Advanced glycation end-products (AGE) trapping agents: Design and synthesis of nature inspired indeno[2,1-c]pyridinones

Ligand-Based Pharmacophoric Design and Anti-inflammatory Evaluation of Triazole Linked Semisynthetic Labdane Conjugates

This study employed a ligand-based pharmacophoric approach to design and synthesize 33 novel semisynthetic labdane-appended triazolyl isatins to discover potential anti-inflammatory agents. The anti-inflammatory efficacy of the derivatives was evaluated by their ability to inhibit the production of NO, TNF-α, and IL-6, in lipopolysaccharide-induced RAW264.7 macrophages. The initial screening revealed that compound 7a ((1-(2-(2,3-dioxoindolin-1-yl)ethyl)-1H-1,2,3-triazol-4-yl)methyl (E)-3-formyl-5-((1S,4aS,8aS)-5,5,8a-trimethyl-2-methylenedecahydronaphthalen-1-yl)pent-3-enoate) exhibited an anti-inflammatory effect (NO inhibition, IC50 = 3.13 μΜ), surpassing both the positive control indomethacin (NO inhibition, IC50 = 7.31 μΜ) and the parent compound labdane dialdehyde. Notably, 7a reduced the levels of pro-inflammatory cytokines TNF-α and IL-6 while increasing the levels of the anti-inflammatory cytokine IL-10. Mechanistic studies revealed that 7a downregulated the expression of COX-2 and iNOS by inhibiting the NF-κB signaling pathway. In silico molecular modeling studies on NF-κB proteins support these findings, suggesting that 7a is a promising candidate for developing into a potent anti-inflammatory clinical agent.

Linker-Based Pharmacophoric Design and Semisynthesis of Labdane Conjugates Active against Multi-Faceted Inflammatory Targets

Prolonged inflammation leads to the genesis of various inflammatory diseases such as atherosclerosis, cancer, inflammatory bowel disease, Alzheimer's, etc. The uncontrolled inflammatory response is characterized by the excessive release of pro-inflammatory mediators such as nitric oxide (NO), tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), interleukin-1alpha (IL-1α), and inflammatory enzymes such as cyclooxygenase-2 (COX-2). Hence, the downregulation of these inflammatory mediators is an active therapy to control aberrant inflammation and tissue damage. To address this, herein, we present the rational design and synthesis of novel phytochemical entities (NPCEs) through strategic linker-based molecular hybridization of aromatic/heteroaromatic fragments with the labdane dialdehyde, isolated from the medicinally and nutritionally significant rhizomes of the plant Curcuma amada. To validate the anti-inflammatory potential, we employed a comprehensive in vitro study assessing its inhibitory effect on the COX-2 enzyme and other inflammatory mediators, viz., NO, TNF-α, IL-6, and IL-1α, in bacterial lipopolysaccharide-stimulated macrophages, as well as in-silico molecular modeling studies targeting the inflammation regulator COX-2 enzyme. Among the synthesized novel compounds, 5f exhibited the highest anti-inflammatory potential by inhibiting the COX-2 enzyme (IC50 = 17.67 ± 0.89 μM), with a 4-fold increased activity relative to the standard drug indomethacin (IC50 = 67.16 ± 0.17 μM). 5f also significantly reduced the levels of LPS-induced NO, TNF-α, IL-6, and IL-1α, much better than the positive control. Molecular mechanistic studies revealed that 5f suppressed the expression of COX-2 and pro-inflammatory cytokine release dose-dependently, which was associated with the inhibition of the NF-κB signaling pathway. This infers that the labdane derivative 5f is a promising lead candidate as an anti-inflammatory agent to further explore its therapeutic landscape.

(+)-Catechin mitigates impairment in insulin secretion and beta cell damage in methylglyoxal-induced pancreatic beta cells

BACKGROUND

The formation of advanced glycation end products (AGEs) is the central process contributing to diabetic complications in diabetic individuals with sustained and inconsistent hyperglycemia. Methylglyoxal, a reactive carbonyl species, is found to be a major precursor of AGEs, and its levels are elevated in diabetic conditions. Dysfunction of pancreatic beta cells and impairment in insulin secretion are the hallmarks of diabetic progression. Exposure to methylglyoxal-induced AGEs alters the function and maintenance of pancreatic beta cells. Hence, trapping methylglyoxal could be an ideal approach to alleviate AGE formation and its influence on beta cell proliferation and insulin secretion, thereby curbing the progression of diabetes to its complications.

METHODS AND RESULTS

In the present study, we have explored the mechanism of action of (+)-Catechin against methylglyoxal-induced disruption in pancreatic beta cells via molecular biology techniques, mainly western blot. Methylglyoxal treatment decreased insulin synthesis (41.5%) via downregulating the glucose-stimulated insulin secretion pathway (GSIS). This was restored upon co-treatment with (+)-Catechin (29.9%) in methylglyoxal-induced Beta-TC-6 cells. Also, methylglyoxal treatment affected the autocrine function of insulin by disrupting the IRS1/PI3k/Akt pathway. Methylglyoxal treatment suppresses Pdx-1 and Maf A levels, which are responsible for beta cell maintenance and cell proliferation. (+)-Catechin could significantly augment the levels of these transcription factors.

CONCLUSION

This is the first study to examine the impact of a natural compound on methylglyoxal with the insulin-mediated autocrine and paracrine activities of pancreatic beta cells. The results indicate that (+)-Catechin exerts a protective effect against methylglyoxal exposure in pancreatic beta cells and can be considered a potential anti-glycation agent in further investigations on ameliorating diabetic complications.

DBU-Catalyzed Diastereo/Regioselective Access to Highly Substituted Spiro-oxetane Oxindoles via Ring Annulation of Isatins and Allenoates

A facile and efficient method for the diastereo/regioselective synthesis of highly functionalized spiro-oxetane oxindoles has been described. The 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)-catalyzed reaction proceeds via spiro-annulation of isatins and allenoates. The reaction is compatible with a wide range of isatins containing electron-donating groups (EDGs) and electron-withdrawing groups (EWGs) with various allenoates affording the corresponding products in acceptable yields. It is noteworthy that this is the first protocol for constructing structurally diverse motifs of highly functionalized spiro-oxetane oxindoles of pharmaceutical relevance.

Antibacterial natural products from microbial and fungal sources: a decade of advances

Throughout the ages the world has witnessed the outbreak of many infectious diseases. Emerging microbial diseases pose a serious threat to public health. Increasing resistance of microorganisms towards the existing drugs makes them ineffective. In fact, anti-microbial resistance is declared as one of the top public health threats by WHO. Hence, there is an urge for the discovery of novel antimicrobial drugs to combat with this challenge. Structural diversity and unique pharmacological effects make natural products a prime source of novel drugs. Staggeringly, in spite of its extensive biodiversity, a prominent portion of microorganism species remains unexplored for the identification of bioactives. Microorganisms are a predominant source of new chemical entities and there are remarkable number of antimicrobial drugs developed from it. In this review, we discuss the contributions of microorganism based natural products as effective antibacterial agents, studied during the period of 2010-2020. The review encompasses over 140 structures which are either natural products or semi-synthetic derivatives of microbial natural products. 65 of them are identified as newly discovered natural products. All the compounds discussed herein, have exhibited promising efficacy against various bacterial strains.

Multicomponent Synthesis of Spiro-dihydropyridine Oxindoles via Cascade Spiro-cyclization of Knoevenagel/Aza-Michael Adducts

An efficient, straightforward, and one-pot synthesis of biologically relevant spiro-dihydropyridine oxindoles was described via readily available isatin, malononitrile, allenoate, and amines. The metal/organocatalyst-free, Et₃N-mediated reaction proceeds via cascade spiro-cyclization of in situ generated Knoevenagel/aza-Michael adducts. The reaction has great flexibility over electron-rich and electron-poor substituents affording desired products in good to excellent yields. We have also demonstrated the selected spiro-dihydropyridines for late-stage diversification into new spiro-dihydropyridine hybrids of pharmaceutical relevance.

Marine Based Natural Products: Exploring the Recent Developments in the Identification of Antimicrobial Agents

The marine ecosystem is the less explored, biologically diverse, and vastest resource to discover novel antimicrobial agents. In recent decades' antimicrobial drugs are losing their effectiveness due to the growing resistance among pathogens, which causes diseases to have considerable death rates across the globe. Therefore, there is a need for the discovery of new antibacterials that can reach the market. There is a gradual growth of compounds from marine sources which are entering the clinical trials. Thus, the prominence of marine natural products in the field of drug design and discovery across the academia and pharmaceutical industry is gaining attention. Herein,  the present review covers nearly 200 marine based antimicrobial agents of 11 structural classes discovered from the year 2010 to 2022. All the discussed compounds have exhibited medium to high antimicrobial activity in inhibiting various microorganisms.