_____________________________________________________________________________________________________ *Corresponding author: E-mail: celinegarciasmc123@gmail.com; Journal of Pharmaceutical Research International 34(46B): 7-16, 2022; Article no.JPRI.88343 ISSN: 2456-9119 (Past name: British Journal of Pharmaceutical Research, Past ISSN: 2231-2919, NLM ID: 101631759) 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) Celine Angelica Garcia a* , Khristy Joy Flores a , Mikko Gamalo a , Gezer Gandeza a , Naomi Francise Garcia a , Jenn Lori Gepaya a , Maria Gerber a , Shera Heart Go a , Ore May Faith Gomez a , Sarah Myza Katrina Guinta a , Roanne Paula Herrero a , Jo Anne Himagan a , Cecile Melisse Derecho a and Genevieve D. Tupas a a Department of Pharmacology, Davao Medical School Foundation, Medical School Dr., Poblacion District, Davao City, 8000 Davao del Sur, Philippines. Authors’ contributions This work was carried out in collaboration among all authors. All authors read and approved the final manuscript. Article Information DOI: 10.9734/JPRI/2022/v34i46B36384 Open Peer Review History: This journal follows the Advanced Open Peer Review policy. Identity of the Reviewers, Editor(s) and additional Reviewers, peer review comments, different versions of the manuscript, comments of the editors, etc are available here: https://www.sdiarticle5.com/review-history/88343 Received 13 May 2022 Accepted 23 July 2022 Published 03 August 2022 ABSTRACT 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. Original Research Article