Antimicrobial and antioxidant activities of crude extracts of two Nigerian chewing sticks

Abstract

In vitro determinations of the antimicrobial and antioxidant activities of ethanol and aqueous extracts of Disthemonanthus benthamianus Baill. (Caesalpiniaceae) and Zanthoxylum zanthoxyloides Lam. (Rutaceae), which are used as chewing sticks in Nigeria, were investigated. The extracts were screened against eight strains of Escherichia coli, Enterococcus faecalis, Staphylococcus aureus, one methicillin-resistant strain of Staphylococcus epidermidis, twelve strains of Pseudomonas aeruginosa, five strains of Candida albicans and four strains of Bacillus cereus. The in vitro antimicrobial assay was performed by using a Mast Multipoint Inoculator based on the principles of an agar dilution technique. The aqueous extracts had no inhibitory effects on any of the tested microorganisms. The ethanol D. benthamianus extract inhibited P. aeruginosa, E. faecalis, and B. cereus with MIC ≤ 2.64 mg mL−1 and S. aureus and S. epidermidis with MIC ≤ 0.44 mg mL−1. Z. zanthoxyloides ethanol extract was less effective but noteworthy was the MIC ≤ 2.52 mg mL−1 against C. albicans and 0.28 mg mL−1 against some S. aureus strains. D. benthamianus ethanol extract had the best antioxidant activity and Z. zanthoxyloides ethanol extract second best. IC50 for DPPH free radical scavenging of these extracts were 87.76 and 128.28 μg mL−1/mL, respectively; ascorbic acid equivalents were 2.4 and 9.5 mg mg−1 and total antioxidant capacities using the FRAP assay were 4068.06 mM Fe++ mg−1 and 624.86 mM Fe++ mg−1, respectively. The ethanol extracts of D. benthamianus and Z. zanthoxyloides showed significant antimicrobial and antioxidant activities which could be beneficial in oral hygiene.