60–0.79) to very strong (r > 0.8) significant positive correlations with all the antioxidant assays except the NO radical-scavenging assay. Polyphenols and ascorbic acid
showed only weak (r = 0.2–0.39) to moderate (r = 0.4–0.59) positive correlation with the NO radical-scavenging assay. This implies the ability of the polyphenols and ascorbic Lapatinib datasheet acid in B. racemosa to act as reducing agents and hydrogen donors in neutralising free radicals. Previous studies have reported positive correlation between FRAP and TEAC values and the corresponding polyphenol and ascorbic acid contents ( Djeridane et al., 2006, Liu et al., 2008 and Razab and Aziz, 2010). Flavonoids, on the other hand only showed moderate positive correlation with the NO radical-scavenging assay and no correlation with the remaining antioxidant assays. A recent study reported no correlation between polyphenol content and NO -scavenging activities ( Royer et al., 2011). Carotenoid content, on the other hand, demonstrated negative relationships with all the antioxidant assays, implying minimal contribution of carotenoids towards the observed antioxidant activities. Müller, Fröhlich, and Böhm (2011)
did not detect DPPH radical-scavenging activities with carotenoids, in agreement with our study. Correlation studies between carotenoids and antioxidant activities are scarce learn more and those that are available have shown conflicting Adenosine triphosphate results with some studies showing positive correlations (Egea, Sánchez-Bel, Romojaro, & Pretel, 2010) and others showing negative correlation (Müller et al., 2011). The types and quantities of carotenoids present in plants could, to a certain extent, influence the resulting antioxidant activities, due to different reaction kinetics (Van Den Berg, Haenen, Van Den Berg, & Bast, 1999). The plant samples were initially subjected to acid hydrolysis to release sugars conjugated to the
polyphenols, hence allowing easy identification of the aglycone or free polyphenols. The development of UHPLC has allowed for more sensitive and rapid analyses of polyphenols in plant samples while still maintaining resolution and stability of the compounds. Fig. 4a and b shows the chromatograms of the leaf and stem extracts of B. racemosa after acid hydrolysis. The chromatogram for the leaf extract of B. racemosa indicated the presence of gallic acid, protocatechuic acid, ellagic acid, quercetin and kaempferol ( Fig. 4a) while only gallic acid, protocatechuic acid and ellagic acid were detected in the stem extract of B. racemosa ( Fig. 4b). The polyphenols in the plant extracts were confirmed by comparing the retention times of the samples with the standards, as well as comparing the absorption spectra between the samples and the standards obtained on the diode array detector. Quercetin-3-O-rutinoside, which is a conjugated form of quercetin, has been detected in the seeds of B. racemosa ( Samanta et al.