Monocarbonyl Curcuminoids with Improved Stability as Antibacterial Agents against Staphylococcus aureus and Their Mechanistic Studies

Curcumin has been known to possess diverse pharmacological effects at relatively nontoxic doses; however, its therapeutic potential is severely restricted because of its low aqueous solubility and poor stability under physiological conditions. To overcome its limitations, we had previously designed several monocarbonyl curcuminoids by modifying the central β-diketone moiety of curcumin. In this study, the antibacterial activity of 33 curcuminoids from this designed library has been screened, six of which displayed potent antibacterial activity against clinically relevant Staphylococcus aureus. These curcuminoids were found to be very stable at physiological conditions and did not cause any toxicity toward mammalian cells. Mechanistically, out of these six curcuminoids, five caused instant membrane depolarization and were able to permeabilize the bacterial membrane, which could be the reason for their potent bactericidal activity and the sixth one killed staphylococcal cells without damaging the bacterial membrane. Overall, the present work established the staphylocidal potency of six water-soluble, nontoxic curcuminoids, thereby providing an impetus for the development of these lead curcuminoids for therapeutic use against S. aureus