Resin glycosides are part of a very extensive family of secondary metabolites known as glycolipids or lipo-oligosaccharides and are constituents of complex resins (glycoresins) (1) unique to the morning glory family, Convolvulaceae (2). These active principles are responsible for the drastic purgative action of all the important Convolvulaceous species used in traditional medicine throughout the world since ancient times. Several commercial purgative crude drugs can be prepared from the roots of different species of Mexican morning glories. Their incorporation as therapeutic agents in Europe is an outstanding example of the assimilation of botanical drugs from the Americas as substitutes for traditional Old World remedies (3). Even though phytochemical investigations on the constituents of these drugs were initiated during the second half of the nineteenth century, the structure of their active ingredients still remains poorly known for some examples of these purgative roots. During the last two decades, the higher resolution c- abilities of modern analytical isolation techniques used in conjunction with pow- ful spectroscopic methods have facilitated the elucidation of the active principles of these relevant herbal products. This chapter describes the ethnobotanical information associated with the p- gative morning glory species and how traditional usages were instrumental in plant selection for chemical studies. The advantages and limitations of available analy- cal techniques for the isolation, puri?cation, and structure characterization of the individual constituents of these complex glycoconjugates are also discussed.

The volumes of this classic series, now referred to simply as "Zechmeister" after its founder, L. Zechmeister, have appeared under the Springer Imprint ever since the series' inauguration in 1938. The volumes contain contributions on various topics related to the origin, distribution, chemistry, synthesis, biochemistry, function or use of various classes of naturally occurring substances ranging from small molecules to biopolymers.

The volumes of this classic series, now referred to simply as "Zechmeister" after its founder, L. Zechmeister, have appeared under the Springer Imprint ever since the series' inauguration in 1938. The volumes contain contributions on various topics related to the origin, distribution, chemistry, synthesis, biochemistry, function or use of various classes of naturally occurring substances ranging from small molecules to biopolymers. Each contribution is written by a recognized authority in his field and provides a comprehensive and up-to-date review of the topic in question. Addressed to biologists, technologists, and chemists alike, the series can be used by the expert as a source of information and literature citations and by the non-expert as a means of orientation in a rapidly developing discipline.

Sulfonium compounds have been known to the organic chemist for almost 90 years. During most of this period they remained curiosities, well suited for didactic purposes to illustrate certain similarities to ether adducts and to organic ammonium compounds. Their exploration remained largely in the academic realm, because no unusual practical applications were found in spite of a steady increase in the attention paid to them. An event that occasionally puts a class of compounds into the center of interest is the recognition of its occurrence in nature and of special biological significance. The first natural sulfonium compound was discovered less than 20 years ago, somewhat by chance rather than as the climax of some coveted biochemical problem. Gradually, however, the unique role of sulfonium compounds, especially of S-adenosyl methionine, in enzymatic group transfer reactions such as trans methylation was recognized, and the recent upsurge of interest has been exceptional. The present review is directed toward an interpretation of the properties and functions of biological sulfonium compounds with frequent reference to their structural chemistry. The data presented here may suggest novel or improved analytical techniques and new interpretations of the mechanism of group transfer. Furthermore, a stimulus may be derived for the design of sulfonium compound analogues. The availability of competitive analogues of biochemical key compounds has aided in the understanding of the function of virtually all metabolic intermediates, prosthetic groups of enzymes, vitamins, amino acids, and other compounds. The pattern will be similar in sulfonium biochemistry.