Amino Acid Conjugated Sophorolipids: A New Family of Biologically Active Functionalized Glycolipids

Sophorolipids (SLs) are extra cellular glycolipids produced by Candida bombicola ATCC 22214 when grown in the presence of glucose and fatty acids. These compounds have a disaccharide head group connected to a long-chain hydroxyl−fatty acid by a glycosidic bond. To explore structure−activity of modified SLs, a new family of amino acid−SL derivatives was prepared. Synthesized analogs consist of amino acids linked by amide bonds formed between their α-amino moiety and the carboxyl group of ring-opened SL fatty acids. Their preparation involved the following:  (i) hydrolysis of a natural SL mixture with aqueous alkali to give SL free acids, (ii) coupling of free acids to protected amino acids using dicarbodiimide, and (iii) removing amino acid carboxyl protecting groups. These conjugates were evaluated for their antibacterial, anti-HIV, and spermicidal activity. All tested analogs showed antibacterial activity against both gram +ve and gram −ve organisms. Leucine-conjugated SL was most efficient. For example,...