Abstract
Context: Aqueous decoction of Syzygium polyanthum (ADSP) leaf is one of Malay traditionalremedial- preparations for hypertension. Intravenous ADSP reduced blood pressure of anesthetized Wistar-Kyoto (WKY) and Spontaneously-Hypertensive rats (SHR); however, acute and sub-acute effects of oral ADSP on conscious rats and its bioactive compound(s) are not comprehensively studied. This study aims to examine the acute and sub-acute effects of ADSP in comparison to methanol extract (MESP) on systolic blood pressure (SBP) of conscious WKY and SHR rats, as well as to identify their major phenolic-compound using highperformance- liquid-chromatography (HPLC). Methodology: For acute study, SHR and WKY rats were gavaged with single-dose of ADSP or MESP (2.00, 2.50 or 3.00 g/kg), vehicles, or losartan (0.01 g/kg). SBP was measured after 1, 3, 5, 6 and 24 hr-post-administration. For subacute experiment, SHR rats were gavaged once-daily with ADSP or MESP (2.50 g/kg/day), vehicles, or losartan (0.01 g/kg/day) for 3-week and their SBP was weekly-measured. Phenolic compounds were screened using ferric-chloride test, then gallic acid was determined using HPLC. Results: Acute administration of ADSP (2.50 to 3.00 g/kg) and MESP (2.00 to 3.00 g/ kg) significantly reduced SBP of SHR, but not of WKY rats. Repeated-daily-dose administration of MESP (2.5 g/kg/day) significantly reduced SBP of SHR after 2-week and sustained until 3-week, while ADSP (2.5 g/kg/day) significantly reduced SBP only after 3-week. Gallic acid was the major phenolic-compound in ADSP (157.09 ± 4.18 ppm) and MESP (134.04 ± 10.30 ppm). Conclusion: Oral ADSP and MESP that contain gallic acid possess acute and sub-acute antihypertensive effects in SHR, but MESP’s effect was more prominent than ADSP.
Highlights
Syzygium polyanthum (Wight) Walp or its synonym, Eugenia polyantha is a plant under Myrtaceae family.[1]
There was no significant difference between the means systolic blood pressure (SBP) of the two negative control groups in WKY rats at any specified time intervals used in this study
Our acute study has shown that both oral aqueous decoction (ADSP) and methanol extract (MESP) of S. polyanthum leaves caused significant reductions in SBP of Spontaneously-Hypertensive rats (SHR) rats, observed between the first to six hr post-administration with complete recovery achieved after 24-hr
Summary
Syzygium polyanthum (Wight) Walp or its synonym, Eugenia polyantha is a plant under Myrtaceae family.[1]. Our in vivo study has shown that both extracts significantly lowered the blood pressure of pentobarbital-anesthetized WKY and SHR when administered intravenously.[2] In addition, recent in vivo studies have shown that sub-chronic daily oral treatment for 6-week with ultrasound-assisted methanol extract of S. polyanthum leaves significantly reduced the blood pressure[4] and protected the kidney and aorta of SHR.[4,5] Even though this later study may have addressed the sub-acute antihypertensive ability of S. polyanthum leaves, but the acute 24-hr single-dose effect of oral S. polyanthum leaves was not yet being described This acute study is important for evaluating the sustenance and recovery
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