Flavonoid Profiles of Arbutus unedo L. pomaces

The fruits of Arbutus unedo L., an evergreen shrub/small tree widespread in the region of Algarve, are the raw material used to prepare "Aguardente de Medronho" a Portuguese protected geographical indication distillate. This spirit drink has been mainly prepared traditionally in small distilleries. However, the expected increase of cultivated areas demands for the development of new modern distilleries as well as the search for a fate to the resulting pomaces. In searching for the valorization of "Aguardente de Medronho" pomaces a detailed characterization of the final product is necessary. The fermentation as well as the distillation processes are expected to play a major role in defining the compounds of the resulting pomaces. In this work, we present a study of the change of Arbutus unedo fruits flavonoids after distillation. The identification as well as the quantification of major compounds in fruits and pomaces was performed by LC-MS. The fermentation and distillation processes significantly change the flavonoid profiles. Major flavonoids of fruits are flavonol glycosides, most likely quercetin glucoside and quercetin rhamnoside, while in pomaces the correspondent aglycone structures were observed. This observation suggests that fermentation/distillation processes lead to deglycosylation of flavonols. Total contents of flavonols in fruits were estimated to be about 2.5 mg/100 g. Fermentation/distillation increased the total flavonoid content about to 2 times.