A RAPID UHPLC-DAD-ESI-MSn METHOD FOR ANTHOCYANINS QUANTIFICATION FROM Euterpe oleracea FRUITS HARVESTED AT DIFFERENT TIMES

摘要

Euterpe oleracea is a palm tree widely distributed in northern South America. Its greatest occurrence and economic importance happens in the floodplains of the Amazonian delta. The fruits called açai are an interesting source of different anthocyanins. Lately they have gained popularity in North America and in the European countries in the food industry and in the health sector due to their extremely high antioxidant capacity and potential anti-inflammatory activities [1].Some studies have characterized chemically açaí pulps and have reported anthocyanin profiles which differ both qualitatively and quantitatively. Among other reasons, these differences may be associated with the stages of ripening of the fruits, since açai fruits are generally harvested in different maturation stages. The evaluation of the anthocyanin profile of açai fruits during different maturation stages is thus important for the post-harvest industry. In addition a rapid separation by UHPLC and an unambiguous identification by MSn are very useful for an effective quality control of the fruits.Thus, the aim of this study was to characterize the anthocyanin profiles of açai fruits at different stages of maturity. The fruits were harvested during the peak harvesting season, between July and October 2009, in the floodplains of the eastern Amazonian region (State of Pará, Brazil).A protocol of solid-liquid extraction of phenolic compounds was developed. Characterisation of the anthocyanins present in the fruits of Euterpe oleracea was conducted by UHPLC–DAD–ESI–MSn analysis, in positive ionization mode. All identified compounds was separated in 10 minutes of a total run time of 21 min instead of 55 min in the previously developed HPLC method. Six anthocyanins were identified in the extracts namely: cyaniding-3-glucoside, cyaniding-3-rutinoside, pelargonidin-3-glucoside, peonidin-3-glucoside, peonidin-3-rutinoside and cyanidin. The first two compounds were the major constituents in all maturity stages, with similar proportions, except for the first maturity stage for which the anthocyanins were under the limit of quantification. However, in the last maturity stage, cyanidin-3-glucoside became less abundant than cyanidin-3-rutinoside. On the other hand, cyanidin decreased with maturation. For the other compounds, proportions were similar along maturation.Hence, this work was important as it provides valid information on variation of anthocyanin profiles of açai fruits during maturation. This may contribute to the selection of an optimal maturity stage for harvesting as well as it will allow a rapid quality control of the fruits.[1]: Heinrich, M., et al., Açai (Euterpe oleracea Mart.)- A phytochemical and pharmacological assessment of the species’ health claims. Phytochem. Lett. (2010), doi: 10.1016/j.phytol.2010.11.005