Ontogenic variation of biologically active metabolites of Pteridium aquilinum (L. Kuhn), pterosins A and B, and ptaquiloside in a bracken population of the tropical Andes. - Alonso-Amelot,M..E..; Perez-Mena,M..; Calcagno,M..P..; Jaimes-Espinoza,R..; Castello,U.. (Journal of Chemical Ecology, 1992)