Occurrence of the Methylene-dioxy Bridge in the Phenolic Components of Plants

Abstract

THE methylene-dioxy bridge is a common feature of the structure of several groups of plant alkaloids and occurs also, though less commonly, among natural phenolic substances. Geissman and Hinreiner¹, in a recent review of natural phenols, list twenty-four different substances containing the methylene-dioxy bridge; fourteen of them are C₆—C₃ type and all are characterized by a generally high degree of methylation of hydroxyl groups in the molecule; indeed, none of them bears a free hydroxyl in the ring that bears the bridge. The alkaloids are similarly characterized by a high degree of methylation of phenolic hydroxyl groups². Botanically, the methylene-dioxy phenolic substances are distributed widely but not haphazardly, for they occur in six families of Polypetalae (Anonaceae, Magnoliaceae, Rutaceae, Leguminosae, Rosaceae and Umbelliferae), three of Apetalae (Myristicaceae, Lauraceae and Piperaceae) and one of the monocotyledons (Orchidaceae). Of these families, Lauraceae and Piperaceae are much the most abundant sources, and it seems from this (as from the occurrences in Magnoliaceae, Rutaceae, Umbelliferae and Myristicaceae) that there may be some relationship between aromatic properties and the occurrence of the bridge. It may be significant, too, that of the eleven families of plants which have yielded methylene-dioxy alkaloids, no fewer than four occur in the above list of phenolic-bearing families (Anonaceae, Rutaceae, Leguminosae and Piperaceae²).