Proximate Composition, Acute Toxicity and Antimicrobial Activity of Methanol Extract of Picralima nitida Stem Bark

Abstract

The existence of essential bioactive compounds in the Picralima nitida stem bark has demonstrated useful advantages in terms of antioxidant,  antibacterial, and antifungal activities. In this work, concentrated methanol extract of the Picralima nitida stem bark was investigated for its proximate  composition, phytochemical constituents, acute toxicity and antimicrobial activity. The results revealed the presence of saponins, glycosides, tannins,  alkaloids, eugenols, flavonoids, proteins, reducing sugars and terpenoids. From the proximate analysis of P. nitida stem bark, the moisture content, ash  value, acid insoluble ash, water soluble ash, water extractive value and alcohol soluble extractive values were found to be 4.00%, 7.00 %, 6.50 %, 4.00 %,  3.20 %, and 0.60 % respectively. Investigation of the acute toxicity effect revealed that the lethal dose (LD₅₀) of the extract was ≥ 5000 mg/kg body weight  which was considered practically non toxic conforming to the toxicity standards. The outcome of the antimicrobial study revealed that the  methanol extract of P. nitida stem bark has higher inhibitory effect on the bacterial isolates (S. aureus and E. coli) with improved activity against E. coli at  higher concentrations. But the extract was inactive to the fungi isolates (A. flavus and C. Albicans) even at a higher dosage (100mg/ml). The minimum  inhibitory concentration revealed that the extract was capable of inhibiting the growth of both S. aureus and E. coli at 100 mg/ml, and the minimum  bactericidal concentration of the extract against the tested isolates was 150mg/ml and 125 mg/ml for S. aureus and E. coli respectively.