Bicycloalternarenes produced by the phytopathogenic fungus Alternaria alternata

Eleven compounds, ACTG toxins A and B and nine new substances named bicyclo alternarenes (BCAs), were isolated and characterized from the culture filtr ate of the phytopathogenic fungus Alternaria alternata. Under acidic condit ions these mixed terpenoids convert to pairs of tricycloaltenarenes that ca n be used for identification of the native compounds. We could not confirm the phytotoxic effects reported with ACTG-toxins in the past. However, BCA 2 at concentrations of 10(-4) M strongly inhibited germination and growth o f Spirodela polyrhiza turions. (C) 2000 Elsevier Science Ltd. All rights re served.