Abstract
Increasing interest in flavonoids in kiwifruit is due to the health-promoting properties of these bioactives. Inhibition of the angiotensin-converting enzyme (ACE) is one of the main therapeutic targets in controlling hypertension. The present study investigated the ACE inhibitory activity of flavonoid-rich extracts obtained from different kiwifruit genotypes. The flavonoid-rich extracts were prepared from fruits of Actinidia macrosperma, Actinidia deliciosa cv Hayward (Green kiwifruit), and Actinidia chinensis cv Hort 16A (Gold kiwifruit) by steeping the lyophilized fruit samples in 70% aqueous acetone, followed by partitioning the crude extracts with hexane. The composition of each extract was analyzed using ultrahigh-performance liquid chromatography-mass spectrometry (UPLC-MS/MS). The ACE inhibitory activity of the fruit extracts was performed using a fluorescence-based biochemical assay. The subclass flavonol was the most abundant group of flavonoids detected in all the extracts tested from three different kiwifruit cultivars. Quercetin-3-O-galactoside, quercetin-3-O-glucoside, quercetin-3-O-rhamnoside, quercetin-3-O-rutinoside, quercetin-3-O-arabinoglucoside, catechin, epigallocatechin gallate, epigallocatechin, chlorogenic, ferulic, isoferulic, and caffeic acid were prominent phenolics found in A. macrosperma kiwifruit. Overall, the flavonoid-rich extract from A. macrosperma showed a significantly (p < 0.05) high percentage of inhibition (IC50 = 0.49 mg/mL), and enzyme kinetic studies suggested that it inhibits ACE activity in vitro. The kiwifruit extracts tested were found to be moderately effective as ACE inhibitors in vitro when compared to the other plant extracts reported in the literature. Further studies should be carried out to identify the active compounds from A. macrosperma and to validate the findings using experimental animal models of hypertension.
Highlights
Hypertension has become a common risk factor for cardiovascular disease around the world, which affects all ages, from children to adults [1]
The present study investigated the in vitro angiotensin-converting enzyme (ACE) inhibitory activity of flavonoid-rich extracts obtained from kiwifruit cultivars, namely A. macrosperma, A. deliciosa (Hayward), and A. chinensis (Hort 16A), using a fluorescence-based biochemical assay, followed by determination of the kinetic parameters of the inhibition
As far as we are aware, there are no reports on ACE inhibitory activity found in kiwifruits
Summary
Hypertension has become a common risk factor for cardiovascular disease around the world, which affects all ages, from children to adults [1]. Inhibition of ACE has been identified as a major therapeutic target for controlling over-activation of RAAS. Prescription drugs such as captopril, ramipril, lisinopril, and enalaprilare are synthetic. Foods 2018, 7, 146 drugs are often reported to have undesirable side effects, interest in searching natural sources of ACE inhibitors has increased. Most studies have shown that plant extracts, which are rich in specific peptides and flavonoids are found to be effective as natural ACE inhibitors [5,6,7,8,9,10,11,12,13,14,15,16]. Flavonoid-rich fruits and vegetables and their products have gained attention for their capability to manage blood pressure [17,18,19,20]
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