There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Naphthoquinones are the most commonly occurring type of quinones in nature. They are a diverse family of secondary metabolites that occur naturally in plants, lichens and various microorganisms. This subgroup is constantly being expanded through the discovery of new natural products and by the synthesis of new compounds via innovative techniques. Interest in quinones and the search for new biological activities within the members of this class have intensified in recent years, as evidenced by the evaluation of the potential antimicrobial activities of quinones. Among fungi of medical interest, yeasts of the genus Candida are of extreme importance due to their high frequency of colonization and infection in humans. The objective of this review is to describe the development of naphthoquinones as antifungals for the treatment of Candida species and to note the most promising compounds. By using certain criteria for selection of publications, 68 reports involving both synthetic and natural naphthoquinones are discussed. The activities of a large number of substances were evaluated against Candida albicans as well as against 7 other species of the genus Candida. The results discussed in this review allowed the identification of 30 naphthoquinones with higher antifungal activities than those of the currently used drugs.

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The Antifungal Activity of Naphthoquinones: An Integrative Review

New family of antimicrobial agents derived from 1,4-naphthoquinone.

Low melting oxalic acid/proline mixture as dual solvent/catalyst for efficient synthesis of 13-aryl-13H-benzo[g]benzothiazolo[2,3-b]buinazoline-5,4-diones under microwave irradiation

Discovery of new pharmaceutical substances is currently boosted by the possibility of utilization of the Synthetically Accessible Virtual Inventory (SAVI) library, which includes about 283 million molecules, each annotated with a proposed synthetic one-step route from commercially available starting materials. The SAVI database is well-suited for ligand-based methods of virtual screening to select molecules for experimental testing. In this study, we compare the performance of three approaches for the analysis of structure-activity relationships that differ in their criteria for selecting of "active" and "inactive" compounds included in the training sets. PASS (Prediction of Activity Spectra for Substances), which is based on a modified Naive Bayes algorithm, was applied since it had been shown to be robust and to provide good predictions of many biological activities based on just the structural formula of a compound even if the information in the training set is incomplete. We used different subsets of kinase inhibitors for this case study because many data are currently available on this important class of drug-like molecules. Based on the subsets of kinase inhibitors extracted from the ChEMBL 20 database we performed the PASS training, and then applied the model to ChEMBL 23 compounds not yet present in ChEMBL 20 to identify novel kinase inhibitors. As one may expect, the best prediction accuracy was obtained if only the experimentally confirmed active and inactive compounds for distinct kinases in the training procedure were used. However, for some kinases, reasonable results were obtained even if we used merged training sets, in which we designated as inactives the compounds not tested against the particular kinase. Thus, depending on the availability of data for a particular biological activity, one may choose the first or the second approach for creating ligand-based computational tools to achieve the best possible results in virtual screening.

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How to Achieve Better Results Using PASS-Based Virtual Screening: Case Study for Kinase Inhibitors

In the present paper, we report the synthesis, characterization, and biological evaluation as antifungal, antibacterial, antioxidant, and cytotoxic/anticancer agents of N-, S-, O-substituted-1,4-naphtho- and 2,5-bis(amino-substituted)-1,4-benzoquinone derivatives. In the synthesized compounds, antimicrobial activity at low concentrations against Escherichia coli B-906, Staphylococcus aureus 209-P, and Mycobacterium luteum B-917 bacteria and Candida tenuis VKM Y-70 and Aspergillus niger F-1119 fungi in comparison with controls was identified. 2-(N-Diphenylmethylpiperazin-1-yl)-3-chloro-1,4-naphthoquinone 9a was the most potent, with a minimum inhibitory concentration value of 3.9 µg/mL against test culture M. luteum. The synthesized compounds were screened for their antioxidant capacity using the cupric-reducing antioxidant capacity (CUPRAC) method. 2,2'-[1-(2-Aminoethyl)piperazin-1-yl]-3,3'-dichloro-bis(1,4-naphthoquinone) 10 showed the highest antioxidant capacity, with a 0.455 CUPRAC-trolox equivalent antioxidant capacity (TEAC) coefficient. Other parameters of antioxidant activity (scavenging effects on OH(·), O2(·－), and H2O2) of these compounds were also determined. The cytotoxic activity of the compounds was investigated by employing the sulforhodamine B cell viability assay against A549 (lung), MCF-7 (breast), DU145 (prostate), and HT-29 (colon) cancer cell lines. Compound 10 exhibited the most powerful cytotoxic activity at a concentration of 20 µM against all cell lines. In addition to the strongest antioxidant activity of compound 10, it also had lowest IC50 values (<3 µM), warranting further in vivo studies due to its anticancer activity.

Design, Synthesis, Biological Evaluation, and Antioxidant and Cytotoxic Activity of Heteroatom-Substituted 1,4-Naphtho- and Benzoquinones

Mono(thio)substituted nitrodienes 1a-b give the compounds 7a and 7b cohen treated with piperazine. S, N-substituted nitrodiene 3a was obtained from the reaction of la with p-phenylendiamine. Under the same conditions the compounds la-b and benzidine give the compounds 5a-b. The compounds la-b from the reaction with aniline in ether yielded 9s-b. Mono(thio)substituted nitrodienes la-b give 11a-b by the reaction with piperidine in ether. 13a-c are prepared by the reaction of compounds la-c with morpholine.

S,n-substituierte diene und s,n-subtituierte tetraene aus mono(thio)subtituierten 2-nitrodienverbindungen

Anticancer activity as an associated action for a series of dithiocarbamates of 9,10-anthracenedione was predicted using the PASS computer program and analysed with PharmaExpert software. The predicted cytotoxic activity of the dithiocarbamate derivatives of 9,10-anthracenedione was evaluated in vitro on cancer cells of the human lung (A549), prostate (PC3), colon (HT29) and human breast (MCF7) using the sulforhodamine B (SRB) cell viability assay. Among these compounds, 9,10-dioxo-9,10-dihydroanthracen-1-yl pyrrolidin-1-carbodithioate and 9,10-dioxo-9,10-dihydroanthracen-2-yl pyrrolidin-1-carbodithioate were identified as the most potent anticancer agents with cytotoxic activity against the MCF-7 human breast cell line with GI50 values of 1.40 μM and 1.52 μM, whereas the GI50 value for the reference anticancer drug mitoxantrone was 3.93 μM. Thus, anticancer activity predicted by PASS with a probability Pa > 30% was confirmed by the experiment. Relatively small Pa values estimated by PASS indicat...

Computer-aided prediction and cytotoxicity evaluation of dithiocarbamates of 9,10-anthracenedione as new anticancer agents.

Mono(thio)substituted dienes 1a-1b gave compounds 3a-c and 5d-g with piperazine and piperidine derivatives in dichloromethane. Compounds 8 , 9 , and 10 were obtained from the reactions of perchlorobutadiene ( 6 ) with 1,4-butanedithiol ( 7 ) in ethanol in the presence of sodium hydroxide. Compounds 12a-b , 13a-b were obtained from the reactions of perchlorobutadiene ( 6 ) with allylmercaptan (CH 2 =CH--CH 2 --SH) and mercaptoethanol (HO--CH 2 --CH 2 --SH).

N,S-Substituted Dienes from Mono(arylthio)substituted- and S-, S,S-Substituted Dienes

Hexachlorobutadiene 1 reacts with 3-mercapto-1-hexanol in water-ethanol mixture in the presence of sodium hydroxide to give the new monosubstituted thioether 3-(perchlorobuta-1,3-dienyl-thio)-hexan-1-ol 3a and the disubstituted thioether 3,3′ -(perchlorobuta-1,3-diene-1,4-diyl) bis(sulfane-diyl)-dihexan-1-ol 4a . 1-Chlorohexan-3-yl-pentachlorobutadienyl-sulfide 5a , 2-chloroethyl-penta-chlorobutadienyl-sulfide 5b , 2-chloropropyl-pentachlorobutadienyl-sulfide 5c and 1,2,3,4-tetra-chlorobuta-1,4-bis(2-chloroethylsulfanyl)-buta-1,3-diene 6b were obtained from the reaction of 3a–c and 4b with SOCl2 in pyridine. The derivatives 8b–k and 9a were synthesized from the reaction of componds 5b and 5c in water-ethanol mixture in the presence of sodium hydroxide with the corresponding thiol, respectively.

Zeliha Gökmen

Papers

Design, Synthesis, Biological Evaluation, and Antioxidant and Cytotoxic Activity of Heteroatom-Substituted 1,4-Naphtho- and Benzoquinones

S,n-substituierte diene und s,n-subtituierte tetraene aus mono(thio)subtituierten 2-nitrodienverbindungen

Computer-aided prediction and cytotoxicity evaluation of dithiocarbamates of 9,10-anthracenedione as new anticancer agents.

N,S-Substituted Dienes from Mono(arylthio)substituted- and S-, S,S-Substituted Dienes

New Perchlorobutadienyl Sulfanes