Evaluation of Phytochemical, Antimicrobial and Antioxidant Capacities of Pennisetum purpureum (Schumach) Extracts

Abstract

Medicinal plants are valuable natural sources for the development of potentially safe drugs. The biological activities associated with these plants are due to the presence of certain phytochemicals that act individually or synergistically. Thus, this study examined the phytochemical components, antioxidant and antimicrobial activities of n-hexane, ethylacetate and methanolic extracts of Pennisetum purpureum (Schumach). Qualitative and quantitative phytochemical assays of P. purpureum showed the presence of alkaloids (0.004%), saponins (0.002%), flavonoids (0.021%), steroids, terpenoids and glycosides (0.008%). Methanol, n-hexane and ethylacetate extracts of P. purpureum were examined for antimicrobial activity using the disc diffusion method. Six microbial strains were exposed to six different concentrations of each extracts; 200 mg/ml, 100 mg/ml, 50 mg/ml, 25 mg/ml, 12.5 mg/ml and 6.25 mg/ml. The three extracts demonstrated varied concentration-dependent antimicrobial activities against the test organisms. The methanolic extract showed antibacterial activity against E. coli, S. aureus, B. cereus and antifungal activity against T. mentagrophyte and A. niger. Among all extracts, the methanolic extract of P. purpureum exhibited relatively strong antifungal activity against A. niger (10.3±0.12 mm) when compared to the standard antifungal agent, fluconazole (13.9±0.12 mm). Furthermore, antioxidant activities were spectrophotometrically studied using vitamin C as standard; methanol and ethylacetate extracts of P. purpureum showed pronounced scavenging activity on 2,2-diphenyl-1-picrylhydrazyl (DPPH); and had a potent reductive ability on ferric ion and phosphomolybdate. However, only the non-polar extract of P. purpureum showed a non-significant correlation and significant differences when compared to vitamin C. Antioxidant activities of the plant extracts were observed in the order of methanol >ethylacetate> n-hexane extracts. The results showed that P. purpureum contains phytochemicals that significantly contributed to the observed antimicrobial and antioxidant abilities of the plant and could be used as a potential source for the development of novel therapeutic drugs.