Screening enzyme-inhibitory activity in several ascidian species from Orkney Islands using protein tyrosine kinase (PTK) bioassay-guided fractionation

Bioassay-guided fractionation led to the identification of several fractions enhancing or moderately reducing the enzyme activity. Strong inhibitory effects were detected in the ethyl acetate and the n-butanol fractions of the baked bean ascidian, Dendrodoa grossularia. NMR analysis indicated the presence of the guanidinostyrene derivative tubastrine. This is the first documentation of this metabolite in ascidians. Structure analysis of tubastrine in comparison to other known PTK inhibitors may enhance our understanding of the structure and effect of the compounds and may help in the development of efficient therapeutic agents.