Extraction, Purification And Antioxidant Activity Of Polyphenols From Pineapple Peels

Recently, the health care and disease prevention of polyphenols have increasingly been of concern to people. The discovery of their bioactivity, including radicals scavenging ability, cancer prevention, radioresistance, anti-allergenic, anti-inflammatory, anti-microbial, antioxidant, anti-thrombotic, cardioprotective and vasodilatory effects, have made the research and application of polyphenols increasingly important.Pineapples have become a pillar industry of rural economy of major producing areas in southern part of China. A small part of pineapples are used for direct selling while a large part are used for producing, since the fruit cannot be stored easily. However, not only do the by-product-pineapple peels contain rich protein, crude fibre, but also contain some elements which are need by people, like P、 K、 Ca、 Mg、 Na、 Cu、 Zn、 Fe、 Ni、 Mn、 Co, etc and polyphenols. Therefore, if these peels are not utilized, it is a waste of sources and can be pollute the environment.Pineapple peels were used as materials in this paper. Solvent and ultrasonic extraction were used to extract polyphenols; the resin was used to study the absorption and desorption of polyphenols. The types of polyphenolic compounds were identified. The antioxidant abilities and their antioxidant interactions were evaluated. The results are as follows:1The solvent extraction and ultrasonic extraction of polyphenols from pineapples were studied. The optimal measurement was established by UV-Vis spectrophotometer. The conditions for solvent extraction was optimized by single factor and response surface method:extraction temperature48.4℃, extraction time73.6min, the liquid-solid ratio46.8:1(mL/g), the concentration of ethanol41.6%. The total polyphenols extracted in this conditionwas7.77mg/g. The conditions for ultrasonic extraction was optimized by single factor and orthogonal experiment:the concentration of ethanol50%, liquid-solid ratio40:1(mL/g), extraction time20min, the total polyphenols extracted in this conditionwas7.98mg/g;2The absorption and desorption capability of polyphenols in pineapple peels through macroporous absorption resin were evaluated. The suitable resin was selected by comparing5kinds of macroporous absorption resin’s adsorption and desorption capacity and optimum conditions for absorption and elution of total polyphenols were performed. The results showed that D101is the best and the optimum conditions were:flow rate1.5mL/min, polyphenol concentration3.9mg/mL, washing solution80%ethanol and elution rate1.0mL/min. The content of polyphenols in pineapple peels purified by D101was39.03%;3Three antioxidant models were used to evaluate the antioxidant abilities of pinapple peels extracts (PPE) and sample treated by D101(SD). The results indicated that the total antioxidant activity of PPE was0.037g Vit C equivalents/g while SD was0.029g Vit C equivalents/g; the reducing power of PPE was0.187g Vit C equivalents/g while SD was0.166gVit C equivalents/g; for the DPPH· scavenging ability, the IC50value of PPE was1.13mg/mL while the IC50value of SD was1.47mg/mL. It can be concluded that the antioxidant ability of PPE was better than that of SD;4High Performance Liquid Chromatography-Mass Spectrometry was used to identify the polyphenolic compounds in pineapple peels and their antioxidant interactions were evaluated. The results indicated that gallic acid (31.76mg/100g), catechin58.51mg/100g), epicatechin (50.00mg/100g) and ferulic acid (19.50mg/100g) were found to be the main polyphenolics in pineapple peels. The results of antioxidant activity assays indicated that the order of DPPH· scavenging capacity of these polyphenolic compounds was gallic acid> epicatechin> catechin> ferulic acid. Additive effects were found in the combinations of ferulic acid-epicatechin and ferulic acid-gallic acid but antagonistic effects were found in the other four combinations; while the order of the total antioxidant activity of per mole of these compounds was epicatechin.> catechin> gallic acid> ferulic acid and additive effects were found in all the combinations. Therefore, the compounds contributing the most to the pineapple peels may be polymeric phenolics or some other antioxidant compounds.