Inhibitory Effect of Garlic, Purple Onion, and White Onion on Key Enzymes Linked with Type 2 Diabetes and Hypertension

Abstract

Spices are used in soup preparation in many homes and serve as ingredients in the preparation of several traditional delicacies endowed with natural antioxidants such as polyphenols. The aim of this study is to evaluate the effect of aqueous extract of garlic, white onion, and purple onion on angiotensin-converting enzyme, α-amylase, and α-glucosidase activity in vitro and determine their antioxidant properties via various antioxidant assays such as OH, Fe chelation, and 2, 2'-azino-bis 3-ethylbenzothiazoline-6-sulphonic acid (ABTS) radical-scavenging assays. The results reveal that aqueous extract of garlic, purple onion, and white onion inhibited angiotensin-converting enzyme, α-amylase, and α-glucosidase in a concentration-dependent manner (0-4 mg/ml). However, purple onion (IC = 0.59 mg/ml) had higher inhibitory effect on angiotensin-converting enzyme than white onion (IC = 0.66 mg/ml) and purple onion (IC = 0.96 mg/ml). Furthermore, white onion had significantly (p < .05) stronger inhibitory effect on α-amylase (IC = 3.93 mg/mL) than garlic (IC = 8.19 mg/ml) and purple onion (IC = 8.27 mg/ml). Conversely, garlic (IC = 4.50 mg/ml) had no significantly higher inhibitory effect on α-glucosidase activity than white onion and purple onion. In addition, the aqueous extracts were able to scavenge 2,2- diphenyl-1-picrylhydrazyl (DPPH) free radical and reduce Fe to Fe in a dose-dependent manner. Therefore, a possible mechanism by which garlic, white onion, and purple onion exert antidiabetes and antihypertensive properties could be through the inhibitory effect on ACE, α-amylase, and α-glucosidase coupled with their ability to prevent lipid peroxidation in the pancreas and heart, which justify their strong antioxidant properties.

Phenolic compounds and bioactivity evaluation of aqueous and methanol extracts ofAllium mongolicumRegel

“…ACE, another enzyme that have an important impact on metabolic syndrome, plays a pivotal role in the regulation of blood pressure (Villiger, Sala, Suter, & Butterweck, 2015). Several plants in Liliaceae family from Allium were found as a potential effective remedy of hypertension possibly due to the inhibitory effects on ACE (Oboh, Ademiluyi, Agunloye, Ademosun, & Ogunsakin, 2018). Plenty of synthetic drugs, such as captopril, that used in the treatment of hypertension were ACE inhibitors.…”

“…Recently, searching for ACE-inhibitor from natural plants has been attacked much attention. Several plants in Liliaceae family from Allium were found as a potential effective remedy of hypertension possibly due to the inhibitory effects on ACE (Oboh, Ademiluyi, Agunloye, Ademosun, & Ogunsakin, 2018).…”

Insights to potential antihypertensive activity of berry fruits

“…In addition, phenolic acid improved NO bioavailability, increased catalase activity, and decreased glutathione level. Findings have demonstrated that hydroxyl and carboxyl groups, in phenolic acids, interact with Zn 2+ and the disulfide bridge residues at the active site of the ACE and prevents its activity (Oboh, Ademiluyi, Agunloye, Ademosun, & Ogunsakin, 2019).…”

Grown to be Blue—Antioxidant Properties and Health Effects of Colored Vegetables. Part I: Root Vegetables

“…Similar results were reported by Zhang et al [232] in a study comparing white, yellow, and red onion, with the latter showing considerably higher total anthocyanin, flavonoid, and polyphenol content, which was also correlated to high antioxidant activity measured through DPPH, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS• + ), and fluorescence recovery after photobleaching (FRAP) assays. Bulb extracts are potent bioactive natural matrices, and, according to the study of Oboh et al [233], extracts of purple onion were effective against angiotensin-converting enzyme, α-amylase, and α-glucosidase activity, showing significant antidiabetic and anti-hypertensive effects. Moreover, skins of pearl onion exhibited significant anti-inflammatory properties and inhibitory effects against radical-induced DNA scission [234].…”