Influence of cooking on anthocyanins in black rice (Oryza sativa L. japonica var. SBR).

The composition and thermal stability of anthocyanins in black rice (Oryza sativa L. japonica var. SBR) produced in California were investigated. Six anthocyanin pigments were identified and quantified by high performance liquid chromatography using photo diode-array detection (HPLC-PDA) and electrospray ionization mass spectrometry [LC-(ESI)MS/MS]. The predominant anthocyanins are cyanidin-3-glucoside (572.47 microg/g; 91.13% of total) and peonidin-3-glucoside (29.78 microg/g; 4.74% of total). Minor constituents included three cyanidin-dihexoside isomers and one cyanidin hexoside. Thermal stability of anthocyanins was assessed in rice cooked using a rice cooker, pressure cooker, or on a gas range. All cooking methods caused significant (P < 0.001) decreases in the anthocyanins identified. Pressure cooking resulted in the greatest loss of cyanidin-3-glucoside (79.8%) followed by the rice cooker (74.2%) and gas range (65.4%). Conversely, levels of protocatechuic acid increased 2.7 to 3.4 times in response to all cooking methods. These findings indicate that cooking black rice results in the thermal degradation of cyanidin-3-glucoside and concomitant production of protocatechuic acid.

Characterization of inhibitors of postprandial hyperglycemia from the leaves of Nerium indicum.

Nerium indicum is an India-Pakistan-originated shrub belonging to the oleander family. The ingestion of leaves of N. indicum before a meal is known to effect the lowering of postprandial glucose levels in Type II diabetic patients and this plant is now used as a folk remedy for Type II diabetes in some regions of Pakistan. In the present study, the hot-water extract of N. indicum leaves was found to reduce the postprandial rise in the blood glucose when maltose or sucrose was loaded in rats. It was also found that the extract strongly inhibited alpha-glucosidase, suggesting that the suppression of the postprandial rise in the blood glucose is due to the occurrence of some inhibitors of alpha-glucosidase in the leaves. We, therefore, tried to isolate the active principles from the leaf extract, using alpha-glucosidase-inhibitory activity as the index. Employing Sephadex G-15, silica gel and reversed-phase HPLC, we isolated two active compounds. The UV, mass and NMR spectrometric analyses established that the chemical structures of these compounds are 3-O-caffeoylquinic acid (chlorogenic acid) and its structural isomer, 5-O-caffeoylquinic acid. Both compounds were shown to inhibit alpha-glucosidases in a non-competitive manner. The authentic chlorogenic acid was found to suppress the postprandial rise in the blood glucose in rats and also inhibited the absorption of the glucose moiety from maltose and glucose in the everted gut sac system prepared from rat intestine. These results demonstrate that chlorogenic acid is one of the major anti-hyperglycemic principles present in the leaves of N. indicum. Furthermore, among polyphenol compounds tested, quercetin and catechins were shown to have strong inhibitory activity against alpha-glucosidase.

Effect of a hypolipidemic drug, Di (2-ethylhexyl) phthalate, on mRNA-expression associated fatty acid and acetate metabolism in rat tissues.

Di (2-ehtylhexyl) phthalate (DEHP) is a peroxisome proliferator and a drug having a hypolipidemic effect. The body-weight change of rats treated with DEHP was lower than that of rats in an untreated control group. Expressions of long-chain acyl-CoA dehydrogenase and 3-ketoacyl-CoA thiolase, which are involved in fatty acid oxidation and acetate formation in mitochondria, showed an increase in the liver and testes of rats treated with DEHP. The expression of acetyl-CoA synthetase 1 was significantly decreased in the testes and relatively decreased in the liver, while the expression of acetyl-CoA synthetase 2 was significantly increased in the heart. Furthermore, the expressions of acetyl-CoA carboxylase in heart and testes showed a tendency to decrease. From these results, it is suggested that DEHP-treatment increased fatty acid oxidation and acetate formation in liver and testes, and that acetate utilization was increased in peripheral tissues such as the heart.