Abstract
Many Premna species have been used in traditional medicine to treat hypertension and cardiac insufficiency, and as a tonic for cardiac-related problems. Some have been reported to possess cardiovascular protective activity through several possible mechanisms, but not Premna foetida. In the present study, the methanol extract of P. foetida leaves (PFM) and its isolated compounds were evaluated for their ability to inhibit copper-mediated human low-density lipoprotein (LDL) oxidation and arachidonic acid (AA)- and adenosine diphosphate (ADP)-induced platelet aggregation. Six flavonoids, three triterpenoids, vanillic acid and stigmasterol were successfully isolated from PFM. Of the isolated compounds, quercetin was the most active against LDL oxidation (IC50 4.25 µM). The flavonols were more active than the flavones against LDL oxidation, suggesting that hydroxyl group at C-3 and the catechol moiety at B-ring may play important roles in protecting LDL from oxidation. Most tested flavonoids showed stronger inhibition towards AA-induced than the ADP-induced platelet aggregation with apigenin exhibiting the strongest effect (IC50 52.3 and 127.4 µM, respectively) while quercetin and kaempferol showed moderate activity. The results suggested that flavonoids, especially quercetin, apigenin and kaempferol were among the major constituents of P. foetida responsible for anti-LDL oxidation and anti-platelet aggregation.
Highlights
Herbs have been widely used as food supplements, flavors, and in traditional medicine, which directly and indirectly benefit the body against cardiovascular risk conditions such as hyperlipidemia or hypercholesterolemia
The plants could be acting as lipid lowering agents, antioxidants, especially towards low-density lipoproteins (LDL), regulator of biochemicals and immunochemicals contributing to atherogenesis, and as antithrombotic agents [1,2]
The results indicated that: (i) more free hydroxyl groups would likely result in higher antioxidant activity; (ii) two adjacent hydroxyl groups on the B ring exerted superior antioxidant effect compared to the double bond and carbonyl groups on the C ring; (iii) a free hydroxyl group at C-3 and C-7 of the C ring contributed to the antioxidant activity with free 3-OH providing better antioxidant capacity than the 7-OH
Summary
Herbs have been widely used as food supplements, flavors, and in traditional medicine, which directly and indirectly benefit the body against cardiovascular risk conditions such as hyperlipidemia or hypercholesterolemia. The cardiovascular-protective activity from these plants is often derived through interventions in lipid metabolism and/or protein regulation of the vascular and related homeostasis systems. The plants could be acting as lipid lowering agents, antioxidants, especially towards low-density lipoproteins (LDL), regulator of biochemicals and immunochemicals contributing to atherogenesis, and as antithrombotic agents [1,2]. LDL is a unique molecule that can fuel the atherogenosis process once it has gone through oxidation or modification process within the arterial wall due to chronic immune-inflammation [3]. The oxidized LDLs (Ox-LDLs) are taken up by the macrophages which engulf the lipids (especially cholesterol) including the ox-LDL and convert the macrophage into lipid-laden foam cells. Ox-LDL attracts the monocytes and induces more inflammation and endothelial dysfunction, contributing to the more advanced atherosclerotic lesion stage [4]
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