Abstract:

The extraction process for pigments from the grains of “Laoheigu” rice, a red-grained rice variety grown in
Pantiange town, Diqing prefecture, Yunnan province was optimized by quadratic general rotary design based on single
factor experiments and the antioxidant activities in vitro of the extracted pigments were investigated. The results showed
that the best extraction solvent for the pigments was determined as alcohol and the maximum absorption peaks appeared
at 282 and 342 nm, suggesting that they were flavonol compounds. The optimum extraction conditions were as follows:
extraction temperature, 30 ℃; liquid to material ratio, 20:1 (mL/g); and extraction time, 40 min. The pigments had potent
antioxidant activities; DPPH radical scavenging activity was (3 512.56 ± 26.28) μg ferulic acid equivalents/g; ferric reducing
antioxidant power (FRAP) was (44.04 ± 6.60) mmol Fe2+ equivalents/L; reducing power (RP) was (203.47 ± 23.75) μg ascorbic
acid equivalents/g; hydrogen peroxide scavenging activity was (3 676.60 ± 114.32) μg ferulic acid equivalents/g, and 2,2’-azinobis
(3-ethylbenzothiazoline-6-sulfonate) (ABTS) radical scavenging activity was (2 778.70 ± 262.90) μg Trolox equivalents/g.

Key words: “Laoheigu&rdquo, rice, pigments, quadratic general rotary design, extraction, antioxidant activity