ANTIOXIDANT AND ANGIOTENSIN-1-CONVERTING ENZYME INHIBITORY PROPERTIES OF LEAF AND FRUIT EXTRACTS OF SOLANUM DASYPHYLLUM (IN-VITRO)

Abstract

The renin-angiotensin system and oxidative stress participate extensively in the pathophysiology of hypertension and congestive heart failure. This study aimed at investigating the anti-oxidative properties and effects of aqueous methanol leaf and fruit extracts of Solanum dasyphyllum and its fractions on the activity of angiotensin-1 converting enzyme (ACE-1) (in vitro). Methanol (80%) was used to extract the leaf and fruit of S. dasyphyllum separately; Freeze dried extracts were further partitioned in four different solvents of varying polarities, n-hexane, dichloromethane, ethylacetate and methanol. Extracts and fractions were screened for phytoconstituents and the total phenolic content (TPC), total flavonoid content (TFC) as well as total steroids content (TSC) were determined. Antioxidant activity was determined by evaluating the metal chelating ability, nitric oxide scavenging capacity, reducing power ability and inhibition of lipid peroxidation. Also ACE-1 inhibitory activities of the extracts were determined using furylacryloylphenylglyyclglycine (FAPGG) as substrate. Phytochemical Screening revealed the presence of phenols, flavonoids, steroids, terpenoids and cardiac glycosides. Ethylacetate fraction of the leaf extract had the highest total phenolic content of 30.21 ± 0.3 mg GAE/g sample and total flavonoid content of 3.14 ± 0.03 mg QE/g sample. The antioxidant assays showed potency in all fractions of leaf and fruit extracts in a concentration dependent manner, with ethyl acetate fractions of the leaf and fruit revealing the highest metal chelating ability, with EC50 values of 0.14 ± 0.01mg/ml and 0.48 ± 0.01 mg/ml respectively while methanol fraction of fruit and ethylacetate fraction of leaf showed the highest inhibitory potential against lipid peroxidation with IC50 values of 0.21 ± 0.01mg/ml and 0.23 ± 0.01 mg/ml respectively, ethylacetate fractions of the leaf and fruit showed the highest nitric oxide scavenging abilities with EC50 values of 0.45 ± 0.02mg/ml and 0.58 ± 0.03 mg/ml respectively and dichloromethane fraction of fruit and ethylacetate fraction of leaf had the highest reducing power of 7.37 ± 0.14 mg ascorbic acid equivalent/g sample and 7.13 ± 0.11 mg ascorbic acid equivalent/g sample. All fractions except methanol fraction of leaf and n-hexane fraction of fruit exhibited ACE-1 inhibition in a concentration dependent manner with ethylacetate fraction of the leaf extract having the highest inhibitory activity with IC50 (0.05 ± 0.1 mg/ml) and exhibited a competitive type of inhibition against ACE-1 when FAPGG was used as substrate. These findings showed that Solanum dasyphyllum exhibited high in vitro antioxidant and ACE-1 inhibitory properties with the ethyl acetate fraction having the most potent ACE-1 inhibitory activity. Hence the ethylacetate fraction of Solanum dasyphyllum could be a source of an antihypertensive agent.