Gökalp İşcan

Synthesis and biological evaluation of some hydrazone derivatives as new anticandidal and anticancer agents

New hydrazone derivatives were synthesized via the nucleophilic addition-elimination reaction of 2-[(1-methyl-1H-tetrazol-5-yl)thio)]acetohydrazide with aromatic aldehydes/ketones. The compounds were tested in vitro against various Candida species and compared with ketoconazole. Genotoxicity of the most effective anticandidal compounds was evaluated by umuC and Ames assays. All compounds were also investigated for their cytotoxic effects on NIH3T3 and A549 cell lines. Compound 8 was the most effective antifungal derivative against C. albicans (ATCC-90028) with a MIC value of 0.05 mg/mL. Compound 5 can be identified as the most promising anticancer agent against A549 cancer cell lines due to its inhibitory effect on A549 cell lines and low toxicity to NIH3T3 cells.

Synthesis and the selective antifungal activity of 5,6,7,8-tetrahydroimidazo[1,2-a]pyridine derivatives.

Even though there are new classes of compounds now frequently used in treatment of fungal infections, the density of deeply invasive candidiasis has increased at least 10-fold during the past decade. Furthermore, many infections due to Candida species are actually refractory to antifungal therapy. In this present study, it was aimed to synthesize, new hydrazide derivatives of tetrahydroimidazo[1,2-a]pyridine and evaluate their anticandidal activity and cytotoxicity in vitro. The reaction of tetrahydroimidazo[1,2-a]pyridine-2-carboxylic acid hydrazides with various benzaldehydes gave tetrahydroimidazo[1,2-a]pyridine-2-carboxylic acid benzylidene hydrazide derivatives. The chemical structures of the compounds were elucidated and confirmed by IR, 1H NMR, MS-FAB+ spectroscopy and elemental analyses. Eight new tetrahydroimidazo[1,2-a]pyridine derivatives were synthesized and screened for their antifungal effects against a panel of ten human pathogenic Candida albicans, Candida glabrata, Candida krusei, Candida parapsilosis, Candida tropicalis, Candida utilis, and Candida zeylanoides using agar diffusion and broth microdilution assays, respectively. Furthermore, their cytotoxicity was tested against six mammalian cell lines. Among the analogues, the compound 5,6,7,8-tetrahydroimidazo[1,2-a]pyridine-2-carboxylic acid-(4-cyanobenzylidene) showed very strong inhibitory activity (up to MIC 0.016 mg/mL) against the screened Candida species. The same compound showed no in vitro toxicity up to 25 microg/mL concentration suggesting that its antifungal activity (MICs 0.016-1 mg/mL) is selective.

Antimicrobial activities of Ferulago essential oils.

Essential oils from Ferulago asparagifolia Boiss., F. galbanifera (Miller) W. Koch, F. humilis Boiss. (Endemic), F. trachycarpa Boiss. growing in Turkey were evaluated against 15 microorganisms for their antifungal and antibacterial activity using an agar tube dilution and microdilution broth susceptibility assay, respectively. The essential oil compositions were investigated by GC/MS. Inhibitory effects against Escherichia coli, Enterobacter aerogenes, Candida albicans, Gaeumannomyces graminis var. tritici, Sclerotium rolfsii and Fusarium moniliforme were remarkable. Results are discussed in comparison with the chemical composition of the essential oils.

Essential oils of three species of Heracleum. Anticandidal activity

Fruits of Heracleum crenatifolium Boiss., Heracleum sphondylium L. subsp. ternatum (Velen.) Brummitt, and Heracleum platytaenium Boiss. (Umbelliferae) were hydrodistilled to obtain essential oils that were then analyzed by GC and GC/MS. The major component was identified as octyl acetate (93.7, 87.6 and 31.6% respectively). Octyl butyrate was also characterized as the main component in H. platytaenium oil. Furthermore, anticandidal activity of the oils was evaluated using the microdilution broth method. All the oils showed good inhibitory effects against C. glabrata.

Biotransformation of (-)-(R)-α-phellandrene: antimicrobial activity of its major metabolite.

Terpene derivatives converted by microbial biotransformation constitute an important resource for natural pharmaceutical, fragrance, and aroma substances. In the present study, the monoterpene α‐phellandrene was biotransformed by 16 different strains of microorganisms (bacteria, fungi, and yeasts). The transformation metabolites were initially screened by TLC and GC/MS, and then further characterized by NMR spectroscopic techniques. Among the six metabolites characterized, 6‐hydroxypiperitone, α‐phellandrene epoxide, cis‐p‐menth‐2‐en‐1‐ol, and carvotanacetone, which originated from (−)‐(R)‐α‐phellandrene, are reported for the first time in this study. Additionally, the substrate and the metabolite 5‐p‐menthene‐1,2‐diol were subjected to in vitro antibacterial and anticandidal tests. The metabolite showed moderate‐to‐good inhibitory activities (MICs=0.125 to >4 mg/ml) against various bacteria and especially against Candida species in comparison with its substrate (−)‐(R)‐α‐phellandrene and standard antimicrobial agents.

Studies on hydrazone derivatives as antifungal agents

The increasing clinical importance of drug-resistant fungal pathogens has urged additional need to fungal research and new antifungal compound development. For this purpose, some N-(1-benzyl-2-phenylethylidene)-N′-[4-(aryl)thiazol-2-yl]hydrazone (1a-e) and N-(1-phenylbutylidene)-N′-[4-(aryl)thiazol-2-yl]hydrazone (2a-e) derivatives were synthesised and evaluated for antifungal activity. Their antifungal activities against standard and clinical strands of Candida albicans, Candida glabrata, Candida utilis, Candida tropicalis, Candida krusei, Candida zeylanoides, and Candida parapsilosis were investigated. A significant level of activity was observed.

The bioactive essential oil of Heracleum sphondylium L. subsp. ternatum (Velen.) Brummitt.

The essential oil of Heracleum sphondylium L. subsp. ternatum (Velen.) Brummit (Umbelliferae) was isolated from crushed seeds by means of hydrodistillation and analyzed by GC and GC/MS. Major components were identified as 1-octanol (50.3%), octyl butyrate (24.6%), and octyl acetate (7.3%). Furthermore, antimicrobial activity of the oil was evaluated using microdilution broth and agar diffusion methods. The bioactive constituent of the essential oil was determined as 1-octanol by using a bioautography assay.

Synthesis and anticandidal activity of new triazolothiadiazine derivatives

New triazolothiadiazine derivatives were synthesized via the ring closure reaction of 4-amino-5-substituted-2,4-dihydro-3H-1,2,4-triazol-3-thiones with phenacyl bromides. The compounds were tested in vitro against various Candida species and compared with ketoconazole. Among these compounds, the compound bearing cyclohexyl moiety and p-chlorophenyl substituent on triazolothiadiazine ring (2i) was found to be the most potent derivative against Candida albicans (ATCC 90028). It is clear that there is a positive correlation between anticandidal activity and two functional moieties, namely cycloaliphatic group and p-chlorophenyl substituent on triazolothiadiazine ring. The compounds were also investigated for their cytotoxic effects using MTT assay. Compound 2a exhibited the highest cytotoxic activity, whereas compound 2f possessed the lowest cytotoxic activity against NIH/3T3 cells.

Composition and Antimicrobial Activity of the Essential Oils of Two Endemic Species from Turkey: Sideritis cilicica and Sideritis bilgerana

Aerial parts of Sideritis cilicica Boiss. & Bal. and Sideritis bilgerana P.H. Davis (Lamiaceae) were hydrodistilled to obtain essential oils that were then analyzed by GC and GC/MS. β-Pinene (39%), α-pinene (28%), and β-phellandrene (20%) were the main components in the oil of S. cilicica, while β-pinene (48%), and α-pinene (32%) were the major constituents in the oil of S. bilgerana. The antimicrobial activities of the oils were evaluated by using the microdilution broth method. Both of the oils showed good inhibitory effects on C. albicans.

Preparation of some pyrazoline derivatives and evaluation of their antifungal activities.

The synthesis of a new series of 1-[(benzazole-2-yl)thioacetyl]-3,5-diaryl-2-pyrazoline derivatives was obtained by reacting 1-(chloroacetyl)-3,5-diaryl-pyrazolines with 2-mercaptobenzimidazole/benzoxazole/benzothiazole. The chemical structures of the compounds were elucidated by 1H-NMR, 13C-NMR, and FAB+-MS spectral data. Their antifungal activities against Candida albicans, Candida glabrata, Candida utilis, Candida tropicalis, Candida krusei, and Candida parapsilosis were investigated. A significant level of activity was observed.