Synthesis and in vitro antimycobacterial and antileishmanial activities of hydroquinone-triazole hybrids

Synthetic product-based approach toward potential antileishmanial drug development

Leishmaniasis is a parasitic disease and is categorized as a tropically neglected disease (NTD) with no effective vaccines available. The available chemotherapeutics against leishmaniasis are associated with an increase in the incidence of toxicity and drug resistance. Consequently, targeting metabolic pathways and enzymes of parasites which differs from the mammalian host can be exploited to treat and overcome the resistance. The classical methods of identifying the structural fragments and the moieties responsible for the biological activities from the standard compounds and their modification are options for developing more effective novel compounds. Significant progress has been made in refining the development of potent non-toxic molecules and addressing the limitations of the current treatment available. Several examples of synthetic product-based approach utilizing their core heterocyclic rings including furan, pyrrole, thiazole, imidazole, pyrazole, triazole, quinazoline, quinoline, pyrimidine, coumarin, indole, acridine, oxadiazole, purine, chalcone, carboline, phenanthrene and metal containing derivatives and their structure-activity relationships are discussed in this review. It also analyses the groups/fragments interacting with the host cell receptors and will support the medicinal chemists with novel antileishmanial agents.

Synthesis of Bench-stable Polycyclic Organophosphorus Heterocycles via Staudinger-type Annulations of ortho-Azidophenols

The formation of a five- or six-membered ring is known to stabilize unstable molecular structures such as hemiacetals. This idea can also be extended to stabilize other high-coordinated p-block element species. Herein, we synthesized two novel polycyclic organophosphorus heterocycles via Staudinger-type annulations. Reactions of either ortho-phosphinoarenesulfonyl fluorides 1 or ortho-phosphinobenzoic acid methyl esters 4 with ortho-azidophenols 2 gave rise to penta-coordinated P(V) heterocycles, benzo-benzo-1,2,3-thiazaphospholo-1,3,2-oxazaphosphole (B-B-TAP-OAP) 3 and benzo-benzo-1,2-azaphospholo-1,3,2-oxazaphosphol-12-one (B-B-AP-OAP) 5 in satisfactory yields. It is remarkable that heterocycles 3 and 5 are both bench-stable and exhibit considerable stability in a 10 % aqueous tetrahydrofuran solution. Preliminary computational studies disclosed that the formation of nitrogen gas is the key driving force for the annulations. In addition, the formation of a strong Si-F bond is another contributor to the annulation of 1 and 2.

New tetrahydropyrimidine-1,2,3-triazole clubbed compounds: Antitubercular activity and Thymidine Monophosphate Kinase (TMPKmt) inhibition

Two series of new tetrahydropyrimidine (THPM)-1,2,3-triazole clubbed compounds were designed, synthesized and screened for their antitubercular (anti-TB) activity against M. tuberculosis H₃₇Rv strain using microplate alamar blue assay (MABA). The most active compounds 5c, 5d, 5e and 5f were further examined for their cytotoxicity against the growth of RAW 264.7 mouse macrophage cells using MTT assay. The four compounds showed safety profiles better than or comparable to that of ethambutol (EMB). These compounds were evaluated for their inhibition activity against mycobacterium tuberculosis thymidine monophosphate kinase (TMPKmt). Compounds 5c and 5e were the most potent exhibiting comparable inhibition activity to that of the natural substrate deoxythymidine monophosphate (dTMP). An in silico study was performed including docking of the most active compounds 5c and 5e into the TMPKmt (PDB: ID 1G3U) binding pocket in addition to prediction of their physicochemical and pharmacokinetic properties to explore the overall activity of these anti-TB candidates. Compounds 5c and 5e are promising anti-TB agents and TMPKmt inhibitors with acceptable oral bioavailability, physicochemical and pharmacokinetic properties.

Synthesis and in vitro antileishmanial activity of alkylene-linked nitrofurantoin-triazole hybrids

Leishmaniasis is a vector-borne parasitic disease that mostly affects populations in tropical and sub-tropical countries. There is currently no protective anti-leishmanial vaccine and only a paucity of clinical drugs is available to treat this disease albeit their toxicity. Leishmaniasis is curable but its eradication and elimination have been hampered by the emergence of multidrug resistant strains of the causative pathogens. This heightens the necessity for new and effective antileishmanial drugs. In search for such agents, nitrofurantoin, a clinical antibiotic, was appended to triazole scaffold through alkylene linkers of various length, and the resulting hybrids were evaluated for in vitro antileishmanial efficacy against Leishmania (L.) parasite of two strains. The hybrid 13, harboring a n-pentylene linker was uncovered as a leishmanicidal hit with micromolar activity against antimonial-resistant L. donovani, the causative of deadly visceral Leishmaniasis.

The 1,2,3-triazole 'all-in-one' ring system in drug discovery: a good bioisostere, a good pharmacophore, a good linker, and a versatile synthetic tool

INTRODUCTION

The 1,2,3-triazole ring occupies an important space in medicinal chemistry due to its unique structural properties, synthetic versatility and pharmacological potential making it a critical scaffold. Since it is readily available through click chemistry for creating compound collections against various diseases, it has become an emerging area of interest for medicinal chemists.

AREAS COVERED

This review article addresses the unique properties of the1,2,3-triazole nucleus as an intriguing ring system in drug discovery while focusing on the most recent medicinal chemistry strategies exploited for the design and development of 1,2,3-triazole analogs as inhibitors of various biological targets.

EXPERT OPINION

Evidently, the 1,2,3-triazole ring with unique structural features has enormous potential in drug design against various diseases as a pharmacophore, a bioisoster or a structural platform. The most recent evidence indicates that it may be more emerging in drug molecules in near future along with an increasing understanding of its prominent roles in drug structures. The synthetic feasibility and versatility of triazole chemistry make it certainly ideal for creating compound libraries for more constructive structure-activity relationship studies. However, more comparative and target-specific studies are needed to gain a deeper understanding of the roles of the 1,2,3-triazole ring in molecular recognition.[Figure: see text].

Synthesis, in vitro antileishmanial efficacy and hit/lead identification of Nitrofurantoin-triazole hybrids

Leishmaniasis is a vector‐borne neglected parasitic infection affecting thousands of individuals, mostly among populations in low‐ to moderate‐income developing countries. In the absence of protective vaccines, the management of the disease banks solely on chemotherapy. However, the clinical usefulness of current antileishmanial drugs is threatened by their toxicity and the emergence of multidrug‐resistant strains of the causative pathogens. This emphasizes the imperative for the development of new and effective antileishmanial agents. In this regard, we synthesized and evaluated in vitro the antileishmanial activity and cytotoxicity profile of a series of nitrofurantoin‐triazole hybrids. The nitrofurantoin derivative 1 featuring propargyl moiety was distinctively the most active of all, was nontoxic to human cells and possessed submicromolar cellular activity selectively directed towards the pathogens of the life threatening visceral leishmaniasis. Hence it was identified as potential antileishmanial lead for further investigation into its prospective to act as alternative to therapies.

Synthesis and in vitro antileishmanial efficacy of benzyl analogues of nifuroxazide

Leishmaniasis is a vector-borne parasitic disease that mostly affects populations in tropical and subtropical countries. There is currently no vaccine to protect against and only a handful of drugs are available to treat this disease. Leishmaniasis is curable, but its eradication and elimination are hindered by the emergence of multidrug resistant strains of the causative pathogens, accentuating the need for new and effective antileishmanial drugs. In search for such agents, nifuroxazide, a clinical antibiotic, was evaluated through investigation of its benzyl analogues for in vitro antileishmanial efficacy against promastigotes of various Leishmania (L.) strains. The monobenzylated analogues 1 and 2 were the most potent of all, possessing nanomolar activities up to 10-fold higher than the parent drug nifuroxazide against all three tested Leishmania strains. Both analogues stand as antipromastigote hits for further lead investigation into their potential to act as new antileishmanial agents.

Bifidobacterium β-Glucosidase Activity and Fermentation of Dietary Plant Glucosides Is Species and Strain Specific

Dietary plant glucosides are phytochemicals whose bioactivity and bioavailability can be modified by glucoside hydrolase activity of intestinal microbiota through the release of acylglycones. Bifidobacteria are gut commensals whose genomic potential indicates host-adaption as they possess a diverse set of glycosyl hydrolases giving access to a variety of dietary glycans. We hypothesized bifidobacteria with β-glucosidase activity could use plant glucosides as fermentation substrate and tested 115 strains assigned to eight different species and from different hosts for their potential to express β-glucosidases and ability to grow in the presence of esculin, amygdalin, and arbutin. Concurrently, the antibacterial activity of arbutin and its acylglycone hydroquinone was investigated. Beta-glucosidase activity of bifidobacteria was species specific and most prevalent in species occurring in human adults and animal hosts. Utilization and fermentation profiles of plant glucosides differed between strains and might provide a competitive benefit enabling the intestinal use of dietary plant glucosides as energy sources. Bifidobacterial β-glucosidase activity can increase the bioactivity of plant glucosides through the release of acylglycone.

Synthesis, study of antileishmanial and antitrypanosomal activity of imidazo pyridine fused triazole analogues

Thirty-five novel 1,2,3-triazole analogues of imidazo-[1,2-a]-pyridine-3-carboxamides were designed, synthesized and evaluated for in vitro antileishmanial and antitrypanosomal activity against L. major and T. brucei parasites, respectively.