In this study, two methods for preparation of the shoots of B. racemosa were tested, either freeze drying or air drying. The former method gave a higher content of polyphenolic compounds compared to the latter ( Table 2). Generally, there was an approximately 5–41% reduction (p < 0.05) in the free and bound polyphenols Docetaxel in the air dried samples, compared to the freeze dried samples. In the air drying method, the shoots were dried at room temperature to minimise degradation
of polyphenols. However, lower temperature was associated with prolonged drying time, whereas freeze drying provided a more rapid drying process ( López et al., 2010). Other studies have reported contrasting results. Korus (2011) reported lower amounts of phenolic compounds in air-dried kale leaves at 55 °C compared to freeze-dried samples. In contrast, Katsube, Tsurunaga, Sugiyama, Furuno, and Yamasaki (2009) showed no significant difference in the phenolic content of air-dried mulberry leaves (temperature below 60 °C) with freeze-dried leaves. Nonetheless, a previous kinetics study reported that extended drying time led to a noticeable deterioration of phenolic compounds ( López et al., 2010). Our study showed that freeze drying is a better method for preparation Bortezomib of polyphenols from the shoots of B. racemosa. Levels of gallic acid, protocatechuic
acid, ellagic acid, quercetin and kaempferol in B. racemosa leaves are comparable if not higher than several teas, raspberry, carob and vegetables such as lettuce, leek, onion, endive, celery and curry kale ( Hertog et al., 1992, Manach et al., 2004 and Sakakibara et al., 2003). Mirabegron Nevertheless, the efficiency of aglycones derivation and their deterioration are essential issues that need to be taken into consideration to obtain more accurate quantitative
data. Higher levels of TBARS indicated higher levels of lipid oxidation. At lower concentrations (25–50 μg/ml), the aqueous extract of B. racemosa leaf showed a concentration-dependent decrease in TBARS formation, although at higher concentrations, inhibition was not significantly different ( Fig. 3(a)). On the other hand, the aqueous extract of B. racemosa stem was less effective in preventing lipid peroxidation and did not show significant changes in TBARS formation over the concentration range used in this study. The higher ability of the leaf extract to prevent serum oxidation compared to the stems is likely due to its higher polyphenolic content ( Table 2). In addition to the four polyphenols that were found in both the leaves and the stems, the leaves also contained quercetin and kaempferol, which were not detected in the stems. Polyphenols, particularly the free forms, have the structural features required for radical scavenging and metal chelation, hence are good antioxidants and inhibitors of lipid peroxidation ( Fraga, Galleano, Verstraeten, & Oteiza, 2010).