Hypertension is a major risk factor for cardiovascular diseases which is one of the leading causes of death worldwide. Piper sarmentosum(PS) has been widely used in traditional medicine with proven antihypertensive and antioxidant effects. This study aims to evaluate the antihypertensive potential of PS aqueous extract (PSAE) and to investigate the factors modulating nitric oxide (NO) production through its anti-oxidant activities. Methods:PS leaves were extracted with distilled water, freeze-dried and examined to quantify their antioxidant activities through 2,2-diphenyl-1-picrylhydrazyl and ferric reducing ability plasma test. The antihypertensive effect of PSAE in spontaneous hypertensive rats (SHR) was evaluated using four different groups (n=6); C (negative control), K (PSAE 500mg/kg), P (3 mg/kg perindopril) and M (PSAE 500 mg/kg + 1.5 mg/kg perindopril). PSAE and other treatments were given via oral gavage for 28 days. The blood pressure (BP) was determined using the non-invasive BP monitoring tail cuff technique and recorded weekly. SHR’s blood was collected to determine the serum NO level using Griess assay. Asymmetric dimethylarginine (ADMA) and arginine levels were determined using high performance liquid chromatography. Results:The extract showed good in-vitro antioxidant activities and a significant reduction in both systolic and diastolic BP compared to control group. They were also a decrease in plasma ADMA and an increase in serum NO level. Meanwhile, arginine level does not change significantly. Conclusion:High in-vitro antioxidant activities in PSAE enhances the clearance of ADMA that leads to an increase in serum NO production hence ameliorating the blood pressure of SHR.
Piper sarmentosum is a tropical plant in Southeast Asia known for its traditional use in curing various ailments including hypertension. Previous research works have provided evidence for the herb's antihypertensive property. However, the exact mechanisms involved are still in question. The present study investigated the effects of Piper sarmentosum leaves aqueous extract (PSAE) treatment on vascular endothelin system in spontaneously hypertensive rats (SHRs). Four groups of SHRs were treated for 28 consecutive days, with negative and positive control groups receiving distilled water and 3 mg/kg perindopril, respectively. Another two groups are the treatment groups, which received PSAE and combination of 1.5 mg/kg perindopril and PSAE. Weekly measurements of blood pressure showed that PSAE significantly reduced the systolic, diastolic, and mean arterial pressures (P < 0.05) of the rats. PSAE also increased mesenteric artery nitric oxide (NO) level (P < 0.05) and reduced endothelin-1 (ET-1) level (P < 0.05) in the treatment groups. Our results demonstrate that oral administration of PSAE reduced blood pressure in SHRs by reducing the ET-1 level while increasing NO production.