Evaluation of aldose reductase inhibition and docking studies of some secondary metabolites, isolated from Origanum vulgare L. ssp. hirtum

Overview of Ethnobotanical-Pharmacological Studies Carried Out on Medicinal Plants from the Serra da Estrela Natural Park: Focus on Their Antidiabetic Potential

The Serra da Estrela Natural Park (NPSE) in Portugal stands out as a well-preserved region abundant in medicinal plants, particularly known for their pharmaceutical applications in diabetes prevention and treatment. This comprehensive review explores these plants' botanical diversity, traditional uses, pharmacological applications, and chemical composition. The NPSE boast a rich diversity with 138 medicinal plants across 55 families identified as traditionally and pharmacologically used against diabetes globally. Notably, the Asteraceae and Lamiaceae families are prevalent in antidiabetic applications. In vitro studies have revealed their significant inhibition of carbohydrate-metabolizing enzymes, and certain plant co-products regulate genes involved in carbohydrate metabolism and insulin secretion. In vivo trials have demonstrated antidiabetic effects, including glycaemia regulation, insulin secretion, antioxidant activity, and lipid profile modulation. Medicinal plants in NPSE exhibit various activities beyond antidiabetic, such as antioxidant, anti-inflammatory, antibacterial, anti-cancer, and more. Chemical analyses have identified over fifty compounds like phenolic acids, flavonoids, terpenoids, and polysaccharides responsible for their efficacy against diabetes. These findings underscore the potential of NPSE medicinal plants as antidiabetic candidates, urging further research to develop effective plant-based antidiabetic drugs, beverages, and supplements.

Oregano as a potential source of antidiabetic agents

Oregano is the name given to a great variety of herbs belonging mainly to the Lamiaceae and Verbenaceae botanical families. Oregano species are rich sources of phytochemicals such as phenolic compounds like rosmarinic acid, salvianolic acid, and luteolin, among others. A few articles have previously accessed some potential pharmacological bioactivities of oregano plants; however, none has focused on the antidiabetic studies. This review aims to summarize recent studies about the potential effect of phenolic compounds from oregano plant species. The reports were retrieved from electronic databases such as PubMed, Web of Science, National Center for Biotechnology Information (NCBI), and Scopus. In addition, articles related to the mentioned topics and published between 2004-2022 were selected. The results from this study show that the antidiabetic pharmacological reports of oregano phenolic compounds are mainly in vitro reports. Therefore, the diversity of oregano species yields a broad variety of phenolic constituents, where preclinical and clinical studies are strongly recommended.

Determination of the Phenolic Profile, and Evaluation of Biological Activities of Hydroethanolic Extract from Aerial Parts of Origanum compactum from Morocco

Origanum compactum belonging to the family Lamiaceae is widely used in food and pharmaceutical fields due to its biologically active substances. We aimed to investigate the total phenol and flavonoid contents and the phenolic composition, and to evaluate the antioxidant and antibacterial properties of hydroethanolic extract from of Origanum compactum. Total phenol and flavonoid contents were evaluated using gallic acid and quercetin as standards, respectively, and the phenolic profile was characterized using high-performance liquid chromatography coupled to a photodiode array and electrospray ionization mass spectrometry (HPLC-PDA-ESI/MS). The antioxidant activity was determined by two methods: ferric reducing power (FRAP) assay and the phosphomolybdate method. The antibacterial effect was evaluated against four bacteria (Escherichia coli, Salmonella typhimurium, Staphylococcus aureus and Listeria monocytogenes) using the broth microdilution method. The findings show that the total phenolic and flavonoid contents were 107.789 ± 5.39 mg GAE/g dm and 14,977 ± 0.79 mg QE/g dm, respectively. A total of sixteen phenolic compounds belonging to phenolic acids and flavonoids were detected. Furthermore, the extract showed strong antioxidant activity, and displayed a bacteriostatic effect against Escherichia coli and Salmonella typhimuriumn, and a bactericidal effect against Staphylococcus aureus and Listeria monocytogenes. Therefore, this study reveals that Origanum compactum extracts display potential as antibacterial and natural antioxidant agents for fighting against pathogenic bacteria and preventing oxidative stress.

Natural Compounds as Source of Aldose Reductase (AR) Inhibitors for the Treatment of Diabetic Complications: A Mini Review

BACKGROUND

Aldol reductase (AR) is the polyol pathway's main enzyme that portrays a crucial part in developing 'complications of diabetes' involving cataract, retinopathy, nephropathy, and neuropathy. These diabetic abnormalities are triggered tremendously via aggregation of sorbitol formation (catalyzed by AR) in the polyol pathway. Consequently, it represents an admirable therapeutic target and vast research was done for the discovery of novel molecules as potential AR inhibitors for diabetic complications.

OBJECTIVE

This review article has been planned to discuss an outline of diabetic complications, AR and its role in diabetic complications, natural compounds reported as AR inhibitors, and benefits of natural/plant derived AR inhibitors for the management of diabetic abnormalities.

RESULTS

The goal of AR inhibition remedy is to stabilize the increased flux of blood glucose and sorbitol via the 'polyol pathway' in the affected tissues. A variety of synthetic inhibitors of AR have been established such as tolrestat and sorbinil, but both of these face limitations including low permeability and health problems. Pharmaceutical industries and other scientists were also undertaking work to develop newer, active, and 'safe' AR inhibitors from natural sources. Therefore, several naturally found molecules were documented to possess a potent inhibitory action on AR activity.

CONCLUSION

Natural inhibitors of AR appeared as harmless pharmacological agents for controlling diabetic complications. The detailed literature throughout this article shows the significance of herbal extracts and phytochemicals as prospective useful AR inhibitors in treating diabetic complications.

A Review of the Phytochemistry and Antimicrobial Properties of Origanum vulgare L. and Subspecies

Origanum vulgare L. (O. vulgare) is an important medicinal herb of the family Lamiaceae. In the current study, we explained the critical evaluation of traditional uses, the phytochemistry and the antimicrobial properties of O. vulgare and its subspecies, with a focus on the mechanisms of actions of the most important phytochemicals from O. vulgare subspecies. The most important phytochemicals of O. vulgare are volatile (essential oil) and non-volatile phenolic compounds (phenolic acids & flavonoids). The constituents of the O. vulgare essential oil (EO) include high percentages of thymol and carvacrol with excellent antimicrobial activity alone or in combination with other antibiotics. Interesting results have been reported the remarkable antimicrobial activities of infusion or tea products of O. vulgare with a high amount of EO against multidrug-resistant bacterial and fungal microorganism (such as Escherichia coli, Staphylococcus aureus, Candida albicans and Pseudomonas aeruginosa). The most important antibacterial mechanisms of O. vulgare are enzyme inhibition, efflux pump inhibition, ATP depletion, biofilm formation inhibition and cytoplasmic membrane damage. The antimicrobial activity of the hirtum subspecies has been confirmed in different in-vitro and in-vivo studies. The present review confirms the clinical and preclinical research showing the O. vulgare and its subspecies antimicrobial effects.

Evaluation of the Anti-Diabetic Activity of Some Common Herbs and Spices: Providing New Insights with Inverse Virtual Screening

Culinary herbs and spices are widely used as a traditional medicine in the treatment of diabetes and its complications, and there are several scientific studies in the literature supporting the use of these medicinal plants. However, there is often a lack of knowledge on the bioactive compounds of these herbs and spices and their mechanisms of action. The aim of this study was to use inverse virtual screening to provide insights into the bioactive compounds of common herbs and spices, and their potential molecular mechanisms of action in the treatment of diabetes. In this study, a library of over 2300 compounds derived from 30 common herbs and spices were screened in silico with the DIA-DB web server against 18 known diabetes drug targets. Over 900 compounds from the herbs and spices library were observed to have potential anti-diabetic activity and liquorice, hops, fennel, rosemary, and fenugreek were observed to be particularly enriched with potential anti-diabetic compounds. A large percentage of the compounds were observed to be potential polypharmacological agents regulating three or more anti-diabetic drug targets and included compounds such as achillin B from yarrow, asparasaponin I from fenugreek, bisdemethoxycurcumin from turmeric, carlinoside from lemongrass, cinnamtannin B1 from cinnamon, crocin from saffron and glabridin from liquorice. The major targets identified for the herbs and spices compounds were dipeptidyl peptidase-4 (DPP4), intestinal maltase-glucoamylase (MGAM), liver receptor homolog-1 (NR5A2), pancreatic alpha-amylase (AM2A), peroxisome proliferator-activated receptor alpha (PPARA), protein tyrosine phosphatase non-receptor type 9 (PTPN9), and retinol binding protein-4 (RBP4) with over 250 compounds observed to be potential inhibitors of these particular protein targets. Only bay leaves, liquorice and thyme were found to contain compounds that could potentially regulate all 18 protein targets followed by black pepper, cumin, dill, hops and marjoram with 17 protein targets. In most cases more than one compound within a given plant could potentially regulate a particular protein target. It was observed that through this multi-compound-multi target regulation of these specific protein targets that the major anti-diabetic effects of reduced hyperglycemia and hyperlipidemia of the herbs and spices could be explained. The results of this study, taken together with the known scientific literature, indicated that the anti-diabetic potential of common culinary herbs and spices was the result of the collective action of more than one bioactive compound regulating and restoring several dysregulated and interconnected diabetic biological processes.

Effect of rosmarinic acid on the arterial blood pressure in normotensive and hypertensive rats: Role of ACE

BACKGROUND

In recent years, it has been demonstrated the inhibitory effect of some plant species on the angiotensin-converting enzyme and rosmarinic acid is a prominent constituent of these species.

HYPOTHESIS/PURPOSE

This study was carried out to verify the effect of rosmarinic acid on blood pressure through inhibitory activity on angiotensin-converting enzyme in rats.

STUDY DESIGN

The arterial hypertension was promoted using 2-kidneys 1-clip model in rats. The potential inhibitory rosmarinic acid effect on angiotensin-converting enzyme activity was compared with captopril actions by analyzing in vivo blood pressure dose-response curves to angiotensin I and bradykinin. The in vitro plasma angiotensin-converting enzyme activity was measured by fluorimetry using the substrate Abz-FRK(Dnp)P-OH substrate. In addition, dosages of nitrite/nítrate analysis were carried out.

RESULTS

(1) rosmarinic acid caused systolic blood pressure dose-dependent decrease in hypertensive rats; (2) The angiotensin I dose-response curves demonstrated that rosmarinic acid promotes minor changes in systolic blood pressure only in the hypertensive group; (3) The bradykinin dose-response curves showed that both rosmarinic acid and captopril promoted a systolic blood pressure reduction, but only the captopril effect was significant; (4) The angiotensin-converting enzyme activity in rat lung tissue was inhibited by the rosmarinic acid in a dose dependent manner; (5) The analysis of nitrite/nítrate plasma concentrations showed no significant difference among the experimental groups.

CONCLUSION

The rosmarinic acid is effective in reducing blood pressure, selectively, only in hypertensive animals. The rosmarinic acid (173µM) promoted almost a 98.96% reduction on angiotensin-converting enzyme activity.

Identification of Novel Aldose Reductase Inhibitors from Spices: A Molecular Docking and Simulation Study

Hyperglycemia in diabetic patients results in a diverse range of complications such as diabetic retinopathy, neuropathy, nephropathy and cardiovascular diseases. The role of aldose reductase (AR), the key enzyme in the polyol pathway, in these complications is well established. Due to notable side-effects of several drugs, phytochemicals as an alternative has gained considerable importance for the treatment of several ailments. In order to evaluate the inhibitory effects of dietary spices on AR, a collection of phytochemicals were identified from Zingiber officinale (ginger), Curcuma longa (turmeric) Allium sativum (garlic) and Trigonella foenum graecum (fenugreek). Molecular docking was performed for lead identification and molecular dynamics simulations were performed to study the dynamic behaviour of these protein-ligand interactions. Gingerenones A, B and C, lariciresinol, quercetin and calebin A from these spices exhibited high docking score, binding affinity and sustained protein-ligand interactions. Rescoring of protein ligand interactions at the end of MD simulations produced binding scores that were better than the initially docked conformations. Docking results, ligand interactions and ADMET properties of these molecules were significantly better than commercially available AR inhibitors like epalrestat, sorbinil and ranirestat. Thus, these natural molecules could be potent AR inhibitors.

Induced fit docking, pharmacophore modeling, and molecular dynamic simulations on thiazolidinedione derivatives to explore key interactions with Tyr48 in polyol pathway

To obtain a scientific thought and expedition to explore key interactions with Tyr48 in aldose reductase (ALR), combined study of pharmacophore modeling, induced fit docking, and dynamics studies were performed on ALR. A stereo chemically and energetically valid model of ALR-NADP+ complex was developed using homology modeling technique. Statistically a significant five point pharmacophore model was designed on a set of 54 thiazolidinedione derivatives with good external and internal predictive ability. Rigid and induced fit docking protocols were applied on ALR protein for both with and without NADP+ cofactor to identify a suitable binding mode that facilitates the key hydrogen bond interactions with Tyr48. Docking of thiazolidinedione derivatives into ALR-NADP+ complex gave more promising results by reducing false positive binding of inhibitors into the co-factor binding site. Structural changes within Try48 and Asp43 during the binding process in enzyme inhibitor complex were analyzed using molecular dynamics (MD) simulations. The results obtained from dynamic simulations emphasized the role of Tyr48 in maintaining inter or intra molecular hydrogen bond interaction with the protein or inhibitor respectively. New molecules were designed and checked for their binding interactions and showed improved results compared to existing thiazolidinediones derivatives. Hence, these combined protocols will be helpful and cooperative to design and optimize molecules with better inhibitory activity against the biologically active target.

Aldose reductase inhibitors of plant origin

Diabetic complications are attributed to hyperglycaemic condition which is in turn associated with the polyol pathway and advanced glycation end products. Aldose reductase (AR) is the principal enzyme of polyol pathway which plays a vital role in the development of diabetic complications. AR inhibitory activity can be screened by both in vitro and in vivo methods. In vitro assays for AR enzyme are further classified on the basis of the source of enzyme such as rat lens, rat kidney, cataracted human eye lens, bovine eyes and human recombinant AR enzymes, whereas the in vivo model is based on the determination of lens galactitol levels. A number of synthetic AR inhibitors (ARIs) including tolrestat and sorbinil have been developed, but all of these suffer from drawbacks such as poor permeation and safety issues. Therefore, pharmaceutical companies and many researchers have been carrying out research to find new, potent and safe ARIs from natural sources. Thus, many naturally occurring compounds have been reported to have AR inhibitory activity. The present review attempts to highlight phytochemicals and plant extracts with potential AR inhibitory activity. It also summarizes the classes of compounds which have proven AR inhibitory activity. Phytochemicals such as quercetin, kaempferol and ellagic acid are found to be the most promising ARIs. The exhaustive literature presented in this article clearly indicates the role of plant extracts and phytochemicals as potential ARIs.

Is rosmarinic acid underestimated as an experimental cardiovascular drug?

PURPOSE

The rationale of the present review is to analize the activity of Rosmarinus officinalis in the the cardiovascular system

METHODS

A MEDLINE database search (from January 1970 to December 2011) using only rosmarinic acid as searched term.

RESULTS

The references search revealed 509 references about rosmarinic acid in 40 years (the first reference is from 1970). There is a powerful prevalence of antioxidant and cancer studies. Other diseases are few cited, as inflammation, brain (Alzheimer and Parkinson disease) and, memory; allergy; diabetes; atherosclerosis, and; hypertension. It is necessary to consider the complete absence of studies on coronary artery disease, myocardial ischemia, heart failure or ischemia/reperfusion injury.

CONCLUSION

Rosmarinic acid is underestimated as an experimental cardiovascular drug and deserves more attention.

The inhibitory effect of Prunella vulgaris L. on aldose reductase and protein glycation

To evaluate the aldose reductase (AR) enzyme inhibitory ability of Prunella vulgaris L. extract, six compounds were isolated and tested for their effects. The components were subjected to in vitro bioassays to investigate their inhibitory assays using rat lens aldose reductase (rAR) and human recombinant AR (rhAR). Among them, caffeic acid ethylene ester showed the potent inhibition, with the IC(50) values of rAR and rhAR at 3.2 ± 0.55 μM and 12.58 ± 0.32 μM, respectively. In the kinetic analyses using Lineweaver-Burk plots of 1/velocity and 1/concentration of substrate, this compound showed noncompetitive inhibition against rhAR. Furthermore, it inhibited galactitol formation in a rat lens incubated with a high concentration of galactose. Also it has antioxidative as well as advanced glycation end products (AGEs) inhibitory effects. As a result, this compound could be offered as a leading compound for further study as a new natural products drug for diabetic complications.

Renal protective effects of extracts from guava fruit (Psidium guajava L.) in diabetic mice

This study analyzed the content of phenolic acids and flavonoids in extracts of guava fruit (Psidium guajava L.), and examined the renal protective effects of guava aqueous extract (GAE) and ethanol extract (GEE) in diabetic mice. GAE had more caffeic acid, myricetin, and quercetin; and GEE had more cinnamic, coumaric and ferulic acids. GAE or GEE at 1 and 2 % was supplied in diet for 12 weeks. GAE or GEE intake at 2 % significantly reduced glucose and blood urea nitrogen levels, increased insulin level in plasma of diabetic mice (p < 0.05). GAE or GEE treatments dose-dependently reserved glutathione content, retained activity of catalase and glutathione peroxidase, and decreased reactive oxygen species, interleukin (IL)-6, tumor necrosis factor-α and IL-1β levels in kidney (p < 0.05). GAE and GEE treatments at 2 % significantly declined renal N (ε)-(carboxymethyl)lysine, pentosidine and fructose levels (p < 0.05), and suppressed renal activity of aldose reductase (p < 0.05). These findings support that guava fruit could protect kidney against diabetic progression via its anti-oxidative, anti-inflammatory and anti-glycative effects.

CoMFA and CoMSIA analysis of 2,4-thiazolidinediones derivatives as aldose reductase inhibitors

Diabetes remains a life-threatening disease. The clinical profile of diabetic subjects is often worsened by the presence of several long-term complications, for example neuropathy, nephropathy, retinopathy, and cataract. Comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) were performed on a series of 2,4-thiazolidinediones derivatives as aldose reductase (ALR2) inhibitors. Molecular ligand superimposition on a template structure was finished by the database alignment method. The 3D-QSAR models resulted from 44 molecules gave q (2) values of 0.773 and 0.817, r (2) values of 0.981 and 0.979 for CoMFA and CoMSIA, respectively. The contour maps from the models indicated that a large volume group next to the R-substituent will increase the ALR2 inhibitory activity. In fact, adding a -CH(2)COOH substituent at the R-position would generate a new compound with higher predicted activity.

Reaction of rosmarinic acid with nitrite ions in acidic conditions: discovery of nitro- and dinitrorosmarinic acids as new anti-HIV-1 agents

Rosmarinic acid was reacted with nitrite ions under acidic conditions to give 6'-nitro- and 6',6''-dinitrorosmarinic acids according to the reaction time. Both compounds were active as HIV-1 integrase inhibitors at the submicromolar level. They also inhibited the viral replication in MT-4 cells with modest and similar selectivity indexes. The nitration of rosmarinic acid strongly improves the anti-integrase inhibition and the antiviral activity without increasing the cellular toxicity.

Inhibitory effect of polar oregano extracts on aldose reductase and soybean lipoxygenase in vitro

The effect of methanol and aqueous methanol extract of Origanum vulgare L. ssp. hirtum on aldose reductase and soybean lipoxygenase was investigated. The results revealed a promising potential of oregano for preventing diabetes complications in the long term and an antiinflammatory efficacy by inhibiting soybean lipoxygenase.