Evaluation of γ-oryzanol content and composition from the grains of pigmented rice-germplasms by LC-DAD-ESI/MS.

BACKGROUND

Rice is the staple food and one of the world’s three major grain crops. Rice contains more than 100 bioactive substances including phytic acid, isovitexin, γ-oryzanol, phytosterols, octacosanol, squalene, γ-aminobutyric acid (GABA), tocopherol, tocotrienol derivatives, etc. Out of them, γ-oryzanol is known to have important biological profile such as anti-oxidants, inhibitor of cholesterol oxidation, reduce serum cholesterol levels in animals, effective in the treatment of inflammatory diseases, inhibit tumor growth, reduce blood pressure and promotes food storage stability when used as a food additive, etc. Hence in the present investigation, we aimed to evaluate the content and composition of γ-oryzanol from pigmented rice germplasms using a liquid chromatography with diode array detection and electrospray ionization-mass spectrometry (LC-DAD-ESI/MS).

FINDINGS

In the present study, 33 exotic pigmented rice accessions (red, white and purple) have been evaluated. Among them, the contents of γ-oryzanol varied from 3.5 to 21.0 mg/100 g with a mean of 11.2 mg/100 g. A total of ten components of γ-oryzanol including Δ⁷-stigmastenyl ferulate were identified of which, cycloartenyl ferulate, 24-methylenecycloartanyl ferulate, campesteryl ferulate and sitosteryl ferulate were identified as the major components. The mean proportions of steryl ferulates were in the descending order of 24-methylenecycloartanyl ferulate > cycloartenyl ferulate > campesteryl ferulate > sitosteryl ferulate > Δ⁷-campestenyl ferulate > campestanyl ferulate > sitostanyl ferulate > Δ⁷-stigmastenyl ferulate > stigamsteryl ferulate > Δ⁷-sitostenyl ferulate. Almost 11 accessions (33%) showed higher content than the control rice Chucheongbyeo and higher proportions ranged from 10 to 15 mg/100 g. Interestingly, the red rice accession Liberian Coll. B11/B-11 (21.0 mg/100 g) showed higher content γ-oryzanol than control rice Jeokjinjubyeo (19.1 mg/100 g) and the purple rice accession Padi Adong Dumarat, Mardi No.4376 (20.3 mg/100 g) showed a similar content with control rice Heugjinjubyeo (21.4 mg/100 g).

CONCLUSIONS

Most of analyzed rice accessions were found to possess higher contents of γ-oryzanol than the control rice, Chucheongbyeo. In particular, the red accessions showed highest content than the white and purpleaccessions. The content and composition of γ-oryzanol in 33 exotic pigmented rice accessions have been evaluated and compared significantly by the present investigation.