Flavonoid-Rich Extract of Actinidia macrosperma (A Wild Kiwifruit) Inhibits Angiotensin-Converting Enzyme In Vitro

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.

The Health Benefits of Fruits and Vegetables

“…Several biological activities have already been reported for kiwifruit (Actinidia macrosperma) cultivars, such as antioxidant, anticancer, anti-inflammatory, and antimicrobial activities. This Special Issue contains the first report on a study supporting the potential anti-hypertensive activities of kiwifruits [1]. The results of this study clearly indicate that the flavonoid-rich extract from A. macrosperma shows potential as a food or nutraceutical source of anti-hypertensive agents.…”

Quercetin and Its Metabolites Inhibit Recombinant Human Angiotensin-Converting Enzyme 2 (ACE2) Activity

“… 39 In vitro studies have demonstrated that flavonoid-rich foods are capable of inhibiting ACE activity. 40 − 42 Also, an acute hypertensive rat model supports the antihypertensive potential of quercetin through reduced plasma ACE activity. 43 In contrast, ACE inhibition by flavonoids has not been observed in other human and animal studies.…”

Actinidia chinensis Planch.: A Review of Chemistry and Pharmacology

“…UPLC-MS/MS showed that polyphenols (231.32 µg/g DW) in the extract are mainly flavonols, flavanols, and phenolic acids. Specifically, quercetin-3-O-galactoside (205.19 µg/g DW), quercetin-3-O-glucoside (0.45 µg/g DW), quercetin-3-O-rhamnoside (0.61 µg/g DW), quercetin-3-O-rutinoside (0.29 µg/g DW), epicatechin (5.15 µg/g DW), catechin (0.75 µg/g DW), epigallocatechin (0.61 µg/g DW), phloridzin (2.03 µg/g DW), and isoferulic acid (15.12 µg/g DW) are major compounds in the extract (Hettihewa et al, 2018). These compounds could be responsible for the observed in vitro ACE inhibitory activity of Hort 16A fruit, though the active compounds identifying and in vivo animal studies remain to be investigated and conducted.…”