Investigation of antimicrobial and antioxidant properties of extracts of the stem bark of Drypetes floribunda (Euphorbiaceae)

Abstract

Background: The use of the stem bark of Drypetes floribunda in the treatment of microbial infections is common amongst the people of Kwahu Asakraka in the Eastern Region of Ghana. However not much studies have been done to establish the scientific basis of this and to isolate the bioactive principles from the stem bark. Objectives: To assess the antimicrobial and antioxidant properties of the stem bark and to isolate some bioactive principles and investigate their antimicrobial activity.

Methods: An antioxidant assay was conducted on the crude flavonoid extract and crude phenolic acid extract using ascorbic acid as control. A crude methanolic extract of the stem bark was obtained, its total phenolic content was determined and was further subjected to column chromatography. The fractions obtained were structurally elucidated using the various spectroscopic techniques and the High Throughput Spot Culture Growth Inhibition antimicrobial bioassay was conducted on it using six microbes (Pseudomonas aeroginosa, Salmonella typhi, Escherichia coli, Streptococcus pyogenes, Staphylococcus aureus, and Candida albicans).

Results: The crude flavonoid extract was found to have a higher antioxidant activity with an IC₅₀ of 27.7843 µg/mL compared to the control (51.3925 µg/mL) and the crude phenolic acid extract (283.8573 µg/mL). The total phenolic content (TPC) of the crude methanolic extract varied from 34.56 ± 1.5997 mg/g to 68.79 ± 0.9568 mg/g. The crude with an MIC range of 125-250 µg/mL and the fractions (F₁₀ and F₁₄) with MIC ranges of 125-500 µg/mL and 31.25-500 µg/mL respectively were found to be active against the microbes except for Pseudomonas aeroginosa, Streptococcus pyogenes.

Conclusions: The stem bark of Drypetes floribunda possesses antioxidant and antimicrobial activity.