Isolation and characterization of an antibacterial peptide fraction from the pepsin hydrolysate of half-fin anchovy (Setipinna taty).

Enzymatic proteolysis of food proteins is considered a promising method to generate antibacterial peptides. The objective of the present study was to isolate and characterize peptide fraction from the pepsin hydrolysate of half-fin anchovy (Setipinna taty) with antibacterial activity against Escherichia coli. The most active peptide fraction HAHp2-3-I was isolated by a series of chromatographic methods, including Sephadex G-25 chromatography, reverse high-performance liquid chromatography (RP-HPLC) and Source 5RPC ST. Peptides identification of HAHp2-3-I was carried out using UPLC-LTQ-Orbitrap mass spectrometer. HAHp2-3-I contained five cationic peptides (MLTTPPHAKYVLQW, SHAATKAPPKNGNY, PTAGVANALQHA, QLGTHSAQPVPF and VNVDERWRKL) and three anionic peptides (LATVSVGAVELCY, NPEFLASGDHLDNLQ and PEVVYECLHW). Prediction of peptide secondary structure indicated that these anionic peptides should have extended strand and random coil structures, whereas cationic peptides PTAGVANALQHA and VNVDERWRKL could form alpha helixes. In addition, results of scanning electron microscopy (SEM) revealed that treatment by HAHp2-3-I could cause the morphological changes of E. coli and destruction of the cell integrity via irreversible membrane damage. The results could provide information for investigating the antibacterial model of antibacterial peptides derived from fish protein hydrolysates.

Lobophorin C and D, new kijanimicin derivatives from a marine sponge-associated actinomycetal strain AZS17.

Marine sponge Hymeniacidon sp. was collected from coastal waters of the East China Sea to isolate symbiotic microorganisms. The resulting sponge-associated actinomycete, Streptomyces carnosus strain AZS17, was cultivated in a 20 L volume of medium for production of bioactive secondary metabolites. Bioassay-guided isolation and purification by varied chromatographic methods yielded two new compounds of kijanimicin derivatives, AS7-2 and AS9-12. Their structures were elucidated by spectroscopy and comparison with literatures. Results showed these two compounds were structurally similar to the previously reported compounds lobophorin A and B, yet differed in specific bond forms, stereochemistry and optical activities. The two novel compounds were named lobophorin C and D. In vitro cytotoxicity investigation by MTT assay indicated their selective activities. Lobophorin C displayed potent cytotoxic activity against the human liver cancer cell line 7402, while lobophorin D showed significant inhibitory effect on human breast cancer cells MDA-MB 435.