Polyphenol Compounds and Antioxidant activity of Water Lettuce (Pistia stratiotes) Leaf Extract with Different Drying Methods

Abstract

Increasing of free radicals cause damage to cells and tissues in the body. This is due to the lack of antioxidant ability in the body, therefore it requires external antioxidants. One of the plants that can be used as a source of antioxidants is water lettuce (Pistia stratiotes) because it contained polyphenol compounds. However, polyphenolic compounds are thermolabile, so the drying process is important in preparation and extraction. Thus, this study aimed to extract polyphenolic compounds from the leaves of the water lettuce (Pistia stratiotes) with different drying methods and to determine the antioxidant activity of these compounds. Drying was carried out by 3 different methods, namely sun drying, oven at 40ºC, and freeze drying and with 3 times repetition. The data were analyzed using a one-way analysis of variance (ANOVA) with Duncan’s post-hoc test and presented in graphical form. The freeze-drying (15.64±1.19%) method showed high extraction yield when compared to oven-drying (13.54±1.83%) and sun-drying (8.48±3.34%). Total polyphenols and flavonoids were also high in the freeze-drying method (32.94±1.34 mg GAE/g dry sample and 146.80±5.29 mg QE/g dry sample, respectively). Whereas the antioxidant activity of freeze-drying (IC50 266.33±5.77 mg/mL) and oven-drying (IC50 305.67±22.85 mg/mL) had more effective in inhibiting free radicals when compared with sun-drying (IC50 462.67±56.52 mg/mL). Therefore, freeze-drying and oven-drying can be an option as an appropriate drying method to extract polyphenol and flavonoid compounds which are used as antioxidants.