Antimicrobial activity of N-methyl 4-piperidone derived monoketone curcuminoids

In this study, fifteen N-methyl-4-piperidone-derived monoketone curcuminoids (MKCs) were synthesized using an environmentally friendly base-catalyzed Claisen-Schmidt condensation between an aromatic aldehyde (R-PhCHO) and N-methy-4-piperidonein ethanol using NaOH as the catalyst. These compounds were evaluated for their antibacterial activity against a representative panel of cariogenic bacteria, along with their antifungal activity against Candida krusei and C. albicans. The antimicrobial activity was determined based on the Minimum Inhibitory Concentration (MIC) values. Most of the compounds were obtained in about 2 hours in yields ranging from 40 to 70%. None of the compounds displayed antifungal activity, even at 100 µg/mL, the highest tested concentration. Similarly, none of the compounds were active against Enterococcus faecalis. On the other hand, compounds 1 (R=H), 10 (R=3,4,5-OMe), and 13 (R=3-F) displayed moderate activity against Streptococcus mutans (13), S. salivarus (1), L. paracasei (1 and 10), S. mitis (1, 10, and 13), S. sanguinis (1, 10, and 13), and S. sobrinus (13), with MIC values of 250 µg/mL and 500 µg/mL. The presence of the N-methyl-4-piperidone ring was found to boost the antibacterial activity as compared to the corresponding acetone-derived MKCs. Moreover, the antibacterial activity of compounds 10 and 13 was associated with the presence and position of the fluor atom and the methoxy groups at the aromatic ring. This study contributed to a better un-derstanding of the antimicrobial activity of MKCs, whose data in the literature are still scarce.