Abstract
Eight selected wild vegetables from Nepal (Alternanthera sessilis, Basella alba, Cassia tora, Digera muricata, Ipomoea aquatica, Leucas cephalotes, Portulaca oleracea and Solanum nigrum) were investigated for their antioxidative potential using 2,2-dyphenyl-1-picrylhydrazyl (DPPH) scavenging, hydrogen peroxide (H2O2), ferric reducing antioxidant power (FRAP), and ferric thiocyanate (FTC) methods. Among the selected plant extracts C. tora displayed the highest DPPH radical scavenging activity with an IC50 value 9.898 μg/mL, whereas A. sessilis had the maximum H2O2 scavenging activity with an IC50 value 16.25 μg/mL—very close to that of ascorbic acid (16.26 μg/mL). C. tora showed the highest absorbance in the FRAP assay and the lowest lipid peroxidation in the FTC assay. A methanol extract of A. sessilis resulted in the greatest phenolic content (292.65 ± 0.42 mg gallic acid equivalent (GAE)/g) measured by the Folin–Ciocalteu reagent method, while the smallest content was recorded for B. alba (72.66 ± 0.46 GAE/g). The greatest flavonoid content was observed with extracts of P. oleracea (39.38 ± 0.57 mg quercetin equivalents (QE)/g) as measured by an aluminium chloride colorimetric method, while the least was recorded for I. aquatica (6.61 ± 0.42 QE/g). There was a strong correlation between antioxidant activity with total phenolic (DPPH, R2 = 0.75; H2O2, R2 = 0.71) and total flavonoid content (DPPH, R2 = 0.84; H2O2, R2 = 0.66). This study demonstrates that these wild edible leafy plants could be a potential source of natural antioxidants.
Highlights
The generation of highly reactive oxygen species (ROS) with a lone unpaired electron induce oxidative stress and plays a key role in the pathogenesis of numerous physiological conditions, including cellular injury, aging, cancer, and hepatic, neurodegenerative, cardiovascular and renal disorders [1,2]
A detailed literature review into the phenolic and flavonoid content of the wild vegetables consumed in the Nepalese diet including their antioxidant activity has not been carried out to date [16]
The results were derived from a calibration curve (y = 9.53x − 0.13, R2 = 0.996) of gallic acid (0–250 μg/mL) and expressed in gallic acid equivalents (GAE) per gram dry extract weight (Table 2)
Summary
The generation of highly reactive oxygen species (ROS) with a lone unpaired electron induce oxidative stress and plays a key role in the pathogenesis of numerous physiological conditions, including cellular injury, aging, cancer, and hepatic, neurodegenerative, cardiovascular and renal disorders [1,2]. There are a number of endogenous antioxidant enzymes, such as glutathione peroxidase, catalase and superoxide dismutase, which are capable of deactivating free radicals and maintaining optimal cellular functions [4]. Plants 2019, 8, 96 optimal cellular functions under increased oxidative stress and dietary antioxidants may be necessary [5]. Natural antioxidants from leafy vegetables play a vital role in protecting against the action of free radicals [11]. Many epidemiological studies have shown that the consumption of leafy plant vegetables containing phenolic and flavonoid compounds with potent antioxidant activity are associated with a lower incidence of cardiovascular diseases, cancer, diabetes and neurodegenerative diseases [12]. Nepal were selected to evaluate the phenolic and flavonoid content along with the antioxidant activity for the first time
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