Influence of Extracting Solvent on Pharmacological Activity and Cytotoxicity of Polygonum minus, a Commonly Consumed Herb in Southeast Asia

OBJECTIVE: To investigate the antihyperlipidemic, antioxidant, and cytotoxic effect of aqueous and methanol extract of leaves of Polygonum minus. MATERIALS AND METHODS: Acute antihyperlipidemic effect was studied on chemically induced hyperlipidemic rat model. Treated groups received aqueous and methanol extract of leaves of P. minus respectively (1000 mg/kg; oral) whereas standard treated group received atorvastatin (60 mg/kg; oral) for 3 consecutive days. Blood samples were collected at fixed intervals for lipid profile analysis. Antioxidant effects were studied using 1,1-diphenyl-2-picrylhydrazyl, 2,2-azinobis 3-ethylbenzothiazoline 6-sulfonate, and ferric reducing antioxidant power assays. The total flavonoids content and total phenolic contents were also estimated. Cytotoxicity of both extracts was studied on one normal and three cancer cell lines using 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) assay method. RESULTS: The methanol extract showed significant reduction in total cholesterol (P < 0.001), triglycerides (P < 0.01), LDL (P < 0.05), VLDL (P < 0.01), atherogenic index (P < 0.001), and elevation of HDL (P < 0.05) levels than the aqueous extract. Similarly, the antioxidant investigations also demonstrated that the methanol extract had higher antioxidant capacity than aqueous extract. Both extracts were not toxic to normal (EA.hy926) as well as to cancer (HCT116, HT29, and HeLa) cells. Significant correlation was demonstrated between total phenolic and total flavonoids contents with the antioxidant activity but not with the antihyperlipidemic effect, suggesting other groups of chemical constituents may be mainly responsible for the antihyperlipidemic effect of this plant. CONCLUSION: The study demonstrated that the presence and extent of bioactivities are influenced by solvents used for extraction. This study confirmed the antihyperlipidemic effect of leaves of P. minus in acute hyperlipidemic rat model. SUMMARY: Polygonum minus is an herbaceous flowering plant. This plant possess high amount of phenolics and flavonoids. This study focused on the antioxidant, cytotoxicity and antihyperlipidemic effect of aqueous and methanol extracts of leaves of P. minus. The extracts possess significant antioxidant activity and antihyperlipidemic activity but they are not toxic to normal and cancer cells tested. The antioxidant activity is well correlated with phenolic and flavonoids contents but the antihyperlipidemic activity is not correlated with antioxidant effect. Abbreviations used: CVDs: Cardiovascular diseases, LDL: Low-density lipoprotein, DDPH: 1,1-Diphenyl-2-picrylhydrazyl radical, TPTZ: 2,4,6,-tris(1-pyridyl)-5-triazine, ABTS: 2,2’-Azino-di-[3-ethylbenzthiazoline Sulfonate], HDL: High-density lipoprotein, VLDL: Very low-density lipoprotein, TC: Total cholesterol, TG: Triglycerides, EC50: Half maximal effective concentration, LD50: Median lethal dose.