Synthesis and biological activity of a cyclic hexapeptide from Dianthus superbus

Plant-originated cyclopolypeptide (XIII) was synthesized by coupling of dipeptide Boc-l-asn(bzh)-l-phe-OH and tetrapeptide gly-l-leu-l-ala-l-tyr-OMe followed by cyclization of a linear hexapeptide segment. Structure elucidation of XIII was done on basis of detailed spectral analysis including FTIR, ¹H NMR, ¹³C NMR, FAB MS and elemental analysis. From the results of pharmacological screening, it was concluded that XIII possesses high cytotoxic activity against DLA and EAC cell lines with CTC₅₀ values of 15.1 μM and 18.6 μM, and potent antimicrobial activity against pathogenic fungi C. albicans with MIC of 6 μg mL⁻¹. Moreover, XIII possesses moderate anthelmintic activity against earthworms M. konkanensis, P. corethruses, and Eudrilus sp. at 2 mg mL⁻¹ dose level.