New insights into phenol and polyphenol composition of Stevia rebaudiana leaves.

The diversity in phenols and polyphenols of stevia leaf has been simplified applying sequential fractionation techniques on its ethanol extract through ultrasound assisted maceration. Two of the fractions obtained by reverse-phase column chromatography resulted differently active in an extensive antioxidant and cytotoxic screening. Both fractions were chemically profiled by ultra-performance liquid chromatography (UHPLC) coupled with electrospray ionization (ESI) quadrupole/time-of-flight (QqTOF) mass spectrometry (MS). One of the fractions was composed mainly of chlorogenic acids and flavonol triglycosides, whereas the other was rich in flavonoids mono- and diglycosides and in their hydroxycinnamoyl derivatives. Among the fifty compounds identified, non-phenol metabolites, such as benzyl primeveroside and roseoside, as well as a lignan polyphenol (5'), are reported for the first time as constituents of the Stevia leaf.