Chemical Composition, Antimicrobial and Free Radical Scavenging Activities of Extracts from the Leaves of Desmodium adscendens

Abstract

Background: Desmodium adscendens is a potential source of different phytochemicals that may be responsible for its numerous pharmacological properties. The aim of this study is to analyse the constituents of leaf extracts of Desmodium adscendens using Gas Chromatography-Mass Spectrometry, and evaluate the antimicrobial and free radical scavenging activities of the plant extracts. Methods: The dried and grind leaves of Desmodium adscendens were successively extracted with hexane, ethyl acetate and methanol. The extracts were concentrated using rotary evaporator, and screened for the presence of phytochemicals. The hexane, ethyl acetate and methanol extracts of the plant were evaluated for antimicrobial and antioxidant activities using agar diffusion and DPPH assays respectively, while the GC-MS analysis of the plant extracts were done. Results: Preliminary phytochemical investigation of crude n-hexane, ethyl acetate and methanol extracts from the leaves of Desmodium adscendens revealed the presence of steroids, terpenoids, flavonoids, saponins, anthraquinones and glycosides. All the crude extracts gave a clear zone of inhibition against the growth of the test bacteria (Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Pseudomona aeruginosa, Salmonella typhi, Klebsiellae pneumonae) at moderate to high concentrations, as well as test fungi (Candida albicans, Aspergillus niger, penicillium notatum and Rhizopus stolonifer) at high concentrations. N-hexane and methanol extracts of the plant leaves possessed significant antioxidant activity by exhibiting DPPH free radical scavenging property with IC50 50.66 μg/mL and 5.44 μg/mL respectively, using DPPH antioxidant assay. The compounds present in the extracts were characterized using Gas chromatography-Mass spectroscopy (GC-MS). GC-MS of Nhexane extract showed a total number of five chemical constituents while Ethyl acetate and methanol extracts revealed six and eight compounds respectively. Conclusion: The antimicrobial and antioxidant properties of Desmodium adscendens may be attributed to the presence of the most abundant bioactive compounds present in synergy with all other compounds present in relatively small amounts. This accounted for the use of the plant in ethnomedicine for the treatment of toothache, stomach disorder and other pathogenic infections. This plant may be a potential source of novel antimicrobial drugs. Keywords: Desmodium adscendens, phytochemicals, antimicrobial, antioxidant, GC-MS analysis.