Free radical scavenging activities of guava extract in vitro

Abstract

Introduction: Psidium guajava (guava) is used in folk medicine in treating diverse human ailments. The therapeutic benefit of medicinal plants is often attributed to their antioxidant properties. Objectives: This study evaluated the radical scavenging potentials of ethanolic extract of Psidium guajava (EEPG) in vitro. Method: Radical scavenging potential of EEPG was determined by assessing its reducing power, extent of LPO, NO, H202 , DPPH inhibition and TEAC. Result: AAPH-induced LPO was significantly (P<0.05) inhibited by 56.5%, 65.3%, 55.1 %, 54.4%, 53.1%, at 25-400/xg of EEPG. The reference drug, catechin at 50/µg, produced 39.5% inhibition of LPO induced by AAPH respectively with respect to control. EEPG produced significant (p<0.05) inhibition of deoxyribose degradation at 100-800/µg concentrations by 30.9% (p<0.01), 42.5%, 55.7%, 72.8% (p<0.001) respectively with respect to control. Catechin also show potency, producing 55.5% at 25/zg (p<0.001). Furthermore, the antioxidant activity of EEPG ranged from 763.08 to 1206.2 /µmol trolox equivalent in the TEAC assay at 50-200jtg (p<0.001) and 24.62 to 14.77 /µmol trolox equivalent at 800-2000/µg (p<0.001). Catechin exhibited a TEAC value of 2338.5 /µmol trolox equivalent (p<0.001). EEPG exhibited maximum radical scavenging activities of 30.1% on NO radical (p<0.01), 98.72% on H,0 , (p<0.001), at 50/µg and 70.45% on DPPH radical (p<0.001) at 100/µg. EEPG also demonstrated marked reducing power, increasing absorbance values from 0.24±0.01 to 1.86±0.20at 25-1600/µg. The reducing power of EEPG at 200/µg (0.41 ±0.07) almost compares with that of catechin at 50/µg (0.45±0.028). Conclusion: These results demonstrate that the ethanolic extract of Psidium guajava (EEPG) exhibited significant free radical scavenging and antioxidant activities in vitro.