INTRODUCTION
Plants produce a wide variety of secondary metabolites known as phenolic compounds or polyphenols that possess various biological functions in plants, including phytoalexins, attractants for pollinators, plant pigmentation, antioxidants, and protection against UV light.1,2 Extraction of phenolic compounds depends on the specific forms in which they are present in plants. Extractable phenolics can be in free or in conjugated forms; the latter are generally soluble glycosides of phenolic acids and flavonoids.3 Many phenolic compounds are insoluble, being bound to cell wall polymers through ester and glycosidic links, and are therefore not extractable using organic solvents alone.3 Hydrolysis under alkaline, acidic, or enzymatic conditions is often performed to release these bound phenolics.2 Typical acid hydrolysis conditions for cleaving glycosidic bonds of conjugated phenolic acids or flavonoids to obtain their respective aglycons involve heating at high temperature (>80 °C) for 1−3 h in an aqueous methanol or ethanol solution containing 2−4 N HCl.4,5