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

Abstract

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 alpha-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, the minimum inhibitory concentrations (MIC) for Moraxella sp. and E. coli were 0.83 and 1.67 mg/mL, respectively. Among the alkyl esters of amino acid conjugated SLs, the ethyl ester of leucine-SLs was most active. Against Moraxella sp., S. sanguinis, and M. imperiale, MIC values are 7.62 x 10(-4), 2.28 x 10-(3) and 1.67 mg/mL, respectively. All compounds displayed virus-inactivating activity with 50% effective concentrations (EC50) below 200 microg/mL. The EC50 of leucine-SL ethyl ester was 24.1 microg/mL, showing that it is more potent than commercial spermicide nonoxynol-9 (EC50 approximately 65 microg/mL).

Selective Production of Acid-form Sophorolipids from Glycerol by <i>Candida floricola</i>

“…The 1 H-NMR spectrum of GL-A was similar to that of previously reported SLs 26 . GL-A was a disaccharide, and H-1 and -1 protons were detected at 4.45 and 4.55 ppm, respectively.…”

1-Methoxycarbonyl-2-(4-nitrophenyl)ethanaminium nitrate

“…For details of -amino acid derivatives, see: Lucchese et al (2007); Arki et al (2004); Hauck et al (2006); Dai & Fu (2008); Wen (2008); Azim et al (2006).…”

“…Amino acid derivatives are important compounds due to their biological activities, and there has been an increased interest in the enantiomeric preparation of α-amino acid derivatives as precursors for the synthesis of novel biologically active molecules (Lucchese et al, 2007;Arki et al, 2004;Hauck et al, 2006;Azim et al, 2006;Dai et al, 2008;Wen, 2008). Here we report the crystal structure of the title compound.…”

Production of Sophorolipids from Non-edible Jatropha Oil by Stamerella bombicola NBRC 10243 and Evaluation of their Interfacial Properties

“…1 that can be obtained easily from culture media by precipitation 19 . Moreover, SLs and their derivatives have antimicrobial 20 , anticancer 21 , and antiviral 22 activities, and therefore the cosmetic, food, and detergent industries are increasingly interested in using SLs.…”