Complex C-glycosyl flavonoid phytoalexins from Cucumis sativus

J Nat Prod. 2003 Sep;66(9):1280-3. doi: 10.1021/np030150y.

Abstract

Extraction of cucumber leaf tissue expressing induced resistance against powdery mildew fungi revealed the presence of two new major C-glycosyl flavonoid products: vitexin-6-(4-hydroxy-1-ethylbenzene) (cucumerin A, 1) and isovitexin-8-(4-hydroxy-1-ethylbenzene) (cucumerin B, 2). In addition, the known C-glycosyl flavonoids apigenin-8-C-beta-D-glucopyranoside (vitexin, 3), apigenin-6-C-beta-D-glucopyranoside (isovitexin, 4), luteolin-8-C-beta-D-glucopyranoside (orientin, 5), and luteolin-6-C-beta-D-glucopyranoside (isoorientin, 6), as well as 4-hydroxycinnamic acid (p-coumaric acid, 7) and its methyl ester (p-came, 8), were found in higher quantities within resistant plants. The structures of 1-8 were elucidated using spectroscopic methods and unambiguously confirmed for 3-8 using co-chromatography experiments with authentic standards. On the basis of the results of this study and the reported biological activities of C-glycosyl flavonoids, these compounds would play a vital role in the defense strategy of this species by acting as phytoalexins.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cucumis sativus / chemistry*
  • Flavonoids / chemistry
  • Flavonoids / isolation & purification*
  • Flavonoids / pharmacology
  • Fungi / drug effects
  • Glycosides / chemistry
  • Glycosides / isolation & purification*
  • Glycosides / pharmacology
  • Manitoba
  • Molecular Structure
  • Nuclear Magnetic Resonance, Biomolecular
  • Plant Extracts / chemistry
  • Plant Extracts / isolation & purification*
  • Plant Extracts / pharmacology
  • Plant Leaves / chemistry
  • Plants, Medicinal / chemistry*
  • Sesquiterpenes
  • Stereoisomerism
  • Terpenes

Substances

  • Flavonoids
  • Glycosides
  • Plant Extracts
  • Sesquiterpenes
  • Terpenes
  • phytoalexins