In the case of DPPH radical scavenging assay (Fig. 4A), samples
were collected from HPLC analysis from the same amount of
injected polar-soluble crude white and gold sesame seed extracts.
The collected F1 fractions (2 mg/ml) exhibited good DPPH scavenging
activity with values of 38.62% and 27.57% for white and gold
sesame seeds, respectively, whereas the oligosaccharide fraction
F2 (5 mg/ml) had very low activity with values of only 6.33% and
2.91% for white and gold sesame seeds, respectively. For ORAC
assay, different concentrations of F1 and F2 fractions were investigated
(Fig. 4B). F1 fraction exhibited high ORAC values at 50 and
100 lg/ml, corresponding to average values of 50,953 and
54,420 lmol TE/100 g for white and gold sesame seed extracts,
respectively. The ORAC values of the F2 fraction were measured
at 250 and 500 lg/ml, corresponding to 5347 and 6068 lmol TE/
100 g for white and gold sesame seed extracts, respectively.
Both DPPH radical scavenging and ORAC methods showed that
F1 exhibited around 10-fold higher antioxidant activity than the
oligosaccharide fraction F2. F1 from both seed types was
characterized by a dark brown color compared to F2, which had a
yellowish white color. Xu et al. (2005) isolated brown pigment
from the ethanolic extract of black sesame seeds that showed antioxidant
activity in vitro. Furthermore, melanoidin-like browning
compounds produced during roasting of sesame seeds are also
believed to be involved in the antioxidant activity of roasted sesame
seed oil (Kumazawa et al., 2003). Thus, the F1 fraction may
be related to such compounds. However, neither the structure
nor antioxidant mechanisms of such compounds have yet been
elucidated.