Kinetics of the Inhibition of Renin and Angiotensin I Converting Enzyme by Polar and Non-polar Polyphenolic Extracts of Vernonia Amygdalina and Gongronema Latifolium Leaves

Abstract

The aim of this study was to determine the in vitro modulation of the renin-angiotensin system by polyphenolic extracts and fractions of two green leafy vegetables, Vernonia amygdalina (VA) and Gongronema latifolium (GL), that are used for food and medicinal purposes. An 80% acetone extract of each leaf was fractionated on silicic acid-packed column to give two main fractions: acetone eluate (flow-through) and ethanol eluate (column-bound), that consist mostly of chlorophyllic and non-chlorophyllic fractions, respectively. Column fractionation resulted in polyphenolic fractions that displayed higher potency against angiotensin converting enzyme (ACE) and renin than the crude acetone extracts; generally, the chlorophyllic fraction was more active than the non-chlorophyllic fraction. ACE-inhibitory activity was significantly higher (p < 0.05) for the chlorophyllic fraction of VA than GL, with IC(50) values of 0.207 and 0.413 mg/ml, respectively. Similarly, the chlorophyllic fraction of VA had significantly higher (p < 0.05) renin inhibition than GL, with IC(50) values of 0.172 and 0.513 mg/ml, respectively. Kinetics studies showed that the chlorophyllic fractions of VA and GL exhibited mostly mixed-type ACE and renin inhibitions. We concluded that the hydrophobic nature of the chlorophyllic fraction may have contributed to the increased interaction with enzyme protein and inhibition of activities of ACE and renin.

Processed dietary plants demonstrate broad capacity for angiotensin converting enzyme and angiotensin II receptor binding inhibition in vitro

“…In particular, ACE inhibitory bioactivity has previously been strongly associated with peptide extracts from plant and animal protein sources (De Leo, Panarese, Gallerani, & Ceci, 2009;Guang & Phillips, 2009). Also, as demonstrated in this study, there is a strong correlation between the polyphenolic component of the edible plant product and ACE inhibitory activity which has been demonstrated by other workers in the field (Ajibola, Eleyinmi, & Aluko, 2011;Balasuriya & Rupasinghe, 2011;Yang, Chen, Li, & Tsai, 2007). Inhibition of binding of angiotensin ligands to AT 1 R have been associated largely with plant metabolites of several chemical classes that were extracted by either organic solvents (Caballero-George et al, 2001, 2002a or aqueous media (Huang et al, 2008).…”

Kinetics of in vitro renin and angiotensin converting enzyme inhibition by chicken skin protein hydrolysates and their blood pressure lowering effects in spontaneously hypertensive rats

“…More importantly is the direct inhibition of renin activity which has been reported to completely block the RAS pathway since renin is known to catalyze the rate-limiting step in RAS (Fitzgerald, 2011). Several synthetic antihypertensive compounds (e.g., captopril, alacepril, lisinopril, enalapril and fosinopril) developed as ACE inhibitors have long been used to inhibit RAS and treat hypertension including other associated cardiovascular disease conditions (Ajibola, Eleyinmi, & Aluko, 2011;Erdmann et al, 2008;Samanarayaka, Kitts, & Li-Chan, 2010). Aliskiren is however, the only available drug therapy for use as renin inhibitor (He, Malomo, Girgih, Ju, & Auko, 2013).…”

Anatomical characters of the medicinal leaf and stem of Gymnanthemum amygdalinum (Delile) Sch.Bip. ex Walp. (Asteraceae)

“…Studies of different extracts have shown antioxidant (Igile et al, 1994;Farombi, Owoeye, 2011), antimicrobial (Erasto, Grierson, Afolayan, 2006;Okigbo, Mmeka, 2008), antiparasitic (Tadesse et al, 1993;Ademola, Eloff, 2011;Adiukwu, Amon, Nambatya, 2011), antidiabetic (Akinola et al, 2011;Ong et al, 2011) and antihypertensive (Ajibola, Eleyinmi, Aluko, 2011;Saliu et al, 2011) properties.…”