Folate-Synthesizing Enzyme System as Target for Development of Inhibitors and Inhibitor Combinations against Candida albicansSynthesis and Biological Activity of New 2,4-Diaminopyrimidines and 4‘-Substituted 4-Aminodiphenyl Sulfones

Abstract

The paper describes the design, synthesis, and testing of inhibitors of folate-synthesizing enzymes and of whole cell cultures of Candida albicans. The target enzymes used were dihydropteroic acid synthase (SYN) and dihydrofolate reductase (DHFR). Several series of new 2,4-diaminopyrimidines were synthesized and tested as inhibitors of DHFR and compared with their activity against DHFR derived from mycobacteria and Escherichia coli. To test for selectivity, also rat DHFR was used. A series of substituted 4-aminodiphenyl sulfones was tested for inhibitory activity against SYN and the I(50) values compared to those obtained previously against Plasmodium berghei- and E. coli-derived SYN. Surprisingly, QSAR equations show very similar structural dependencies. To find an explanation for the large difference in the I(50) values observed for enzyme inhibition (SYN, DHFR) and for inhibition of cell cultures of Candida, mutant strains with overexpressed efflux pumps and strains in which such pumps are deleted were included in the study and the MICs compared. Efflux pumps were responsible for the low activity of some of the tested derivatives, others showed no increase in activity after pumps were knocked out. In this case it may be speculated that these derivatives are not able to enter the cells.

Structure-Guided Development of Efficacious Antifungal Agents Targeting Candida glabrata Dihydrofolate Reductase

“…Moreover, when the propargyl compounds were assayed with human DHFR, selectivity ratios as high as 156-fold (Table 1) were observed. The IC 50 value of trimethoprim, 7 µM, is included in these enzyme inhibition assays as a reference and compares similarly with the value obtained with other eukaryotic DHFR species ( Candida albicans 30 µM (Otzen et al, 2004), Pneumocystis carinii 12 µM (Rosowsky et al, 2002), Cryptosporidium 14 µM (Pelphrey et al, 2007), Toxoplasma gondii 8 µM (Pelphrey et al, 2007)).…”

“…There have been very few studies focusing on DHFR as an antifungal target. While there has been some effort to develop inhibitors of C. albicans DHFR (CaDHFR) (Czaplinski et al, 1995; Kuyper et al, 1996; Otzen et al, 2004) and the crystal structure of CaDHFR (Whitlow et al, 2001; Whitlow et al, 1997) guided the development of a class of molecules (Chan et al, 1995) with some promising activity, up until now there have been no reported efforts to discover inhibitors of C. glabrata DHFR (CgDHFR).…”

Retigeric Acid B Attenuates the Virulence of Candida albicans via Inhibiting Adenylyl Cyclase Activity Targeted by Enhanced Farnesol Production

“…aMIC 80 in vitro has been reported [41], [42].bMIC 80 of FLC in vitro has been reported [43].cMIC 80 in vitro has been reported in our lab [10].…”

Design and Synthesis of New Phthalazinone Derivatives Containing Benzyl Moiety with Anticipated Antitumor Activity

“…The structure of compound 20 was confirmed from spectroscopic data. The IR showed band at 1737 cm 35) and inhibitors for several 36) cyclic oxygenase-2 (COX-2). Compounds containing C=N may act as a Michael acceptor for nucleophiles containing NH 2 or sulfhydryl SH groups.…”