Composition and activity changes of the soluble water and ethanol extracts from white mulberry (Morus alba L.) fruits in response to thermal treatment

Abstract

This study investigated the impact of a thermal treatment at 100 °C on the compositions and activities of the two soluble extracts from white mulberry fruits. Lyophilized white mulberry fruits were extracted using water and ethanol–water (75%, v/v) solvents, followed by various extract treatments like ethanol removal, activated carbon-mediated dephenolization, or 100 °C thermal treatment of 15–45 min. The thermal treatment caused increased values for total phenols and flavonoids contents; subsequently, the values for total phenol contents (expressed as gallic acid equivalent) of the water- and ethanol-extracts were enhanced from 110.0 and 146.5 to 120.9 and 161.3 mg/L, while the values for total flavonoid contents (expressed as quercetin equivalent) were increased from 19.0 and 23.4 to 28.2 and 30.4 mg/L, respectively. However, the thermal treatment time-dependently decreased the anti-oxidation of these heated extracts that consistently showed lower activities to scavenge the DPPH, ABTS, and hydroxyl radicals, or lower efficiencies to reduce Fe3+. The water- and ethanol-extracts also showed three activities in human colon cancer HCT-116 cells, resulting in growth inhibition, morphology change, and the generation of intracellular reactive oxygen species. Moreover, the heated extracts received activity increases in the cells, compared with the unheated extracts. In brief, the Maillard reaction during the thermal treatment might partly make contribution for the activity increases. It is thus concluded that the thermal treatment of these extracts at 100 °C resulted in composition and activity changes due to the Maillard reaction and other unidentified reactions, which might endow the heated extracts with weakened anti-oxidation but increased activity against HCT-116 cells.