Synthesis and biological evaluation of ricinoleic acid-based lipoamino acid derivatives

A series of novel ricinoleic acid based lipoamino acid derivatives were synthesized from (Z)-methyl-12-aminooctadec-9-enoate and different l-amino acids (glycine, alanine, phenyl alanine, valine, leucine, isoleucine, proline and tryptophan). The structures of all the prepared compounds were characterized by ¹H NMR, ¹³C NMR and mass spectral studies. The title compounds were evaluated for their antimicrobial and anti-biofilm activities. Among all the derivatives, compound 7a (Z)-methyl-12-(2-aminoacetamido)octadec-9-enoate exhibited promising antibacterial activity (MIC, 3.9-7.8μg/mL) and compounds 7b (Z)-methyl 12-(2-aminopropanamido)octadec-9-enoate and 7g (Z)-methyl-12-(pyrrolidine-2-carboxamido)octadec-9-enoate exhibited moderate activity (MIC, 7.8-31.2μg/mL) selectively against four different Gram-positive bacterial strains such as Staphylococcus aureus MTCC 96, Bacillus subtilis MTCC 121, S. aureus MLS-16 MTCC 2940, Micrococcus luteus MTCC 2470. These compounds also exhibited excellent antifungal activity against studied fungal strains. Further, the compounds 7a, 7b and 7g were also screened for anti-biofilm activity. Among these lipoamino acid derivatives, compound 7a exhibited good anti-biofilm activity (IC₅₀, 1.9-4.1μg/mL) against four Gram-positive bacterial strains.