Isolation, structure and biological activity of polysaccharides from the fruits of Lycium ruthenicum Murr: A review.

The ripe fruits of Lycium ruthenicum Murr. (black wolfberry) have been utilized as folk medicine and nutritional food for thousands of years. L. ruthenicum fruits are rich in polysaccharides, anthocyanins, phenolic acids, carotenoids, alkaloids, vitamins, essential oils, etc. Among them, polysaccharides are considered as the major bioactive components in L. ruthenicum fruits. In the past decade, polysaccharides have been isolated from L. ruthenicum fruits by physical and enzymatic methods. The structural characterization of L. ruthenicum polysaccharides (LRPS) is associated with the separation and purification methods of polysaccharides as well as the planting region of L. ruthenicum. Moreover, LRPS possess several biological activities, such as anti-oxidant, anti-radiation, anti-fatigue, heptatoprotective, immunomodulatory, neuroprotective, hypoglycemic, anti-osteoporosis, anti-tumor and prebiotic activities. For the first time, this review presents the recent advances on the isolation, structure and bioactivities of LRPS. Also this review highlights the challenges of existing studies and future perspectives on LRPS.

Structure, stability and antioxidant activity of dialdehyde starch grafted with epicatechin, epicatechin gallate, epigallocatechin and epigallocatechin gallate.

BACKGROUND: Catechins, a member of the flavonoids, exist widely in teas, and have health benefits. However, catechins have poor stability, which greatly limits their application. In order to improve the stability of catechins, different catechins including (-)-epicatechin (EC), (-)-epicatechin gallate (ECG), (-)-epigallocatechin (EGC) and (-)-epigallocatechin gallate (EGCG) were conjugated onto dialdehyde starch by acid-mediated coupling method. The structure, stability and antioxidant activity of dialdehyde starch-catechin conjugates were determined. RESULTS: Thin-layer chromatography and ultraviolet-visible spectroscopy, fluorescence, nuclear magnetic resonance and infrared spectra revealed that catechins were successfully conjugated onto dialdehyde starch, coupling between 6-H/8-H of catechins' A ring and dialdehyde starch's aldehyde groups. The conjugates presented an amorphous structure and sheet-like and/or blocky morphologies. As compared to dialdehyde starch, the conjugates showed enhanced thermal stability. Furthermore, the stability of catechins in pH 7.4 phosphate-buffered saline was improved after conjugating onto dialdehyde starch. The conjugates exhibited significantly higher antioxidant activities than dialdehyde starch, decreasing in the following order: dialdehyde starch-ECG, dialdehyde starch-EGCG, dialdehyde starch-EC, dialdehyde starch-EGC and dialdehyde starch. CONCLUSION: Dialdehyde starch-catechin conjugates have great potential as stable antioxidant agents. © 2022 Society of Chemical Industry.

Development of chitosan films incorporated with rambutan (Nephelium lappaceum L.) peel extract and their application in pork preservation.

Chitosan (CS) films containing 0, 1, 3 and 5% (w/w) of polyphenol-rich rambutan peel extract (RPE) were developed. The micro-structural characterization and physical and functional properties of the films were determined. Results showed RPE formed strong interactions with CS, making film inner micro-structure become uniform and film crystallinity decline. Amongst different films, CS film containing 5% of RPE showed the lowest light transmission, moisture content (28.35%), water solubility (46.07%), water vapor permeability (8.41 × 10-10 g m-1 s-1 Pa-1) and oxygen permeability (0.28 cm3 mm m-2 day-1 atm-1). Meanwhile, CS film containing 5% of RPE exhibited the highest tensile strength (38.87 MPa) and elongation at break (51.73%) and the strongest antioxidant and antimicrobial activities. Finally, pork was wrapped with the films and stored at 4 °C for 8 days. Results showed pork wrapped with CS film containing 5% of RPE presented the lowest total volatile basic nitrogen level (9.17 mg/100 g), thiobarbituric acid reactive substance value (0.51 mg malondialdehyde/kg) and total viable count (4.53 log colony forming unit/g) and the best sensory attributes on the eighth day. Our results suggested the potential of CS film containing 5% of RPE as an active packaging material in pork preservation.