Rapid wound-activated transformation of the green algal defensive metabolite caulerpenyne

The invasive green macro-alga Caulerpa taxifolia reacts upon wounding with rapid transformation of its main defensive metabolite caulerpenyne. The three acetate groups of this sesquiterpene are enzymatically cleaved within minutes after mechanical damage. Transformation of the 1,4-bis-enol acetate moiety of caulerpenyne results in labile 1,4-dialdehydes after tautomerisation. Normal phase HPLC/APCI-MS measurements of freshly prepared algal extracts allow characterization of these reactive products, which are of the oxytoxin family. Final structural elucidation was achieved after trapping of the aldehydes with 2,4-dinitrophenylhydrazine. The role of wound-induced transformation in activated chemical defence of C. taxifolia is suggested.