Preparation of a novel chitosan-based biosorbent cross-linked with phenethylamine for adsorption of aromatic amino acids

Preparation and Antioxidant Activities of High Fischer’s Ratio Oligopeptides from Goat Whey

This study aimed to obtain high Fischer’s ratio oligopeptides from goat whey (HFO) and investigate antioxidant property of it. Hydrolysis of goat whey was done with the approach of sequential digestion of pepsin and flavourzyme. With the adsorption of aromatic amino acids by activated carbon, HFO with a Fischer’s ratio of 27.070 and a molecular weight of 200–1,000 Da were obtained, and the branched-chain amino acids accounted for 22.87%. Then the antioxidant activity of HFO was evaluated. At the concentrations of 2.0 mg/mL and 0.50 mg/mL, HFO scavenged 77.27% and 99.63% of 1,1-diphenyl-2-picrylhydrazyl and 3-ethylbenzthiazoline-6-sulphonate free radicals respectively. The scavenging rate of HFO against hydroxyl radicals reached 92.31% at the concentration of 0.25 mg/mL. Animal experiments demonstrated that HFO could moderate the changes of malondialdehyde, superoxide dismutase and glutathione peroxidase caused by CCl₄-induced oxidative stress in vivo. This study indicated that HFO from goat whey was capable of oxidation resistance both in vivo and in vitro, which provided a scientific basis for the high-value processing and application of goat milk whey.

[Advances in separation and analysis of aromatic amino acids in food]

Amino acids are important building blocks of proteins in the human body, which are involved in many metabolic pathways. Patients with metabolic diseases such as phenylketonuria, tyrosinemia, and hepatic encephalopathy are genetically defective and cannot metabolize aromatic amino acids (AAA) in food; hence, a regular diet may lead to permanent physiological damage. For this reason, it is necessary to restrict the intake of AAA in their daily diet by limiting natural protein intake, while ensuring normal intake of low protein foods and supplementation with low-AAA protein equivalents. Sources of low-AAA protein equivalents currently rely on free amino acid complex mixtures and low-AAA peptides (also known as high-Fischer-ratio peptides), which have better absorption availability and palatability. AAA separation and analysis techniques are essential for the preparation and detection of low-AAA peptides. Researchers in this field have explored a variety of efficient adsorption materials to selectively remove AAA from complex protein hydrolysates and thus prepare low-AAA peptide foods, or to establish analysis strategies for AAA. Covering more than 70 publications on AAA removal and separation in the last decade from Web of Science Core Collection and China National Knowledge Infrastructure, this review analyzes the structural characteristics and physicochemical properties of AAA, and summarizes the technological progress of AAA removal based on adsorbents such as activated carbon and resin. The applications of two-dimensional nanomaterials, molecular imprinting, cyclodextrins, and metal-organic frameworks in AAA adsorption and analysis from three dimensions, i. e., sample pretreatment, chiral separation and adsorption sensing, are also reviewed. The mainstream adsorbents for AAA removal, such as activated carbon, still suffer from poor specificity and cause environmental pollution during post-use treatment. Existing AAA separating materials show impressive selective adsorption capability in food samples and chiral mixtures as well as high sensitivity in adsorption sensing. The development of an efficient detection technology for AAA may help in detecting trace AAA in food and in evaluating chiral AAA adulteration in food samples. By exploring the advantages and disadvantages of each type of technology, we provide support for the advancement of the removal and analysis techniques for AAA.

Study on imperatorin extracted from Angelica dahurica and its UV photocatalytic reaction with collagen

Soxhlet extraction method was used to extract imperatorin from Angelica dahurica, and the extraction ratio under different extraction condition was optimized to attain the best condition. Then, XAD-16 macroporous resin was selected as the optimal resin to boost the extraction ratio of imperatorin. Afterwards, the higher purity of imperatorin (96.84±0.2%) was separated by preparative HPLC system. Next, the photocatalytic reaction between the above imperatorin and collagen which the highest levels in skin was investigated using UV-vis spectroscopy, amino acid analysis and HPLC analysis. The results showed that imperatorin reacted with collagen only under ultraviolet light which caused the denaturation of collagen, and three new products were generated. The ultraviolet products were isolated by preparative HPLC system and separately detected by high-resolution mass spectrum. The possible UV photocatalytic reaction mechanism between imperatorin and collagen is that ultraviolet light induces the increase of the activity of the imperatorin to react with the tyrosine in the collagen, resulted in the denaturation of collagen and reestablish of the normal epidermal tissue in skin.

Megamerger of biosorbents and catalytic technologies for the removal of heavy metals from wastewater: Preparation, final disposal, mechanism and influencing factors

Heavy metal pollution, because of its high toxicity, non-biodegradability and biological enrichment, has been identified as a global aquatic ecosystems threat in recent decades. Due to the high efficiency, low cost, satisfactory recyclability, easy storage and separation, biosorbents have exhibited a promising prospect for heavy metals treatment in aqueous phase. This article comprehensively summarized different types of biosorbents derived from available low-cost raw materials such as agricultural and forestry wastes. The raw materials obtained are treated with conventional pretreatment or novel methods, which can greatly enhance the adsorption performance of the biosorbents. The suitable immobilization methods can not only further enhance the adsorption performance of the biosorbents, but also facilitate the process of separating the biosorbents from the wastewater. In addition, once biosorbents are put into large-scale use, the final disposal problems cannot be avoided. Therefore, it is necessary to review the currently accepted final disposal methods of biosorbents. Moreover, through the analysis of the adsorption and desorption mechanisms of biosorbents, it is not only beneficial to find the better methods to improve the adsorption performance of the biosorbents, but also better to explain the influencing factors of adsorption effect for biosorbents. Especially, different from many researches focused on biosorbents, this work highlighted the combination of biosorbents with catalytic technologies, which provided new ideas for the follow-up research direction of biosorbents. Finally, the purpose of this paper is to inject new impetus into the future development of biosorbents.

Hydrolysis of radish anthocyanins to enhance the antioxidant and antiproliferative capacities

Radish anthocyanins were extracted from red radish. The total anthocyanins content (TAC) of the extracts under different extractants was optimized to reach the optimal condition. XAD-7HP was selected as the best resin to enhance TAC in the extracts. β-Glucosaccharase was chosen as the enzyme to hydrolyse radish anthocyanins. HPLC-MS analysis showed that hydrolysis resulted in an obvious change of the major constituents of radish anthocyanins. Four new constituents in hydrolysed radish anthocyanins were identified. The HPLC-MS results indicated successful hydrolysis of the attachments of glucosides and acids of radish anthocyanins. Furthermore, the FT-IR spectra of radish anthocyanins before and after hydrolysis further described the hydrolysis, which reached 53.36 ± 0.98% under the best performance. Thus, hydrolysis can significantly enhance the antioxidant and antiproliferative capacities of radish anthocyanins.