Effect of Drying Methods on the Antioxidant Capacity, Color and Phytochemicals of Portulaca oleracea L. Leaves

Khaled M Youssef,Sayed M Mokhtar

doi:10.4172/2155-9600.1000322

Abstract

Portulaca oleracea is globally used both as a vegetable and as an herb for medical and therapeutic purposes; hence the need to investigate its phytonutrients. The aim of this study was to evaluate the effects of different drying methods (hot-air drying, microwave drying and freeze-drying) on the color, phytochemicals content and antioxidant capacity of purslane leaves. The fresh purslane leaves had high contents of total phenolics (1447.59 mg GAE/ 100 g) and flavonoids (5011.87 mg QE/ 100 g) on dry weight basis. They exhibited high antioxidant capacity (53.23% and 147.78 μmol trolox/ 100 g) measured by DPPH and ABTS assay, respectively. Chromatic coordinates (L*, a* and b*) as well as total color difference (ΔE) were affected by drying methods. Drying methods caused a significant decrease in total phenolics, total flavonoids and antioxidant capacity of purslane leaves. Drying by hot-air at 50oC and freezedrying had the lowest adverse effects on antioxidant capacities of purslane leaves while microwave drying cannot be a competitive process for preserving antioxidants and antioxidant capacity of purslane leaves. The changes in the antioxidant capacity due to the drying methods were positively correlated with the content of phenolics (R2= 0.9043- 0.9885). Therefore, it can be suggested that special care should be taken when processing method is selected for the exploration of purslane leaves.

Highlights

Purslane (Portulaca oleracea L., Portulacaceae family) is a wellknown edible plant, widespread in temperate and tropical regions of the world
A 100 g of purslane leaves were spread on the glass plate inside the microwave cavity and processed until the leaves were completely dried at three microwave output powers (360, 900 and 1250 W)
All drying methods increased brightness (L*), which indicated that dried leaves had a bright color as compared with fresh samples

Summary

Introduction

Purslane (Portulaca oleracea L., Portulacaceae family) is a wellknown edible plant, widespread in temperate and tropical regions of the world It is an herbaceous and annually plant with a fleshy stem and thick, green, succulent leaves and small black seeds that have medicinal properties. From the point of view of traditional medicine, the nature of purslane is cold and wet, astringent and diuretic, bile anodyne that relieves temperature of blood, liver and stomach. It is useful in the elimination of headaches, thirst relief, stoppage of bleeding, crushing of bladder stones and reduction of coughing and irritation of urethra, bladder, intestines, and hemorrhoids and used as a health food for patients with cardiovascular diseases [3]. The methanolic extract of purslane was found to exhibit moderate antimicrobial activity against Bacillus subtilis, which referred to a monoterpene glucoside named portuloside A [4]

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