Relationship between antioxidant activity of apples derivatives and polyphenols content determined by different methods

The antioxidant activity of apple and apple derivatives was determined by the DPPH· radical scavenging activity (RSA) using different types of extraction and the products total polyphenol (TPP) content was evaluated both by the Folin-Ciocalteau reaction and an electrochemical biosensor. Alcoholic extraction of polyphenols showed high efficiency on solids matrices whilst water extraction showed high efficiency on liquid matrices. Extraction by hot solvents did not determined higher extractive efficiency than cold extraction. Alcoholic extracts from solid matrices showed higher antioxidant activity than the respective acqueous extracts. Hot solvent extraction determined higher antioxidant activity of the extracts than cold solvent extraction but similar phenolic content, thus showing to influence to a greater extent the quality of the extracted phenolic compounds than their overall quantity.The antioxidant activity of apple products extracted using different solvents showed to be significantly related to the concentration of polyphenols determined by both the electrochemical and the Folin-Ciocalteau methods, also if the former was better correlated to RSA. This because the electrochemical detection of TPP with the biosensor minimize the interference of reducing substances that could interfere in the TPP determination by the Folin-Ciocalteau method; in fact the former method is based on an enzymatic reaction specific for the phenolic functional groups.[...]