A galacturonic acid-rich polysaccharide from Diospyros kaki peel: Isolation, characterization, rheological properties and antioxidant activities in vitro.

This research elucidated the structural characteristics and antioxidant activity of a galacturonic acid-rich polysaccharide (PPP-2) isolated from Diospyros kaki peel. PPP-2 was extracted by subcritical water and subsequently purified by DEAE-Sepharose FF column. PPP-2 (12.28 kDa) mainly contained galacturonic acid, arabinose, and galactose with the molar ratios of 87.15: 5.86: 4.31. The structural characteristics of PPP-2 were revealed through FT-IR, UV, XRD, AFM, SEM, Congo red, methylation, GC/MS assay and NMR spectrum. PPP-2 owned the triple helical structure and degradation temperature of 251.09 ℃. The backbone of PPP-2 was formed by â†’4)-α-d-GalpA-6-OMe-(1→ and â†’4)-α-d-GalpA-(1→ with the side chains of â†’5)-α-l-Araf-(1→, →3)-α-l-Araf-(1→, →3,6)-ß-d-Galp-(1→ and α-l-Araf-(1→. Moreover, the inhibitory concentration (IC50) of PPP-2 to ABTS•+, DPPH•, superoxide radical and hydroxyl radical were 1.96, 0.91, 3.63, and 4.08 mg/mL, respectively. Our results suggested that PPP-2 might be a novel candidate of natural antioxidant in pharmaceuticals or functional food.

Extraction optimization and characterization of persimmon peel pectin extracted by subcritical water.

Persimmon peel pectin (PPP) was extracted by subcritical water via the response surface methodology. The optimal crude PPP extraction yield of 7.62 ± 0.7 % was found at 138 °C, 2.84 min, and liquid-solid ratio of 1:10.02. After treatment of deproteinization and decolorization with papain and hydrogen peroxide, 83.19 % of protein and 78.56 % of the colour in crude PPP were removed, respectively. PPP owned the Mw of 21.79 kDa and its uronic acids content was 64.03 %. PPP was further affirmed by fourier transform infrared, X-ray diffractometer and 1H NMR analysis. Moreover, the degradation temperature (228.05 â„ƒ) of PPP was verified via differential scanning calorimetry. Then, the IC50 of PPP to ABTS•+ was 9.8 times that of commercial citrus pectin. Moreover, PPP could change microbial communities and selectively enrich Bacteroides, Cetobacterium, Erysipelatoclostridium, Parabacteroides and Phocaeicola sartorii. This study demonstrated that subcritical water was practicable for extraction of persimmon peel pectin.