A Study on the Skin Whitening Activity of Digesta from Edible Bird’s Nest: A Mucin Glycoprotein

Edible bird’s nest (EBN) is an unusual mucin glycoprotein. In China, it is popular among consumers due to its skin whitening activity. However, the relationship between protein, sialic acid, and the whitening activity of EBN after digestion is still unclear. In the present work, the whitening activity (antioxidant activity and tyrosinase inhibitory activity) of digested EBN were studied by HepG2 and B16 cell models. The dissolution rate of protein and sialic acid was 49.59% and 46.45% after the simulated digestion, respectively. The contents of free sialic acid and glycan sialic acid in EBN digesta were 17.82% and 12.24%, respectively. HepG2 cell experiment showed that the digested EBN had significant antioxidant activity, with EC50 of 1.84 mg/mL, and had a protective effect on H2O2-induced oxidative damage cells. The results of H2O2-induced oxidative damage showed that the cell survival rate increased from 40% to 57.37% when the concentration of digested EBN was 1 mg/mL. The results of the B16 cell experiment showed that the digested EBN had a significant inhibitory effect on tyrosinase activity, and the EC50 value of tyrosinase activity was 7.22 mg/mL. Cell experiments showed that free sialic acid had stronger antioxidant activity and tyrosinase inhibitory activity than glycan sialic acid. The contribution rate analysis showed that protein component was the main antioxidant component in digestive products, and the contribution rate was 85.87%; free sialic acid was the main component that inhibited tyrosinase activity, accounting for 63.43%. The products of the complete digestion of EBN are suitable for the development of a new generation of whitening health products.

Probing the effect of aroma compounds on the hydrodynamic properties of mucin glycoproteins

Aroma compounds are diverse low molecular weight organic molecules responsible for the flavour of food, medicines or cosmetics. Natural and artificial aroma compounds are manufactured and used by the industry to enhance the flavour and fragrance of products. While the low concentrations of aroma compounds present in food may leave no effect on the structural integrity of the mucosa, the effect of concentrated aroma volatiles is not well understood. At high concentrations, like those found in some flavoured products such as e-cigarettes, some aroma compounds are suggested to elicit a certain degree of change in the mucin glycoprotein network, depending on their functional group. These effects are particularly associated with carbonyl compounds such as aldehydes and ketones, but also phenols which may interact with mucin and other glycoproteins through other interaction mechanisms. This study demonstrates the formation of such interactions in vitro through the use of molecular hydrodynamics. Sedimentation velocity studies reveal that the strength of the carbonyl compound interaction is influenced by compound hydrophobicity, in which the more reactive short chain compounds show the largest increase in mucin-aroma sedimentation coefficients. By contrast, the presence of groups that increases the steric hindrance of the carbonyl group, such as ketones, produced a milder effect. The interaction effects were further demonstrated for hexanal using size exclusion chromatography light scattering (SEC-MALS) and intrinsic viscosity. In addition, phenolic aroma compounds were identified to reduce the sedimentation coefficient of mucin, which is consistent with interactions in the non-glycosylated mucin region.

The Catalytic Acid-Base in GH109 Resides in a Conserved GGHGG Loop and Allows for Comparable α-Retaining and β-Inverting Activity in an N-Acetylgalactosaminidase from Akkermansia Muciniphila

The study describes the first glycoside hydrolase that exhibits comparable levels of activity on α- and β-linked saccharide substrates. This enzyme, assigned into GH109, is encoded by the genome of the human gut symbiont Akkermansia muciniphila that is a model primary degrader of the heavily O-glycosylated mucin glycoprotein that coats the epithelial enterocytes.The elusive catalytic acid/base catalyst in GH109 enzymes is identified as a histidine that is presented by a flexible loop that positions it for catalysis on both α- and β-substrates. This dual activity may be an evolutionary adaptation to extend the range of substrates targeted by a single non-canonical NAD+-dependant GH. <br>

The Catalytic Acid-Base in GH109 Resides in a Conserved GGHGG Loop and Allows for Comparable α-Retaining and β-Inverting Activity in an N-Acetylgalactosaminidase from Akkermansia Muciniphila

The study describes the first glycoside hydrolase that exhibits comparable levels of activity on α- and β-linked saccharide substrates. This enzyme, assigned into GH109, is encoded by the genome of the human gut symbiont Akkermansia muciniphila that is a model primary degrader of the heavily O-glycosylated mucin glycoprotein that coats the epithelial enterocytes.The elusive catalytic acid/base catalyst in GH109 enzymes is identified as a histidine that is presented by a flexible loop that positions it for catalysis on both α- and β-substrates. This dual activity may be an evolutionary adaptation to extend the range of substrates targeted by a single non-canonical NAD+-dependant GH. <br>

Acrylated Chitosan Nanoparticles with Enhanced Mucoadhesion

The aim of this study was to investigate the effect of acrylate modification on the mucoadhesion of chitosan at the nanoscale. Nanoparticles were fabricated from acrylated chitosan (ACS) via ionic gelation with tripolyphosphate and were characterized in terms of size, zeta potential, stability, and nanoparticle yield. Chitosan (CS) nanoparticles, serving as a control, were fabricated using the same procedure. The mucoadhesion of the nanoparticles was evaluated using the flow-through method after different incubation periods. The retention percentages of ACS nanoparticles were found to be significantly higher than those of CS nanoparticles, for all studied time intervals. An additional indication for the increased mucoadhesion of ACS nanoparticles was the increase in particle size obtained from the mucin particle method, in which mucin and nanoparticles are mixed at different ratios. NMR data verified the presence of free acrylate groups on the ACS nanoparticles. Thus, the improved mucoadhesion could be due to a Michael-type addition reaction between the nanoparticles and thiol groups present in mucin glycoprotein, in addition to entanglements and hydrogen bonding. Overall, ACS nanoparticles exhibit enhanced mucoadhesion properties as compared to CS nanoparticles and could be used as vehicles for drug delivery systems.