Seasonal monitoring of the antioxidant activity of Erythroxylum suberosum A. St.-Hil. leaves: Correlation with hyperoside and isoquercitrin contents

Abstract

This study evaluated the seasonal effects of two flavonoids on antioxidant activity and chromatographic profiles by thin layer chromatography and high-performance liquid chromatography (HPLC) in Erythroxylum suberosum A. St.-Hil, a species used by the Brazilian indigenous community. These variables were observed from August 2013 to May 2014 in correlation with climatic variables, such as temperature, rainfall index and global radiation. The chromatographic profiles were found to be similar in the aqueous and ethanol extracts, and flavonoid hyperoside and isoquercitrin were identified and quantified. In the inhibition of the DPPH• radical, the most active was the aqueous extract from the 2nd collection (IC50: 4.45 μg/mL). For the phosphomolybdenum complex reduction method, the ethanol extract from the 1st collection was the most active (206.39 μg/mL equivalent ascorbic acid). Regarding the environmental correlations, it was observed that a higher global radiation index had a strong influence on the concentrations of hyperoside and contributed to the antioxidant activity. On the other hand, higher temperatures contributed to a higher isoquercitrin content in the aqueous extracts. These results indicate that August is the best month for the collection of Erythroxylum suberosum A. St.-Hil. leaves which have the highest isoquercitrin and hyperoside content and, thus, a high antioxidant activity.