There are many techniques to recover antioxidants from
plants, such as Soxhlet extraction, maceration, supercritical
fluid extraction, subcritical water extraction, and ultrasoundassisted
extraction. However, extraction yield and antioxidant
activity not only depend on the extraction method but
also on the solvent used for extraction. The presence of
various antioxidant compounds with different chemical
characteristics and polarities may or may not be soluble in a
particular solvent [5]. Polar solvents are frequently used for
recovering polyphenols from plant matrices. The most suitable
solvents are aqueous mixtures containing ethanol,
methanol, acetone, and ethyl acetate. Ethanol has been
known as a good solvent for polyphenol extraction and is
safe for human consumption. Methanol has been generally
found to be more efficient in extraction of lower molecular
weight polyphenols, whereas aqueous acetone is good for
extraction of higher molecular weight flavanols [6]. The
maximum total phenolic content was obtained from barley
flour by extraction using a mixture of ethanol and acetone [7].
For extracting flavonoids from tea, aqueous ethanol performed
better than aqueous methanol and aqueous acetone
[8]. Extracts with the greatest antioxidant activity were obtained
in mate tea and black tea by using 50% aqueous
ethanol and 50% aqueous acetone, respectively [5].