In this work, synthesis of alkylamino and aralkylamino derivatives of sesquiterpene quinone avarone and its model compound tert-butylquinone was described. For all obtained derivatives biological activity was studied. Cytotoxic activity of the synthesized derivatives towards multidrug resistant MDR human non-small cell lung carcinoma NCI-H460/R cells, their sensitive counterpart NCI-H460 and human normal keratinocytes (HaCaT) as well as detection of cell death superoxide anion generation were investigated. Antimicrobial activity towards Gram positive and Gram negative bacteria and fungal cultures was determined. The results showed that strong cytotoxic activity toward cancer cells was improved with simple avarone mimetics. Some derivatives were selective towards MDR cancer cells. The most active derivatives induced apoptosis in both cancer cell lines, but not in normal cells. Superoxide production was induced by 2,6-disubstituted compounds in MDR cancer cells and not by less active 2,5-disubstituted compounds and was accompanied by the collapse of the mitochondrial transmembrane potential. Two tert-butylquinone derivatives were particularly selective towards MDR cancer cells. Some tert-butylquinone derivatives exhibited a strong antimicrobial activity.

Medicinal value of natural products comes from symbiotic and competitive evolution in Earth’s complex biosphere. Billions of years of co-evolutionary interactions among millions of species have produced a large repertoire of defense molecules effective in fighting bacteria, viral, and fungal pathogens. Each species contains millions of different and useful molecules and new research technologies enabled the screening of molecules and complex mixtures from diverse biological sources. Traditional use of plants and other species led to the discovery of many bioactive compounds with various properties. In the last four decades, a large number of them were evaluated for their potential to treat cancer. Penetration of drugs into the cancer cell is necessary for their lethal pharmacological effect through interaction with intracellular target molecules. Increased activity of membrane efflux pumps reduces the intracellular drug accumulation, thereby preventing drug-target interactions. The discovery of the efflux transporter P-glycoprotein (P-gp) in multidrug resistant (MDR) cancer cells prompted the efforts in overcoming drug resistance by P-gp inhibition. The search for nontoxic anticancer agents from natural sources able to overcome MDR has been imperative in the field of drug design and discovery. Herein, we review various natural compounds from diverse sources emphasizing their potential to inhibit P-gp activity and/or expression.

No abstract

A Schiff base of 3-acetylpyridine with semicarbazide as well as the corresponding tetrahedral Zn(II) complex were synthesized and characterized by X-ray crystal structure analysis and spectroscopic methods. It is interesting to note that the ligand coordinated as a monodentate although there are several donor atoms in it. Computational studies showed that such structure is more stable than the hypothetical structure with one ligand bound as a bidentate. The complex exibited moderate antibacterial, antifungal and cytotoxic activities while the ligand was mostly inactive. The complex strongly induced formation of reactive oxygen species in tumor cell lines. It also influenced cell cycle progression in tumor cell lines, and induced autophagy. The latter effect is, at least in part, a protective onehis work was supported by the Ministry of Education and Science of the Republic of Serbia (Grant OI 172055 and III41025). We thank the Slovenian Research Agency (ARRS) thrugh program P-0175 for financial support and EN-FIST Centre of Excellence, Dunajska 156, 1000 Ljubljana, Slovenia, for using SuperNova diffractometer. The following organizations are thanked for financial support: the Ministerio de Ciencia e Innovacion (MICINN, project number CTQ2011-25086/BQU), and the DIUE of the Generalitat de Catalunya (project number 2009SGR528). Financial support from MICINN (Ministry of Science and Innovation, Spain) and the FEDER fund (European Fund for Regional Development) was provided by grant UNGI08-4E-003. Excellent service by the Centre de Serveis Cientifics i Academics de Catalunya (CESCA) is gratefully acknowledge

In this paper, the synthesis of fourteen alkylamino and arylamino derivatives of sesquiterpene quinone avarone and its model compound tert-butylquinone is described. Branched, cyclic, allylic and benzylic alkylamino/arylamino groups were introduced into the quinone moiety. For all the obtained derivatives, their biological activity and redox properties were studied. The cytotoxic activity of the synthesized derivatives towards multidrug resistant (MDR) human non-small cell lung carcinoma NCI-H460/R cells, their sensitive counterpart NCI-H460 and human normal keratinocytes (HaCaT) was investigated. The antimicrobial activity towards Gram-positive and Gram-negative bacteria, and fungal cultures was determined. Some of the synthesized derivatives showed selectivity for cancer cells, including MDR cells. Regarding their cell death induction potential, the most promising compounds were allylamino derivatives, preferentially triggering apoptosis, with high selectivity for cancer cells, including MDR cells. Several compounds showed promising antimicrobial activity, comparable to those of commercial antibiotic and antimycotic agents.