In-vitro Study of the Inhibitory Activity of the Fractions of Onion (Allium cepa) and Shallot Bulb (Allium ascalonicum) Extracts on Angiotensin-Converting Enzyme (ACE)

The impact of hypertension as being the leading cause of death in industrialized societies pressed the importance of low-cost and accessible therapeutic agents present in food sources. This study was undertaken to evaluate the in-vitro Angiotensin-converting Enzyme (ACE) inhibitory activity of flavonoid-rich Onion and Shallot bulb extracts. Ethyl acetate, Butanol and Aqueous fractions of onion and shallot bulb extracts at varying concentrations were obtained through purification by solvent extraction. Positive control was the prototype ACE-inhibitor, Captopril. ACE-inhibitory activity was determined using the ACE-kit commercially manufactured by Dojindo, Inc. (Japan). All fractions of onion and shallot bulb extracts exhibited greater than 50% inhibitory activity towards ACE. The aqueous fractions of both bulbs showed the highest ACE-inhibitory activity exceeding the flavonoid standard, Quercetin, and were comparable with the prototype ACE-I, Captopril.

Based on the study findings, onion and shallot bulbs can be potential sources of bioactive compounds that can inhibit the activity of ACE which can be used to provide a natural, perhaps safer, cost-effective alternative in reducing blood pressure.