Stemona

Introduction

Stemonaceae represent a rather isolated family within the Monocotyledons consisting of 3 genera and about 32 species. Many species prefer a seasonal climate and occur as perennial climbers or subshrubs with tufted tuberous roots in rather dry vegetation ranging from continental Asia and Japan through Southeast Asia to tropical Australia (1, 2). Stemona is the largest genus with about 25 species occurring as subshrubs or twining herbs mostly with perennial tuberous roots.

In spite of the good delimitation of Stemona from the nearest related genera Croomia and Stichoneuron, there are still many taxonomic problems at the species level that remain to be solved. Since the roots of several species are widely used as insecticides and for medicinal purposes, they are offered for sale on local markets and herb-shops under vernacular names like e.g. "Bai Bu" in China, "Bach Bo" in Vietnam or "Non Tai Yak" and "Pong Mot Ngam" in Thailand. However, because of the similar shape of the fleshy tuberous roots, the same vernacular names are often used for different species and even for representatives from other plant families. This uncertainty in purchasing appropriate plant material has already led to confusions in chemical and pharmaceutical literature (3).


Phytochemicals

Even though the genus Stemona has long been recognized for its broad range of bioactivities, phytochemical investigations have been restricted to few species (4). However, Stemona is characterized by family-specific alkaloids, showing an unusual molecular architecture with a pyrrolo[1,2-a]azepine nucleus (5) or a pyrido[1,2-a]azepine nucleus (6). Moreover, the accumulation of stilbenoids is a typical chemical trend of many Stemona species: S. collinsae is characterized by the formation of many rare phenylbenzofurans, designated as stemofurans A-K, furthermore by the accumulation of two stilbenes and dihydrostilbenes [more....] (7).


Bioactivities - Why are we interested in Stemona?

S. tuberosa Lour., S. japonica (Bl.) Miq., and S. sessilifolia (Miq.) Miq. have long been used in China and Japan for various medicinal and biological properties. Especially extracts from the fleshy tuberous roots are still used to treat respiratory disorders, including pulmonary tuberculosis and bronchitis, but are also recommended against different insect pests (8, 9). Despite the well-known insect toxicity of crude extracts of some Stemona species, only a few investigations were carried out to determine the causative compounds. Moreover, nearly nothing is known about antifungal properties of Stemona species (10). To contribute to a better understanding of the bioactive capacities of Stemona chemicals, we compare the capacities of different compounds isolated from various species and geographical provenances using several test organisms (5, 6, 7, 11).


Literature

(1) Duyfjes, B. E. E. Stemonaceae. Flora Malesiana ser. I, 1993, 11, 399-409.
(2) Tsi, Z. H. ; Duyfjes, B. E. E. Stemonaceae. In Flora of China Vol. 24; Wu, Z. Y., Raven, P. H. Eds.; Science Press: Beijing, 2000; pp 70-72.
(3) Taguchi, H.; Kanchanapee, P.; Amatayakul, T. The constituents of Clitoria macrophylla Wall. Cat., a Thai medicinal plant. The structure of a new rotenoid, clitoriacetal. Chem. Pharm. Bull. 1977, 25, 1026-1030.
(4) Pilli, R. A.; Ferreira de Oliveira, M. C. Recent Progress in the chemistry of the Stemona alkaloids. Nat. Prod. Rep. 2000, 17, 117-127.
(5) Brem, B., Seger, C., Pacher, T., Hofer, O., Vajrodaya, S., Greger, H. (2002): Feeding deterrence and contact toxicity of Stemona alkaloids - a source of potent natural insecticides. Journal of Agricultural and Food Chemistry 50 (22): 6383-6388.
(6) Kaltenegger, E., Brem, B., Mereiter, K., Kalchhauser, H., Kählig, H., Hofer, O., Vajrodaya, S., Greger, H.. Insecticidal pyrido[1,2-a]azepine alkaloids and related derivatives from Stemona species. Phytochemistry 2003, 63, 803 –816
(7) Pacher, T., Seger, C., Engelmeier, D., Vajrodaya, S., Hofer, O., Greger, H. (2002): Antifungal stilbenoids from Stemona collinsae. Journal of Natural Products 65(6): 820-827.
(8) Terada, M.; Sano, M.; Ishii, A. I.; Kino, H.; Fukushima, S.; Noro, T. Nippon Yakurigku Zasshi 1982, 79, 93-103.
(9) Sakata, K.; Aoki, K.; Chang, C. F.; Sakurai, A.; Mura-koshi, J. Agric. Biol. Chem. 1978, 42, 457-463.
(10) Zhao, W. M.; Qin, G. W.; Ye, Y.; Xu, R. S.; Le, X. F. Phytochemistry 1995, 38, 711-713.
(11) Kostecki, K., Engelmeier, D.,Pacher, T.,Hofer, O., Vajrodaya, S., Greger, H. Dihydrophenanthrenes and other antifungal stilbenoids from Stemona cf.pierrei. Phytochemistry 2004, 65, in press.