ISOLATION AND CHARACTERIZATION OF CHEMICAL CONSTITUENTS FROM G. DON-HOLL. STEM-BARK EXTRACTS AND THEIR ANTIOXIDANT AND ANTIBACTERIAL PROPERTIES.

BACKGROUND

The plant, is indigenous to Nigeria and its stem-bark has wide application in traditional medicine for the treatment of infections and oxidative stress related diseases. The aim of the study was to isolate the chemical constituents responsible for the antioxidant and antibacterial activity from the stem-bark of the plant in order to justify some of its ethnomedicinal uses.

MATERIALS AND METHODS

Crude extract of stem-bark of obtained from 80% ethanol was successively partitioned with ethyl acetate (EtOAc) and -butanol. The solvent fractions and isolated compounds were tested for antioxidant property using 2-2-diphenyl-1-picrylhydrazyl. Antibacterial activities were also assessed by means of agar-diffusion and broth micro dilution methods. EtOAc fraction was repeatedly fractionated on column chromatography to afford four compounds and their chemical structures were established using NMR (1D and 2D) and MS.

RESULTS

Chromatographic fractionation of EtOAc fraction with the highest antioxidant and antimicrobial activities afforded stigmasterol (),: epicatechin (),: epigallocatechin (): and procyanidin B5 ().: Procyanidin B5 isolated for the first time from genus demonstrated the highest antioxidant activity with IC50 values of 8.8 μM and 11.20 μM in DPPH and nitric oxide assays respectively and equally demonstrated the highest inhibitory activity against (MIC 156.25 μg/mL), (MIC 156.25 μg/mL), (MIC 625 μg/mL) and (MIC 156.25 μg/mL).

CONCLUSION

The antibacterial and antioxidant activities of epicatechin, epigallocatechin and procyanidin B5 isolated from stem-bark validate the folkloric uses.