Insight into anti-oxidative carbohydrate polymers from medicinal plants: Structure-activity relationships, mechanism of actions and interactions with bovine serum albumin

The relationship between polysaccharide structure and its antioxidant activity needs to be systematically elucidated

Polysaccharides have a wide range of applications due to their excellent antioxidant activity. However, the low purity and unclear structure of polysaccharides have led some researchers to be skeptical about the antioxidant activity of polysaccharides. The current reports on the structure-activity relationship of polysaccharides are sporadic, so there is an urgent need to systematically summarize the antioxidant effects of polysaccharides with clear structures and the relationships between the structures to provide a scientific basis for the development and application of polysaccharides. This paper will systematically elucidate the structure-activity relationship of antioxidant polysaccharides, including the molecular weight, monosaccharide composition, glycosidic linkage, degree of branching, advanced conformation and chemical modification. For the first time, the antioxidant activity of polysaccharides is related to their chemical structure through histogram and radar map, and further studies using principal component analysis and cluster analysis. We critically discussed how the source, chemical structure and chemically modified groups of polysaccharides significantly contribute to their antioxidant activity and summarized the current research status and shortcomings of the structure-activity relationship of antioxidant polysaccharides. This review provides a theoretical basis and new perspective for further research on the structure-activity relationship of antioxidant polysaccharides and the development of natural antioxidants.

Structural characteristics and structure-activity relationship of four polysaccharides from Lycii fructus

At present, the structure-activity relationship of polysaccharides is a common and important focus in the fields of glycobiology and carbohydrate chemistry. To better understand the effect of specific polysaccharide structures on bioactive orientation, four homogeneous polysaccharides from Lycii fructus, one neutral along with three acidic polysaccharides, were purified, structurally characterized and comparatively evaluated on the antioxidative and anti-aging activities. The GC-MS-based monosaccharide composition analysis and methylation results showed that the LFPs had similar glycosyl types but varied proportions. Nuclear magnetic resonance (NMR) spectroscopy showed that LFPs consisted of arabinogalactan, rhamnogalacturonan and homogalacturonan structural domains. The results of the structure-activity relationship indicated that the antioxidative activity was positively correlated with the galacturonic acid (GalA) content, while the neutral multi-branched chains might be responsible for the anti-aging activity. This study is the first time to compare the principal structures and multiple biological activities of LFPs, which provided a reference for the industrial development and deep excavation of the health value of LFPs.

Plant type II arabinogalactan: Structural features and modification to increase functionality

Type II arabinogalactans (AGs) are a highly diverse class of plant polysaccharides generally encountered as the carbohydrate moieties of certain extracellular proteoglycans, the so-called arabinogalactan-proteins (AGPs), which are found on plasma membranes and in cell walls. The basic structure of type II AG is a 1,3-β-D-galactan main chain with 1,6-β-D-galactan side chains. The side chains are further decorated with other sugars such as α-l-arabinose and β-d-glucuronic acid. In addition, AGs with 1,6-β-D-galactan as the main chain, which are designated as 'type II related AG' in this review, can also be found in several plants. Due to their diverse and heterogenous features, the determination of carbohydrate structures of type II and type II related AGs is not easy. On the other hand, these complex AGs are scientifically and commercially attractive materials whose structures can be modified by chemical and biochemical approaches for specific purposes. In the current review, what is known about the chemical structures of type II and type II related AGs from different plant sources is outlined. After that, structural analysis techniques are considered and compared. Finally, structural modifications that enhance or alter functionality are highlighted.

Polysaccharides of Salsola passerina: Extraction, Structural Characterization and Antioxidant Activity

The above-ground part of the Salsola passerine was found to contain ~13% (w/w) of polysaccharides extractable with water and aqueous solutions of ammonium oxalate and sodium carbonate. The fractions extracted with aqueous sodium carbonate solutions had the highest yield. The polysaccharides of majority fractions are characterized by similar monosaccharide composition; namely, galacturonic acid and arabinose residues are the principal components of their carbohydrate chains. The present study focused on the determination of antioxidant activity of the extracted polysaccharide fractions and elucidation of the structure of polysaccharides using nuclear magnetic resonance (NMR) spectroscopy. Homogalacturonan (HG), consisting of 1,4-linked residues of α-D-galactopyranosyluronic acid (GalpA), rhamnogalacturonan-I (RG-I), which contains a diglycosyl repeating unit with a strictly alternating sequence of 1,4-linked D-GalpA and 1,2-linked L-rhamnopyranose (Rhap) residues in the backbone, and arabinan, were identified as the structural units of the obtained polysaccharides. HMBC spectra showed that arabinan consisted of alternating regions formed by 3,5-substituted and 1,5-linked arabinofuranose residues, but there was no alternation of these residues in the arabinan structure. Polysaccharide fractions scavenged the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical at 0.2-1.8 mg/mL. The correlation analysis showed that the DPPH scavenging activity of polysaccharide fractions was associated with the content of phenolic compounds (PCs).

Lycium barbarum (Goji) as functional food: a review of its nutrition, phytochemical structure, biological features, and food industry prospects

Lycium genus (Goji berry) is recognized as a good source of homology of medicine and food, with various nutrients and phytochemicals. Lately, numerous studies have focused on the chemical constituents and biological functions of the L. barbarum L., covering phytochemical and pharmacological aspects. We aim to provide exclusive data on the nutrients of L. barbarum L. fruits and phytochemicals, including their structural characterization, the evolution of extraction, and purification processes of different phytochemicals of L. barbarum L. fruit while placing greater emphasis on their wide-ranging health effects. This review also profitably offers innovative approaches for the food industry and industrial applications of L. barbarum L. and addresses some current situations and problems in the development of L. barbarum L. in deep processing products, which can provide clues for the sustainable development of L. barbarum L. industry.

Application of protein-polysaccharide Maillard conjugates as emulsifiers: Source, preparation and functional properties

The protein-polysaccharide conjugates formed by Maillard reaction can be used as novel emulsifiers in the food industry. Proteins and polysaccharides have extensive sources, and their emulsifying properties are highly dependent on their structural features. The Maillard conjugates can be prepared from conventional and novel methods, and these methods have different advantages and limitations in industrial applications. After an appropriate glycation, the conjugates show some modified or enhanced functional properties, including solubility, emulsifying property, thermal stability, foaming capacity, and gelation property. However, the research on the structure-function relationship of both proteins and polysaccharides is limited. It is necessary to well understand the characteristics of these biopolymers, and select appropriate conditions to control the process of Maillard reaction. Overall, the Maillard conjugates show great potential as the emulsifiers and stabilizers in the emulsion system. This review introduces the sources and structural characteristics of commonly used proteins and polysaccharides for Maillard reaction, outlines the methods (dry-heating, wet-heating, electrospinning, ultrasound, pulsed electric field, and microwave) for preparing Maillard conjugates and focuses on the improved functional properties (solubility, emulsifying, foaming and thermal properties) and the potential mechanisms.