Evaluation of combined antioxidant potential of p-coumaric acid and/or lisinopril — in vitro and in vivo

p-coumaric acid (p-CA) is a phenolic acid abundantly present in several foods, and lisinopril is a widely employed angiotensin-converting enzyme inhibitor for the treatment of hypertension and endothelial dysfunction. This study was convened to determine the combined antioxidative effect of p-CA and/ lisinopril — in vitro and in vivo. Stock solutions of p-CA (50 mM) and lisinopril (50 mM) were separately prepared. Subsequently, preparation of different combinations of samples (50% p-CA: 50% lisinopril; 75% p-CA: 25% lisinopril; 25% p-CA: 75% lisinopril, 100% p-coumaric acid and 100% lisinopril) was carried out for the determination of in vitro antioxidant properties as typified by DPPH, ABTS, and hydroxyl radical scavenging abilities, Fe²⁺ chelating ability, reducing property, and inhibition of Fe²⁺-induced lipid peroxidation. Furthermore, p-coumaric acid (50 and 100 mg/kg) and/or lisinopril (10 mg/kg) were administered orally (p.o.) to rats daily for 14 days. Then, the liver was excised, blood was collected, and the plasma was subsequently prepared. The antioxidant status was assessed by determining catalase, superoxide dismutase, glutathione peroxidase, and glutathione-S-transferase activities as well as the levels of reduced glutathione, total thiol, and lipid peroxidation in rat liver. Combination of p-coumaric acid and lisinopril influenced the antioxidant capacity of lisinopril in vitro, improved antioxidant defense status when compared to control in vivo, and significantly decreased lipid peroxidation in vitro and in vivo. Results from this study indicate that the combination approach of p-CA and lisinopril could represent crucial alternative therapy in the management of free radical mediated damage.