PTP1B inhibitory effects of tridepside and related metabolites isolated from the Antarctic lichen Umbilicaria antarctica

Pleiotropic Potential of Evernia prunastri Extracts and Their Main Compounds Evernic Acid and Atranorin: In Vitro and In Silico Studies

Evernia prunastri is a lichen widely distributed in the Northern Hemisphere. Its biological properties still need to be discovered. Therefore, our paper focuses on studies of E. prunastri extracts, including its main metabolites evernic acid (EA) or atranorin (ATR). Phytochemical profiles using chromatographic analysis were confirmed. The antioxidant activity was evaluated using in vitro chemical tests and in vitro enzymatic cells-free tests, namely superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR), and catalase (CAT). The anti-inflammatory potential using cyclooxygenase-2 (COX-2) and hyaluronidase were determined. The neuroprotective potential using acetylcholinesterase, (AChE), butyrylcholinesterase (BChE), and tyrosinase (Tyr) was estimated. The hypoglycemic activity was also confirmed (α-glucosidase). Principal component analysis was performed to determine the relationship between the biological activity of extracts. The inhibitory effect of EA and ATR on COX-2 AChE, BChE, Tyr, and α-glucosidase was evaluated using molecular docking techniques and confirmed for EA and ATR (besides α-glucosidase). The penetration of EA and ATR from extracts through the blood-brain barrier was confirmed using the parallel artificial membrane permeability assay blood-brain barrier test. In conclusion, depending on chemical surroundings and the concentration, the E. prunastri extracts, EA or ATR, showed attractive pleiotropic properties, which should be further investigated.

Tridepsides as potential bioactives: a review on their chemistry and the global distribution of their lichenic and non-lichenic natural sources

Tridepsides, as fully oxidized polyketides, have been known to exist in lichens for more than a century. Recent studies have showed that these possible defensive lichenochemicals possess various biological activities. Also, a candidate biosynthetic gene cluster was recently reported for gyrophoric acid (GA), an important tridepside. The present study focused on biosynthesis, natural sources, biological activities, and bioanalytical methods of tridepside molecules. Our survey shows that, so far, lichenic tridepsides have been reported from 37 families, 111 genera, and 526 species of lichen. Because many of their species contain tridepsides, the families Parmeliaceae, Lobariaceae, and Peltigeraceae can be considered critical lichenic sources of tridepsides. Furthermore, several species of Hypotrachyna in Parmeliaceae family showed lichenic tridepsides, suggesting that this genus is a viable source of tridepsides. This research also explored tridepsides from non-lichenic sources, such as non-lichenized fungi, lichenicolous fungi, endophytes, parasites, and liverworts, which offer substantial potential as biotechnological sources to produce tridepsides, which are produced in small amounts in lichen thalli. Two lichenic tridepsides have also been detected in non-lichenic sources: GA and tenuiorin (TE). Additionally, no significant correlation was found between tridepside biosynthesis and geographical distribution patterns for several potentially tridepside-producing lichens. We further showed that GA is the most studied tridepside with various reported biological activities, including anticancer, wound healing, photoprotection, anti-aging, antioxidant, cardiovascular effect, DNA interaction, anti-diabetes, anti-Alzheimer's, anti-bacterial, and antifungal. Last but not least, this study provides an overview of some bioanalytical methods used to analyze tridepsides over the past few years.

Biological Effects of Gyrophoric Acid and Other Lichen Derived Metabolites, on Cell Proliferation, Apoptosis and Cell Signaling pathways

Secondary metabolites from fungi, algae and lichens have remarkable biological activities as antibiotics, fungicides, antiviral drugs, and cancer therapeutics. This review focuses on the lichen-derived metabolite gyrophoric acid and other select secondary metabolites (e.g., usnic acid, salazinic acid, physodic acid, vulpinic acid ceratinalone, flavicansone, ramalin, physciosporin, tumidulin, atranorin, parmosidone) that modulate a number of cellular pathways relevant to several biomedical diseases and disorders, including cancer, diabetes and cardiovascular disease. We discuss the chemical structure and biochemical activities of gyrophoric acid and other compounds relative to the molecular mechanisms and cellular processes that these metabolites target in a distinct human and rodent cell types. The therapeutic promise of gyrophoric acid and similar lichen derived metabolites is associated with the chemical versatility of these compounds as polyaromatic depsides with functional carboxyl and hydroxyl side-groups that may permit selective interactions with distinct enzymatic active sites. Gyrophoric acid has been examined in a series of studies as an effective anticancer drug because it impinges on topoisomerase 1 activity, as well as causes cell cycle arrest, comprises cell survival, and promotes apoptosis. Because gyrophoric acid has cytostatic properties, its biological roles and possible medicinal utility may extend beyond effects on cancer cells and be relevant to any process that is controlled by cell growth and differentiation.

In silico analysis of a potential antidiabetic phytochemical erythrin against therapeutic targets of diabetes

Diabetes mellitus is a multifactorial disorder characterized by a chronic elevation in blood glucose levels. Currently, antidiabetic drugs are available to counteract the associated pathologies. Their concomitant effects necessitate the investigation for an effective and safe drug aimed to diminish blood glucose levels with fewer side effects. Several researchers are taking new initiatives to explore plant sources as they are known to contain a wide variety of active agents. Hence, the present study was undertaken to study the role of natural products using in silico interaction studies. Erythrin a compound present in lichens was selected as a potential anti-diabetic agent. Molecular docking studies were carried out with 14 target proteins to evaluate its antidiabetic potential. Molecular docking analysis resulted in favourable binding energy of interaction ranging as low as - 119.676 to - 92.9545 kcal/mol for erythrin, Analogue showed the highest interactions with 3C45 (- 119.676 kcal/mol) followed by 2Q5S (- 118.398 kcal/mol), 1XU7 (- 117.341 kcal/mol), 3K35 (- 114.267 kcal/mol). Erythrin was found to fare better than the three clinically used antidiabetic compounds, metformin, repaglinide and sitagliptin. Further, the molecular interactions between erythrin and the diabetes related target proteins was established by analysing the interactions with associated amino acids. In silico pharmacokinetics and toxicity profile of erythrin using admetSAR software predicted erythrin as non-carcinogenic and non-mutagenic. The drug-likeliness was calculated using molsoft software respecting Lipinski's rule of five. The compound was found to comply with Lipinksi rules violating only one filter criterion. The study suggested that erythrin could be a potential anti-diabetic agent.

Natural allosteric modulators and their biological targets: molecular signatures and mechanisms

Covering: 2008 to 2018Over the last decade more than two hundred single natural products were confirmed as natural allosteric modulators (alloNPs) of proteins. The compounds are presented and discussed with the support of a chemical space, constructed using a principal component analysis (PCA) of molecular descriptors from chemical compounds of distinct databases. This analysis showed that alloNPs are dispersed throughout the majority of the chemical space defined by natural products in general. Moreover, a cluster of alloNPs was shown to occupy a region almost devoid of allosteric modulators retrieved from a dataset composed mainly of synthetic compounds, further highlighting the importance to explore the entire natural chemical space for probing allosteric mechanisms. The protein targets which alloNPs bind to comprised 81 different proteins, which were classified into 5 major groups, with enzymes, in particular hydrolases, being the main representative group. The review also brings a critical interpretation on the mechanisms by which alloNPs display their molecular action on proteins. In the latter analysis, alloNPs were classified according to their final effect on the target protein, resulting in 3 major categories: (i) local alteration of the orthosteric site; (ii) global alteration in protein dynamics that change function; and (iii) oligomer stabilisation or protein complex destabilisation via protein-protein interaction in sites distant from the orthosteric site. G-protein coupled receptors (GPCRs), which use a combination of the three types of allosteric regulation found, were also probed by natural products. In summary, the natural allosteric modulators reviewed herein emphasise their importance for exploring alternative chemotherapeutic strategies, potentially pushing the boundaries of the druggable space of pharmacologically relevant drug targets.

Discovery of Novel Multi-target Inhibitor of angiotensin type 1 receptor and neprilysin inhibitors from Traditional Chinese Medicine

Angiotensin II type-1 receptor–neprilysin inhibitor (ARNi) is consisted of Angiotensin II type-1 receptor (AT1) antagonist and neprilysin (NEP) inhibitor, which could simultaneously increase the vasodilators of the natriuretic peptides and antagonize vasoconstrictors of Ang II. ARNi has been proved a superior effect and lower risks of death on chronic heart failure (CHF) and hypertension. In this paper, ARNi from Traditional Chinese Medicines (TCM) was discovered based on target combination of AT1 and NEP by virtual screening, biological assay and molecular dynamics (MD) simulations. Two customized strategies of combinatorial virtual screening were implemented to discover AT1 antagonist and NEP inhibitor based on pharmacophore modeling and docking computation respectively. Gyrophoric acid (PubChem CID: 135728) from Parmelia saxatilis was selected as AT1 antagonist and assayed with IC₅₀ of 29.76 μM by calcium influx assay. And 3,5,3′-triiodothyronine (PubChem CID: 861) from Bos taurus domesticus was screened as NEP inhibitor and has a dose dependent inhibitory activity by biochemistry fluorescence assay. Combined with MD simulations, these compounds can generate interaction with the target, key interactive residues of ARG167, TRP84, and VAL108 in AT1, and HIS711 in NEP were also identified respectively. This study designs the combinatorial strategy to discover novel frames of ARNi from TCM, and gyrophoric acid and 3,5,3′-triiodothyronine could provide the clues and revelations of drug design and therapeutic method of CHF and hypertension for TCM clinical applications.

Protein tyrosine phosphatase 1B inhibitors from natural sources

Since PTP1B enzyme was discovered in 1988, it has captured the research community's attention. This landmark discovery has stimulated numerous research studies on a variety of human diseases, including cancer, inflammation, and diabetes. Tremendous progress has been made in finding PTP1B inhibitors and exploring PTP1B regulatory mechanisms. This review investigates for the natural PTP1B inhibitors, and focuses on the common characteristics of the discovered structures and structure-activity relationships. To facilitate understanding, all the natural compounds are here divided into five different classes (fatty acids, phenolics, terpenoids, steroids, and alkaloids), according to their skeletons. These PTP1B inhibitors of scaffold structures could serve as a theoretical basis for new concept drug discovery and design.

Potential of Lichen Compounds as Antidiabetic Agents with Antioxidative Properties: A Review

The advancement in the knowledge of potent antioxidants has uncovered the way for greater insight in the treatment of diabetic complications. Lichens are a rich resource of novel bioactive compounds and their antioxidant potential is well documented. Herein we review the antidiabetic potential of lichens which have received considerable attention, in the recent past. We have correlated the antidiabetic and the antioxidant potential of lichen compounds. The study shows a good accordance between antioxidant and antidiabetic activity of lichens and points out the need to look into gathering the scarce and scattered data on biological activities for effective utilization. The review establishes that the lichen extracts, especially of Parmotrema sp. and Ramalina sp. have shown promising potential in both antidiabetic and antioxidant assays. Ubiquitous compounds, namely, zeorin, methylorsellinate, methyl-β-orcinol carboxylate, methyl haematommate, lecanoric acid, salazinic acid, sekikaic acid, usnic acid, gyrophoric acid, and lobaric acid have shown promising potential in both antidiabetic as well as antioxidant assays highlighting their potential for effective treatment of diabetic mellitus and its associated complications. The available compilation of this data provides the future perspectives and highlight the need for further studies of this potent herbal source to harvest more beneficial therapeutic antidiabetic drugs.

Natural products possessing protein tyrosine phosphatase 1B (PTP1B) inhibitory activity found in the last decades

This article provides an overview of approximately 300 secondary metabolites with inhibitory activity against protein tyrosine phosphatase 1B (PTP1B), which were isolated from various natural sources or derived from synthetic process in the last decades. The structure-activity relationship and the selectivity of some compounds against other protein phosphatases were also discussed. Potential pharmaceutical applications of several PTP1B inhibitors were presented.

Protein tyrosine phosphatase 1B and α-glucosidase inhibitory Phlorotannins from edible brown algae, Ecklonia stolonifera and Eisenia bicyclis

The present work investigates protein tyrosine phosphatase 1B (PTP1B) and the α-glucosidase inhibitory activities of two edible brown algae, Ecklonia stolonifera and Eisenia bicyclis, as well as in their isolated phlorotannins. Since the individual extracts and fractions showed significant inhibitory activities, column chromatography was performed to isolate six phlorotannins, phloroglucinol (1), dioxinodehydroeckol (2), eckol (3), phlorofurofucoeckol-A (4), dieckol (5), and 7-phloroeckol (6). Phlorotannins 3-6 were potent and noncompetitive PTP1B inhibitors with IC(50) values ranging from 0.56 to 2.64 µM; 4-6 exhibited the most potent α-glucosidase inhibition with IC(50) values ranging from 1.37 to 6.13 µM. Interestingly, 4 and 6 were noncompetitive, while 5 exhibited competitive inhibition in an α-glucosidase assay. E. stolonifera and E. bicyclis as well as their isolated phlorotannins therefore possessed marked PTP1B and α-glucosidase inhibitory activities; this could lead to opportunities in the development of therapeutic agents to control the postprandial blood glucose level and thereby prevent diabetic complications.