Synthesis, cytotoxic and antimicrobial screening of a proline-rich cyclopolypeptide

Present study describes the first total synthesis of a cyclic heptapeptide, stylisin 1 (8) via coupling of tetrapeptide Boc-L-tyrosinyl-L-prolyl-L-leucyl-L-proline-OH and tripeptide L-phenylalanyl-L-isoleucyl-L-proline-OMe followed by cyclization of linear heptapeptide segment. Structure elucidation of synthesized cyclopeptide was done on basis of detailed spectral as well as elemental analysis. From the results of pharmacological screening, it was concluded that cyclopeptide 8 possessed moderate cytotoxicity against Dalton's lymphoma ascites (DLA) and Ehrlich's ascites carcinoma (EAC) cell lines with IC(50) (inhibitory concentration, 50%) values of 10.6 and 14.6 microM. Furthermore, cyclopeptide 8 exhibited moderate to good antimicrobial activity against Gram -ve (negative) bacteria Klebsiella pneumoniae and Pseudomonas aeruginosa, dermatophytes and Candida albicans with minimum inhibitory concentration (MIC) of 6 microg/ml.