Phytochemical Analysis, Antioxidant and Antimicrobial Activities of the Leaves of Combretum bauchiense Hutch & Dalziel (Combretaceae)

Aim: The phytochemicals, antioxidant and antimicrobial investigations of Combretum bauchiense leaves used in folkloric medicine to treat majorly infectious diseases were explored in the present study.

Study Design: Evaluation of antioxidant, antimicrobial and HPLC-DAD profiling of the extract and fractions of the leaves of Combretum bauchiense.

Place and Duration of Study: Department of Pharmaceutical Chemistry, Enugu State University of Science and Technology, Enugu, Nigeria between January 2021 and May 2023.

Methodology: The methanol extract (MECB), n-hexane fraction (HFCB), ethyl acetate fraction (EFCB) and n-butanol fraction of C. bauchiense (BFCB) were screened for phytoconstituents using HPLC-DAD. The antioxidant activity of the extract and fractions were assayed by DPPH free radical scavenging model while the antimicrobial activity of extract and fractions were carried out by agar well diffusion method.

Results: The following phytoconstituents: dukurolide, shanzinmethyl ester, piperchabamide, isovitexin, straitisporolide, kaempferol, apigenin, protocatechuic acid, aureonitol, luteolin, rutin and quercetin were identified from the extracts and fraction by dereplication based on their retention time and wavelength. The result of antioxidant assay indicated that MECB showed strong free radical scavenging activity with IC50 value of 3.22 µg/mL. Among the fractions, EFCB and BFCB have moderate free radical scavenging activity (IC50 value of 5.69 and 6.35 µg/mL respectively), compared to that of ascorbic acid (IC50 value of 0.21 µg/ mL). HFCB showed the least free radical scavenging activity (IC50 value of 10.78 µg/mL).

Conclusion: The extract and the fractions at the concentration of 6.25-100 mg/mL showed inhibition zone diameters, which ranged from 10-27 mm against all tested bacteria. The antioxidant and antimicrobial properties, exhibited by the extracts and fractions may be as a result of the presence of high concentrations of the phenolic compounds identified by HPLC-DAD analysis. The results further substantiated the folkloric uses of the plant in treating infections and some disease conditions associated with oxidative stress.