Evaluation of Alpha-Amylase Inhibitory, Antioxidant, and Antimicrobial Potential and Phytochemical Contents of Polygonum hydropiper L

Abstract

Polygonum hydropiper L. is a traditionally used medicinal plant. The present study was designed to explore the α-amylase inhibitory, antioxidant, and antimicrobial activities of Polygonum hydropiper L. Polarity-based solvent extracts (n-hexane, acetone, chloroform, methanol, ethanol, and water) of Polygonum hydropiper leaves and stem were used. Antioxidant activity was assessed by free radical scavenging assay (FRAP) and 2,2-diphenylpicrylhydrazyl (DPPH) free radical scavenging activity methods. Quantitative phytochemical analyses suggested that the stem of Polygonum hydropiper L. contains higher levels of bioactive compounds than its leaves (p < 0.05). The results suggested that stem-derived extracts of Polygonum hydropiper L. are more active against bacterial species, including two Gram-positive and three Gram-negative strains. Moreover, our results showed that the bioactive compounds of Polygonum hydropiper L. significantly inhibit α-amylase activity. Finally, we reported the polarity-based solvent extracts of Polygonum hydropiper L. and revealed that the stem, rather than leaves, has a high antioxidant potential as measured by FRAP and DPPH assay with IC₅₀ values of 1.38 and 1.59 mg/mL, respectively. It may also be deducted from the data that the Polygonum hydropiper L. could be a significant candidate, which should be subjected to further isolation and characterization, to be used as an antidiabetic, antimicrobial and antioxidant resource in many industries, like food, pharmaceuticals and cosmetics.

Keywords: DPPH; FRAP; Water-pepper; polarity-based solvent extraction; α-amylase inhibition.

Figure 1

Inhibition of α-amylase activity by different extracts (ethanol, (A); acetone, (B); methanol, (C); n-hexane, (D); chloroform, (E) and water, (F)) of P. hydropiper leaves (PHL) and stem (PHS). Solid lines represent hyperbolic dose–response curves, which were generated in GraphPad Prism. Values represent the means of triplicate measurements (n = 3).

Figure 2

α-Amylase inhibitory activity of the different extracts tested: comparison of IC₅₀ values. The IC₅₀ values were calculated from dose-dependent percent inhibition. Values represent the means of triplicate measurements (n = 3). Bars represent the standard deviation.