In the present study we tested

In the present study, we tested α-glucosidase and tyrosinase inhibitory effects of the methanol extract from lower stems and INCB3344 of Q. coccifera (1) as well as the isolated compounds [lyoniresinol-9-O-β-xylopyranoside (2) and lyoniresinol-9-O-β-glucopyranoside (3), cocciferoside (4), (-)-8-chlorocatechin (5), polydatin (6)] to find new hits (Fig. 1). We predicted druglikeness and pharmacokinetic properties of the active compounds in silico. We performed molecular docking studies in the catalytic and predicted allosteric ligand binding sites of mushroom tyrosinase to provide insights into tyrosinase inhibition mechanism of the active compounds.
Materials and methods
Results and discussion
Conclusions In this study, we tested tyrosinase and α-glucosidase inhibitory effects of an extract from the bark of Q. coccifera and the compounds isolated from it. Especially, the extract exhibited stronger α-glucosidase inhibitory activity with an IC50 value of 3.26 ± 0.08 µg/mL than acarbose (IC50: 50.45 ± 0.20 µg/mL). Among the isolated compounds, 6 inhibited tyrosinase significantly, it was 12.5 fold more potent than kojic acid. Also, tyrosinase inhibitory effect of 5 was close to kojic acid. 5 was found to be a competitive tyrosinase inhibitor whereas 6 was an uncompetitive inhibitor. Further, 5 was determined as the most potent α-glucosidase inhibitor among the isolated compounds and more potent than acarbose with an IC50 43.60 ± 0.67 µg/mL. According to the kinetic studies, 5 was a noncompetitive α-glucosidase inhibitor with value of 30.05 ± 0.25 µg/mL. These results supports use of bark of Q. coccifera for the treatment of diabetes in folk medicine. Upon predicting druglikenes and pharmacokinetic properties of 5 and 6 in silico we found that they mostly complied with the rules of druglike chemical space. The compounds were also predicted to have favorable pharmacokinetic properties despite a few exceptions. Molecular docking studies with multiple software and QM/MM approach showed that the 5 fit well to the catalytic site of tyrosinase and the 4-chromanone moiety with its hydroxyl groups was mainly responsible for the key interactions. The ionized form of 5 (5i) probably bound to this site tighter with better stability, especially with a better interaction profile with the Cu2+ ions. 6, on the other hand, supposedly bound to the predicted allosteric sites rather than to the catalytic site, which was supported by the results from the enzyme kinetics study.
Introduction Enzymes play an important role in contemporary industry due to their excellent properties, such as high efficiency and specificity compared to general chemical catalyst. However, there are many disadvantages that hinder the widespread applications of free enzyme in industry, such as the short catalytic lifetime, unsatisfactory reusability and low operational stability against thermal [1,2,6]. Study of enzyme immobilization is usually applied to deal with the problems. Many materials are used for enzyme immobilization. Generally, different materials had different methods to immobilize enzyme. The common way to immobilize enzyme can be divided into three categories: enzyme molecule attachment to a solid support, entrapment into a matrix, and molecule cross-linking. All approaches have their advantages and disadvantages [3]. Enzyme molecule attachment is easy and cheap to carry out. Entrapment enzyme into a matrix can improve the ability to resist the microbial and protease around the environment. Molecule cross-linking can achieve the high enzymatic activity [4]. With the rapid development of carrier materials, the study of nanoparticles has been of great interest in enzyme immobilization techniques [5,6]. Nanoparticles have many attractive properties for enzyme immobilization, such as biocompatibility, small size, and they have applied to immobilize different kinds of enzyme, such as glucose oxidase [7], β-glucosidase [8], α-amylase [9].