Genetic characterization and authentication of Dimocarpus longan Lour. using an improved RAPD technique.

Dimocarpus longan Lour. is an edible and traditional herb in China, commonly referred to as longon. An improved randomly amplified polymorphic DNA (RAPD) protocol was here developed in order to determine the geographical origins of D. longan samples collected from 5 provinces in the southern and southwestern areas of China, including Sichuan, Hainan, Fujian, Guangdong, and Guangxi. Generally, the improved RAPD method generated good fingerprinting of the 5 samples using the selected 17 primers. In particular, primers SBS-A5, SBS-A13, SBS-I9, SBS-I20, SBS-M1, and SBS-Q12 produced distinguishable bands that clearly separated all 5 cultivars, suggesting that there are variations in RAPD genetic sites among the samples. The similarity index ranged from 0.69 to 0.76. The Sichuan and Hainan clades clustered together with a 0.73 similarity index. The Guangxi and Fujian clades clustered together with a 0.76 similarity index, and they formed the sister clade to the Sichuan/Hainan clade with a 0.71 similarity index. The Guangdong clade was in a basal polytomy with a 0.70 similarity index. Based on the abundant DNA polymorphisms, these longan accessions are distinguishable using our improved RAPD technique. Therefore, RAPD analysis is an effective technique in distinguishing the geographical origins of D. longan. Moreover, the improved method could also be employed for a variety of applications including genetic diversity and fingerprinting analyses.

A combination of grape seed-derived procyanidins and gypenosides alleviates insulin resistance in mice and HepG2 cells.

This study investigated the effects of grape seed-derived procyanidins (GSP), gypenosides (GPE), and combination procyanidins/gypenosides on insulin resistance in mice and HepG2 cells. ICR mice were randomly divided into 2 control and 4 treatment groups. The control mice were to receive either normal diet (ND) or high-fat diet (HFD), and the treatment groups were fed high-fat diet with either 80 mg/kg of GSP (GSP80), GPE (GPE80), GSP + GPE (1: 1, GSP40 + GPE40), or 500 mg/kg of metformin for a 6-wk period. All the groups of mice except the normal control were on high-fat diet along with fructose (15%) administered in drinking water throughout the period of treatment. An insulin-resistant HepG2 cell model was developed after 24 h of 5 x 10(-7) mol/L insulin incubation. The treatment of GPE80 could significantly reduce the index of insulin resistance (HOMA-IR) and increase hepatic glycogen concentration, compared with HFD group (P < 0.05). When GSP and GPE were administered simultaneously, synergic effects were observed in decreasing the HOMA-IR index and serum total cholesterol (TC) level and enhancing glucose tolerance. All treatment groups showed considerable raise of hepatic glucokinase activity (P < 0.05 compared with HFD group). GSP application increased the consumption of extracellular glucose in HepG2 cells. Our data suggest that the combination of GSP and GPE may have functional efficacy in consumers with insulin resistance.