Antioxidant capacity and oligosaccharides profile of pineapple peel (Ananas comosus cv. Haiti)

Fruit consumption has become a concern of health due to the vital fruit nutrients content and secondary phytochemical compounds. Diets rich in bioactive compounds have been associated with a reduced risk of diseases such as certain types of cancer, inflammation and neurodegenerative and gastrointestinal disorders. Therefore, research on the functional compounds presents in fruits has increasingly engaged the interest of scientists in recent years¹. Pineapple is a tropical fruit popular throughout the world. It is rich in the antioxidants namely flavonoids, vitamin A and C. After pineapple processing, many thousands of tons of peel are produced as an agricultural byproduct. The pineapple peel is well known ingredients in ethnomedicine and could be a potential source for the extraction of beneficial bioactive compounds.² The present study was carried out in order to evaluate the antioxidant capacity and oligosaccharides profile in pineapple peel. The ripe fruits were obtained at local market and the peel were manually separated and freeze-dried. The extraction of bioactive compounds was performed according Neri-Numa et al.³, with modifications. The pineapple peel freeze-dried powder (PPD) was homogenized with aqueous ethanol (1:1 v/v, water:ethanol) for 1 min with Ultra Turrax (11,000 RPM) at room temperature. The homogenate was centrifuged at 10,000 RPM for 10 min under 5°C; the supernatant was utilized for analysis. Total phenolics (TP) were determined using the Folin-Ciocalteu method and the results were expressed as g of gallic acid equivalents (GAE)/100g of fruit dry weight (DW). Furthermore, flavonoids content (FC) was measured using a colorimetric assay, the results were expressed as g of catechin equivalents (CE)/100g DW. Antioxidant capacity (TAC) was determined through two different method including ABTS and DPPHIC50. TP, FC and TAC were determined as described by Neri-Numa et al.3 The oligosaccharides content was analyzed by high performance anion exchange chromatography-pulsed amperometric detection (HPAEC-PAD) according the method described by Der Agopian et al.4, with modifications. TP and FC were 0.79±0.01 g GAE/100g and 0.39±0.05 g CE/100g DW, respectively. About the free radicals scavenging assays pineapple peel showed 4.45±0.10 mg DW/mL and 46.37±2.48 μmol trolox equivalents/g DW to DPPHIC50 and ABTS, respectively. These data suggest that pineapple peel is good dietary source for phenolic antioxidants. The total oligosaccharides content were 117.23±1.14 mg/100g DW, of which 1-kestose (GF2), maltotriose (G3) and maltotetraose (G4) were the principal compounds detected, observing values in order of 43.33±0.86, 48.53±0.31 and 17.86±0.28 mg/100g DW, respectively. Due to the low quantities present, below the functional recommended dose, PPD cannot be considered a good source of oligosaccharides. However, some compounds could not be identified because absence of commercial standards. Therefore, the content of oligosaccharides can be major than presented in this work. Thus, is clear that PPD is valuable source of some biologically active compounds, including antioxidants and prebiotics. The obtainment these bioactive compounds from agricultural byproducts is a relevant aspect, thus future studies should be conducted to better characterize the functional compounds and promote the food technology application of pineapple peel.