1H NMR profiling and antioxidant activity of Chloroform, Ethyl Acetate, and aqueous fractions of Bauhinia rufescens stem extract

Abstract

This study investigates the metabolite profile and antioxidant potential of aqueous, ethyl acetate, and chloroform fractions of Bauhinia rufescens stem extract.The stem bark was extracted using 85% methanol. ¹H Nuclear Magnetic Resonance (NMR) spectroscopy was employed to analyze the metabolites present in each fraction, and antioxidant activity was evaluated using the 2,2-Diphenyl-1-picrylhydrazyl (DPPH) assay. The results revealed significant differences in metabolite composition across the fractions, with the aqueous fraction exhibiting the highest antioxidant activity. At a concentration of 1000 µg/mL, the aqueous fraction (AQ) exhibited 94.74 ± 0.58% inhibition, while the ethyl acetate (AE) fraction showed 94.33 ± 0.37%, and the chloroform (AC) fraction exhibited 81.59 ± 0.97%. The antioxidant activity decreased as the concentration reduced, with the aqueous fraction still maintaining the highest activity across other concentrations. A total of 22 metabolites were tentatively identified, including flavonoids, phenolics, and alkaloids, which are known for their bioactive properties. These findings suggest that Bauhinia rufescens extracts, particularly the aqueous fraction, could serve as a potential source of natural antioxidants. Further studies are needed to isolate and characterize the bioactive compounds responsible for the observed effects.