Researchers at the Federal University of Technology in Nigeria evaluated the effects of the aqueous extract of garlic, white onion and purple onion on the activity of angiotensin-converting enzyme (ACE), a-amylase and a-glucosidase in vitro. They reported their findings in an article published in the Journal of Dietary Supplements.
Spices are used in cooking and serve as ingredients in several traditional delicacies that contain natural antioxidants, such as polyphenols.
To assess the beneficial properties of garlic, white onion and purple onion extracts, the researchers investigated their effects on the activity of various enzymes.
They also determined the extracts’ antioxidant capacities using OH*, Fe2+ chelation, and 2, 2?-azino-bis 3-ethylbenzothiazoline-6-sulphonic acid (ABTS) radical-scavenging assays.
The researchers found that the garlic, purple onion and white onion extracts inhibited the activities of ACE, a-amylase and a-glucosidase in a concentration-dependent manner.
The purple onion extract (IC50 = 0.59 mg/ml) had a higher inhibitory effect on ACE than the white onion (IC50 = 0.66 mg/ml) and garlic (IC50 = 0.96 mg/ml) extracts.
White onion (IC50 = 3.93 mg/mL), on the other hand, had a significantly stronger inhibitory effect on a-amylase than garlic (IC50 = 8.19 mg/ml) and purple onion (IC50 = 8.27 mg/ml).
Garlic (IC50 = 4.50 mg/ml) showed a similar inhibitory effect on ?-glucosidase activity to white onion and purple onion.
All three extracts were able to scavenge DPPH and reduce Fe3+ to Fe2+ in the antioxidant assays in a dose-dependent manner.
Based on these findings, the researchers concluded that garlic, white onion and purple onion exert anti-diabetes and antihypertensive properties by inhibiting ACE, a-amylase and a-glucosidase activity and preventing lipid peroxidation in the pancreas and heart through their antioxidant activities.
Oboh, G, Ademiluyi AO, Agunloye OM, Ademosun AO, Ogunsakin BG. INHIBITORY EFFECT OF GARLIC, PURPLE ONION, AND WHITE ONION ON KEY ENZYMES LINKED WITH TYPE 2 DIABETES AND HYPERTENSION. Journal of Dietary Supplements. 09 March 2018;16(1):105-118. DOI: 10.1080/19390211.2018.1438553