 mg/mL. Total phenol content was 55.33 ± 3.51 mg of gallic acid equivalent (GAE)/g and higher when compared with flavonoids (4.00 ± 0.35 mg of quercetin equivalent [QE]/mg) and tannin content (28.00 ± 1.73 mg of GAE/g). The most effective antimycobacterial activity against Mycobacterium smegmatis was observed with the lowest inhibitory concentrations of acetone (0.27 mg/mL), dichloromethane (0.32 mg/mL), and ethyl acetate (0.32 mg/mL) in that order. In massive extraction, hexane and dichloromethane had the greatest inhibitory bands on benzene/ethanol/ammonium hydroxide bioautograms. Antimmycobacterial activity gives promising potential leads of S pinnata extracts to be used in the development of antimycobacterial drugs. The presence of antioxidant and antimycobacterial compounds requires further isolation and purification.