Abstract:
Abstract
Rice bran is one of the most abundant co-products produced in the rice milling industry
and research conducted in last two decades has shown that it contains a unique complex of
naturally occurring antioxidant compounds. Rice is the staple food in Sri Lanka and there
are over 300 different traditional Sri Lankan rice varieties (RV). However, no antioxidant
activity evaluation study has been conducted on these indigenous varieties. Present study
evaluates the antioxidant properties of some Sri Lankan traditional red RV.
Freeze-dried 70% ethanolic extracts of brans of 4 traditional red RV (Oryza sativa)
namely Masuran (M), Dik Wee (DW), Goda Heeneti (GH) and Sudu Heeneti (SH) were
used in this study. Antioxidant properties of bran extracts of selected RV were evaluated
using total polyphenolic content (TPC) (n=6), 1,1-diphenyl-2-picryl-hydrazyl (DPPH)
radical scavenging (n=4), 2-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid [ABTS]
radical scavenging (n=4) and ferric reducing antioxidant power (FRAP) (n=6) in vitro
antioxidant assays.
Significant differences were observed among bran extracts of selected RV for investigated
antioxidant properties (P<0.05). Mean TPC, DPPH, ABTS and FRAP antioxidant
properties were in the range of 11.74 - 29.75 mg gallic acid equivalents/g, 5.14 ± 0.17 -
6.77 ± 0.06 mmol Trolox equivalents (TE)/100g, 8.67 ± 0.14 - 14.25 ± 0.46 mmol
TE/100g, 8.30 ± 0.15 - 11.02 ± 0.25 mmol FeSO4/100 g rice bran respectively. The order
of mean TPC was SH > M > GH > DW. Bran extracts of all the RV exhibited dose
dependent radical scavenging activity against both DPPH· and ABTS radicals. Bran
extracts of GH demonstrated maximum radical scavenging activity for both radicals.
However, the order of scavenging was observed to be different among bran extracts of
different RV for DPPH·
and ABTS radicals. The order of scavenging for DPPH·
was GH
> SH > DW > M and for ABTS it was observed as GH > SH > M > DW. Highest mean
290
FRAP was observed for bran extract of GH variety while lowest for bran extract for SH
variety. The antioxidant power of the bran extracts for FRAP was in the order of GH > M
> DW > SH
