Elsevier

Phytochemistry

Volume 53, Issue 3, 2 February 2000, Pages 331-337
Phytochemistry

Variability of phenylpropanoid precursors in the biosynthesis of phenylphenalenones in Anigozanthos preissii

Dedicated to Professor H.-R. Schütte on the occasion of his 70 birthday.
https://doi.org/10.1016/S0031-9422(99)00544-0Get rights and content

Abstract

Feeding experiments using 13C labelled precursors and NMR spectroscopic studies revealed general biosynthetic incorporation of phenylalanine and variable incorporation of cinnamic acid, p-coumaric acid, caffeic acid and ferulic acid into phenylphenalenones in root cultures of Anigozanthos preissii. Evidence was obtained for parallel pathways of phenylphenalenone biosynthesis, with respect to the left phenylpropanoid unit, and a sequence involving utilisation of p-coumaric acid with late generation of an intermediate catechol moiety in the right phenylpropanoid unit.

Introduction

Phenylphenalenones are characteristic constituents of the Haemodoraceae plant family (Cooke & Edwards, 1980). They accumulate in roots of Anigozanthos preissii and have also been found in root cultures of that species (Hölscher & Schneider, 1997). Recent biosynthetic studies demonstrated the symmetrical incorporation of two molecules of cinnamic acid and p-coumaric acid into anigorufone (1) (Hölscher & Schneider, 1995a) and hydroxyanigorufone (2) (Hölscher & Schneider, 1995b), respectively. The involvement of diarylheptanoids in the phenylphenalenone biosynthesis was shown by feeding a labelled precursor of that type, 1-phenyl-7-(3,4-dihydroxyphenyl)-hepta-1,3-dien-5-one, carrying a catechol moiety (Hölscher & Schneider, 1995a). It has been suggested that the catechol portion undergoes oxidation to an o-quinone, generating an excellent dienophile capable of involvement in a proposed Diels–Alder cycloaddition, resulting in the phenylphenalenone ring system (Bazan et al., 1978, Schmitt & Schneider, 1999). However, details of the biosynthetic pathway are still hypothetical. Until now, for example, it was uncertain whether the second hydroxyl group of the catechol moiety in the diarylheptanoid intermediate, originated from caffeic acid or, alternatively, whether it was introduced by hydroxylation at a later stage of the biosynthesis. In this paper, we describe in vivo feeding experiments using labelled phenylpropanoids, having different substitution patterns in the phenyl ring, and how these precursors are biosynthetically incorporated into phenylphenalenones.

Section snippets

Results

Previous feeding experiments using 14C labelled phenylalanine have established the ready incorporation into phenylphenalenones in Haemodorum corymbosum (Thomas, 1971) and Lachnanthes tinctoria (Edwards, Schmitt & Weiss, 1972). Specific incorporation of label from [1-13C]phenylalanine into C-7 but not C-6 of lachnanthoside aglycone was observed in L. tinctoria (Harmon, Edwards & Highet, 1977). In our biosynthetic studies, two molecules of [1-13C]phenylalanine were shown to be specifically

Discussion

The experiments described here clearly demonstrate that in Anigozanthos preissii two phenylpropanoids are being utilized to form the phenylphenalenone skeleton. Equal distribution of labelling from [1-13C]phenylalanine into C-6 and C-7 of the phenylphenalenones provided evidence for symmetric incorporation of early precursors into both halves of the molecule. Symmetric incorporation of cinnamic acid and p-coumaric acid into anigorufone (1) and hydroxyanigorufone (2), representing the major

Plant material, synthesis and administration of labelled compounds

Root cultures of Anigozanthos preissii (L.) were initiated as previously described (Hölscher & Schneider, 1997) and grown in liquid MS medium (Murashige & Skoog, 1962) (100 ml in 300 ml conical flasks) at 22°C on a gyratory shaker (100 rpm) under permanent light (4.4 μmol m−2 s−1). Three days before administration of the precursors the cultured roots (about 15 g) were transferred to fresh medium. [1-13C]Phenylalanine (99% 13C) was from Deutero GmbH, Kastellaun, Germany. [2-13C]Phenylpropanoic

Acknowledgements

The authors wish to thank Dr. N. Oldham, Jena, for recording mass spectra and for improving the English of the manuscript. The Deutsche Forschungsgemeinschaft (Bonn) is gratefully acknowledged for providing the NMR spectrometer, and for other financial support. This investigation was supported by the Fonds der Chemischen Industrie (Frankfurt/Main).

Cited by (0)

1

Present address: Institute of Biological Chemistry, Washington State University, Pullman, WA 99164-6340.

View full text