Purification, Characterization and Antibacterial Properties of Peptide from Marine Ascidian Didemnum sp.

Marine ecosystems are unique and a largely diverse chest of natural resources which are still to be explored for new marine species. They are still unexplored for their pharmacological properties. Ascidians or sea squirts are invertebrate and fruitful candidate of a wide variety of biologically active secondary metabolites from cyclic peptides to aromatic alkaloids. In this study, we have purified peptides through isolation with buffer assay method and purification method by RP-HPLC. The molecular weight of purified ascidian peptide P1 was determined through the SDS-PAGE analysis and confirmed the molecular weight below 40 kDa. The purified peptides P1 were characterized by Fourier Transform Infrared spectroscopy (FTIR) and Circular Dichroism (CD) analysis. The purified peptides P1 confirmed by peaks at 555.82 (Amide VI), 642.12 (Amide V), 674.17 (Amide IV), 1527.19 (Amide II), 3281.97 (Amide A) and CD spectrum showed the positive peaks at 196 nm and two negative peaks at 193 and 199 nm, which is characteristic of the presence of a helical confirmation presence of peptides. The purified peptides P1 demonstrated the antibacterial activity against the highest inhibition reported the gram-positive bacteria, E. faecalis (11.60 +/- 0.16 mm) and lowest inhibition shown the gram negative bacteria, P. aeruginosa (10.33 +/- 0.12 mm) in 100 mu g/ml concentration. The present study was concluded that purified peptides of the ascidian, Didemnum sp. has a potential antibacterial effect against human pathogens.