Evaluation of apple pomace extracts as a source of bioactive compounds

Pomaces of four different apple cultivars (Gala v. Royal Gala Tenroy, Golden v. Golden, Granny Smith, and Pink Lady v. Cripps Pink) were submitted to microwave assisted extraction with various solvents (MeOH/H2O mixture, ethanol and ethyl acetate) in order to recover their bioactive compounds. The analyses of the obtained extracts by HPLC coupled to different detection modes such as UV, ELSD or MS revealed the presence of various phenolic and terpenic compounds. Major phenols were benzoic acids (gallic acid), hydroxycinnamic acids (chlorogenic acid), flavanols (catechin), flavonols (rutin) and chalcones (phloridzin). Among the terpenes, triterpenic acids as ursolic acid were the most abundant but triterpenic acid derivatives with coumaryl group were also detected. The apple pomace extracts and fractions obtained by successive liquid-liquid extraction were able to inhibit the DPPH free radical. According to the FRAP assay results, these extracts presented also good reducing properties. The total phenolic and total flavonoid contents were correlated to the antioxidant activity thus confirming that apple pomaces are a valuable source of bioactive molecules. (C) 2013 Elsevier B.V. All rights reserved.