The use of repeatedly heated frying oil is hazardous to health, due to oxidative process that occurs in the oil. Addition of an additive with antioxidant property could lessen the detrimental effects of repeated frying in the oils. Citrus leaf extract (CLE) supplementation was reported to possess antioxidant and blood pressure-lowering properties. Our study aimed to determine the effects of CLE addition into frying oil in rats fed with repeatedly heated oil diet. Seven groups of male Sprague-Dawley rats were given fresh and heated oil diets (five-time-and tentime-heated palm oil), with and without the CLE addition for 16 weeks. CLE addition decreased peroxide value and augmented the total phenolics content in the heated oils. CLE addition reversed the negative effects of heated oil on nitric oxide level, systolic blood pressure, and vascular reactivity. In conclusion, these findings show that CLE has the ability to reduce oxidative damage caused by thermal degradation in frying oil and subsequently lowers the risk of hypertension in rats that consumed heated oil.

Background: Hypertension is a major risk factor for cardiovascular disease (CVD), which is the number one cause of global mortality. The potential use of natural products to alleviate high blood pressure has been demonstrated to exert a cardioprotective effect. Centella asiatica (L.) Urb. belongs to the plant family Apiaceae (Umbelliferae). It contains a high amount of triterpenoid and flavonoid that have antioxidant properties and are involved in the renin-angiotensin-aldosterone system which is an important hormonal system for blood pressure regulation.Objective: This study aimed to investigate the effects of C. asiatica ethanolic extract on blood pressure and heart in a hypertensive rat model, which was induced using oral N(G)-nitro-l-arginine methyl ester (l-NAME).Methods: Male Sprague-Dawley rats were divided into five groups and were given different treatments for 8 weeks. Group 1 only received deionized water. Groups 2, 4, and 5 were given l-NAME (40 mg/kg, orally). Groups 4 and 5 concurrently received C. asiatica extract (500 mg/kg, orally) and captopril (5 mg/kg, orally), respectively. Group 3 only received C. asiatica extract (500 mg/kg body weight, orally). Systolic blood pressure (SBP) was measured at weeks 0, 4, and 8, while serum nitric oxide (NO) was measured at weeks 0 and 8. At necropsy, cardiac and aortic malondialdehyde (MDA) contents, cardiac angiotensin-converting enzyme (ACE) activity, and serum level of brain natriuretic peptide (BNP) were measured.Results: After 8 weeks, the administrations of C. asiatica extract and captopril showed significant (p < 0.05) effects on preventing the elevation of SBP, reducing the serum nitric oxide level, as well as increasing the cardiac and aortic MDA content, cardiac ACE activity, and serum brain natriuretic peptide level.Conclusion:C. asiatica extract can prevent the development of hypertension and cardiac damage induced by l-NAME, and these effects were comparable to captopril.