cooking. The authors suggested that RBO as cooking oil should be included in daily
routine because of several advantages and health benefits. The above-mentioned
studies suggested that the RBO unsaponifiable fraction contains γ-oryzanol
accredited to these health benefits in humans. To ascertain the role of γ-oryzanol
concentration in creating any variation in cholesterol levels, another study was
conducted wherein 30 hypercholesterolemic subjects were chosen and divided into
two groups. γ-oryzanol at a level of 0.05 g per day (low level) or 0.8 g per day (high
level) concentrations were given for 4 weeks. Regardless of the concentration used,
the LDL and HDL cholesterol, total plasma cholesterol, and triacylglycerol were
lowered in both the groups compared to its initial level (assessed at the start of the
study). Low and high gamma-oryzanol containing RBO feeding for 4 weeks lowered
total plasma cholesterol (6.3%), LDL-C (10.5%), and the LDL-C/HDL-C ratio
(18.9%). Methylated sterols (phytosterols) in gamma-oryzanol is ineffective at
inhibiting dietary cholesterol absorption, but 4-desmethylsterols could enhance its
cholesterol-lowering ability. If all ferulated sterols (esterification of plant sterols)
become de-ferulated (de-esterified) in the gut, γ-oryzanol at low and high concentration (level of 0.05 g per day or 0.8 g per day in the present study) in RBOs
provided intestinal loads of 453 and 740 mg/day free 4-desmethylsterols, respectively. This intestinal load of 453–740 mg/day of efficacious free plant sterol
equivalents had similar effects on lipoproteins. The study further confirmed that
γ-oryzanol might improve lipid metabolism (Berger et al. 2005).
The mechanism by which RBO works on the metabolism of lipid has not been
completely elucidated. Rice bran oil contains unsaponifiable and saponifiable lipid
fractions. The unsaponifiable fraction such as phytosterols, polyphenols, and other
RBO extracted bioactive components are supposed to contribute toward the
antihyperlipidemic effect, while the saponifiable lipid fractions did not seem to
contribute toward lipid metabolism. γ-oryzanol is a natural antioxidant and is
composed
of
four
main
components
(cycloartenyl
ferulate,
24-methylenecycloartanyl ferulate, campesteryl ferulate, and sitosteryl ferulate).
γ-oryzanol composition and its amount in rice depend upon the rice species and its
cultivation environment (Krishna et al. 2001; Bergman and Xu 2003). In vitro
scavenging activity of each form of γ-oryzanol had been investigated separately
and similar scavenging ability had been found in all of its constituents viz.,
cycloartenyl ferulate, 24-methylenecycroartanyl ferulate, campesteryl ferulate, and
beta-sitosteryl ferulate (Akiyama et al. 2001). γ-oryzanol stops the free radical chain
reaction at higher concentrations compared to tocopherol fraction that captures
organic radicals at very fewer concentrations. Therefore, tocopherol fraction of
RBO had come out to be a more effective antioxidant (Juliano et al. 2005). In
general, all the bioactive constituents viz., γ-oryzanol, phytosterols, tocols, squalene,
octacosanol, etc., of RBO contribute toward the antioxidant and hypolipidemic
effect. In this perspective, the notion that a variety of RBO constituents collectively
are liable for the overall effect on lipid balance is the most valid proposition
concerning the valuable effects of these bioactive constituents (Cicero and Gaddi
2001).
16 Rice (Oryza sativa) Bran
405
routine because of several advantages and health benefits. The above-mentioned
studies suggested that the RBO unsaponifiable fraction contains γ-oryzanol
accredited to these health benefits in humans. To ascertain the role of γ-oryzanol
concentration in creating any variation in cholesterol levels, another study was
conducted wherein 30 hypercholesterolemic subjects were chosen and divided into
two groups. γ-oryzanol at a level of 0.05 g per day (low level) or 0.8 g per day (high
level) concentrations were given for 4 weeks. Regardless of the concentration used,
the LDL and HDL cholesterol, total plasma cholesterol, and triacylglycerol were
lowered in both the groups compared to its initial level (assessed at the start of the
study). Low and high gamma-oryzanol containing RBO feeding for 4 weeks lowered
total plasma cholesterol (6.3%), LDL-C (10.5%), and the LDL-C/HDL-C ratio
(18.9%). Methylated sterols (phytosterols) in gamma-oryzanol is ineffective at
inhibiting dietary cholesterol absorption, but 4-desmethylsterols could enhance its
cholesterol-lowering ability. If all ferulated sterols (esterification of plant sterols)
become de-ferulated (de-esterified) in the gut, γ-oryzanol at low and high concentration (level of 0.05 g per day or 0.8 g per day in the present study) in RBOs
provided intestinal loads of 453 and 740 mg/day free 4-desmethylsterols, respectively. This intestinal load of 453–740 mg/day of efficacious free plant sterol
equivalents had similar effects on lipoproteins. The study further confirmed that
γ-oryzanol might improve lipid metabolism (Berger et al. 2005).
The mechanism by which RBO works on the metabolism of lipid has not been
completely elucidated. Rice bran oil contains unsaponifiable and saponifiable lipid
fractions. The unsaponifiable fraction such as phytosterols, polyphenols, and other
RBO extracted bioactive components are supposed to contribute toward the
antihyperlipidemic effect, while the saponifiable lipid fractions did not seem to
contribute toward lipid metabolism. γ-oryzanol is a natural antioxidant and is
composed
of
four
main
components
(cycloartenyl
ferulate,
24-methylenecycloartanyl ferulate, campesteryl ferulate, and sitosteryl ferulate).
γ-oryzanol composition and its amount in rice depend upon the rice species and its
cultivation environment (Krishna et al. 2001; Bergman and Xu 2003). In vitro
scavenging activity of each form of γ-oryzanol had been investigated separately
and similar scavenging ability had been found in all of its constituents viz.,
cycloartenyl ferulate, 24-methylenecycroartanyl ferulate, campesteryl ferulate, and
beta-sitosteryl ferulate (Akiyama et al. 2001). γ-oryzanol stops the free radical chain
reaction at higher concentrations compared to tocopherol fraction that captures
organic radicals at very fewer concentrations. Therefore, tocopherol fraction of
RBO had come out to be a more effective antioxidant (Juliano et al. 2005). In
general, all the bioactive constituents viz., γ-oryzanol, phytosterols, tocols, squalene,
octacosanol, etc., of RBO contribute toward the antioxidant and hypolipidemic
effect. In this perspective, the notion that a variety of RBO constituents collectively
are liable for the overall effect on lipid balance is the most valid proposition
concerning the valuable effects of these bioactive constituents (Cicero and Gaddi
2001).
16 Rice (Oryza sativa) Bran
405