1,4-Benzothiazine and 1,4-benzoxazine imidazole derivatives with antifungal activity: a docking study

We have recently described the synthesis and antifungal activity of a series of 1,4-benzothiazine and 1,4-benzoxazine imidazole derivatives that mainly showed in vivo activity against a murine experimental model of candidiasis but that very often lacked in vitro activity. Here, we report a docking study of a representative set of our molecules in a 3D model of CYP51 of Candida albicans (CA-CYP51). The model was constructed on the basis of the sequence homology relationship with the recently reported crystal structure of the CYP51 of Mycobacterium tuberculosis (MT- CYP51).     

1,4-benzothiazine analogues and apoptosis: structure-activity relationship

We have previously shown 1,4-benzothiazine (1,4-B) derivatives induce thymocyte apoptosis in vitro and thymus cell loss in vivo. Apoptosis is mediated through a complex of biochemical events including phosphatidylcholine specific-phospholipase C (PC-PLC) activation, acidic sphingomyelinase (aSMase) activation and ceramide generation, caspase-8 and caspase-3 activation. As preliminary analysis of the structure-activity relationship (SAR) suggested some structural features were responsible for apoptosis, we synthesised several derivatives and tested for apoptosis activity at equimolar concentrations. In particular, we synthesised analogues that differed in the nature of skeleton (1,4-benzothiazine, 1,4-benzoxazine and 1,2,3,4-tetrahydroquinoline) and in the nature of side chain (imidazole, benzimidazole or piperazine as azole substituent; presence, absence or transformation of alcoholic group). Results of apoptosis induction indicate that transforming the 1,4-benzothiazine skeleton into 1,2,3,4-tetrahydroquinoline does not result in significant change. Transformation into 1,4-benzoxazine decreased activity. Replacing imidazole at the side chain with different piperazines also decreased activity while replacing it with benzimidazole does not change apoptotic activity. Finally, removal of the alcoholic group by dehydration to olefin, or by transforming it into ether, increased activity. Moreover, in an attempt to analyse further the SAR characteristics that are responsible for 1,4-B-activated apoptosis we tested the effect on caspase-8,-9 and-3 activation. 1,4-B analogues activate caspases and the structural requirements correlate with those responsible for apoptosis induction.     

Antifungal activity of the amyrin derivatives and in vitro inhibition of Candida albicans adhesion to human epithelial cells

AIMS: The antifungal activity of amyrin pentacyclic triterpene and 15 synthetic derivatives was evaluated against Candida species. Additionally, inhibition of adhesion of Candida albicans to human epithelial cells in vitro was determined. METHODS AND RESULTS: Esterification of alpha- and beta-amyrin with a variety of acyl chlorides produced a series of analogue derivatives. These substances were synthesized to evaluate the antifungal properties against Candida species. Among the 15 derivatives, alpha- and beta-amyrin formiate (2) and alpha- and beta-amyrin acetate (3) were the most active, inhibiting all the Candida species tested in concentrations that ranged from 30 to 250 microg ml(-1). alpha- and beta-amyrin formiate inhibited the adhesion ability of C. albicans to buccal epithelial cells (BEC) in 65.3%. CONCLUSIONS: alpha- and beta-amyrin formiate and alpha- and beta-amyrin acetate derivatives exhibited potential antifungal activity against Candida spp. and amyrin formiate showed inhibition of the adhesion ability of C. albicans to buccal epithelial cells. SIGNIFICANCE AND IMPACT OF THE STUDY: This study demonstrated that two derivatives of amyrin pentacyclic triterpene exhibited significant antifungal activity against Candida species. Additionally, alpha- and beta-amyrin formiate was as effective as fluconazole in inhibiting the adhesion of C. albicans to buccal epithelial cells.     

Antifungal activities of recombinant antifungal protein by conjugation with polyethylene glycol.

Tenecin 3, an antifungal protein isolated from coleopteran insect Tenebrio molitor larvae, inhibited growth of the fungus Candida albicans. We have previously reported that tenecin 3 has a propensity of random structure with very loose turn-like elements by circular dichroism (CD) analysis and 2D nuclear overhauser effect spectroscopy [Lee et al. (1999)]. However, the antifungal mechanism of tenecin-3 has not yet been studied due to its very low availability from natural sources. As an initial step to study the antifungal mechanism of tenecin 3, recombinant tenecin 3 (RT-3) obtained from an expression system in Escherichia coli showed antifungal activity against C. albicans as did natural tenecin 3. To elucidate the antifungal mechanism of RT-3 and to explore the possibility of preparing polyethylene glycol (PEG) conjugated derivative, we synthesized PEG conjugated RT-3 (RT-3-PEG) and examined its antifungal activity against C. albicans in vitro. RT-3-PEG showed greater antifungal activity against C. albicans than RT-3 alone at the same dose. When C. albicans was treated with RT-3-PEG in vitro, K+ in the C. albicans cell was leaked out rapidly compared to the C. albicans treated with RT-3 alone. When the morphological change of RT-3-PEG treated C. albicans was examined by scanning electron microscopy, string-like substances, which may have been derived from the fungus, were stacked around the cell whose wall was damaged. Also, no appreciable hemolysis of mouse erythrocytes was detected under conditions in which 1% melittin caused 100% hemolysis. These results suggested that the RT-3-PEG derivative probably does not interact with mammalian cell appreciably, although it has antifungal activity.     

Synthesis and vasorelaxant activity of new 1,4-benzoxazine derivatives potassium channel openers

As part of a search for new potassium channel openers, the synthesis and vasorelaxant activity of new 1,4-benzoxazine derivatives derived from transformation of the benzopyran skeleton of cromakalim were described. Several new 1,4-benzoxazine derivatives were provided with significant vasorelaxant activity with an overall pharmacological behavior similar to CRK (1f, 1i, 2d, 2e, 2f and 2i).     

2-(2,4-Dihydroxyphenyl)-1,3,4-thiadiazole analogues: antifungal activity in vitro against Candida species

The antifungal activity in vitro of the newly synthesized and previously reported compounds of 5-substituted 2-(2,4-dihydroxyphenyl)-1,3,4-thiadiazole series was evaluated. Their structures were confirmed by elemental analyses and IR, 1H and 13C NMR and mass spectra. The azole-resistant clinical isolates of C. albicans and nonalbicans Candida spp. were used in the antifungal tests. Some compounds exhibit higher activities than the comparatively studied antifungal drugs. 2-Amino-1,3,4-thiadiazole derivatives exhibited higher (than other analogues) antifungal effects against Candida nonalbicans spp. than against C. alhicans. Derivatives with strong antifungal activity have a narrow range of lipophilicity values determined by the Villar approach.     

Synthesis and evaluation of N-substituted 1,4-oxazepanyl Sordaricins as selective fungal EF-2 inhibitors

Sordaricin analogues possessing 6-methoxy-7-methyl-1,4-oxazepane moiety instead of the sugar part were synthesized and evaluated. It was found that N-substituents on the oxazepane ring had influence on biological activity. In particular, N-(2-methylpropenyl) derivative 12p exhibited potent in vitro antifungal activity. Furthermore, 12p maintained significant activity (MIC 0.25 microg/mL) against Candida albicans SANK51486 even in the presence of 20% horse serum.     

Synthesis of (1,4)-naphthoquinono-[3,2-c]-1H-pyrazoles and their (1,4)-naphthohydroquinone derivatives as antifungal, antibacterial, and anticancer agents

A series of (1,4)-naphthoquinono [3,2-c]-1H-pyrazoles and their (1,4)-naphthohydroquinone derivatives 2-7 were synthesized and evaluated for antifungal, antibacterial, and anticancer activities. The structure-activity relationship of these compounds was studied and the results show that the compound 2b exhibited in vitro antifungal activity against Candida albicans and Cryptococcus neoformans, and also possessed antibacterial profile against Klebsiella pneumoniae and Escherichia coli whereas 1c showed anticancer activity against Walker 256 Carcinosarcoma in rats.     

Structure-antifungal activity relationship of His-Phe-Arg-Trp-Gly-Lys-Pro-Val-NH2 and analogues

The synthesis, in vitro evaluation and conformational study of His-Phe-Arg-Trp-Gly-Lys-Pro-Val-NH(2) and analogues acting as antifungal agents are reported. Among them, His-Phe-Lys-Trp-Gly-Arg-Phe-Val-NH(2) exhibited a moderate but significant antifungal activity against Cryptococcus neoformans, Candida albicans and Candida tropicalis. A theoretical study allows us to propose a biologically relevant conformation for these octapeptides acting as antifungal agents. In addition, these theoretical calculations allow us to determine the minimal structural requirements to produce the antifungal response and can provide a guide for the design of compounds with this biological activity.     

Synthesis and antifungal activities of new fluconazole analogues with azaheterocycle moiety

A series of fluconazole analogues 5-20 incorporating azaindole and indole moieties were prepared using oxirane intermediates synthesized under microwave irradiation. All of the compounds were evaluated in vitro against two clinically important fungi, Candida albicans and Aspergillus fumigatus. Four derivatives 6, 13, 14 and 18 exerted high antifungal activity against C. albicans with MIC(80) values 3- to 28-fold lower than that of fluconazole.     

Synthesis and evaluation of novel macrocyclic antifungal peptides

Echinocandins are a novel class of macrocyclic antifungal peptides that act by inhibiting the β-(1,3)-D-glucan synthase complex, which is not present in mammalian cells. Due to the large number of hydroxyl groups present in these complex macrocyclic lipopeptides, most structure-activity relationship studies have relied upon semisynthetic derivatives. In order to probe the influence of the cyclic peptide backbone on the antifungal activity we developed a successful strategy for the synthesis of novel echinocandins analogues by on-resin ring closing metathesis or disulfide formation. The specific minimum inhibitory activity of each mimic was determined against Candida albicans. Our results indicate that ring size is an important factor for antifungal activity.     

Synthesis, antimicrobial activity and molecular modeling studies of halogenated 4-[1H-imidazol-1-yl(phenyl)methyl]-1,5-diphenyl-1H-pyrazoles

During the course of our studies in the azole antifungals area, we synthesized a number of 1,5-disubstituted 4-[1H-imidazol-1-yl(phenyl)methyl]-1H-pyrazoles, analogues of bifonazole. 1,5-Diphenyl-1H-pyrazole 3 showed weak antimycotic and antibacterial activities in vitro against Candida albicans, Cryptococcus neoformans and Staphylococcus aureus. In order to increase these properties, given that the halo substitution was found to be capable of enhancing antifungal effects, we prepared a series of fluoro and chloro derivatives of 3. The microbiological evaluation carried out on newly synthesized compounds included in vitro assays for antifungal, antibacterial and antimycobacterial activities. Among the tested compounds, some dichloro and trichloro-derivatives showed interesting antimicrobial properties. In particular, compounds 10j,k,l produced inhibitory effects against pathogen representatives of yeast (C. albicans, C. neoformans) and Gram positive bacteria (S. aureus) similar or superior to those of bifonazole. In addition, their activity against Mycobacterium tuberculosis was superior to that of clotrimazole and econazole, which were used as reference drugs. The replacement, in these compounds, of chlorine with fluorine atoms led to inactive derivatives. Docking studies were carried out on the most active compounds, in order to rationalize the pharmacological results.     

Microwave-assisted synthesis of antimicrobial dihydropyridines and tetrahydropyrimidin-2-ones: novel compounds against aspergillosis

Ten 4-aryl-1,4-dihydropyridine and three 4-aryl-1,2,3,4-tetrahydropyrimidin-2-one derivatives have been synthesized and examined for their activity against pathogenic strains of Aspergillus fumigatus and Candida albicans. Although none of the three compounds belonging to pyrimidin-2-one series showed any activity against two pathogens, two of the compounds of the dihydropyridine series, that is, diethyl 4-(4-methoxyphenyl)-2,6-dimethyl-1,4-dihydropyridin-3,5-dicarboxylate and dimethyl 4-(4-methoxyphenyl)-2,6-dimethyl-1,4-dihydropyridin-3,5-dicarboxylate, exhibited significant activity against A. fumigatus in disc diffusion, microbroth dilution and percent spore germination inhibition assays. The most active diethyl dihydropyridine derivative exhibited a MIC value of 2.92 microg/disc in disc diffusion and 15.62 microg/ml in microbroth dilution assays. The MIC(90) value of the most active compound by percent germination inhibition assay was found to be 15.62 microg/ml. The diethyl dicarboxylate derivative of dihydropyridine also exhibited appreciable activity against C. albicans. The in vitro toxicity of the most active diethyl dihydropyridine derivative was evaluated using haemolytic assay, in which the compound was found to be non-toxic to human erythrocytes even at a concentration of 625 microg/ml. The standard drug amphotericin B exhibited 100% lysis of erythrocytes at a concentration almost 16 times less than the safer concentration of the most active dihydropyridine derivative.     

Resveratrol lacks antifungal activity against Candida albicans

The putative candicidal activity of resveratrol is currently a matter of controversy. Here, the antifungal activity as well as the antioxidant response of resveratrol against Candida albicans, have been tested in a set of strains with a well-established genetic background At the doses usually employed in antifungal tests (10-40 μg/ml), resveratrol has no effect on the exponential growth of the C. albicans CAI.4 strain, a tenfold increase (400 μg/ml) was required in order to record a certain degree of cell killing, which was negligible in comparison with the strong antifungal effect caused by the addition of amphotericin B (5 μg/ml). An identical pattern was recorded in the prototrophic strains of C. albicans SC5314 and RM-100, whereas the oxidative sensitive trehalose-deficient mutant (tps1/tps1 strain) was totally refractory to the presence of resveratrol. In turn, the serum-induced yeast-to-hypha transition remained unaffected upon addition of different concentrations of resveratrol. Determination of endogenous trehalose and catalase activity, two antioxidant markers in C. albicans; revealed no significant changes in their basal contents induced by resveratrol. Collectively, our results seem to dismiss a main antifungal role as well as the therapeutic application of resveratrol against the infections caused by C. albicans.     

Design, synthesis, and preliminary biological evaluation of 2,3-dihydro-3-hydroxymethyl-1,4-benzoxazine derivatives

We synthesized a series of novel small molecules, 2,3-dihydro-3-hydroxymethyl-1,4-benzoxazine derivatives, by tandem reduction-oxirane opening of 2-nitroaroxymethyloxiranes in moderate or excellent yields. We investigated the effects of all of the compounds on HUVEC apoptosis and A549 cell growth. The results showed that 6,8-dichloro-2,3-dihydro-3-hydroxymethyl-1,4-benzoxazine was the most effective small molecule in promoting HUVEC apoptosis and inhibiting A549 cell proliferation, but 6-amino-2,3-dihydro-3-hydroxymethyl-1,4-benzoxazine could remarkably inhibit HUVEC apoptosis and might induce the formation of microvessel.     

抗白念珠菌感染的疫苗及抗体研究进展

白念珠菌是与人类共生的条件致病真菌,能引起免疫力低下患者皮肤黏膜和全身系统性持续感染.系统性念珠菌病是引起免疫力低下患者死亡的主要原因之一.由于临床缺乏念珠菌病的早期诊疗手段、可用的抗真菌药物种类有限且毒副作用大、耐药菌株越来越普遍、新药研发难度大等因素,抗真菌治疗依然面临着严峻挑战.目前有较多研究者致力于阐明白念珠菌感染的宿主免疫应答机制,并试图研发抗白念珠菌感染的免疫治疗方法,使免疫治疗有望成为预防和治疗真菌感染的有效手段.该文将几种抗白念珠菌感染的疫苗和抗体研究进展作简要概述,旨在为新型抗白念珠菌感染疫苗及抗体的研究提供参考.     

CX3CL1 expression induced by Candida albicans in oral fibroblasts

Oral fibroblasts as well as keratinocytes are thought to influence host inflammatory responses against Candida albicans. However, little is known about chemokine expressions in oral fibroblasts against C. albicans infection. We therefore examined whether C. albicans induced several chemokines including fractalkine/CX3CL1 (CX3CL1), a unique chemokine that has properties of both chemoattractants and adhesion molecules, in fibroblasts and keratinocytes. The addition of C. albicans live cells to human immortalized oral keratinocytes (RT7) resulted in increases in the mRNA levels of multiple chemokines, but not of CX3CL1. In contrast, live and heat-killed C. albicans caused an increase in CX3CL1 mRNA and protein expression in human immortalized oral fibroblasts (GT1). CX3CL1 mRNA expression in GT1 cells was also enhanced by stimulation with a nonalbicans species of Candida. Further, the CX3CL1 chemokine domain showed antifungal activity against C. albicans. CX3CL1 secreted by oral fibroblasts appears to play an important role in the oral immune response to C. albicans infection.     

2-(2,4-dihydroxyphenyl)-1,3,4-thiadiazole analogues: Antifungal activity in vitro against <Emphasis Type="Italic">Candida</Emphasis> species

The antifungal activity in vitro of the newly synthesized and previously reported compounds of 5-substituted 2-(2,4-dihydroxyphenyl)-1,3,4-thiadiazole series was evaluated. Their structures were confirmed by elemental analyses and IR, ¹H and ¹³C NMR and mass spectra. The azole-resistant clinical isolates of Candida albicans and no-albicans Candida spp. were used in the antifungal tests. Some compounds exhibit higher activities than the comparatively studied antifungal drugs. Amino-1,3,4-thiadiazole derivatives exhibited higher (than other analogues) antifungal effects against Candida no-albicans spp. than against C. albicans. Derivatives with strong antifungal activity have a narrow range of lipophilicity values determined by the Villar approach.     

Antiprotozoal and antimicrobial activities of O-alkylated and formylated acylphloroglucinols

In the present article, we examined the antileishmanial, antimalarial, antibacterial, and antifungal activities of several newly synthesized O-alkylated phloroglucinol compounds (11-19) which are analogues of the naturally occurring antimalarial compound 1. Analogues 12 and 16 exhibited antileishmanial activity against, Leishmania donovani promastigotes with IC(50)s of 5.3 and 4.2microg/mL, respectively. Naturally occurring monomeric formylated acylphloroglucinol compounds, grandinol (2), jensenone (3), and their analogues (29-37), were also synthesized and evaluated for antileishmanial, antimalarial, antibacterial, and antifungal activities. Amongst these, both grandinol and jensenone showed mild to moderate antibacterial, antifungal, and antileishmanial activities. Jensenone (3) was effective against Candida albicans with an IC(50) of 5.5microg/mL but was ineffective against Cryptococcus neoformans and methicillin-resistant Staphylococcus aureus. Among the analogues, 34 was the most active against C. albicans and C. neoformans with IC(50)s of 2.0 and 2.5microg/mL, respectively, and was fungicidal toward Candida albicans.