Anticandidial effect of phenylbutene derivatives and their interaction with ergosterol

This paper reports the effect of phenylbut-3-en-2-one, of its analogues, bearing 3-nitro, 4-nitro, 4-chloro- and 4-dimethylamino substituents at the phenyl moiety, and of the hydrazide, phenylhydrazide and oxime of 4-nitrophenylbut-3-en-2-one on the growth and germ-tube formation of Candida spp., as well as their ability to interact with ergosterol in water/dimethylformamide (DMF) solution and their acute toxicity for mice. 3-Nitro-, 4-nitro- and 4-chlorophenylbut-3-en-2-ones inhibit candidial growth in vitro in concentrations ranging from 0.01 to > 0.4 mM and their activity is comparable to that of ketoconazole (in mg/l) and lower than that of amphotericin B. The rest of the compounds are inactive at > 0.4 mM. Germ-tube formation of C.albicans is inhibited at 0.04 mM 4-nitrophenylbut-3-en-2-one and at 0.005 mM of the 3-nitro isomer. A decrease in the absorption maxima in ergosterol mixtures with 4-dimethylamino, 3-nitrophenylbut-3-en-2-one and the oxime of the 4-nitrophenylbut-3-en-2-one was observed, indicative of interaction in water/DMF solutions, while no changes in the UV spectra of the remaining compounds were detectable. That suggests that the growth inhibiting effect is not in correlation with their ability to interact with ergosterol, despite the resemblance to polyenes. LD50 for mice is 367 mg/kg for 4-nitrophenylbut-3-en-2-one and 398 mg/kg for the 3-nitro isomer.