Alternative pathways of xanthone biosynthesis in cell cultures of Hypericum androsaemum L

Abstract

The biosynthesis of xanthones was studied in cell cultures of Hypericum androsaemum L. We have detected a new benzophenone synthase, for which the preferred substrate is benzoyl-CoA, itself supplied by 3-hydroxybenzoate:coenzyme A ligase. The stepwise condensation of benzoyl-CoA with three molecules of malonyl-CoA, catalyzed by benzophenone synthase, yields 2,4,6-trihydroxybenzophenone. This intermediate is subsequently converted by benzophenone 3P-hydroxylase, a cytochrome P450 monooxygenase. These biosynthetic steps, leading to the formation of 2,3P,4,6-tetrahydroxybenzophenone, represent an alternative pathway to that recently proposed for cell cultures of Centaurium erythraea [Peters et al., Planta (1997) in press].z 1997 Federation of European Biochemical Societies.

Xanthone biosynthesis and accumulation in calli and suspended cells of Hypericum androsaemum

“…Cinnamic acid, benzoic acid, m-hydroxybenzoic acid and malonic acid were found to be efficient precursors of this compound [22]. Beerhues and coworkers [21,23] have studied also the biosynthesis of xanthones in H. androsaemum cell suspensions. Their findings indicate that 3-hydroxybenzoic and benzoic acids are efficient precursors of an intermediate tetrahydroxybenzophenone that is subsequently converted to the xanthone backbone.…”

Four New Phenones from the Cortexes of Polygala tenuifolia

“…1 H-, 13 C-NMR, HMQC and HMBC spectra were measured on a JEOL JNM-A300 or Bruker AM-500 spectrometer. D101 resin was purchased from Tianjin Chemical Extraction and Isolation The air-dried cortexes of P. tenuifolia (11 kg) were ground and refluxed with 95% EtOH (77 l) for three times.…”

“…[11][12][13] Except the two above reported benzophenones 1 and 2, several xanthone and its O-glycosides or C-glycosides with the similar structural characteristics to 1 and 2 have been also isolated from P. tenuifolia, 1,5,8) which supply another evidence to the hypothesis that xanthone is biosynthesized from benzophenone in the plants. 14) In the HMBC spectrum, the proton signal at ϩ in the EI-MS spectrum.…”

“…On acid hydrolysis, 1 afforded glucose and rhamnose, and the GC analyses of their L-cysteine derivatives showed their retention times were identical with those of D-glucose and L-rhamnose, respectively. The 13 C-NMR spectrum (Table 1) displayed 24 carbon signals in total, among which twelve were assigned to the sugar moiety, one for a methoxyl and the remaining eleven were reminiscent of a benzopheonone or a xanthone skeleton. The chemical shift of carbonyl signal (d 194.5) indicated 1 was a benzophenone compound.…”

“…The difference between 3 and 4 was the length of the alkane chain: 3 was a triacontenoylphloroglucinol, while 4 was a dotriacontenoylphloroglucinol. The Z-configuration of the double bond was deduced from the J value (4.8 Hz) and 13 C-NMR data (d 130.44, 27.67), 14) and its position was deduced to be at the terminal C-6 position through the following segment ion peaks: 71 [CH 3 Compounds 5-7 were determined to be 6-hydroxy-1,2,3,7-tetramethoxyxanthone (5), 1) 1,7-dimethoxyxanthone (6) and 7-hydroxy-1,2,3-trimethoxyxanthone (7) 15) by comparing their spectral data with the literature values.…”