Current Bioactive Compounds - Volume 20, Issue 10, 2024

4-Substituted- 5-oxo-prolinates (pyroglutamates) are important components in various natural products, e.g. (-)-bulgecinine, (-)-anatoxin, salinosporamide, as well as ACE inhibitors.

These also act as important intermediates in the synthesis of many of the bioactive molecules. Due to these reasons, the synthesis of 4-substituted-(2S)-5-oxo-prolinates has received much attention over the globe in the last three decades. However, most of the synthetic strategies available in the literature describe either the use of expensive lithium enolate-derived low-temperature chemistry or the rigorous reaction conditions, and therefore, a simple, environment-friendly, and cost-effective approach was truly demanding.

In our ongoing research program, we required different 4-substituted pyroglutamates as intermediates, and with that very basic objective, we were looking for an alternate strategy which should be simple, requiring cheap reagents and consequently, in the process, it was thought to attempt proline catalyzed aldol/alkylation reactions on pyroglutamates, and the idea provided excellent outcome.

Herein we wish to report the L-proline catalyzed asymmetric functionalization at C-4 of (2S)-5-oxoproline methyl ester, which furnished desired products at room temperature at the same time, not requiring expensive reagents and, therefore, in turn, cost-effective.

This new strategy explored for synthesizing 4-substituted pyroglutamates could be useful for researchers across the globe working in the area and requiring substitution at C-4 of pyroglutamates for synthesizing bioactive molecules/natural products.

A new series of 2-(2-(substituted aldehyde)hydrazinyl)-4-(2-chlorophenyl)-1-methyl-6-oxo-1,6-dihydropyrimidine-5-carbonitrile analogs (1–19) was prepared by using the Biginelli reaction.

TLC was employed to ensure the progress and confirmation of the reactions. Silica gel G was employed as the stationary phase, and mobile phases such as chloroform: toluene and acetone: n-hexane were used for the synthesized compounds. NMR.MS, IR, CHN spectral techniques used for the characterization of synthesized compound.

The prepared derivatives were evaluated in vitro for antimicrobial activity against various bacteria and fungi using the tube dilution technique. Notably, compounds 2-(2-(3-Ethoxy-4-hydroxybenzylidene)hydrazinyl)-4-(2-chlorophenyl)-1-methyl-6-oxo-1,6-dihydropyrimidine-5-carbonitrile T1, 2-(2-(2-Hydroxybenzylidene)hydrazinyl)-4-(2-chlorophenyl)-1-methyl-6-oxo-1,6-dihydropyrimidine-5 carbonitrile T6, and 2-(2-(4-Hydroxybenzylidene)hydrazinyl)-4-(2-chlorophenyl)-1-methyl-6-oxo-1,6-dihydropyrimidine-5-carbonitrile T16, displayed significant antibacterial activity, surpassing the standard drug Ampicillin. In the antifungal category, compounds 2-(2-(3-Ethoxy-4-hydroxybenzylidene)hydrazinyl)-4-(2-chlorophenyl)-1-methyl-6-oxo-1,6-dihydropyri
midine-5-carbonitrile T1, 2-(2-(3,4-Dimethoxybenzylidene)hydrazinyl)-4-(2-chlorophenyl)-1-methyl-6-oxo-1,6-dihydropyrimidine-5-carbonitrile T2, and 2-(2-(2,4-Dichlorobenzylidene)hydrazinyl)-4-(2-chlorophenyl)-1-methyl-6-oxo-1,6-dihydropyrimidine-5-carbonitrile T13, were very much effective against both fungal strains A. niger as well as C. albicans. Furthermore, compounds 2-(2-(2-Hydroxybenzylidene)hydrazinyl)-4-(2-chlorophenyl)-1-methyl-6-oxo-1,6-dihydropyrimidine-5 carbonitrile T6, 2-(2-(2-Nitrobenzylidene)hydrazinyl)-4-(2-chlorophenyl)-1-methyl-6-oxo-1,6-dihydropyri
midine-5-carbonitrile T8, 2-(2-(4-Chlorobenzylidene)hydrazinyl)-4-(2-chlorophenyl)-1-methyl-6-oxo-1,6-dihydropyrimidine-5-carbonitrile T12, and 2-(2-(4-Dimethylaminobenzylidene)hydrazinyl)-4-(2-chlorophenyl)-1-methyl-6-oxo-1,6-dihydropyrimidine-5-carbonitrile T14 demonstrated remarkable antioxidant properties, because of their low IC50 values in the DPPH assay. In the realm of anticancer activity, 2-(2-(substituted aldehyde)hydrazinyl)-4-(2-chlorophenyl)-1-methyl-6-oxo-1,6-dihydro
pyrimidine-5-carbonitrile T9 outperformed the standard drug Adriamycin in terms of its effectiveness against human lung cancer cells (A-549) with a GI50 value of less than 10 according to the SRB assay. In addition, the antidiabetic assessment highlighted the excellent performance of compounds 2-(2-(2-Nitrobenzylidene)hydrazinyl)-4-(2-chlorophenyl)-1-methyl-6-oxo-1,6-dihydropyrimidine-5-carbonitrile T8, 2-(2-(4-Chlorobenzylidene)hydrazinyl)-4-(2-chlorophenyl)-1-methyl-6-oxo-1,6-dihydropyrimidine-5-carbonitrile T12, and 2-(2-(3-Nitrobenzylidene)hydrazinyl)-4-(2-chloro
phenyl)-1-methyl-6-oxo-1,6-dihydropyrimidine-5-carbonitrile T15, with low IC50 values, when tested for their inhibition of α-amylase enzyme activity.

The synthesized derivatives demonstrated strong antimicrobial, antioxidant, anticancer, and antidiabetic properties when assessed using specific methods and compared to established drugs. Notably, compounds 2-(2-(3-Ethoxy-4-hydroxybenzylidene)hydrazinyl)-4-(2-chloro
phenyl)-1-methyl-6-oxo-1,6-dihydropyrimidine-5-carbonitrile T1, 2-(2-(2-Hydroxybenzylidene)
hydrazinyl)-4-(2-chlorophenyl)-1-methyl-6-oxo-1,6-dihydropyrimidine-5 carbonitrile T6, and 2-(2-(2,4-Dichlorobenzylidene)hydrazinyl)-4-(2-chlorophenyl)-1-methyl-6-oxo-1,6-dihydropyrimidine
-5-carbonitrile T13, 2-(2-(4-Chlorobenzylidene)hydrazinyl)-4-(2-chlorophenyl)-1-methyl-6-oxo-1,6-dihydropyrimidine-5-carbonitrile T12 and 2-(2-(substituted aldehyde)hydrazinyl)-4-(2-chloro
phenyl)-1-methyl-6-oxo-1,6-dihydropyrimidine-5-carbonitrile T9 exhibited even higher activity levels than the standard medications. The presence of electron-releasing groups in the synthesized compounds enhanced their antibacterial and antioxidant effects, particularly against B. subtilis. On the other hand, electron-withdrawing groups improved their anticancer and antidiabetic properties.

Rosmarinus officinalis is considered one of the famous plants from ancient times for its therapeutic ability in many diseases, such as headache, spasms, brain disorders, and some pathological conditions associated with toxicity cases in the liver and kidneys.

The current research has aimed, for the first time, to evaluate anti-urolithiatic effect of Rosmarinus officinalis aqueous extract (RMAE) on calcium oxalate stones formation in male rats and its possible therapeutic mechanisms of action. Evaluation of total phenolic and flavonoid contents in the extract was also performed.

A calcium oxalate nephrolithiasis case was established in rats by adding ethylene glycol (1%) to the rats' daily drinking water for a duration of one month. Treatment was achieved by oral co-administration of RMAE to rats administrated ethylene glycol.

Phytochemical results showed that LC/MS-MS analysis led to the identification of 37 compounds in the phytoconstituent profile of RMAE. The biochemical results revealed significant improvement in serum kidney functions (urea, creatinine, and uric acid) in addition to restoring the calcium x phosphorous product and parathyroid hormone (PTH) levels in the plant-treated group compared to the non-treated one. The data have been supported by the significant decrease in lactate dehydrogenase enzyme (LDH) expression in the liver tissues, reflecting the decrease in oxalate synthesis in the liver compared to the non-treated group. Kidneys' histological examinations showed the absence of oxalate crystals in the treated group and the immunohistochemical findings of osteopontin (OPN) protein revealed the impact of RMAE on OPN expression in kidney tissues. Improvements in the femur bone fractures and the parathyroid gland in the treated group were also noticed during microscopic examinations.

The anti-lithiatic effect of the extract was attributed to its influence on serum phosphate, serum PTH, and OPN levels in kidney tissues and decreasing synthesis of LDH in liver tissues in addition to the prevention of secondary disease incidences, such as secondary hyperparathyroidism and cardiovascular diseases. On the other hand, the plant's considerable content of phenolics and flavonoids has been found to play a role in controlling kidney stone progression episodes.

In the immunocompromised population, Candida species are the most aetiologic agents causing severe nosocomial fungal infections. Candida species, irrespective of being commensals in the human microbiome, are the fourth most prevalent source of potentially fatal yeast infections. Monotherapy is frequently employed to treat invasive fungal infections, but sometimes, patients do not favor the monotherapy treatment regime. It may be because of the reduced susceptibility of the pathogen toward traditional antimycotic drugs. Antimycotic drug combination therapy could be a better choice in such specific circumstances. In our study, we evaluated the interactions of fluconazole with diphenyl diselenide.

The antimycotic susceptibilities of Candida species for fluconazole and diphenyl diselenide were determined by broth microdilution assay, and the in-vitro interactions of fluconazole with diphenyl diselenide were studied by using disc diffusion assay and chequerboard assay. The nature of the interactions was assessed by calculating the fractional inhibitory concentration index (FICI). The interactions were also analyzed by the response surface approach.

The minimum inhibitory concentrations (MICs) for fluconazole and diphenyl diselenide as determined by the broth microdilution assay against Candida species were 4 μg/ml-512 μg/ml and 1 μg/ml-32 μg/ml, respectively. The FICI values varied from 0.375 to 2.

Our finding demonstrated that there is no antagonism interaction between fluconazole and diphenyl diselenide in Candida species. Thus, this innovative combination should be explored in the future.

The present study investigated the development of kidney stone formation in animal models involving renal tubular stone formation by ethylene glycol and COX-2 selective inhibitor-induced urolithiasis along with the diuretic potentiality by Lipschitz teston Wistar rats.

Hemidesmus indicus (H. indicus) R. Br. played a prominent role in various ancient traditional systems of medications and possessed various pharmacological applications. Since the last few decades, urolithiasis has been a major constraint in both livestock and human health. Celecoxib administration increased urinary enzyme excretion but did not affect oxalate or citrate excretion in a urolithiasis model.

This research provides a comprehensive account of the ethnobotanical use of H. indicus as an antiurolithiatic and diuretic agent in animal models.

The plant material was dried, pulverized into a dry powder, extracted with ethanol, and analyzed for the presence of various secondary metabolites. The anti-urolithic effect of ethanolic extract of H. indicus roots in albino rats was investigated using ethylene glycol (0.75%) and COX -2 selective inhibitor models.

The experimental data showed the significant effect of H. Indicus root extract (HIEE) as anti-urolithiasis by the prevention of kidney stone formation, also by decreasing crystal nucleation, growth inhibition, decreased aggregation, and crystal retention within the renal tubules. The effect of HIEE supplementation prevents the impairment of renal stone formation, which was also confirmed by the histological findings. HIEE also acts as a potent diuretic, which supports the study.

The results indicated that HIEE was effective against experimentally induced urolithiasis, and it also acts as a potent diuretic in treated animals. So, it needs to perform future research on medicinal plants, including in vivo mechanistic and human studies for urolithiasis.

Diabetes mellitus (DM) is a metabolic disorder caused by insufficient insulin production from pancreatic β-cells or insulin resistance; its prevalence rapidly increases worldwide. Increasing reports indicate that most plant bioactive agents exhibited alternative and safe effects in managing DM.

The study aims to evaluate the in vitro antioxidant and anti-diabetic efficacy of the combination of Annona squamosa Linn. (AS) leaf extract and Oleanolic acid (OA) using in vitro and in-silico approaches.

The leaf of AS was extracted by soxhlet extraction using n-hexane and methanol. The methanol extract of AS (MEAS) was subjected to GC-MS analysis. Quantification of total phenolic and flavonoid content and OA were carried out by HPLC and HPTLC analysis, respectively. In vitro antioxidant (DPPH, NO, and H2O2) and anti-diabetic (α-amylase and α-glucosidase) potentials of MEAS, OA, and a combination of MEAS and OA (MEAS + OA) were studied at different concentrations using ascorbic acid and acarbose as standard, respectively. An in-silico study determined their binding interactions with α-amylase (PDB ID-1B2Y) and α-glucosidase (PDB ID-3W37).

GC-MS analysis of MEAS revealed three major bioactives like bicyclo[7.2.0]undec-4-ene, 4,11,11-trimethyl-8-methylene-,[1R-(1R*,4Z,9S*)]-, germacrene D and undecane. The highest amount of phenolic (tannic acid and gallic acid) (150 μg/ml) and flavonoid (rutin and quercetin) (40 μg/ml) compounds were found in MEAS. OA was quantified as 356.74 ng/ml in MEAS by HPTLC. The significant inhibitory effects of MEAS, OA, and (MEAS + OA) on free radicals and α-amylase and α-glucosidase were observed concentration-dependent. However, MEAS + OA exhibited a greater percentage of inhibition than MEAS and OA alone. The in-silico analysis revealed highest docking-score of OA (-9.8 & -8.8), Germacrene D (-7.5 & -6.5) and Bicyclo[7.2.0]undec-4-ene, 4,11,11-trimethyl-8-methylene-,[1R-(1R*,4Z,9S*)]-, (-7.0 & -6.4) against IB2Y and 3W37 proteins, respectively.

We found that the combination of MEAS + OA exhibited the highest in vitro antioxidant and anti-diabetic activities compared to MEAS and OA. It concluded that OA has a significant role in potentiating the anti-diabetic effect of A. squamosa.