Anti-peroxidation effect of guava (Psidium guajava Linn.) leaf soluble solids in vitro and in streptozotocin/ nicotinamide-induced diabetic rats

BACKGROUND: Many people in oriental countries, including Japan and Taiwan, believe that guava (Psidium guajava Linn.) leaves are helpful in retarding the progress of type 2 diabetes. This study was conducted to investigate the effect of water-soluble solids (WSS) and ethanol-soluble solids (ESS) of guava leaves on lipid peroxidation in vitro and in type 2 diabetic rats in order to obtain a better understanding of the mechanism of retardation of diabetes. RESULTS: It was found that ESS contained significantly higher total phenolic and flavonoid levels than WSS (P < 0.05). Nevertheless, WSS showed higher superoxide dismutase-like activity and lipid peroxidation inhibition ability than ESS in vitro (P < 0.05). Also, reduced levels of serum triglyceride, low-density lipoprotein and liver thiobarbituric acid-reactive substances were found in type 2 diabetic rats fed with either WSS or ESS as compared with control animals (P < 0.05). CONCLUSION: Anti-peroxidation of lipids is a possible mechanism for guava leaves to retard the progress of diabetes.