ABSTRACT
PURPOSE: The aim of this study was to assess the effects of guava leaf extract (GLE) supplementation on antioxidant enzyme activity and expression of endothelial nitric oxide synthase (eNOS) mRNA in ovariectomized rats. METHODS: All animals were randomly assigned to four groups (n = 7 for each group): non-ovariectomized control (Sham), the ovariectomized control (OVX), ovariectomy + 150 mg/kg b.w. of GLE (OVX·GL), and ovariectomy + 300 mg/kg b.w. of GLE (OVX·GH). Treatment groups were administered GLE for 8 weeks every day. RESULTS: Body weight gain was significantly reduced in the OVX·GL group compared with the OVX group (p < 0.05). The level of serum 17β-estradiol (E2) was significantly lower in the OVX groups than the Sham group (p < 0.05). Serum triglyceride (TG) and HDL-cholesterol levels were not significantly different between all groups. However, serum total cholesterol (TC) level was significantly reduced in the OVX·GH group compared with the OVX group (p < 0.05). Serum free fatty acid (FFA) level and liver TG level were significantly reduced in both OVX·GL and OVX·GH groups compared with the OVX group (p < 0.05). Furthermore, serum glutathione peroxidase (GPx) activity was significantly elevated in the GLE groups (p < 0.05). The mRNA expression level of GPx was not affected by ovariectomy. However, administration of GLE resulted in significantly increased nuclear factor erythroid 2-related factor (Nrf2) and catalase (CAT) mRNA expression levels in the liver (p < 0.05). In addition, liver nitric oxide (NO) level was significantly reduced in the OVX·GH group compared with the OVX group (p < 0.05). Expression level of endothelial nitric oxide synthase (eNOS) was significantly elevated in the OVX·GH group compared with the OVX group (p < 0.05). CONCLUSION: These results suggest that GLE could have protective effects in OVX rats by stimulating eNOS expression and improving the antioxidant defense system.