Quantification of chitosan in aqueous solutions by enzymatic hydrolysis and oligomer analysis via HPLC-ELSD

Impact of O-acetylation on chitin oligosaccharides modulating inflammatory responses in LPS-induced RAW264.7 cells and mice

Chitin oligosaccharides have garnered significant attention due to their biological activities, particularly their immunomodulatory properties. However, O-acetylation in chemically preparing chitin oligosaccharides seems inevitable and leads to some uncertainty on the bioactivity of chitin oligosaccharides. In this study, an O-acetyl-free chitin oligosaccharides and three different O-acetylated chitin oligosaccharides with degree of polymerization ranging from 2 to 6 were prepared using ammonia hydrolysis, and their structures and detailed components were further characterized with FTIR, NMR and MS. Subsequently, the effects of O-acetylation on the immunomodulatory activity of chitin oligosaccharides were investigated in vitro and in vivo. The results suggested that the chitin oligosaccharides with O-acetylation exhibited better inflammatory inhibition than pure chitin oligosaccharides, significantly reducing the expression of inflammatory factors, such as IL-6 and iNOS, in the LPS-induced RAW264.7 macrophage. The chitin oligosaccharides with a degree of O-acetylation of 93 % was found to effectively alleviate LPS-induced endotoxemia in mice, including serum inflammation indices reduction and damage repairment of the intestinal liver, and kidney tissues.

Unveiling the inverse antimicrobial impact of a hetero-chitooligosaccharide on Candida tropicalis growth and biofilm formation

Chitosan and chitooligosaccharide (COS) are renowned for their potent antimicrobial prowess, yet the precise antimicrobial efficacy of COS remains elusive due to scant structural information about the utilized saccharides. This study delves into the antimicrobial potential of COS, spotlighting a distinct hetero-chitooligosaccharide dubbed DACOS. In contrast to other COS, DACOS remarkably fosters the growth of Candida tropicalis planktonic cells and fungal biofilms. Employing gradient alcohol precipitation, DACOS was fractionated, unveiling diverse structural characteristics and differential impacts on C. tropicalis. Notably, in a murine model of systemic candidiasis, DACOS, particularly its 70 % alcohol precipitates, manifests a promotive effect on Candida infection. This research unveils a new pathway for exploring the intricate nexus between the structural attributes of chitosan oligosaccharides and their physiological repercussions, underscoring the imperative of crafting chitosan and COS with meticulously defined structural configurations.

Composition and Charge Compensation in Chitosan/Gum Arabic Complex Coacervates in Dependence on pH and Salt Concentration

In this study, complex coacervates of the biopolyelectrolytes chitosan and gum arabic were investigated with respect to their composition and charge compensation depending on the pH and salt concentration. Individual polyelectrolyte yields were deduced from thermogravimetric analysis and chitosan quantification via enzymatic hydrolysis/HPLC-ELSD. The polyelectrolyte mass ratio in the complex coacervate is found to remain approximately constant irrespective of the pH, despite the latter's effect on the polyelectrolyte charge ratio. Two regimes are identified, including either chitosan charges in excess (at pH < 6.0) or gum arabic charges in excess (at pH > 6.0). The amount of extrinsic charge compensation in the complex coacervates is discussed in detail. We show for the first time that the doping level, a quantity traditionally used to describe salt-induced changes of the charge compensation in polyelectrolyte complexes, is also suitable for the description of pH-induced extrinsic charge compensation in such systems.

ELECTROPHORETIC DETERMINATION OF CHITIN IN INSECTS

An electrophoretic method (on-line coupled capillary isotachophoresis with capillary zone electrophoresis with conductometric detection (cITP-CZE-COND)) for the determination of chitin in insects based on the analysis of glucosamine after acidic hydrolysis of the sample is described. Chitin is deacetylated and hydrolyzed to glucosamine by acidic hydrolysis (6 M sulfuric acid, 110 °C, 6 h). Under optimized electrophoresis conditions, glucosamine (GlcN) is separated from other sample components in cationic mode and detected with a conductometer within 15 min. The performance method characteristics of the GlcN assay, i.e., linearity (0.2-20 μmol), accuracy (103 ± 5%), repeatability (1.9%), reproducibility (3.4%), limits of detection (0.06 μmol/L) and quantification (0.2 μmol/L), were evaluated. On a series of 28 insect samples, it was proven that cITP-CZE-COND provides results of chitin content in insects comparable to the literature data. The important features of the developed cITP-CZE-COND method are easy sample treatment, high sensitivity and selectivity, and low running costs. It is clear from the above that the cITP-CZE-COND method is suitable for analysis of insect samples for chitin content.

Quantitative determination of galacturonic acid in pectin and pectin products by combined pectinase hydrolysis and HPLC determination

Pectin is a complex heteropolysaccharide with a predominantly galacturonic acid (GalA) main chain and various branching sugars, leading to some analytical and quantitative determination challenges. By comparison with various acid hydrolysis methods, an effective and precise hydrolysis method for GalA determination from pectin was investigated using a combination of pectinase hydrolysis (PH) and HPLC determination, which was named the PH-HPLC method. With a pectinase loading of 2250 U/g pectin, 4.0 g/L commercial pectin was almost completely hydrolysed to the intact and detectable GalA at 50 °C after 24 h, for quantitative determination by HPLC. Acid-catalysis methods showed obvious disadvantages in terms of GalA degradation or incomplete hydrolysis of pectin, resulting in imprecise determination results. Moreover, the PH-HPLC method was employed for the quantitative determination of GalA in three common natural pectin feedstocks and indicated 45.5-233.1% higher content of GalA than the acid hydrolysis method. Thus, the PH-HPLC method is demonstrated to be a precise approach for analysing and quantifying the GalA of pectin and respective feedstock.

High-throughput vibrational spectroscopy methods for determination of degree of acetylation for chitin and chitosan

The rising demand for chitin and chitosan in chemical, agro-food, and healthcare industries is creating a need for rapid and high-throughput analysis. The physicochemical properties of these biopolymers are greatly dependent on the degree of acetylation (DA). Conventional methods for DA determination, such as LC-MS and ¹H NMR, are time-consuming when performed on many samples, and therefore efficient methods are needed. Here, high-throughput microplate-based FTIR and FT-Raman methods were compared with their manual counterparts. Partial least squares regression models were based on 30 samples of chitin and chitosan with reference DA values obtained by LC-MS and ¹H NMR, and the models were validated on an independent test set of 16 samples. The overall predictive accuracy of the high-throughput methods was at the same level as the manual methods and the well-established LC-MS and ¹H NMR methods. Therefore, high-throughput FTIR and FT-Raman DA determination methods have great potential to serve as fast and economical substitutes for traditional methods.

Recent advances in qualitative and quantitative analysis of polysaccharides in natural medicines: A critical review

Polysaccharides from natural medicines, being safe and effective natural mixtures, show great potential to be developed into botanical drugs. However, there is yet one polysaccharide-based case that has fulfilled the Botanical Guidance definition of a botanical drug product. One of the reasons is the analytical methods commonly used for qualitative and quantitative analysis of polysaccharides fall far behind the quality control criteria of botanical drugs. Here we systemically reviewed the recent advances in analytical methods. A critical evaluation of the strength and weaknesses of these methods was provided, together with possible solutions to the difficulties. Mass spectrometry with or without robust chromatographic separation was increasingly employed. And scientists have made significant progress in simplifying polysaccharide quantification by depolymerizing it into oligosaccharides. This oligosaccharides-based strategy is promising for qualitative and quantitative analysis of polysaccharides. And continuous efforts are still needed to develop a standardized quality control method that is specific, accurate, repeatable, and applicable for analyzing individual components in natural medicine formulas.