Controversy in Buxales systematic positioning

Buxales (sensu Dahlgren 1980) is an order formed by two families: Buxaceae and Daphniphyllaceae. Among the families of Rosiflorae, (or Rosanae), the positioning of Buxaceae and Daphniphyllaceae show great controversy according to the modern botanists. In order to verify the validity of 1980-Dahlgren's positioning of Buxales (with Buxaceae and Daphniphyllaceae) into the superorder Rosiflorae, a detailed study of micromolecular composition of the Rosiflorae families have been made. The triterpene alkaloids were found to be the prevailing class of secondary metabolites (91%) in Buxales. Triterpenes, steroids and flavonoids can also be found together with very low amount of iridoids. It is important to note that it has not been recorded any reference on the hydrolisable tannin production by these two famylies. However tannins are the characteristic natural products produced by Rosiflorae species, so this kind of compounds have been considered the truly chemotaxonomic markers for the superorder. Excluding Buxales, the superorder Rosiflorae, shows a poor tendency for alkaloid production: only 10 from 40 families present such kind of metabolism even so in a very timid way of expression. In conclusion buxales as stipulated by Dahlgren is characterized by an expressive production of squalene-derived alkalois, feeble presence of flavonoids and terpenoids and lack of references about tannin production. On the other hand, the other Rosiflorae families are characterized by the huge production of tannins. Thus these chemical features indicate scarce affinities among these two plant groups.