Rationally designed curcumin based ruthenium(ii) antimicrobials effective against drug-resistant Staphylococcus aureus

Abstract

Two curcumin conjugated ruthenium(ii) polypyridyl complexes, [Ru(NN)2(cur)](PF6) (1, 2), were systematically exploited for their antimicrobial activity in vitro and in vivo and potential selectivity against multidrug resistant S. aureus strains.

Curcumin, a Natural Antimicrobial Agent with Strain-Specific Activity

“…Betts and Wareham [ 43 ] investigated the activity of curcumin on eight MDR clinical isolates and the antibiotic susceptible A. baumannii ATCC 19606, but a too low concentration of the plant substance did not allow for a precise determination of its antibacterial effect with the MIC > 256 µg/mL. For the same reason, the MICs of curcumin against A. baumannii ATCC BAA-1605 and A. baumannii ATCC 17978 were exhibited to be >64 µg/mL [ 38 ] and >500 µg/mL [ 42 ], respectively. In the next work of the authors cited above [ 31 ], the MICs of curcumin were reported as 512–1024 µg/mL.…”

“…The MICs of curcumin against P. aeruginosa PAO1 were determined as 30–512 µg/mL [ 27 , 31 , 57 , 59 ]. For P. aeruginosa ATCC 27853 it was 73.7–512 µg/mL [ 31 , 34 , 58 ], but some authors reported the MICs values as >64 µg/mL [ 38 ], >128 µg/mL [ 33 ], or >375 µg/mL [ 44 ]. In turn, our studies did not show significant activity of curcumin on this strain with a MIC of 5000 µg/mL.…”

“…Most often, the results have been reported for a commensal E. coli strain ATCC 25922. They ranged from 163 [ 34 ] to 302 µg/mL [ 58 ], but some authors determined the MICs as >64 µg/mL [ 38 ], >128 µg/mL [ 33 ], >375 µg/mL [ 44 ], and >500 µg/mL [ 51 ]. Our investigations for this reference strain exhibited even a lower activity of curcumin at the MIC level of 2000 µg/mL.…”

“…In turn, this activity of curcumin against such bacteria as A. lwoffii [ 20 ], Proteus mirabilis [ 24 , 30 ], Serratia marcescens [ 20 , 24 ], Stenotrophomonas maltophilia [ 31 ], and Streptococcus agalactiae [ 30 ] has been examined sporadically. In the contemporary research, the in vitro ability of curcumin to inhibit microbial growth has frequently been tested against a small (4–6) number of species representing a small group of taxa, mostly E. coli , P. aeruginosa , and S. aureus , and less often Bacillus subtilis and Enterococcus faecalis (e.g., [ 32 , 33 , 34 , 35 , 36 , 37 , 38 ]). Some works have reported the minimum inhibitory concentration (MIC) value for only one species and a single, usually reference, strain (e.g., [ 39 , 40 , 41 , 42 ]).…”

Recent Studies on the Antimicrobial Activity of Transition Metal Complexes of Groups 6–12

“…In most cases, the compounds showed good MIC values (0.6-0.7 µM, comparable to gentamicin) against MRSA, they were less effective against E. coli and nearly inactive against P. aeruginosa. More recently, Srivastava et al reported ruthenium(II) polypyridyl complexes [97] coordinated to curcumin, [Ru(NN) 2 (cur)](PF 6 ) [NN = bpy, phen], (30, Figure 7) and tested them against a panel of ESKAPE pathogens, including the drug resistant S. aureus ATCC. The results revealed a good inhibitory effect of the complexes against the latter pathogen and a remarkably high selectivity index (MIC = 1 µg/mL vs 0.25 for levofloxacin, SI = 80).…”