scispace - formally typeset
Search or ask a question
Author

Zdeněk Samek

Bio: Zdeněk Samek is an academic researcher from Czechoslovak Academy of Sciences. The author has contributed to research in topics: Terpene & Allylic rearrangement. The author has an hindex of 18, co-authored 99 publications receiving 1042 citations.


Papers
More filters

Cited by
More filters
Journal ArticleDOI
TL;DR: This review summarizes the present knowledge regarding the biological activities of sesquiterpene lactones and their structure-activity relationships and suggests their evolutionary significance in plants as deterrents against herbivores and anti-fungal, anti-bacterial allelopathic agents.

552 citations

Journal ArticleDOI
TL;DR: The 13 C NMR chemical shifts of 130 naturally occurring steroidal sapogenins and saponin derivatives published up to 1983 are listed and a number of methods for signal assignment are explained as discussed by the authors.

549 citations

Journal ArticleDOI
TL;DR: A review of the present state of knowledge on the biological activities and mechanism of action of some sesquiterpene lactones highlighted in Compositae and other angiosperm families and even in some liverworts.

536 citations

Journal ArticleDOI
TL;DR: The tribal, subtribal and generic distribution of sesquiterpene lactones is examined, the compounds’ utility as taxonomic characters discussed and the biogenetically based methodology shows the efficacy of this analytical methodology.
Abstract: The Asteraceae is characterized by structurally diverse sesquiterpene lactones and furanosesquiterpenes. In this review the tribal, subtribal and generic distribution of sesquiterpene lactones is examined and the compounds’ utility as taxonomic characters discussed. Sesquiterpene lactones fulfill the major requirements for good analytic and synthetic characters. Studies of infraspecific sesquiterpene lactone variation indicate that different elements within complex taxa are often defined by distinct chemistries, termed chemotypes. Chemotypes have been identified within many of the thoroughly investigated taxa:Ambrosia camphorata, A. chamissonis, A. confertiflora, theA. cumanensis-A. psilostachya-A. artemisiifolia complex,A. dumosa, Artemisia tridentata, Gaillardia pulchella andMelampodium leucanthum. Such an analytic usage is mostly restricted to the infraspecific level. Synthetic usage at the interspecific level and above profits from the application of a biogenetically based methodology for sorting out the complex molecules’ carbon-skeletal and substitutional features into unit characters. Cladistics or Hennigian phylogenetic systematics provides a useful framework for such an analysis. Preliminary surveys indicate that sesquiterpene lactones are especially good characters for differentiating subtribes within several major tribes: the Vernonieae, Heliantheae and Mutisieae. As yet, too few data are available for other tribes to discern such patterns. Species surveys inVernonia, Ambrosia, Iva, Parthenium,Tetragonotheca andArtemisia demonstrate that sesquiterpene lactones are useful in discerning infrageneric groups. The biogenetic cladistic analysis of the interspecific sesquiterpene lactone variation inIva shows the efficacy of this analytical methodology. At present, such biogenetically based approaches are impeded by limited biosynthetic evidence and the erratic distribution of sesquiterpene lactones within the family. Instances of apparent displacement of sesquiterpene lactones by other terpenoids (i.e. sesquiterpene furans, alcohols and acids, diterpenes, diterpene acids, etc.) at various taxonomic levels suggest that ultimately sesquiterpene lactones must be interpreted as taxonomic characters in the context of the family’s total terpene chemistry. All taxa from which sesquiterpene lactones have been reported are listed together with the compound names, major structural features and the literature cited. A less-complete listing is provided for taxa producing furanosesquiterpenes. Structures for all reported compounds are included. Two appendices listing alphabetically taxa and compounds and relevant text page numbers permit cross-indexing of plants and compounds.

350 citations