Angiotensin Converting Enzyme (ACE) Inhibition Activity by Syzygium polyanthum Wight (Walp.) Leaves: Mechanism and Specificity

Abstract

Plant collection and authenticationApproximately, 3.26 kg of the plant leaves were collected from Taman Pertanian Jubli Perak, Kuantan, Pahang, Malaysia in May 2019. The plant used in this study was verified as Syzygium polyanthum (Wight) Walp by a botanist on 24th July 2019. The voucher herbarium specimen (PIIUM ABSTRACTIntroduction: One of the potential antihypertensive mechanisms include angiotensin converting enzyme (ACE) inhibition. So far, there is no in-depth study on the ACE inhibition activity of S. polyanthum, an ethnomedicinal plant used in treating hypertension. Thus, we aimed to study the ACE inhibition activity of S. polyanthum leaves by evaluating its potency, mechanism, and specificity. Methods: S. polyanthum leaves were macerated in a bath-sonicator with either water, methanol, ethyl acetate, and hexane producing aqueous (ASP), methanolic (MSP), ethyl acetate (EASP) and hexane (HSP) extracts. Each extract (100 µg/mL) were initially screened for ACE inhibition activity and then compared with standard drug, captopril (2.06 ng/mL), then the most active extract was further tested at 1 to 1000µg/ml. Inhibition mechanism was studied using zinc chloride and bovine serum albumin (BSA), while inhibition specificity was determined upon screening for α-chymotrypsin and trypsin inhibition activity. Results: ASP at 100 μg/ mL exhibited the highest inhibition activity (69.43 ± 0.60 %) compared to MSP (41.63 ± 0.15 %), EASP (9.62 ± 1.60 %), and HSP (45.40 ± 0.15 %). ASP showed dose-dependent ACE inhibition activity with IC 50 of 41 μg/mL. ASP's ACE inhibition activity was significantly reduced in the presence of BSA, but not upon the presence of zinc chloride. ASP did not significantly inhibit α-chymotrypsin and trypsin. Conclusion: This study showed that the enzyme inhibition activity by S. polyanthum leaves was specific towards ACE. The ACE inhibition possibly occurs via protein precipitation and was non-dependent to the chelation with zinc at ACE active site.

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“…37 Another study with Syzygium polyanthum have shown the ACE inhibition potential of aqueous extract exhibiting the ACE inhibitory activity of around 69.43 %. 38 ACE inhibition by reference standard and aqueous extract of the plant were analyzed by Lineweaver Burk's plot (Figure 2). Reciprocals of varying HHL concentrations on the x-axis were used as independent factors in the current study, and reciprocals of HA production were used as the dependent variable (y-axis), to create a linear regression.…”

In Vitro Angiotensin-Converting Enzyme (ACE) Inhibition Test on Extract Dayak Onion Herb (Eleutherine americana (Aubl.) Merr. ex K. Heyne)

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“…Aqueous extract of S. polanthum has inhibitory activity against ACE through protein precipitation (25).…”

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