Polysaccharides from pineapple pomace: new insight into ultrasonic-cellulase synergistic extraction and hypoglycemic activities

Abstract

This study determined the optimal extraction conditions for ultrasonic-cellulase synergistic extraction of polysaccharides from pineapple pomace (PPP) using Plackett–Burman design and response surface methodology. The optimal hydrolysis temperature, ratio of material to water, pH value, hydrolysis time, ultrasonic power and the additive quantity of cellulase were 50 °C, 1:45 g/mL, 6.0, 100 min, 160 W and 2.0%, respectively, giving a extraction yield of 1.10 ± 0.03%. PPP was further isolated and purified by DEAE-52 cellulose and Sephadex G-100 chromatography columns, revealing four main elution peaks, named PPF0, PPF1, PPP2 and PPF3, were obtained. The molecular weight, monosaccharide compositions, structural features and appearance morphology of polysaccharide fractions (PPFs) were analyzed by high-performance liquid chromatography (HPLC), gel permeation chromatography (GPC), UV spectroscopy, fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). Furthermore, the hypoglycemic activities of PPFs with different concentrations were also investigated by insulin resistance HepG2 cells model in vitro. Results showed that PPF0, PPF1, PPF2 and PPF3 were composed of mannose, rhamnose, glucuronic acid, galacturonic acid, glucose, galactose, xylose, arabinose and fucose with molecular weight of 6.71 × 104, 1.11 × 104, 2.22 × 104 and 5.1 × 103 Da, respectively. All of them could alleviate the development of insulin resistance HepG2 cells with a dose-dependent relationship. The glucose consumption increased 46.4%, 50.5%, 82.1% and 53.6%; 86.8%, 81.6%, 86.8% and 84.2% at the concentration of 20 μg/mL, respectively, without or with insulin. These results suggested that PPFs can be explored as a potential hypoglycemic agent in biomedical and functional food.