New 1,2,3-Triazole-Appended Bis-pyrazoles: Synthesis, Bioevaluation, and Molecular Docking.

The present work describes design of a small library of new 1,2,3-triazole-appended bis-pyrazoles by using a molecular hybridization approach, and the synthesized hybrids were evaluated for their antifungal activity against different fungal strains, namely, Candida albicans, Cryptococcus neoformans, Candida glabrata, Candida tropicalis, Aspergillus niger, and Aspergillus fumigatus. All the compounds exhibited broad-spectrum activity against the tested fungal strains with excellent minimum inhibitory concentration values. The molecular docking study against sterol 14α-demethylase (CYP51) could provide valuable insights into the binding modes and affinity of these compounds. Furthermore, these compounds were also evaluated for their antioxidant activity, which also resulted in promising data.

NADP-dependent glutamate dehydrogenases in a dimorphic zygomycete Benjaminiella poitrasii: Purification, characterization and their evaluation as an antifungal drug target.

BACKGROUND: It has been reported that the genes coding for NADP-dependent glutamate dehydrogenases (NADP-GDHs) showed a cause-effect relationship with Yeast-Hypha (YH) reversible transition in a zygomycete Benjaminiella poitrasii. As YH transition is significant in human pathogenic fungi for their survival and proliferation in the host, the NADP-GDHs can be explored as antifungal drug targets. METHODS: The yeast-form specific BpNADPGDH I and hyphal-form specific BpNADPGDH II of B. poitrasii were purified by heterologous expression in E. coli BL-21 cells and characterized. The structural analogs of L-glutamate, dimethyl esters of isophthalic acid (DMIP) and its derivatives were designed, synthesized and screened for inhibition of NADP-GDH activity as well as YH transition in B. poitrasii, and also in human pathogenic Candida albicans strains. RESULTS: The BpNADPGDH I and BpNADPGDH II were found to be homo-hexameric proteins with native molecular mass of 282 kDa and 298 kDa, respectively and subunit molecular weights of 47 kDa and 49 kDa, respectively. Besides the distinct kinetic properties, BpNADPGDH I and BpNADPGDH II were found to be regulated by cAMP-dependent- and Calmodulin (CaM) dependent- protein kinases, respectively. The DMIP compounds showed a more pronounced effect on H-form specific BpNADPGDH II and inhibited YH transition as well as growth in B. poitrasii and C. albicans strains. CONCLUSION: The present study will be useful to design and develop antifungal drugs against dimorphic human pathogens using glutamate dehydrogenase as a target. SIGNIFICANCE: Glutamate dehydrogenases can be explored as a target against human pathogenic fungi.

Molecular studies of NAD- and NADP-glutamate dehydrogenases decipher the conundrum of yeast-hypha dimorphism in zygomycete Benjaminiella poitrasii.

Benjaminiella poitrasii, a zygomycete, shows glucose- and temperature-dependent yeast (Y)-hypha (H) dimorphic transition. Earlier, we reported the biochemical correlation of relative proportion of NAD- and NADP-glutamate dehydrogenases (GDHs) with Y-H transition. Further, we observed the presence of one NAD-GDH and two form-specific NADP-GDH isoenzymes in B. poitrasii. However, molecular studies are necessary to elucidate the explicit role of GDHs in regulating Y-H reversible transition. Here, we report the isolation and characterization of one NAD (BpNADGDH, 2.643 kb) and two separate genes, BpNADPGDH I (Y-form specific, 1.365 kb) and BpNADPGDH II (H-form specific, 1.368 kb) coding for NADP-GDH isoenzymes in B. poitrasii. The transcriptional profiling during Y-H transition showed higher BpNADPGDH I expression in Y cells while expression of BpNADPGDH II was higher in H cells. Moreover, the yeast-form monomorphic mutant (Y-5) did not show BpNADPGDH II expression under normal dimorphism triggering conditions. Transformation with H-form specific BpNADPGDH II induced the germ tube formation in Y-5, which confirmed the cause-effect relationship between BpNADPGDH genes and morphological outcome in B. poitrasii. Interestingly, expression of H-form specific BpNADPGDH II also induced germ tube formation in human pathogenic, non-dimorphic yeast Candida glabrata, which further corroborated our findings.

The puzzle of highly virulent Metarhizium anisopliae strains from Annona squamosa fields against Helicoverpa armigera.

In our search for indigenous virulent strains of the entomopathogenic fungi, we observed that Metarhizium isolates from soils associated with Annona squamosa (custard apple) have higher virulence (>90% mortality of Helicoverpa armigera larvae at 1/10th spore concentration) than strains isolated from Solanum lycopersicum (tomato) fields. Proteomic analysis revealed two insecticidal cyclopeptides of A. squamosa origin in the M. anisopliae strains that led to higher virulence against H. armigera. Transcriptomic and genomic data indicated that M. anisopliae strains and A. squamosa had more than 20 genes in common, including those for cyclic hexapeptide synthase, non-ribosomal peptide synthetase, and plant cyclotide genes, which are involved in the biosynthesis of insecticidal cyclopeptides. These genes were absent in M. anisopliae strains isolated from the S. lycopersicum fields. Further, these strains can establish an endophytic relationship with A. squamosa suggesting that these rhizospheric strains originally could be endophytes, which were eventually released into the soil. Further, Metarhizium strains associated with Capsicum annuum (chili), Azadirachta indica (neem), and Carica papaya (papaya) - plants with insecticidal properties - also had higher virulence against H. armigera. Thus exploration of rhizospheres of plants producing insecticidal metabolites to isolate entomopathogenic fungi, per se, could be a viable strategy in agricultural for crop protection.

Facile and Solvent-free Domino Synthesis of New Quinolidinyl-2,4- thiazolidinones: Antifungal Activity and Molecular Docking.

OBJECTIVE: We have synthesized new quinolidinyl-thiazolidinones via Knoevenagel condensation- alkylation reaction, catalyzed by [Et3NH][HSO4]. The present approach offers several advantages such as higher yields, eco-friendly reaction condition and economic availability of the catalyst. METHOD: The newly synthesized compounds were evaluated for their in vitro antifungal activity against six fungal strains. Some of the synthesized conjugates displayed good to moderate antifungal activity. CONCLUSION: Again, the molecular docking study performed against the fungal sterol 14α-demethylase (CYP51) showed an excellent binding affinity towards the enzyme which could rationalize the promising antifungal activity portrayed by these derivatives and provides a platform for structure based drug design.

Development of Metarhizium anisopliae as a Mycoinsecticide: From Isolation to Field Performance.

A major concern when developing commercial mycoinsecticides is the kill speed compared to that of chemical insecticides. Therefore, isolation and screening for the selection of a fast-acting, highly virulent entomopathogenic fungus are important steps. Entomopathogenic fungi, such as Metarhizium, Beauveria, and Nomurea, which act by contact, are better suited than Bacillus thuringiensis or nucleopolyhedrosis virus (NPV), which must be ingested by the insect pest. In the present work, we isolated 68 Metarhizium strains from infected insects using a soil dilution and bait method. The isolates were identified by the amplification and sequencing of the ITS1-5.8S-ITS2 and 26S rDNA region. The most virulent strain of Metarhizium anisopliae was selected based on the median lethal concentration (LC50) and time (LT50) obtained in insect bioassays against III-instar larvae of Helicoverpa armigera. The mass production of spores by the selected strain was carried out with solid-state fermentation (SSF) using rice as a substrate for 14 days. Spores were extracted from the sporulated biomass using 0.1% tween-80, and different formulations of the spores were prepared. Field trials of the formulations for the control of an H. armigera infestation in pigeon peas were carried out by randomized block design. The infestation control levels obtained with oil and aqueous formulations (78.0% and 70.9%, respectively) were better than the 63.4% obtained with chemical pesticide.

Selection of reference genes for quantitative real-time RT-PCR assays in different morphological forms of dimorphic zygomycetous fungus Benjaminiella poitrasii.

Benjaminiella poitrasii, a dimorphic non-pathogenic zygomycetous fungus, exhibits a morphological yeast (Y) to hypha (H) reversible transition in the vegetative phase, sporangiospores (S) in the asexual phase and zygospores (Z) in the sexual phase. To study the gene expression across these diverse morphological forms, suitable reference genes are required. In the present study, 13 genes viz. ACT, 18S rRNA, eEF1α, eEF-Tu,eIF-1A, Tub-α, Tub-b, Ubc, GAPDH, Try, WS-21, NADGDH and NADPGDH were evaluated for their potential as a reference, particularly for studying gene expression during the Y-H reversible transition and also for other asexual and sexual life stages of B. poitrasii. Analysis of RT-qPCR data using geNorm, normFinder and BestKeeper software revealed that genes such as Ubc, 18S rRNA and WS-21 were expressed at constant levels in each given subset of RNA samples from all the morphological phases of B. poitrasii. Therefore, these reference genes can be used to elucidate the role of morpho-genes in B. poitrasii. Further, use of the two most stably expressed genes (Ubc and WS-21) to normalize the expression of the ornithine decarboxylase gene (Bpodc) in different morphological forms of B. poitrasii, generated more reliable results, indicating that our selection of reference genes was appropriate.

Silicon Incorporated Morpholine Antifungals: Design, Synthesis, and Biological Evaluation.

Known morpholine class antifungals (fenpropimorph, fenpropidin, and amorolfine) were synthetically modified through silicon incorporation to have 15 sila-analogues. Twelve sila-analogues exhibited potent antifungal activity against different human fungal pathogens such as Candida albicans, Candida glabrata, Candida tropicalis, Cryptococcus neoformans, and Aspergillus niger. Sila-analogue 24 (fenpropimorph analogue) was the best in our hands, which showed superior fungicidal potential than fenpropidin, fenpropimorph, and amorolfine. The mode of action of sila-analogues was similar to morpholines, i.e., inhibition of sterol reductase and sterol isomerase enzymes of ergosterol synthesis pathway.

Clerodane type diterpene as a novel antifungal agent from Polyalthia longifolia var. pendula.

Bioactivity-guided chemical examination of methanolic extract of leaves of Polyalthia longifolia var. pendula led to the isolation of the active constituent, a diterpene 1 which was identified as 16α-hydroxycleroda-3,13(14)Z-dien-15,16-olide on the basis of its spectral data. Among the tested strains, diterpene 1 was found to exhibit antifungal activities having MIC90 values of 50.3, 100.6 and 201.2 µM against Candida albicans NCIM3557, Cryptococcus neoformans NCIM3542 (human pathogens) and Neurospora crassa NCIM870 (saprophyte), respectively. Initial, structure-activity-relationship (SAR) data generated by synthesizing some derivatives revealed that the double bond between C3-C4 and the free hydroxyl group at C16 are crucial for the antifungal activity of the diterpene 1. The mode of action of 1 in C. albicans is due to compromised cell membrane permeability and also probably due to disruption of cell wall structures. The red blood cell haemolysis of all the compounds (1-4) did not show any significant haemolysis and was found to be less than 15% for all the compounds when tested at highest concentration, i.e. 1200 µM. Interestingly, all the tested compounds inhibited Y-H transition in dimorphic C. albicans NCIM3557 at much lower concentration than their MIC90 values. Determination of ROS generation by diterpene 1 using DCFH-DA and DHR123 (dihydrorhodamine) staining of C. albicans NCIM3557 indicated production of intracellular ROS as a mechanism of antifungal activity.

Antifungal dimeric chalcone derivative kamalachalcone E from Mallotus philippinensis.

From the red coloured extract (Kamala) prepared through acetone extraction of the fresh whole uncrushed fruits of Mallotus philippinensis, one new dimeric chalcone (1) along with three known compounds 1-(5,7-dihydroxy-2,2,6-trimethyl-2H-1-benzopyran-8-yl)-3-phenyl-2-propen-1-one (2), rottlerin (3) and 4'-hydroxyrottlerin (4) were isolated. The structure of compound 1 was elucidated by 1D and 2D NMR analyses that included HSQC, HMBC, COSY and ROESY experiments along with the literature comparison. Compounds 1-4 were evaluated for antifungal activity against different human pathogenic yeasts and filamentous fungi. The antiproliferative activity of the compounds was evaluated against Thp-1 cell lines. Compounds 1 and 2 both exhibited IC50 of 8, 4 and 16 µg/mL against Cryptococcus neoformans PRL518, C. neoformans ATCC32045 and Aspergillus fumigatus, respectively. Compound 4, at 100 µg/mL, showed 54% growth inhibition of Thp-1 cell lines.

Chitin synthase inhibitors as antifungal agents.

Increased risk of fungal diseases in immunocompromised patients, emerging fungal pathogens, limited repertoire of antifungal drugs and resistance development against the drugs demands for development of new and effective antifungal agents. With greater knowledge of fungal metabolism efforts are being made to inhibit specific enzymes involved in different biochemical pathways for the development of antifungal drugs. Chitin synthase is one such promising target as it is absent in plants and mammals. Nikkomycin Z, a chitin synthase inhibitor is under clinical development. Chitin synthesis in fungi, chitin synthase as a target for antifungal agent development, different chitin synthase inhibitors isolated from natural sources, randomly synthesized and modified from nikkomycin and polyoxin are discussed in this review.

Perspectives for nano-biotechnology enabled protection and nutrition of plants.

Indiscriminate use of pesticides and fertilizers causes environmental pollution, emergence of agricultural pests and pathogens, and loss of biodiversity. Nanotechnology, by virtue of nanomaterial related properties, has potential agro-biotechnological applications for alleviation of these problems. The literature pertaining to the role of nanotechnology in plant and soil systems demonstrates that nanomaterials may assist in a) the controlled release of agrochemicals for nutrition and protection against pests and pathogens, b) delivery of genetic material, c) sensitive detection of plant disease and pollutants and d) protection and formation of soil structure. For instance, porous silica (15nm) and biodegradable, polymeric chitosan (78nm) nanoparticles displayed slow release of encapsulated pesticide and fertilizer, respectively. Further, nanosized gold (5-25nm) delivered DNA to plant cells while iron oxide (30nm) based nanosensors detected pesticides at minute levels. These functions assist the development of precision farming by minimizing pollution and maximizing the value of farming practice.

Stereoselective synthesis and antimicrobial activity of steroidal C-20 tertiary alcohols with thiazole/pyridine side chain.

Stereoselective synthesis of novel steroidal C-20 tertiary alcohols with thiazole and pyridine side chain using Grignard reaction of steroidal ketones and thiazole/pyridine magnesium bromide have been realized. These molecules were evaluated in vitro for their antifungal and antibacterial activities. Most of the compounds exhibited significant antifungal and antibacterial activity against all the tested strains.

Natural yeast flora of different varieties of grapes used for wine making in India.

The natural Saccharomyces and non-Saccharomyces yeast flora present on the grape berries significantly affect wine production. Six grape varieties, Bangalore blue, Zinfandel, Cabernet, Chenin Blanc, Sauvignon Blanc and Shiraz are being used in India for wine making. The yeast diversity was studied on the basis of morphological, colony, physiological characteristics and 5.8S-ITS sequencing of rDNA of the isolates. Eleven different species belonging to seven genera were identified as: Candida azyma, Candida quercitrusa, Debaryomyces hansenii, Hanseniaspora guilliermondii, Hanseniaspora viniae, Hanseniaspora uvarum, Issatchenkia orientalis, Issatchenkia terricola, Pichia membranifaciens, Saccharomyces cerevisiae and Zygoascus steatolyticus. H. guilliermondii was the predominant species while S. cerevisiae was observed occasionally in the six vine varieties. For the first time, C. azyma was isolated from Bangalore blue and Cabernet varieties grown in different localities. This association may be attributed to the change in cropping pattern from sugarcane to viticulture in the vine growing regions and the known association of C. azyma with sugarcane phylloplane. Further analysis of the indigenous strains and the qualitative and quantitative changes in the flora during fermentation will be useful to understand wine quality and to design preservation strategies to control wine spoilage.

Exploration of click reaction for the synthesis of modified nucleosides as chitin synthase inhibitors.

Click reaction approach toward the synthesis of two sets of novel 1,2,3-triazolyl linked uridine derivatives 19a-19g and 21a-21g was achieved by Cu(I)-catalyzed 1,3-dipolar cycloaddition of 5'-azido-5'-deoxy-2',3'-O-(1-methylethylidene)uridine (17) with propargylated ether of phenols 18a-18g and propargylated esters 20a-20g. Structure of one of the representative compound 19d was unambiguously confirmed by X-ray crystallography. Chitin synthase inhibition study of all these compounds 19a-19g and 21a-21g was carried out to develop antifungal strategy. Compounds 19d, 19e, 19f, and 21f were identified as potent chitin synthase inhibitors by comparing with nikkomycin. Compounds 19a, 19b, 19c, 19d, 21a, and 21b showed good antifungal activity against human and plant pathogens. Compounds 19a, 19b, 19f, 21c, 21f, and 21g were identified as lead chitin synthase inhibitors for further modifications by comparing results of inhibition of growth, % germ tube formation and chitin synthase activity.

Synthesis and biological evaluation of bile acid dimers linked with 1,2,3-triazole and bis-beta-lactam.

We report herein the synthesis and biological evaluation of bile acid dimers linked through 1,2,3-triazole and bis-beta-lactam. The dimers were synthesized using 1,3-dipolar cycloaddition reaction of diazido bis-beta-lactams , and terminal alkynes derived from cholic acid/deoxycholic acid in the presence of Cu(i) catalyst (click chemistry). These novel molecules were evaluated in vitro for their antifungal and antibacterial activity. Most of the compounds exhibited significant antifungal as well as antibacterial activity against all the tested fungal and bacterial strains. Moreover, their in vitro cytotoxicities towards HEK-293 and MCF-7 cells were also established.

Synthesis of chimeric tetrapeptide-linked cholic acid derivatives: impending synergistic agents.

Tetrapeptides derived from glycine and beta-alanine were hooked at the C-3beta position of the modified cholic acid to realize novel linear tetrapeptide-linked cholic acid derivatives. All the synthesized compounds were tested against a wide variety of microorganisms (gram-negative bacteria, gram-positive bacteria and fungi) and their cytotoxicity was evaluated against human embryonic kidney (HEK293) and human mammary adenocarcinoma (MCF-7) cell lines. While relatively inactive by themselves, these compounds interact synergistically with antibiotics such as fluconazole and erythromycin to inhibit growth of fungi and bacteria, respectively, at 1-24 microg/mL. The synergistic effect shown by our novel compounds is due to their inherent amphiphilicity. The fractional inhibitory concentrations reported are comparable to those reported for Polymyxin B derivatives.

Synthesis and antimicrobial activity of beta-lactam-bile acid conjugates linked via triazole.

Synthesis of novel 1,2,3-triazole-linked beta-lactam-bile acid conjugates 17-24 using 1,3-dipolar cycloaddition reaction of azido beta-lactam and terminal alkyne of bile acids in the presence of Cu(I) catalyst (click chemistry) have been realized. These molecules were evaluated in vitro for their antifungal and antibacterial activities. Most of the compounds exhibited significant antifungal and moderate antibacterial activity against all the tested strains.

Synthesis and evaluation of antifungal properties of a series of the novel 2-amino-5-oxo-4-phenyl-5,6,7,8-tetrahydroquinoline-3-carbonitrile and its analogues.

A series of 2-amino-5-oxo-4-phenyl-5,6,7,8-tetrahydroquinoline-3-carbonitrile and various analogues have been synthesized in excellent isolated yields starting from various arylidenemalononitrile and 3-amino-2-cyclohexen-1-one in 1-propanol as solvent at reflux temperature in the absence of any added catalyst. All the synthesized compounds were evaluated for their antifungal activity. The relationship between functional group variation and biological activity of the evaluated compounds is discussed in the article.

The extracellular constitutive production of chitin deacetylase in Metarhizium anisopliae: possible edge to entomopathogenic fungi in the biological control of insect pests.

The possible contribution of extracellular constitutively produced chitin deacetylase by Metarhizium anisopliae in the process of insect pathogenesis has been evaluated. Chitin deacetylase converts chitin, a beta-1,4-linked N-acetylglucosamine polymer, into its deacetylated form chitosan, a glucosamine polymer. When grown in a yeast extract-peptone medium, M. anisopliae constitutively produced the enzymes protease, lipase, and two chitin-metabolizing enzymes, viz. chitin deacetylase (CDA) and chitosanase. Chitinase activity was induced in chitin-containing medium. Staining of 7.5% native polyacrylamide gels at pH 8.9 revealed CDA activity in three bands. SDS-PAGE showed that the apparent molecular masses of the three isoforms were 70, 37, and 26 kDa, respectively. Solubilized melanin (10microg) inhibited chitinase activity, whereas CDA was unaffected. Following germination of M. anisopliae conidia on isolated Helicoverpa armigera, cuticle revealed the presence of chitosan by staining with 3-methyl-2-benzothiazoline hydrazone. Blue patches of chitosan were observed on cuticle, indicating conversion of chitin to chitosan. Hydrolysis of chitin with constitutively produced enzymes of M. anisopliae suggested that CDA along with chitosanase contributed significantly to chitin hydrolysis. Thus, chitin deacetylase was important in initiating pathogenesis of M. anisopliae softening the insect cuticle to aid mycelial penetration. Evaluation of CDA and chitinase activities in other isolates of Metarhizium showed that those strains had low chitinase activity but high CDA activity. Chemical assays of M. anisopliae cell wall composition revealed the presence of chitosan. CDA may have a dual role in modifying the insect cuticular chitin for easy penetration as well as for altering its own cell walls for defense from insect chitinase.