Solvent-free synthesis of novel vanillidene derivatives of Meldrum's acid: biological evaluation, DNA and BSA binding study

A series of novel O-alkyl vanillidene derivatives containing Meldrum's acid scaffold under solvent-free conditions were synthesized. The antimicrobial activity was estimated by determination of the minimal inhibitory concentration (MIC) using the broth microdilution. The most active compounds were 5-(4'-hydroxy-2'-iodo-3'-methoxybenzylidenyl)-2,2-dimethyl-1,3-dioxane-4,6-dione (3a), 5-(4'-acetoxy-3'-methoxybenzylidenyl)-2,2-dimethyl-1,3-dioxane-4,6-dione (3f), and 5-(4'-bromopropoxy-3'-methoxybenzylidenyl)-2,2-dimethyl-1,3-dioxane-4,6-dione (3h) with the MIC values ranging from 0.039 to 10 mg mL(-1). Antioxidant activity was evaluated by DPPH free radical scavenging activity. 3h showed the largest scavenging activity with an IC50 value of 55.61 mu g mL(-1) (0.14 mmol L-1). The interaction of 3a and 3h with DNA and bovine serum albumin (BSA) were investigated by the fluorescence spectroscopic method. The results achieved in competitive experiments with ethidium bromide (EB) indicated that 3a and 3h have an affinity to displace EB from the EB-DNA complex through intercalation. Fluorescence spectroscopy data show that the fluorescence quenching of BSA is a result of the formation of the 3a- and 3h-BSA complex species, and indicate that 3a-BSA is more stable, suggesting that 3h-BSA is less suitable for drug-cell interactions.