Combined polyphenols in Psidium guajava-citrus limon leaf extract attenuate fructose-induced cardiac injury by modulating metabolic and oxidative stress pathways in rats

Abstract

BACKGROUND: High fructose consumption is associated with metabolic and cardiovascular dysfunction. Polyphenol-rich lemon and guava leaves may protect the heart. OBJECTIVE: This study investigated the protective effects of Citrus limon leaf extracts, individually and in combination with Psidium guajava, against high fructose-induced cardiac injury in rats. We hypothesized that the polyphenol-rich extracts would attenuate cardiac damage through metabolic and oxidative stress modulation, with synergistic enhancement in the combined treatment. METHODS: The chemical composition of lemon and guava leaves was analyzed using LC-ESI-MS/MS, along with total phenolic, flavonoid, and antioxidant assays. Male Sprague-Dawley rats (n = 6/group) were divided into: a control group, a fructose group (20% w/v in drinking water for 6 weeks), and two treatment groups receiving either lemon leaf extract (200 mg/kg/day) or a lemon-guava leaf extract (200 mg/kg/day, 1:1) for 2 weeks, followed by co-administration with fructose for 6 weeks. Blood glucose, insulin, lipid profiles, troponin I, creatine kinases, oxidative stress markers, and inflammatory markers were measured. Histopathological and immunohistochemical analyses were performed. RESULTS: Sixteen phenolic compounds were identified, with the combined extract showing higher phenolic and flavonoid content and antioxidant activity. Both extracts significantly (p ≤ 0.05) improved insulin resistance and dyslipidemia, significantly (p ≤ 0.05) reduced troponin I and creatine kinase-myocardial band levels, and significantly (p ≤ 0.05) enhanced cardiac antioxidant activity by increasing glutathione, glutathione peroxidase, superoxide dismutase, and catalase, while decreasing malondialdehyde, interleukin-6, and tumour necrosis factor-α. The lemon-guava extract upregulated SIRT1 and NRF2 expression, demonstrating superior efficacy in mitigating fructose-induced cardiac stress. CONCLUSION: The combined lemon-guava leaf extract alleviates fructose-induced cardiac stress, demonstrating potential as a plant-based therapeutic agent for metabolic and cardiovascular protection.