Abstract
<p><strong>Objective: </strong>The current study was to deal the isolation and identification of secondary metabolites from <em>Polygonum equisetiforme</em> and evaluation of antioxidant activity of its extract.</p><p><strong>Methods: </strong>The methanol-water extract (7:3) of the air-dried aerial parts of <em>Polygonum equisetiforme</em> was fractionated and separated to obtain the isolated compounds by different chromatographic techniques. Structures of these compounds were elucidated by UV and 1D⁄2D H⁄ C NMR spectroscopy and compared with the literature data. The crude extract was evaluated for <em>in vitro</em> antioxidant activity using the 2,2 diphenyl dipicryl hydrazine (DPPH) method.</p><p><strong>Results: </strong>Ten secondary metabolites were isolated from <em>Polygonum equisetiforme</em> in this study. Of which three new flavonoids named as 3,5,7,2’,5’ pentahydroxyflavone 3-<em>O</em>-b-D-glucopyranoside (1), 3,5,7,2’,5’ pentahydroxyflavone 3-<em>O</em>-b-D-glucopyranoside 8 C-sulphated (2) and quercetin 3-<em>O-β</em>-D-glucucorinde 6''-methyl ester 8-sulphated (3) as well as quercetin 3-<em>O-β</em>-D-glucucorinde methyl ester (4), quercetin 3-<em>O-</em>β-D-glucopyranoside (5), quercetin 7-<em>O-β-</em>D-glucopyranoside (6),<em> </em>quercetin(7)<sub>, </sub>myricetin (8), <em>P</em><sub>-</sub>methoxy gallic acid methyl ester (9) and gallic acid (10). The antioxidant potential of <em>P. equisetiforme</em> extract was evaluated by investigating it's total phenolic and flavonoid content and DPPH radical scavenging activity whereby the extract showed significant antioxidant activity (IC<sub>50 </sub>= 37.45 μg/ml). The total phenolic and flavonoid content was found to be 130.79±5.502 and 45.8±1.63 μg/ml, respectively.</p><p><strong>Conclusion: </strong><em>Polygonum equisetiforme</em> is a promising medicinal plant, and our study tends to support the therapeutic value of this plant as an antioxidant drug.</p>
Highlights
Polygonaceae comprises about 40 genera and 800 species [1], distributed throughout the world, especially in temperate and warm regions
Ten secondary metabolites were isolated from Polygonum equisetiforme in this study
The secondary metabolites identified in the species of the Polygonum genus are flavonoids [3,4,5,6], anthraquinones [7], lignan glycosides [8], polysaccharides [9], phenylpropanoid glycosides [10], sesquiterpene [11,12,13] and stilbenes [14, 15]
Summary
Polygonaceae comprises about 40 genera and 800 species [1], distributed throughout the world, especially in temperate and warm regions. Polygonum is the largest genus belonging to the family Polygonaceae, which comprises about 300 species. Some species are used in the treatment of cough, diarrhea, diuretic agent and to treat urinary inflammation [16]. The medicinal properties of Polygonum species are due to its high constituents of bioactive compounds. Polysaccharide derivatives with radical scavenging and anti-tumour activities have been isolated from many Polygonum species [24, 25]. Flavonoids and chalcones isolated from some species of Polygonum on the other hand exhibit strong antioxidant effects role against oxidative stress damages, such as arteriosclerosis or cancer [26,27,28,29]. The current study was focused on the isolation and identification of flavonoids from the aqueous methanol extract of P. equisetiforme aerial parts, determination of the total phenolic and flavonoid contents together with studying the antioxidant activity of the extract
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