CAFFEIC ACID: A PHARMACOLOGICALLY ACTIVE PHENOLIC ACID FOUND IN PROPOLIS OBTAINED FROM NIGERIA

Abstract

Studies reveal that chemical composition of propolis is influenced by vegetation surrounding the beehive. This study set out to isolate and characterize chemical compounds from propolis using hexane and ethyl acetate solvents, and to assess its antimicrobial activity in varying polarities; hexane, acetone, ethyl acetate and methanol. Isolation of chemical compounds was carried out by subjecting extract to column chromatography by gradient elution using two solvent mixtures - hexane: ethyl acetate and ethyl acetate: methanol. Isolated compounds were identified using 1H and 13C-NMR spectroscopy and Mass spectrometry with further verification of data on the compound by comparison with literature reports. Microbial assay was carried out using standard procedures. Isolated compound was identified as caffeic acid, a known phenolic acid useful for anti-oxidation, anti-inflammation and anti-carcinogenesis. Percentage (%) yield of propolis in the four solvents was high in hexane (85.60%) and acetone (64.95%). Methanol extract of propolis was active against Escherichia coli and Salmonella typhi at concentrations of 100 mg/mL, 50 mg/mL and 25 mg/mL. Ethyl acetate extract showed activity on Escherichia coli at 100 mg/mL, 50 mg/mL and 25 mg/mL concentrations while Salmonella typhi was inhibited at 100 mg/mL, 50 mg/mL, 25 mg/mL, 12.5 mg/mL and 6.25 mg/mL concentrations of propolis in ethyl acetate solvent. This suggests that, the more polar the solvent used for extraction of propolis obtained from Gboko, the stronger the antimicrobial activity.