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

J Agric Food Chem. 2016 Jul 6;64(26):5345-53. doi: 10.1021/acs.jafc.6b01909. Epub 2016 Jun 22.


Pigmented rice contains anthocyanins and proanthocyanidins that are concentrated in the bran layer. In this study, we determined the phenolic, flavonoid, anthocyanin, and proanthocyanidin content of five rice bran (1 brown, 2 red, and 2 purple) extracts. Each bran extract was evaluated for inhibitory effects on α-amylase and α-glucosidase activity, two key glucosidases required for starch digestion in humans. All purple and red bran extracts inhibited α-glucosidase activity, however only the red rice bran extracts inhibited α-amylase activity. Additionally, each bran extract was examined for their ability to stimulate glucose uptake in 3T3-L1 adipocytes, a key function in glucose homeostasis. Basal glucose uptake was increased between 2.3- and 2.7-fold by exposure to the red bran extracts, and between 1.9- and 3.1-fold by exposure to the purple bran extracts. In red rice bran, the highest enzyme inhibition and glucose uptake was observed with a proanthocyanidin-enriched fraction. Both IITA red bran and IAC purple bran increased expression of GLUT1 and GLUT4 mRNA, and genes encoding insulin-signaling pathway proteins.

Keywords: adipocytes; anthocyanins; brown rice bran; glucose uptake; phenolics; proanthocyanidins; purple rice bran; red rice bran; α-amylase; α-glucosidase.

MeSH terms

  • 3T3 Cells
  • Adipocytes / drug effects
  • Adipocytes / metabolism
  • Animals
  • Diabetes Mellitus / enzymology
  • Diabetes Mellitus / metabolism
  • Glucose / metabolism
  • Humans
  • Hypoglycemic Agents / chemistry
  • Hypoglycemic Agents / pharmacology*
  • Mice
  • Oryza / chemistry*
  • Phenols / chemistry
  • Phenols / pharmacology*
  • Plant Extracts / chemistry
  • Plant Extracts / pharmacology*
  • Seeds / chemistry
  • alpha-Amylases / antagonists & inhibitors
  • alpha-Amylases / metabolism
  • alpha-Glucosidases / metabolism


  • Hypoglycemic Agents
  • Phenols
  • Plant Extracts
  • alpha-Amylases
  • alpha-Glucosidases
  • Glucose