Quick screening of true tyrosinase inhibitors from natural products using tyrosinase-immobilized magnetic nanoparticles and a magnetic microplate

Valorization of biomass polyphenols as potential tyrosinase inhibitors

Tyrosinases (TYRs; EC 1.14.18.1) catalyze two sequential oxidative reactions of the melanin biosynthesis pathway and play an important role in mammalian pigmentation and enzymatic browning of fruit and vegetables. Inhibition of TYR activity is therefore an attractive target for new drugs and/or food ingredients. In addition, increasing evidence suggests that TYR regulation could be a novel target for treatments of cancer and Parkinson's disease. Biomasses, notably industrial byproducts and biowaste, are good sustainable sources of phytochemicals that may be valorized into bioactive compounds including TYR inhibitors. This review presents potential applications of biomass-derived polyphenols targeting TYR inhibition. Insights into structure-activity relationships of several polyphenols and their glycosides are highlighted. Finally, some remarks and perspectives on research into new TYR inhibitors from biomass waste are provided.

A novel high-resolution monophenolase/diphenolase/radical scavenging profiling for the rapid screening of natural whitening candidates from Peaonia lactiflora root and their mechanism study with molecular docking

ETHNOPHARMACOLOGICAL RELEVANCE

The root of Paeonia lactiflora is a traditionally-used whitening medicine in China for thousands of years. Although some tyrosinase inhibitors and/or antioxidants such as 1,2,3,4,6-pentagalloylglucose, gallic acid, have been isolated and identified, their tyrosinase inhibition pathway (monophenolase or diphenolase inhibition, or both two) have not been systematically studied and the underlying tyrosinase inhibition mechanism has not been revealed yet. Moreover, the exploring of new natural tyrosinase inhibitors and antioxidants is urgently needed.

AIM OF THE STUDY

This review aimed to develop a new microplate-based high-resolution tyrosinase inhibition profiling assay and establish a furthermore triple high-resolution monophenolase/diphenolase/radical scavenging profiling for accelerating identification bioactive compounds from complicated plant extract.

MATERIALS AND METHODS

The targeted isolation and structure elucidation were performed with high-performance liquid chromatography-high-resolution mass spectrometry and preparative high-performance liquid chromatography. It allows to be a proof of concept with the root of Paeonia lactiflora crude extract as a natural whitening herbal drug.

RESULTS

The result showed that galloylpaeoniflorin specifically inhibited monophenolase activity. While 1,2,3,4,6-pentagalloylglucose, gallic acid and catechin demonstrated the inhibition towards both monophenolase and diphenolase. Among them, 1,2,3,4,6-pentagalloylglucose can inhibit monophenolase activity was reported for the first time. In addition, antioxidant properties were attributed to catechin, 1,2,3,4,6-pentagalloylglucose and gallic acid. Due to its low content and complicated configuration in the root of Paeonia lactiflora, a new potential tyrosinase inhibitor and radical scavenger which tentatively identified as hexagalloylglucose by high-resolution MS was still need further verification. What's more, the molecular docking unveiled that bioactive enzymatic inhibitors mainly interacted with amino acid catalytic residues of tyrosinase via H-bonds and van der wals, which may be helpful to understand their inhibition mechanisms with tyrosinase in the skin whitening.

CONCLUSIONS

The platform provided a promising and efficient strategy for the rapid screening of whitening active components from natural sources.

Magnetic particles for enzyme immobilization: A versatile support for ligand screening

Enzyme inhibitors represent a substantial fraction of all small molecules currently in clinical use. Therefore, the early stage of drug-discovery process and development efforts are focused on the identification of new enzyme inhibitors through screening assays. The use of immobilized enzymes on solid supports to probe ligand-enzyme interactions have been employed with success not only to identify and characterize but also to isolate new ligands from complex mixtures. Between the available solid supports, magnetic particles have emerged as a promising support for enzyme immobilization due to the high superficial area, easy separation from the reaction medium and versatility. Particularly, the ligand fishing assay has been employed as a very useful tool to rapidly isolate bioactive compounds from complex mixtures, and hence the use of magnetic particles for enzyme immobilization has been widespread. Thus, this review provides a critical overview of the screening assays using immobilized enzymes on magnetic particles between 2006 and 2021.

Rapid screening and identification of anticoagulation component from carthami flos by two-dimensional thrombin affinity chromatography combined with HPLC-MS/MS

Carthami flos, commonly known as Honghua in China, is the dried floret of safflower and widely acknowledged as a blood stasis promoting herb. The study aimed at investigating the relationship between thrombin and carthami flos through a high-performance thrombin affinity chromatography combined with a high-performance liquid chromatography-tandem mass spectrometry system. First, thrombin was immobilized on the glutaraldehyde-modified amino silica gel to prepare the thrombin affinity stationary phase, which was packed into a small column (1.0 × 2.0 mm, id) for recognizing the anticoagulant active components of carthami flos. The target component was enriched and analyzed by the high-performance liquid chromatography-tandem mass spectrometry system. Finally, hydroxysafflor yellow A was screened out and identified as the active component. The anticoagulant effects of hydroxysafflor yellow A were analyzed by anticoagulant experiments in vitro, and the interaction of hydroxysafflor yellow A with thrombin was investigated by the molecular docking method. The results proved that hydroxysafflor yellow A (30 μg/mL, 0.05 mM) and carthami flos extract (30 μg/mL) could prolong activated partial thrombin time and thrombin time by 50 and 11%, respectively. Moreover, hydroxysafflor yellow A exhibits a good hydrogen bond field and stereo field matching with thrombin. Overall, it was concluded that hydroxysafflor yellow A might exert an anticoagulation effect by interacting with thrombin and thus could be potential anticoagulant drugs for the prevention and treatment of venous thrombosis.

Recent advances in screening active components from natural products based on bioaffinity techniques

Natural products have provided numerous lead compounds for drug discovery. However, the traditional analytical methods cannot detect most of these active components, especially at their usual low concentrations, from complex natural products. Herein, we reviewed the recent technological advances (2015–2019) related to the separation and screening bioactive components from natural resources, especially the emerging screening methods based on the bioaffinity techniques, including biological chromatography, affinity electrophoresis, affinity mass spectroscopy, and the latest magnetic and optical methods. These screening methods are uniquely advanced compared to other traditional methods, and they can fish out the active components from complex natural products because of the affinity between target and components, without tedious separation works. Therefore, these new tools can reduce the time and cost of the drug discovery process and accelerate the development of more effective and better-targeted therapeutic agents.

Overview of Recent Advances in Immobilisation Techniques for Phenol Oxidases in Solution

Over the past two decades, phenol oxidases, particularly laccases and tyrosinases, have been extensively used for the removal of numerous pollutants in wastewaters due to their broad substrate specificity and their ability to use readily accessible molecular oxygen as the essential cofactor. As for other enzymes, immobilisation of laccases and tyrosinases has been shown to improve the performance and efficiency of the biocatalysts in solution. Several reviews have addressed the enzyme immobilisation techniques and the application of phenol oxidases to decontaminate wastewaters. This paper offers an overview of the recent publications, mainly from 2012 onwards, on the various immobilisation techniques applied to laccases and tyrosinases to induce and/or increase the performance of the biocatalysts. In this paper, the emphasis is on the efficiencies achieved, in terms of structural modifications, stability and resistance to extreme conditions (pH, temperature, inhibitors, etc.), reactivity, reusability, and broad substrate specificity, particularly for application in bioremediation processes. The advantages and disadvantages of several enzyme immobilisation techniques are also discussed. The relevance and effectiveness of the immobilisation techniques with respect to wastewater decontamination are critically assessed. A perspective on the future directions for large-scale application of the phenol oxidases in immobilised forms is provided.