racemosa leaf extract inhibited 46% of TBARS as opposed to 19% for its stem extract. Gallic acid however did not show much difference in inhibiting lipid peroxidation at the range of concentrations used in this study. Although the TBARS values

seemed to show an increasing trend at lower concentrations of gallic acid (25–100 μg/ml) and lower TBARS at higher gallic acid concentrations (250–1000 μg/ml), this was not statistically significant. We had initially reported the presence of gallic acid, protocatechuic acid, ellagic acid, quercetin and kaempferol in the shoots of IWR-1 research buy B. racemosa ( Kong et al., 2012). In this study, we reported the additional presence of rutin and further quantified the amounts of the polyphenols and performed further validation studies to confirm the identification

of the polyphenols. Our previous study also reported significant levels of ascorbic acid in the leaf water extracts, hence together with polyphenols, they 3 Methyladenine could be the major compounds contributing towards preventing serum oxidation. Results are in agreement with previous studies that described the ability of hydrophilic antioxidants including curcumin and Trolox to inhibit serum lipid peroxidation, in fact better than the lipophilic antioxidant α-tocopherol ( Jalali-Khanabadi et al., 2010 and Schnitzer et al., 1998). Additionally, mutual synergistic effects of different polyphenolic compounds and other non-polyphenolic compounds can also enhance the antioxidative effect (Dai & Mumper, 2010). Fig. 3(b) shows the results for the LDL oxidation assay. There was a concentration-dependent decrease in TBARS in LDL treated

with B. racemosa leaf and stem extracts, indicating the extracts could significantly inhibit copper-mediated LDL oxidation. Lower concentrations of B. racemosa leaf extract (IC50 = 73.0 μg/ml) were adequate to inhibit 50% of TBARS formation compared to its stem extract (IC50 = 226 μg/ml), implying the former to be a more effective inhibitor of LDL oxidation. Polyphenols such as ellagic acid, gallic acid and protocatechuic acid, which were present in the leaves, have been reported to be able to inhibit lipid peroxidation, while specifically, ellagic acid has been shown to inhibit LDL oxidation ( Anderson et al., 2001 and Hseu et al., 2008). The positive control, gallic acid, showed almost constant effect at all concentrations tested with TBARS similar Protein tyrosine phosphatase to that of the negative control (without Cu2+). This observation could be due to the high reactivity of gallic acid as a pure compound whereby low concentrations were already sufficient to inhibit reactivity of the copper (Cu2+) ions. In addition to MDA, LHP, the intermediate product of lipid peroxidation, were also measured. We hypothesised that the plant extracts could have also interfered with the propagation of LHP and hence the chain reaction of lipid peroxidation. Interestingly, a similar trend to TBARS formation was found (Fig. 3(c)). Analyses showed that B.