Tyrosinase inhibitors as potential antibacterial agents

Chemical Characterization, Antioxidant, Enzyme Inhibition and Antimutagenic Properties of Eight Mushroom Species: A Comparative Study

This study aimed to determine the chemical composition and biologic activities of eight mushroom species (Amanita crocea, Hemileccinum depilatum, Cyclocybe cylindracea, Lactarius deliciosus, Hygrocybe acutoconica, Neoboletus erythropus, Russula aurea and Russula sanguinea). The antioxidant, enzyme inhibitory and mutagenic/antimutagenic activities were evaluated to provide data on the biologic activities. With respect to the chemical composition, LC-MS/MS technique was used to determine individual phenolic compounds present in the extracts. Antioxidant properties were investigated by different chemical methods including radical quenching (DPPH and ABTS), reducing power (CUPRAC and FRAP), phosphomolybdenum and metal chelating. In the enzyme inhibitory assays, cholinesterases, tyrosinase, amylase and glucosidase were used. Mutagenic and antimutagenic properties were evaluated by the Ames assay. In general, the best antioxidant abilities were observed from H. depilatum and N. erythropus, which also showed highest level of phenolics. The best cholinesterase inhibition ability was found from C. cylindracea (1.02 mg GALAE/g for AChE; 0.99 mg GALAE/g for BChE). Tyrosinase inhibition ability varied from 48.83 to 54.18 mg KAE/g. The extracts exhibited no mutagenic effects and showed significant antimutagenic potential. H. acutoconica, in particular depicted excellent antimutagenicity with a ratio of 97% for TA100 and with a rate of 96% for TA98 strain against mutagens in the presence of metabolic activation system. Results presented in this study tend to show that the mushroom species could be exploited as potential sources of therapeutic bioactive agents, geared towards the management of oxidative stress, global health problems and cancer.

Indole/isatin-containing hybrids as potential antibacterial agents

The emergence and worldwide spread of drug-resistant bacteria have already posed a serious threat to human life, creating the urgent need to develop potent and novel antibacterial drug candidates with high efficacy. Indole and isatin (indole-2,3-dione) present a wide structural and mechanistic diversity, so their derivatives possess various pharmacological properties and occupy a salient place in the development of new drugs. Indole/isatin-containing hybrids, which demonstrate a promising activity against a panel of clinically important Gram-positive and Gram-negative bacteria, are privileged scaffolds for the discovery of novel antibacterial candidates. This review, covering articles published between January 2015 and May 2020, focuses on the development and structure-activity relationship (SAR) of indole/isatin-containing hybrids with potential application for fighting bacterial infections, to facilitate further rational design of novel drug candidates.

Synthesis and Studies of the Inhibitory Effect of Hydroxylated Phenylpropanoids and Biphenols Derivatives on Tyrosinase and Laccase Enzymes

The impaired activity of tyrosinase and laccase can provoke serious concerns in the life cycles of mammals, insects and microorganisms. Investigation of inhibitors of these two enzymes may lead to the discovery of whitening agents, medicinal products, anti-browning substances and compounds for controlling harmful insects and bacteria. A small collection of novel reversible tyrosinase and laccase inhibitors with a phenylpropanoid and hydroxylated biphenyl core was prepared using naturally occurring compounds and their activity was measured by spectrophotometric and electrochemical assays. Biosensors based on tyrosinase and laccase enzymes were constructed and used to detect the type of protein-ligand interaction and half maximal inhibitory concentration (IC50). Most of the inhibitors showed an IC50 in a range of 20-423 nM for tyrosinase and 23-2619 nM for laccase. Due to the safety concerns of conventional tyrosinase and laccase inhibitors, the viability of the new compounds was assayed on PC12 cells, four of which showed a viability of roughly 80% at 40 µM. In silico studies on the crystal structure of laccase enzyme identified a hydroxylated biphenyl bearing a prenylated chain as the lead structure, which activated strong and effective interactions at the active site of the enzyme. These data were confirmed by in vivo experiments performed on the insect model Tenebrio molitur.