\n\tSummary

\n\tAnti-Hyperglycemic Effect of Extracts from Psidium guajava fruits

\n\tPsidium guajava (Guava) fruit has been shown as a source of antioxidant due to the presence of polyphenols, ascorbic acid and carotenoids. The present study determined in vitro antioxidant activity and anti-hyperglycemic effects of 70% ethanol fruit extracts from white guava and red guava collected in Tien Giang province. In vitro antioxidant activity was determined by malonyl dialdehyde test. The glucose tolerance test and streptozotocin-induced diabetes model were applied for in vivo study. The phytochemical results revealed that ascorbic acid contents were 64.5 and 92.4 mg/100 g fresh weight (fw), total phenolic contents 324.85 and 312.13 mg gallic acid equivalents/100 g fw and total flavonoid contents 161.94 and 157.3 mg quercetin equivalents/100 g fw, in white and red guava, respectively. Red guava extracts showed in vitro antioxidant activity stronger than white guava extracts and quercetin. In normal mice, the extracts administered for 7-14 days has no effects on blood glucose contents but showed hypoglycemic effects during glucose tolerance test. In diabetic mice, the extracts as well as a typical hypoglycemic drug gliclazide, showed anti-hyperglycemic effects after 7-day administration and after glucose overload. The findings suggested that guava may be employed to improve and/or prevent the disease of diabetes mellitus.

\n\tKeywords: Psidium guajava fruit, antioxidant activity, anti-hyperglycemic effects, glucose tolerance test, streptozotocin

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