Evaluation of Free Radical Scavenging and Antibacterial Activity of Acalypha wilkesiana and Terminalia catappa Methanolic Leaf Extracts

Abstract

Aim: This study evaluates the antioxidant and antibacterial activity of Acalypha wilkesiana and Terminalia catappa methanolic leaf extracts. Place and Duration of Study: The study was carried out in the Biochemistry and Microbiology Laboratory, Department of Science Laboratory Technology, School of Pure and Applied Science, Lagos State Polytechnic, Ikorodu, Lagos- Nigeria for the period of three months between August and October 2015. Methodology: Lycophene and β-carotene were assessed using the method of Nagata and Yamashita while total phenolic and total flavonoid content were assessed by the Folin-Ciocalteau assay and aluminium chloride colorimetric assay respectively. The antioxidant activity was evaluated using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and antioxidant compounds profiled on TLC. Antimicrobial activity was assessed by the agar well diffusion technique and mode of action was evaluated by studying the leakage of UV260 and UV280 absorbing materials spectrophotometrically. Results: The Acalypha wilkesiana and Terminalia catappa methanolic leaf extracts evaluated in this study possessed significant amount of antioxidant compounds lycophene, β-carotene, total phenol and flavonoids. The extracts exhibited antioxidant activity by scavenging DPPH radicals in a dose dependent pattern with IC50 of 53.50, 51.21, 41.83 and 25.61 μg/mL for Acalypha wilkesiana, Terminalia catappa, vitamin C and Gallic acid respectively. Also, the plants’ extracts exhibited antimicrobial activity against test organisms and disrupted microbial membrane evident in the increase in absorbance values of UV260 and UV280 absorbing materials with time. Compounds like galangin, morin, chyrinsin, 3-hydroxyflavone, 6-hydroxyflavone were identified in the two extracts. Conclusion: Acalypha wilkesiana and Terminalia catappa methanolic leaf extracts are potential sources of drugs with antioxidant and antimicrobial activity.