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Pandanus Alkaloids in Stemonaceae: Finding of a Plausible Biogenetic Origin of Stemona Alkaloids

Harald Greger*^†, Johann Schinnerl^†, Srunya Vajrodaya^‡, Lothar Brecker^§ and Otmar Hofer^§

Comparative and Ecological Phytochemistry, Faculty Center of Botany, University of Vienna, A-1030 Wien, Austria, Department of Botany, Faculty of Science, Kasetsart University, Bangkok 10900, Thailand, and Institute of Organic Chemistry, University of Vienna, A-1090 Wien, Austria

J. Nat. Prod., 2009, 72 (9), pp 1708–1711

DOI: 10.1021/np900294c

Publication Date (Web): September 2, 2009

* To whom correspondence should be addressed. Tel: +43-1-4277-54072. Fax: +43-1-4277-9541. E-mail: harald.greger@univie.ac.at.,

Deceased February 10, 2009. This paper is dedicated to his memory. His enthusiasm, insights, and unique perspective were an inspiration to many, and his presence is greatly missed.

, †

Comparative Phytochemistry, University of Vienna.

, ‡

Kasetsart University.

, §

Organic Chemistry, University of Vienna.

Abstract

The isolation of (Z,Z)-pandanamine (1) and its corresponding isomers (Z,E)-pandanamine (2) and (E,E)-pandanamine (3) from Stichoneuron calcicola of the family Stemonaceae is of outstanding chemosystematic importance. This alkaloid was previously only known from the family Pandanaceae, where it was accompanied by a series of pyrrolidines, collectively called Pandanus alkaloids. The pyrrolidines pandamarilactonines A (4), B (5), C (6), and D (7) were also detected in the present study, most likely representing artificial cyclization products of pandanamine (1−3) formed by acidic conditions during chromatographic separation on silica gel. Similar structures were found in various Stemona alkaloids, suggesting a close relationship between the two plant families. Structurally, pandanamine (1−3) can be regarded as a direct precursor of croomine (8), originally isolated from Croomia, a genus closely related to Stichoneuron, but later also found in various Stemona species. The co-occurrence of pandanamine (1−3), croomine (8), and stichoneurin (9) in the family Stemonaceae represents a sound argument for a new interpretation of the biogenetic origin of Stemona alkaloids and at the same time substantiates the removal of the family from the order Dioscoreales and its inclusion into Pandanales, as already suggested by DNA sequencing.