Study on the interaction of bioactive compound S-allyl cysteine from garlic with serum albumin

Inhibitory effect and molecular mechanism on tyrosinase and browning of fresh-cut apple by longan shell tannins

Tyrosinase is a biological macromolecule closely related to browning of fruit and vegetables, melanin production, and tyrosinase inhibitors are usually used to prevent browning and pigmentation. In this study, longan shell tannins (LSTs) were screened as tyrosinase inhibitors and their structures were proved to be mixtures of procyanidins (condensed tannins) and ellagitannins (hydrolyzed tannins). Enzymatic experiments verified that LSTs were efficient inhibitors, and the IC50 values for monophenolase and bisphenolase were 176.04 ± 10 and 59.94 ± 5 μg mL-1, respectively. Fluorescence detections and molecular docking revealed that the combination of LSTs to tyrosinase was mainly driven by hydrogen bonding, hydrophobic interaction, as well as van der Waals force, which changed the microenvironment of tyrosine and tryptophan residues as well as enzyme conformation. Circular dichroism and molecular dynamics simulation showed that LSTs affected secondary structures of tyrosinase, resulting in structural stretching and conformational modification of the enzyme. In addition, preservation studies demonstrated that LSTs owned the ability to delay the browning of fresh-cut apples by inhibiting phenolic metabolism, strengthening the antioxidant system, and reducing lipid peroxidation. This paper testified that LSTs are exteaordinary tyrosinase inhibitors, and offered a scientific foundation for the application of LSTs in food industry and medicine.

Effects of composition and storage time of biopolymers-based emulsion-filled gels on the retention and release of aroma compounds: Thermodynamic and kinetic studies

Studies were performed to determine retention (R) and release kinetics (k_r) of aroma compounds (ACs): ethyl butyrate, linalool, 1-octen-3-ol, 2-heptanone and octanal from emulsion-filled gels (EFGs), stabilized by myofibrillar proteins and waxy rice starch (WRS) or tapioca starch (TS). The R and k_r parameters were affected by non-covalent interactions of ACs with biopolymers and the development of a compact structure induced by starch addition. Higher k_r magnitudes were found in WRS-based samples (88.2-12.8 × 10^-3 day^-1) than in counterparts prepared with TS (87.6-8.96 × 10^-3 day^-1). Thermodynamic tests revealed that vaporization enthalpies of ACs were in ranges: 22.6-41.2 kJ mol^-1 or 21.4-39.8 kJ mol^-1 in samples containing WRS or TS, respectively. This study provides new insight into the factors affecting ACs stability in the EFGs, and the results reported can be used by industry to design relevant systems with extended volatiles retention.

Comment on "Physicochemical stimuli as tuning parameters to modulate the structure and stability of nanostructured lipid carriers and release kinetics of encapsulated antileprosy drugs" by R. Kanwar, M. Gradzielski, S. Prevost, G. Kaur, M. S. Appavou and S. K. Mehta, J. Mater. Chem. B, 2019, , 6539

In a recent article [R. Kanwar et al., J. Mater. Chem. B, 2019, 7(42), 6539-6555], the authors characterized the interactions between drug-loaded nanostructured lipid carriers and bovine serum albumin using thermodynamics. They found that the interactions are spontaneous and driven by entropy. In this present paper, we report our analysis of these results in terms of equilibrium thermodynamics to show that the binding reactions exhibit enthalpy-entropy compensation. Our findings may prove useful for designing nanostructured lipid carriers.

Elucidating the active interaction mechanism of phytochemicals withanolide and withanoside derivatives with human serum albumin

Withania somnifera (Ashwagandha) is an efficient medicinal plant known in Ayurveda and Chinese medicine since ancient times, whose extracts are consumed orally as food supplement or as a health tonic owing to its several restorative properties for various CNS disorders, inflammation, tumour, stress, rheumatism etc. In this study, we have analyzed the binding interaction of four derivatives of Withania somnifera (Withanolide A, Withanolide B, Withanoside IV and Withanoside V) with HSA because of their important pharmacological properties. To unravel the binding between derivatives of Withania somnifera and HSA, fluorescence spectroscopy was used. Binding studies were further studied by molecular docking and dynamics and results confirmed greater stability upon binding of derivatives with HSA. Circular dichroism data illustrated change in the secondary structure of protein upon interaction with these derivatives, particularly the helical structure was increased and β-sheets and random coils were decreased. Furthermore, morphological and topological changes were observed using AFM and TEM upon binding of ligands with HSA indicating that HSA-withnoside/withanolide complexes were formed. All the results cumulatively demonstrate strong binding of withanosides and withanolides derivatives with serum albumin, which should further be explored to study the pharmacokinetics and pharmacodynamics of these derivatives.