Search

A dual-target strategy was designed for the application of lignin nanoparticles in the lipase mediated biosynthesis of novel 3- O -ethyl-L-ascorbyl-6-ferulate and 3- O -ethyl-L-ascorbyl-6-palmitate and in their successive solvent-shift encapsulation in order to improve stability and antioxidant activity against temperature and pH-dependent degradation. The loaded lignin nanoparticles were fully characterized in terms of kinetic release, radical scavenging activity and stability under pH 3 and thermal stress (60 °C), showing improved antioxidant activity and high efficacy in the protection of ascorbic acid esters from degradation.

The overproduction of eumelanin leads to a panel of unaesthetic hyper-pigmented skin diseases, including melasma and age spots. The treatment of these diseases often requires the use of tyrosinase inhibitors, which act as skin whitening agents by inhibiting the synthesis of eumelanin, with harmful side effects. We report here that laccase from Trametes versicolor in association with a cocktail of natural phenol redox mediators efficiently degraded eumelanin from Sepia officinalis , offering an alternative procedure to traditional whitening agents. Redox mediators showed a synergistic effect with respect to their single-mediator counterpart, highlighting the beneficial role of the cocktail system. The pro-oxidant DHICA sub-units of eumelanin were degraded better than the DHI counterpart, as monitored by the formation of pyrrole-2,3,5-tricarboxylic acid (PTCA) and pyrrole-2,3-dicarboxylic acid (PDCA) degradation products. The most effective laccase-mediated cocktail system was successively applied in a two-component prototype of a topical whitening cream, showing high degradative efficacy against eumelanin.

Pyomelanin mimics from homogentisic acid (HGA) and gentisic acid (GA) were biosynthesized by the oxidative enzyme T. versicolor laccase at physiological pH to obtain water soluble melanins. The pigments show brown-black color, broad band visible light absorption, a persistent paramagnetism and high antioxidant activity. The EPR approach shows that at least two different radical species are present in both cases, contributing to the paramagnetism of the samples. This achievement can also shed light on the composition of the ochronotic pigment in the Alkaptonuria disease. On the other hand, these soluble pyomelanin mimics, sharing physico-chemical properties with eumelanin, can represent a suitable alternative to replace the insoluble melanin pigment in biotechnological applications.