Biochemical Systematics and Ecology
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Biflavanoid patterns of leaves of 82 species of the order Cycadales comprising 3 families and 10 genera have been determined. The biflavanoids were identified by TLC, UV, NMR and MS studies. Pattern differences between species, when detected, involve the position or degree of methylation of the base compounds. On the other hand, differences in the biflavanoid patterns at the generic and family levels were sufficient to support taxonomic relationships. Thus, the absence of hinokiflavone and its derivatives clearly distinguish the Zamiaceae from the Cycadaceae and Stangeriaceae. The complete absence of biflavanoids in the latter family suggests an advanced evolutionary condition, but morphologically, this family has the most fern-like characters, and therefore has been considered by previous workers to be the most primitive of the cycads.