RESUMO
To investigate the structural characteristics of cell wall pectic polysaccharides from wampee, water soluble pectin (WSP), chelator-soluble pectin (CSP) and sodium carbonate-soluble pectin (SSP) were purified. And the inhibitory effects of wampee polyphenol (WPP) on pectinase when these cell wall pectic polysaccharides were used as substrates were also explored. Purified WSP (namely PWSP) had the lowest molecular weight (8.47 × 105 Da) and the highest GalA content (33.43%). While purified CSP (called PCSP) and SSP contained more abundant rhamnogalacturonan I side chains. All of them were low-methoxy pectin (DE < 50%). Enzyme activity and kinetics analysis showed that the inhibition of pectinase by wampee polyphenol was reversible and mixed type. When SSP was used as the substrate, WPP had the strongest inhibition (IC50 = 1.96 ± 0.06 mg/mL) on pectinase. Fluorescence quenching results indicated that WPP inhibited enzyme activity by interacting with substrates and enzymes. Therefore, WPP has the application potential in controlling softening of fruits and vegetables.
Assuntos
Parede Celular , Pectinas , Poligalacturonase , Polifenóis , Poligalacturonase/química , Poligalacturonase/metabolismo , Pectinas/química , Parede Celular/química , Parede Celular/metabolismo , Polifenóis/química , Polifenóis/farmacologia , Cinética , Peso Molecular , Inibidores Enzimáticos/química , Inibidores Enzimáticos/farmacologia , Polissacarídeos/química , Polissacarídeos/metabolismo , Polissacarídeos/farmacologia , Frutas/química , Extratos Vegetais/química , Extratos Vegetais/farmacologiaRESUMO
This study investigated the regulation effect of magnetic field combined with low temperature storage on postharvest quality and cell wall pectic-polysaccharide degradation of wampee stored for 15 d at 4 °C and 15 °C. Results showed that magnetic field combined with low temperature storage reduced browning rate of fruit after 15 d storage, but its effect on weight loss rate and total soluble solids (TSS) did not surpass that of storage temperature. Interestingly, contents of flavonoid, total phenols and malondialdehyde (MDA) were also lowered at varying degrees by combined treatment. Furthermore, molecular weight distribution and monosaccharide compositions of cell wall pectic-polysaccharides were also affected, which resulted from the coordinated action of cell wall pectin-degrading enzymes. The activities of these enzymes during storage, including polygalacturonase (PG), pectin methylesterase (PME) and ß-galactosidase (ß-Gal) in treated wampee decreased. These findings suggested that magnetic field combined with low temperature storage was an effective technology and had great potential in preservation of postharvest wampee in future.