Design, synthesis and evaluation of PEGylated lipoic acid derivatives with functionality as potent anti-melanogenic agents

Thiol-Ene Click Cross-linking of Starch Oleate Films for Enhanced Properties

Biobased films were synthesized from starch oleate (DS = 2.2) cross-linked with polyethylene glycol with Mn = 2000 and 1000 g · mol-1, and ethylene glycol, all of which were esterified with either lipoic acid (LA) or 3-mercaptopropionic acid (MPA). Cross-linking was achieved through a UV-initiated thiol-ene click, and confirmed by Fourier transform infrared spectroscopy and rheometry. The films exhibit higher degradation temperatures, and an increased degree of crystallinity as cross-linker length increased. The introduction of MPA-based cross-linkers resulted in hydrophilic films, while the contact angle was barely affected by the addition of LA-based cross-linkers. A reduction in maximum strength upon introducing the cross-linkers was observed, while an increase in elongation was observed for most of the LA-based cross-linkers. Our results demonstrate the potential for tuning the mechanical and thermal properties of starch-based films through the cross-linker choice, with some formulations exhibiting increased flexibility that may be well suited for packaging applications.

Synthesis and glutathione peroxidase (GPx)-like activity of selenocystine (SeC) bioconjugates of biotin and lipoic acid

The conjugation of active biomolecules provides insight into their bioreactivity, leading to many applications in biotechnology and materials science. Herein, we report L-selenocystine (SeC) bioconjugates of lipoic acid (universal antioxidant) and biotin (Vitamin-H). The SeC-bioconjugates, SeC-Biotin (1) and SeC-Lipoic acid (2) were synthesized using solid phase peptide synthesis (SPPS) method and were characterized by multinuclear 1D (1H, 13C, 77Se) and 2D (1H-1H COSY and 1H-13C TOCSY) NMR spectroscopy, ESI-MS spectrometry, and RP-HPLC. The GPx-like enzyme mimicking activity of the SeC-bioconjugates 1 and 2 has been investigated through the coupled reductase assay method for the catalytic reductions of hydrogen peroxide into water. A significant enhancement in GPx-like enzymatic activity was observed for both novel bioconjugates SeC-Biotin (1) and SeC-Lipoic acid (2) as compared to diphenyl diselenide (Ph2Se2), L-selenocystine (SeC), biotin, lipoic acid, and ebselen.

Synthesis of Hydroxypropyltrimethyl Ammonium Chitosan Derivatives Bearing Thioctate and the Potential for Antioxidant Application

Hydroxypropyltrimethyl ammonium chloride chitosan (HACC) is one of the most important water-soluble chitosan derivatives; its derivatives have gained growing attention due to their potential biomedical applications. Here, hydroxypropyltrimethyl ammonium chitosan derivatives bearing thioctate (HACTs), with different degrees of substitution of thioctate, were prepared using HACC and α-lipoic acid as the reaction precursors, using an ion exchange method. The structural characteristics of the synthesized derivatives were confirmed by FTIR, ¹H NMR, and ¹³C NMR spectroscopy. In addition, their antioxidant behaviors were also investigated in vitro by the assays of reducing power, and scavenging activities against hydroxyl radicals and DPPH radicals. The antioxidant assay indicated that HACTs displayed strong antioxidant activity compared with HACC, especially in terms of reducing power. Besides, the antioxidant activities of the prepared products were further enhanced with the increase in the test concentration and the degrees of substitution of thioctate. At the maximum test concentration of 1.60 mg/mL, the absorbance value at 700 nm of HACTs, under the test conditions, was 4.346 ± 0.296, while the absorbance value of HACC was 0.041 ± 0.007. The aforementioned results support the use of HACTs as antioxidant biomaterials in food and the biomedical field.

Alpha-lipoic acid-loaded nanostructured lipid carrier: sustained release and biocompatibility to HaCaT cells in vitro

ALA-loaded nanostructured lipid carrier (ALA-NLC) was designed to improve physicochemical stability and water solubility, and promote sustained release of ALA as well as determine the biocompatibility of ALA-NLC. The ALA-NLC manufactured using hot high-pressure homogenization technique was investigated in terms of size, zeta potential, FTIR analysis and release behavior. In vitro cytotoxicity and biocompatibility were determined by incubating with HaCaT cells using the MTT assay, HE staining and Hoechst 33342 staining. Cell behavior and cellular division of HaCaT cells untreated and treated by ALA-NLC were investigated in real-time images gathered using time-lapse imaging system. The release investigation illustrated that only 6.9% of ALA released in 30 min from ALA-NLC formation, whereas it was 30.3% in free ALA system. ALA-NLC possessed a satisfactory release behavior of sustained release up to 72 h. It showed that ALA-NLC did not exert hazardous effect on HaCaT cells up to 81.9 mg/L without morphological alterations, revealing a satisfactory biocompatibility. Evidence was provided from time-lapse imaging system that cell behavior and cellular division of ALA-NLC treated HaCaT cells were in accordance with the control. These results of this investigation demonstrated that NLC encapsulated ALA formation (ALA-NLC) can improve stability, solubility and release of ALA; ALA-NLC was biocompatible to HaCaT cells.

Enzymatic hybridization of α-lipoic acid with bioactive compounds in ionic solvents

The lipase-catalyzed molecular hybridization of α-lipoic acid (LA) with bioactive compounds pyridoxine, tyrosol and tyramine was performed in ionic solvents and deep eutectic solvents. The biocatalytic reactions were catalyzed by Candida antarctica lipase B immobilized onto various functionalized multi-walled carbon nanotubes (f-CNTs-CaLB), as well as by commercial Novozym 435. The use of f-CNTs-CaLB leads, in most cases, to higher conversion yields as compared to Novozym 435. The nature and ion composition of ionic solvents affect the performance of the biocatalytic process. The highest conversion yield was observed in (mtoa)NTf2. The high enzyme stability and the relatively low solubility of substrates in specific media account for the improved biocatalytic synthesis of molecular hybrids of LA. Principal component analysis was used to screen for potential lipoxygenase inhibitors. In vitro studies showed that the synthesized compounds exhibit up to 10-fold increased inhibitory activity on lipoxygenase mediated lipid peroxidation as compared to parent molecules.