No abstract

Spiny burs of Castanea mollissima Blume (Chinese chestnut) are usually discarded as industrial waste during post-harvesting processing. The objective of this study was to establish an extraction and isolation procedure for tannins from chestnut burs, and to assess their potential antioxidant activity. Aqueous ethanol solution was used as extraction solvent, and HPD 100 macroporous resin column was applied for isolation. The influence of solvent concentration in the extraction and elution process on extraction yield, tannins and polyphenols content, as well as antioxidant potential, including DPPH and ABTS radical scavenging ability, reducing power ability and cellular antioxidant ability were assessed. In both the extraction and isolation process, 50% aqueous ethanol led to superior total tannins and polyphenols content as well as significantly higher antioxidant activity. In addition, the antioxidant activity and the total tannins content in extracts and fractions had a positive linear correlation, and the predominant components responsible for antioxidant activities were characterized as hydrolysable tannins. To the best of our knowledge, this is the first report on the enrichment of tannins from burs of C. mollissim using macroporous resin chromatography, and to assess the cellular antioxidant activity of them.

Polyphenol extracts from the burs of Castanea mollissima Blume (CMPE) exhibited potential antioxidant and hypoglycemic activities. The α-glucosidase inhibitory activities of CMPE were assessed as a means of elucidating the mechanism behind its hypoglycemic activities. In vitro studies showed that CMPE significantly inhibited both yeast α-glucosidase, through a noncompetitive mode with an IC 50 of 0.33 μg/mL, and rat intestinal α-glucosidase. In vivo studies revealed that oral administration of CMPE at doses of 600 mg/kg significantly reduced postprandial blood glucose levels by 27.2% in normal rats following sucrose challenges. Gel permeation chromatography revealed that CMPE exhibited typical characteristics of high-molecular-mass polymers with mean (Mn) and weight (Mw) average molecular weights of 35.4 and 50.7 kDa, respectively, and a polydispersity (Mw/Mn) of 1.432. Acid hydrolysis analysis indicated the presence of ellagitannins. These data suggest that CMPE, enriched with ellagitannins, would be an efficacious dietary supplement for diabetes management through the inhibition of alpha-glucosidase.

Substantial evidence suggests that phenolic extracts of Castanea mollissima spiny burs (CMPE) increase pancreatic cell viability after STZ (streptozotocin) treatment as a result of their antioxidant properties. In the present study, the hypoglycemic and hypolipidemic activities of CMPE were studied in normal and STZ-induced diabetic rats CMPE were orally administrated at doses of 150 and 300 mg/kg twice a day for 12 consecutive days. Serum glucose, triglyceride, total cholesterol, HDL- and LDL-cholesterol levels, malondialdehyde (MDA) level and SOD activity in liver, kidney, spleen and heart tissues were measured spectrophotometrically. In normal rats, no significant changes were observed in serum glucose, lipid profiles and tissue MDA and GSH levels after orally administration of CMPE. In diabetic rats, oral administration of CMPE at a dose of 300 mg/kg caused significant decreases in serum glucose, triglyceride, total cholesterol, LDL-cholesterol levels, as well as MDA and GSH levels in spleen and liver tissues. However, the 300 mg/kg dosage caused a significant body weight loss in both normal and diabetic rats. The observed effects indicated that CMPE could be further developed as a drug to prevent abnormal changes in blood glucose and lipid profile and to attenuate lipid peroxidation in liver and spleen tissues.