Abstract
Fruits and vegetables are considered a good source of polyphenols and antioxidant capacities which are beneficial in protecting the human body against damage induced by reactive species. The objective of this work is to conduct an assessment of the polyphenol content and antioxidant activities of different fruit (kiwi, pear, green apple, raspberry, blackberry, strawberry and blueberry) and vegetable (pumpkin, green and red pepper) extracts using both chemical extraction and a modified in vitro digestive enzymatic extraction in order to compare results. Polyphenol content and antioxidant capacity of different fruits, vegetables and fruit juices were determined by Folin-Ciocalteu and FRAP methods, respectively. It was observed that polyphenol content expressed as gallic acid equivalents of extracts obtained with the two extraction methods was significantly (p<0.05) different (on average 310.3 and 231.8 mg per 100 g of fresh sample in enzymatic and methanolic extracts, respectively). Antioxidant capacity was also significantly (p<0.05) different in the extracts obtained by the two methods, with higher values in enzymatic extracts (1.91 mmol of Fe2+ per 100 g of fresh sample). Analyses of apple samples with and without skin also revealed important differences related to methodology and composition. Additionally, the original enzymatic extraction method was improved to avoid interferences caused by the presence of protein residues in the extract.
Highlights
Fruits and vegetables are an essential part of the human diet, and several epidemiological studies show that the content of natural antioxidants, especially flavonoids, may be beneficial in protecting the human body against damage induced by reactive species
The enzymatic extraction clearly showed its effectiveness by enhancing the antioxidant capacity and polyphenol content of extracts
The original enzymatic method was improved in order to avoid interference by protein residues found in the samples, which was accomplished by protein precipitation
Summary
Fruits and vegetables are an essential part of the human diet, and several epidemiological studies show that the content of natural antioxidants, especially flavonoids, may be beneficial in protecting the human body against damage induced by reactive species This is important for maintaining physiological redox equilibrium [1,2]. Polyphenols are compounds with aromatic structure, with one or more hydroxyl groups, which undergo physical and chemical changes by action of enzymes and chemical reactions in plants caused by the activity of other active components, such as coumaroyl and malonyl coenzyme A These changes contribute to the process of maturation and physical alterations of the vegetable matrix [5]. Different chemical methods for extraction of polyphenols from food matrices have been applied in order to study the polyphenol content of food Most of these methods use organic solvents with acidic pH and high temperatures during standardized times to optimize the extraction of compounds. These methods may have lower extraction efficiency [8,9,10,11] and it is necessary to purify the obtained extract or remove interfering components in order to improve the antioxidant activity of the extract
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