Tocotrienols from rice (Oryza sativa L.) bran: occurrence, levels, free-radical scavenging, angiogenic and sunscreening activities

Date

4-2008

Degree

Bachelor of Science in Chemistry

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Evelyn B. Rodriguez

Abstract

SAGARBA1RRIA, MA. IRINA SAMPAGA, College of Arts and Sciences, University of the Philippines Los Banos. April 2008. Tocotrienols from Rice Bran: Occurrence, Levels, Free-Radical Scavenging, Angiogenic and Sunscreening Activities.

ADVISER: Evelyn B. Rodriguez, Ph.D.

The levels of naturally-occurring tocotrienols from rice bran were determined from a tocotrienol-rich extract obtained from the methanol extraction of rice bran. The free-radical scavenging, angiogenic and sunscreening activities of this extract were evaluated. A tocotricnol-rich extract (TE) was obtained by the methanol extraction of stabilized rice bran. The TE weighed 9.61 g, corresponding to 4.78% of the rice bran's weight. The total tocotrienol content of the extract was determined by the Emmerie-Engel method. amounting to 291.66 ± 0.26 ppm or 1.393 mg/100 g rice bran. Through silica gel column chromatography employing gradient elution with mixtures of toluene-ethyl acetate, the components of the TE were isolated. The identities of the components were determined through IR and UV spectroscopy, TLC and chemical tests as: squalene (Fraction A), y-orvzanol (Fraction B), unidentified (Fraction C), and u-tocotrienol (Fraction D). The angiogenic activity of the TE was determined in comparison to quercetin using the duck embryo assay. Results show that the TE has anti-angiogenic activity that is proportional to its concentration. The free-radical scavenging activity of TE was determined using the DPPH assay. The EC50 value for TE was 193.83 ± 0.78 ppm and for BHT it was 11.43 ± 8.99 ppm. The sunscreening activity of the TE was evaluated according its inhibition of the UV-catalyzed reduction of benzophenone to benzopinacol. The TE had a mean % sunscreening activity of 63.10 ± 2.20%. In comparison to a commercial sunscreen (Skinwhite SPF 10) that had a mean % sunscreening activity of 80.33 -± 2.30%, the sunscreening activity of the TE is statistically different by a one-way ANOVA at 95 % confidence limits.

Rice bran is a significant source of tocotrienols as well as y-oryzanol. The tocotrienol-rich extract (TE) obtained from stabilized rice bran has significant anti-angiogenic activity that can be exploited in anti-cancer therapy. It has free-radical scavenging activity that indicates significant antioxidant activity in vitro. Its sunscreening activity shows that the TE can protect against UV-induced oxidative stress on skin. The results indicate that the TE can be used in topical applications (i.e. sunscreens) and dietary supplements.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

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Document Type

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