Antifungal Effect of Novel 2-Bromo-2-Chloro-2-(4-Chlorophenylsulfonyl)-1-Phenylethanone against Candida Strains

Abstract

We investigated the antifungal activity of novel a 2-bromo-2-chloro-2-(4-chlorophenylsulfonyl)-1-phenylethanone (compound 4). The synthesis of compound 4 was commenced from sodium 4-chlorobenzene sulfinate and the final product was obtained by treatment of α-chloro-β-keto-sulfone with sodium hypobromite. The sensitivity of 63 clinical isolates belonging to the most relevant Candida species toward compound 4 using the method M27-A3 was evaluated. We observed among most of the clinical strains of C. albicans MIC ranging from 0.00195 to 0.0078 μg/mL. Compound 4 at 32 μg/mL exhibited fungicidal activity against nine Candida strains tested using the MFC assay. Compound 4 displayed anti-Candida activity (with clear endpoint) against 22% of clinical strains of Candida. Under compound 4, Candida susceptibility and tolerance, namely paradoxical effect (PG), was found for only two clinical isolates (C. glabrata and C. parapsilosis) and reference strain 14053 using both M27-A3 and MFC method. We found that compound 4 does not induce toxicity in vivo against larvae of Galleria mellonella (≥97% survival) and it displays reduced toxicity on mammalian cells in vitro (< CC20 at 64 μg/mL). Furthermore, XTT assay denoted clear metabolic activity of sessile cells in the presence of compound 4. Thus, the effect of compound 4 on formed C. albicans biofilms was minimal. Moreover, strain 90028 exhibited no defects in hyphal growth on Caco-2 monolayer under compound 4 influence at MIC = 16 μg/mL. The MIC values of compound 4 against C. albicans 90028, in medium with sorbitol did not suggest that compound 4 acts by inhibiting fungal cell wall synthesis. Our findings with compound 4 suggest a general strategy for antifungal agent development that might be useful in limiting the emergence of resistance in Candida strains.

Role of Virulence Determinants in Candida albicans’ Resistance to Novel 2-bromo-2-chloro-2-(4-chlorophenylsulfonyl)-1-phenylethanone

“…As is shown in Figure 1 , 2-bromo-2-chloro-2-(4-chlorophenylsulfonyl)-1-phenylethanone (Compound 4 ) was synthesized starting from sodium 4-chlorobenzene sulfinate ( 1 ) which reacted with 2-bromo-1-phenylethanone to obtain 2-(4-chlorophenylsulfonyl)-1-phenylethanone; ( 2 ) was transformed into 2-chloro-2-(4-chlorophenylsulfonyl)-1-phenylethanone; ( 3 ) by the reaction with potassium halide in the presence of hydrogen peroxide and acetic acid. The final product; ( 4 ) was obtained by treatment of β-chloro ( 3 ) with sodium hypobromite [ 2 ].…”

“…Compound 4 was tested at concentrations that ranged from 0.25 to 16 μg/mL. As described in [ 2 ]: (1) compound test wells (PTW) were prepared with stock solution of Compound 4 (1600 µg/mL) dissolved in DMSO (66% in water), then the yeast cell suspension and Compound 4 (final dilution 1:100) were dispensed at a final volume of 250 µL/well into 96-well microplates; (2) growth control wells (GCW) were prepared with planktonic cells at a final density of 2.5 × 10 2 –2.5 × 10 3 cfu/mL suspended in RPMI 1640 medium containing 0.66% DMSO ( v / v ); (3) sterility control wells (SCW) were made with Compound 4 , RPMI 1640 medium (Gibco ® , Waltham, MA, USA), and sterile water replacing inoculum; (4) microtiter plates were incubated at 35 °C without agitation for 48 h. After incubation, the growth of the cells was measured by a microtiter plate reader Spark Control M10 (Tecan Group Ltd., Grödig, Austria). The endpoint was calculated as a 100% reduction in OD 405 as compared to the growth in the control wells according to the formula: % of inhibition = 100—(OD 405 CTW—OD 405 SCW)/(OD 405 GCW—OD 405 SCW).…”

“…Additionally, AmB (Sigma-Aldrich, St. Louis, MO, USA) at 0.5 μg/mL (MIC assessed visually, data not shown) against C. albicans SC5314 was tested. As described in [ 2 ], the minimal inhibitory concentrations (MICs) of the compound were read visually after 18 and 48 h. Paradoxical growth (PG), i.e., the reduced antifungal effect (<99.9% reduction of the starting inoculum) at concentrations of above clear endpoint (100% cell growth reduction) was evaluated. Tests were performed in three independent experiments.…”

“…The emergence of antifungal resistance has driven the field to seek novel antifungal targets that could lead to the development of effective drugs with a new mode of action. Our recent findings [ 1 , 2 ] focused on the antifungal sulfones’ activity, dealing with multiple aspects of the virulence attributes and immune system evasion mechanisms employed by C. albicans . The studies [ 1 , 2 ] included diverse regulators of drug resistance in C. albicans such as: (1) lytic aspartic proteases (Saps), involved in the resistance of C. albicans to azoles (efflux pumps [ 3 ]); (2) subtilisin-type serine convertase Kex2 playing a role in the cell wall formation, interfering with Saps in the cell wall remodeling mechanisms, and responding to antifungal drugs [ 3 , 4 , 5 ]; (3) transcriptional regulators controlling hyphae formation, given that yeast-hyphae implicates morphological alterations (cell wall remodeling [ 5 ]); (4) development of biofilms overcoming environmental stress such as drug exposure and immune system attack (metabolic adaptation) [ 6 ].…”

“…On the basis of our findings [ 2 ] and in continuation of our effort to develop an antifungal target of Compound 4 , we report herein on the in vitro susceptibility of the C. albicans wild type reference strain of SC5314 and mutant strains ( sap4Δsap5Δsap6Δ , efg1Δ , cph1Δ , and kex2Δ ) to Compound 4 . Additionally, screening against the C. glabrata wild type strain and mutants was included.…”