Antioxidant, xanthine oxidase inhibitory and antibacterial activities of selected galactogogue Thai medicinal plant water and ethyl acetate extracts

Water and ethyl acetate extracts of sixteen galactogogue Thai medicinal plants collected in Northeastern Thailand were evaluated for the antioxidant activity in terms of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging property and total phenolic content (TPC), xanthine oxidase inhibitory and antibacterial activities. Among the extracts, both of the water and ethyl acetate extracts from the stem bark of Caesalpinia sappan (CS) and Ochna integerrima (OI) exhibited potent DPPH radical scavenging capacity (IC50 9.47 ± 0.59 µ 13.25 ± 0.52 µg/mL) as compared to ascorbic acid (IC50 5.39 ± 0.32 µg/mL) and high TPC (632.89 ± 10.18 - 985.34 ± 0.76 mg gallic acid equivalent (GAE)/g of extract). The strongest xanthine oxidase inhibitory property was detected in the ethyl acetate extract from the root of Clausena harmandiana (CH) followed by CS and OI extracts showing %inhibition of 99.22 ± 0.22, 78.00 ± 0.79 and 68.67 ± 1.14, respectively, at the tested concentration of 50 μg/mL and referenced to allopurinol. The water extracts of CS and OI also possessed good antibacterial activity against eight tested pathogenic bacteria especially Gram-positive, S. aureus (MSSA) DMST 2933, S. aureus (MRSA) DMST 20651 and Bacillus cereus ATCC 11778, with the MIC and MBC values ranging from 0.39 - 1.56 mg/mL. The antibacterial property of OI extract and xanthine oxidase inhibitory activity of CH and OI extracts were first reported.