Comparing the leaves and the stems, the former had almost double the ferric reducing Selleck BIBF-1120 activities of the latter. The presence of high concentrations of polyphenols and ascorbic acid in the water extracts may explain the high ferric reducing activities. The antioxidant properties of these two compounds are well documented (Katalinic et al., 2006). The hexane extracts contained
the lowest amounts of polyphenols, flavonoids and ascorbic acid and moderate amounts of carotenoids which explained the low antioxidant activities. Peschel et al. (2006) have reported hexane to give lower amounts of polyphenols than other solvents. The ABTS -scavenging capacities of the plant extracts were expressed as trolox equivalent antioxidant capacity (TEAC) and results are shown in Table 2. Similar to the ferric reducing activities, the water extracts had high TEAC values (>0.8 mmol TE/g of extract)
while the remaining extracts mostly had values less than 0.5 mmol TE/g of extract. This is likely contributed by the presence of polyphenols and ascorbic acid in the water extracts. It has been reported that plant Epigenetics inhibitor extracts rich in vitamin C and polyphenols also had high ABTS radical-scavenging capacities (Wang, Chang, Inbaraj, & Chen, 2010). The DPPH radical-scavenging activities of the plant extracts were expressed as EC50, i.e. the concentration required to inhibit 50% of the DPPH radicals (Table 2). The water extracts had low EC50 values, indicating potent radical-scavenging effects, as low concentrations were adequate to inhibit the DPPH radicals. Among the water extracts, Kedah leaf had the lowest EC50 (51.4 μg/ml), followed by Kelantan leaf (57.1 μg/ml), Kelantan stem (120 μg/ml) and Kedah stem (164 μg/ml). The hexane extracts were the least reactive and did not reach 50% inhibition of the DPPH radicals at the concentrations tested. Extracts of B. racemosa in this study had higher DPPH radical-scavenging activities than had cashew shoots (Anacardium occidentale)
(EC50: 72 μg/ml) ( Razali, Razab, Junit, & Aziz, 2008) or common herbs, including basil (EC50: 0.49 mg/ml) and parsley (EC50: 12.0 mg/ml) Molecular motor ( Hinneburg, Dorman, & Hiltunen, 2006). Fig. 1a–d shows the DPPH -scavenging activities of the extracts of B. racemosa, as well as the antioxidant standards, BHT, gallic acid, ascorbic acid and rutin. Overall, the antioxidant activities of the plant extracts showed a concentration-dependent relationship. Activities of the standards, gallic acid, ascorbic acid and rutin, were rapid, reaching maximum inhibition at concentrations below 100 μg/ml, whereas the activity of BHT was slightly lower. The leaf water extracts from Kedah and Kelantan had higher DPPH radical-scavenging activities than had BHT and activities almost similar to gallic acid, rutin and ascorbic acid, implying their potencies.