New skeletons and new concepts in Amaryllidaceae alkaloids

The Amaryllidaceae alkaloids, represent a group of isoquinoline alkaloids, which are produced almost solely by members of the Amaryllidaceae family. The alkaloids of this family have attracted considerable amount of interest due to some important pharmacological activities they were shown to possess. In the last decade, our phytochemical studies on four Galanthus (Amaryllidaceae) species of Turkish origin have yielded quite a number of new alkaloids with diverse structures. Among these alkaloids, gracilines and plicamines constitute two new subgroups for the Amaryllidaceae alkaloids. The gracilines contain an incorporated 10b,4a-ethanoiminodibenzo[b,d]pyrane skeleton. The plicamines are dinitrogenous compounds, where the oxygen atom in position 7 of a tazettine skeleton is replaced by a nitrogen atom substituted by a pendant 4-hydroxyphenethyl moiety. One of the new alkaloids, galanthindole, which possesses a nonfused indole ring, unlike the already known subgroups of Amaryllidaceae alkaloids, may be considered as the prototype of a third new subgroup of the Amaryllidaceae alkaloids. Additionally, two known isoquinoline alkaloids which do not possess one of the established skeletons of the Amaryllidaceae alkaloids, namely (-)-capnoidine and (+)-bulbocapnine, have been isolated from a Turkish Galanthus species. Totally, 21 new, 20 known alkaloids and 2 known lignans have been characterized. In this review, the isolation and structure elucidation of these compounds with interesting chemical structures are described. © 2007 Springer Science+Business Media B.V.this Galanthus project and directed it until they retired. The author would also like to express her gratitude to Prof. Manfred Hesse and Dr. Christa Werner (University of Zurich, Switzerland), to Prof. Robert Verpoorte (Leiden University, The Netherlands), to Prof. Carles Codina, Prof. Jaume Bastida and Prof. Francesc Viladomat (University of Barcelona, Spain) with whom we have collaborated during the course of the project. Special thanks are extended to Prof. Mustafa Ali Önür and Dr. G. İrem Kaya (Ege University, Turkey) for their precious contributions to the Galanthus project. Dr. Anita Latvala, Dr. Seda Noyan and Gülnur Akineri (MSc) are other scientists who collaborated during the course of the project. Their contributions to this work is greatly appreciated. This work was financially supported by the Scientific and Technical Research Council of Turkey (TÜBİTAK) and by the Ege Science and Technology Center (EBILTEM). -