Abstract
Abstract: The objective of this work was to evaluate different solvents and times in the ultrasound-assisted extraction of polyphenols, in order to quantify the total phenolic and flavonoid contents in and the antioxidant activity of mate (Ilex paraguariensis) leaves. The experiment was carried out in a completely randomized design, in a 8x3 (solvent x time of extraction) factorial arrangement. The solvent extractors were distilled water and aqueous solutions of ethanol, acetone, and methanol, acidified or not with hydrochloric acid, and the time of ultrasound-assisted extractions were 15, 30, and 45 min. All extractions were finished with a mechanical agitation of 30 min. Samples treated with acidified hydroalcoholic solvents resulted in higher values of total phenolics and flavonoids and antioxidant activity. The extraction using acidified hydroethanol solvent was not affected by the time in the ultrasound. The contents of total phenolics and flavonoids were highly correlated with each other and with the antioxidant activity, especially when it was determined by the ferric-reducing antioxidant power method. Acidified hydroethanol solvent in ultrasound for 15 min is the most suitable extraction condition for the quantification of the contents of total phenolics and flavonoids in and the antioxidant activity of mate leaves.
Highlights
IntroductionSince the solubility of polyphenols in a given solvent is a peculiar feature of the sample composition, there is a lack of a universal standard procedure and, a careful check of the extraction method for each natural source is necessary (Caetano et al, 2009)
There are some studies on the use of solvents of varying polarity on vegetable matrices that aimed to identify different chemical classes present in the extracts produced with different solvents (Michiels et al, 2012)
The samples treated with acidified hydroalcohol solvents showed higher values of total phenolic and flavonoid contents than nonacidified treatments, and their contents were not affected by the time of extraction with hydroethanol
Summary
Since the solubility of polyphenols in a given solvent is a peculiar feature of the sample composition, there is a lack of a universal standard procedure and, a careful check of the extraction method for each natural source is necessary (Caetano et al, 2009). Solvents such as methanol, ethanol, and acetone can be used for the extraction of polyphenols (Naczk & Shahidi, 2004; Michiels et al, 2012)
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