The leaf water extracts from Kedah and Kelantan have similar ascorbic acid contents which was roughly threefold more than the water extracts of the stems. The ascorbic acid content in the leaf water extracts (260 and 277 mg/100 g of fresh tissue) was higher than that in several commercial vegetables (0.95–218 mg ascorbic acid/100 g of fresh tissue) ( Isabelle et al., 2010). Thus, the shoots of B. racemosa are excellent sources of ascorbic acid. Generally, flavonoids could be detected in all the extracts, although the ethyl acetate extracts of the leaves and stems from both locations had the highest flavonoid
contents, implying the selleck presence of (mainly) semi-polar flavonoids. The flavonoid contents in the ethyl acetate extracts in this study (19.9–21.8 mg RE/g of freeze-dried tissue) were lower than that
GSK1210151A concentration in a previously reported ethanolic extract of B. racemosa leaves (38.6 mg RE/g of freeze-dried tissue) ( Nurul Mariam et al., 2008). This could be due to differences in the condition and location where the plant is grown, as well as the extraction solvent used. Nevertheless, the flavonoid content in this study was higher than those of several Chinese medicinal plants (0.50–158 mg RE/g of freeze-dried tissue) ( Liu et al., 2008), as well as Algerian medicinal plants (1.62–13.1 mg RE/g air-dried tissue) ( Djeridane et al., 2006). Carotenoids were detected mainly in the ethyl acetate extracts, which was in accordance with the less polar
characteristics of these compounds. Among the ethyl acetate extracts, Kelantan leaf had the highest carotenoid content, followed in descending order by Kedah leaf > Kelantan stem > Kedah stem. Green leafy vegetables are rich sources of carotenoids, such as lutein, zeaxanthin, α-carotene and β-carotene, which are either semi-polar or apolar (Khoo, Prasad, Kong, Morin Hydrate Jiang, & Ismail, 2011). Xanthophylls are semi-polar carotenoids which are commonly found at high levels in vegetables, and hence will be mainly found in the ethyl acetate extracts (Khoo et al., 2011). Several in vitro antioxidant assays were selected in this study, based on the ability of antioxidants to act as reducing agents (FRAP) and as radical-scavengers (DPPH, ABTS, O2- and NO radical-scavenging assays). Antioxidants act via several mechanisms, including as hydrogen/electron donors, metal ions chelators and through increasing the activities of the antioxidant enzymes, catalase, glutathione peroxidase and superoxide dismutase. Hence, the use of antioxidant assays that measure the different mechanisms of the antioxidant effect would provide a better insight into the true antioxidant potential of the extracts. Table 2 shows the ferric reducing capacities of the plant extracts. Generally, the water extracts showed high ferric reducing activities and the hexane extracts the least.