Antidiabetic Potential of Purple and Red Rice (Oryza sativa L.) Bran Extracts

Area of Science:

• Nutritional Biochemistry
• Food Science
• Metabolic Health

Background:

• Pigmented rice bran is a rich source of bioactive compounds like anthocyanins and proanthocyanidins.
• These compounds are primarily concentrated in the bran layer, a byproduct of rice milling.
• Understanding the specific health benefits of these compounds is crucial for functional food development.

Purpose of the Study:

• To quantify phenolic, flavonoid, anthocyanin, and proanthocyanidin content in pigmented rice bran extracts.
• To evaluate the inhibitory effects of these extracts on alpha-amylase and alpha-glucosidase enzymes.
• To assess the impact of rice bran extracts on glucose uptake in adipocytes and related gene expression.

Main Methods:

• Extraction and quantification of phenolic compounds from five rice bran varieties (1 brown, 2 red, 2 purple).
• In vitro assays to determine inhibitory effects on alpha-amylase and alpha-glucosidase activities.
• In vitro study using 3T3-L1 adipocytes to measure glucose uptake stimulation.
• Analysis of GLUT1, GLUT4, and insulin-signaling pathway gene expression via mRNA analysis.

Main Results:

• All purple and red rice bran extracts inhibited alpha-glucosidase activity.
• Red rice bran extracts demonstrated inhibitory effects on alpha-amylase activity.
• Red and purple rice bran extracts significantly increased basal glucose uptake in 3T3-L1 adipocytes.
• A proanthocyanidin-enriched fraction of red rice bran showed the highest enzyme inhibition and glucose uptake.
• Specific red and purple rice bran varieties upregulated GLUT1, GLUT4, and insulin-signaling pathway genes.

Conclusions:

• Pigmented rice bran extracts possess significant potential for modulating carbohydrate digestion and improving glucose homeostasis.
• The observed bioactivities are likely attributed to the high content of anthocyanins and proanthocyanidins, particularly in red rice bran.
• These findings support the inclusion of pigmented rice bran in diets for metabolic health management and the development of functional foods.