Screening inhibitory effects of selected flavonoids on human recombinant aldose reductase enzyme: in vitro and in silico study

Resorcinol Derivatives as Novel Aldose Reductase Inhibitors: In Silico and In Vitro Evaluation

Background:

The polyol pathway, an alternative way of carbohydrate metabolism, is activated by hyperglycemia. Aldose reductase (AR), the first and rate-limiting enzyme of the polyol pathway, is responsible for the reduction of glucose to sorbitol. Inhibiting the aldose reductase enzyme and reducing the polyol pathway is considered an effective method to prevent and postpone the onset of diabetic complications.

Objective:

Therefore, in this work, we investigate the inhibition effects of certain resorcinol derivatives and the positive control compound quercetin on the AR enzyme in vitro and in silico. These phenolic compounds, whose inhibitory effects on the AR enzyme were investigated, were also compared with known drugs in terms of their drug-like characteristics.

Methods:

Three methods were used to determine the inhibitory effects of resorcinol derivatives on recombinant human AR enzyme. After the in vitro inhibition effects were determined spectrophotometrically, the binding energy and binding modes were determined by molecular docking method. Finally, the MM-GBSA method was used to determine the free binding energies of the inhibitors for the AR enzyme.

Results:

5-pentylresorcinol compound showed the strongest inhibition effect on recombinant human AR enzyme with an IC50 value of 9.90 μM. The IC50 values of resorcinol, 5-methylresorcinol, 4- ethylresorcinol, 4-hexylresorcinol, 2-methylresorcinol, and 2,5-dimethylresorcinol compounds were determined as 49.50 μM, 43.31 μM, 19.25 μM, 17.32 μM, 28.87 μM, 57.75 μM, respectively.

Conclusion:

The results of this research showed that resorcinol compounds are effective AR inhibitors. These findings are supported by molecular docking, molecular mechanics, and ADME investigations undertaken to corroborate the experimental in vitro results.

In Vitro and In Silico Antioxidant Efficiency of Bio-Potent Secondary Metabolites From Different Taxa of Black Seed-Producing Plants and Their Derived Mycoendophytes

Oxidative stress is involved in the pathophysiology of multiple health complications, and it has become a major focus in targeted research fields. As known, black seeds are rich sources of bio-active compounds and widely used to promote human health due to their excellent medicinal and pharmaceutical properties. The present study investigated the antioxidant potency of various black seeds from plants and their derived mycoendophytes, and determined the total phenolic and flavonoid contents in different extracts, followed by characterization of major constituents by HPLC analysis. Finally, in silico docking determined their binding affinities to target myeloperoxidase enzymes. Ten dominant mycoendophytes were isolated from different black seed plants. Three isolates were then selected based on high antiradical potency and further identified by ITS ribosomal gene sequencing. Those isolated were Aspergillus niger TU 62, Chaetomium madrasense AUMC14830, and Rhizopus oryzae AUMC14823. Nigella sativa seeds and their corresponding endophyte A. niger had the highest content of phenolics in their n-butanol extracts (28.50 and 24.43 mg/g), flavonoids (15.02 and 11.45 mg/g), and antioxidant activities (90.48 and 81.48%), respectively, followed by Dodonaea viscosa and Portulaca oleracea along with their mycoendophytic R. oryzae and C. madrasense. Significant positive correlations were found between total phenolics, flavonoids, and the antioxidant activities of different tested extracts. The n-butanol extracts of both black seeds and their derived mycoendophytes showed reasonable IC50 values (0.81–1.44 mg/ml) compared to the control with significant correlations among their phytochemical contents. Overall, seventeen standard phenolics and flavonoids were used, and the compounds were detected in different degrees of existence and concentration in the examined extracts through HPLC analysis. Moreover, the investigation of the molecular simulation results of detected compounds against the myeloperoxidase enzyme revealed that, as a targeted antioxidant, rutin possessed a high affinity (−15.3184 kcal/mol) as an inhibitor. Taken together, the black seeds and their derived mycoendophytes are promising bio-prospects for the broad industrial sector of antioxidants with several valuable potential pharmaceutical and nutritional applications.

Development of Aldose Reductase Inhibitors for the Treatment of Inflammatory Disorders and Cancer: Current Drug Design Strategies and Future Directions

Aldose Reductase (AR) is an enzyme that converts glucose to sorbitol during the polyol pathway of glucose metabolism. AR has been shown to be involved in the development of secondary diabetic complications due to its involvement in causing osmotic as well as oxidative stress. Various AR inhibitors have been tested for their use to treat secondary diabetic complications, such as retinopathy, neuropathy, and nephropathy in clinical studies. Recent studies also suggest the potential role of AR in mediating various inflammatory complications. Therefore, the studies on the development and potential use of AR inhibitors to treat inflammatory complications and cancer besides diabetes are currently on the rise. Further, genetic mutagenesis studies, computer modeling, and molecular dynamics studies have helped design novel and potent AR inhibitors. This review discussed the potential new therapeutic use of AR inhibitors in targeting inflammatory disorders and cancer besides diabetic complications. Further, we summarized studies on how AR inhibitors have been designed and developed for therapeutic purposes in the last few decades.

Using of group-based selected flavonoids as alternative inhibitors for potato polyphenol oxidase

One of the main problems encountered after fresh-cutting of foods is enzymatic browning causing changes in the texture, taste, and color. The variety of physical and chemical-based antibrowning methods was applied to extend the shelf life of these products. Accordingly, methods using natural compounds are of great importance for health. In this study, it was aimed to prevent enzymatic browning in potato (Solanum tuberosum L. cv. Marfona) by limiting the polyphenol oxidase (PPO) activity with selected flavonoids. First of all, we purified the potato PPO (pPPO) by single-step affinity chromatography. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and native PAGE were applied on pPPO. Then, the inhibition effects of 7-hydroxyflavone, 7-hydroxy-4'-nitroisoflavone, myricetin, luteolin, 7-methoxyflavone, 6-fluoroflavone, diosmetin, rutin, and diosmin on purified PPO enzyme were investigated. Kinetic assays indicated that myricetin was a remarkable inhibitor with the K_i value of 5 µM on pPPO. PRACTICAL APPLICATIONS: Potatoes are one of the important diet in many countries. In the processing of potatoes, enzymatic oxidation catalyzed by polyphenol oxidases (PPOs) is lead to losing its taste, flavor, and color. In this current paper, group-based selected flavonoids were proposed as alternative inhibitors of potato PPO enzyme. These flavonoids allowing to limit the PPO activity are commercially available, and they can be potential candidates to be used as antibrowning agents during potato processing.