Aromatic Secondary Metabolites Research Articles

Short‐term UV‐B radiation and ozone exposure effects on aromatic secondary metabolite accumulation and shoot growth of flavonoid‐deficient Arabidopsis mutants

The presence of UV‐absorptive substances in the epidermal cells of leaves is thought to protect mesophyll tissues from the harmful effects of UV‐B radiation. We examined the influence of short‐term UV‐B exposures on UV‐absorptive (330 nm) sinapates and flavonols, and on shoot growth of the Arabidopsis wild type ecotype Landsberg erecta and two mutants. 114 deficient in chalcone synthase, and 115, deficient in chalcone/flavonone isomerase. Sequential ozone exposures were used to determine the effects of oxidative stress The levels of sinapates and flavonols on a leaf fresh weight basis increased substantially in the wild type and sinapates increased in the 114 mutant in vegetative vegetative/reproductive transitional and reproductive stage plants in response to short‐term (48h) UV‐B radiation. When UV‐B was discontinued the levels generally decreased lo pre‐exposure levels after 48 h in vegetative/reproductive but not in reproductive plants. Exposure to ozone before or alter UV‐B treatment did not consistently affect the levels of these UV‐absorptive compounds. Dry matter accumulation was less affected by UV‐B at the vegetative and reproductive stages than at the vegetative/reproductive stage. At the vegetative/reproductive stage, shoot growth of all 3 genotypes was retarded by UV‐B. Growth was not retarded by short‐term ozone exposure alone but when exposure to ozone followed UV‐B exposure, growth was reduced in all genotypes. Leaf cupping appeared on 115 plants exposed to UV‐B.

Short-term UV-B radiation and ozone exposure effects on aromatic secondary metabolite accumulation and shoot growth of flavonoid-dericient Arabidopsis mutants

Short-term UV-B radiation and ozone exposure effects on aromatic secondary metabolite accumulation and shoot growth of flavonoid-dericient Arabidopsis mutants

The shikimate pathway as an entry to aromatic secondary metabolism.

The shikimate pathway is often referred to as the common aromatic biosynthetic pathway, even though nature does not synthesize all aromatic compounds by this route. This metabolic sequence converts the primary metabolites PEP and erythrose-4-P to chorismate, the last common precursor for the three aromatic amino acids Phe, Tyr, and Trp and for p-amino and p-hydroxy benzoate (Fig. 1). The shikimate pathway is found in bacteria, fungi, and plants. In monogastric animals, Phe and Trp are essential amino acids that have to come with the diet and Tyr is directly derived from Phe. Since bacteria use in excess of 90% of their metabolic energy for protein biosynthesis, for most prokaryotes, the three aromatic amino acids represent nearly the entire output of aromatic biosynthesis, and regulatory mechanisms for shikimate pathway activity are triggered by the intracellular concentrations of Phe, Tyr, and Trp. This is not so in higher plants, in which the aromatic amino acids are the precursors for a large variety of secondary metabolites with aromatic ring structures that often make up a substantial amount of the total dry weight of a plant. Among the many aromatic secondary metabolites are flavonoids, many phytoalexins, indole acetate, alkaloids such as morphine, UV light protectants, and,

Aromatic Secondary Metabolites from the Sponge Tedania ignis

Aromatic Secondary Metabolites from the Sponge Tedania ignis

A Rapid, High Resolution High Performance Liquid Chromatography Profiling Procedure for Plant and Microbial Aromatic Secondary Metabolites

High performance liquid chromatography protocols have been developed to allow the simultaneous analysis of a very wide range of soluble aromatic secondary metabolites in unfractionated biological extracts. The methods are simple, sensitive, and highly reproducible. They are applicable to a wide variety of natural product investigations in both plants and microorganisms. High resolution of metabolites is achieved in 25 minutes by chromatography on a reverse phase C18 column in a gradient of 0 to 55% acetonitrile in water at pH 3. For example, near-baseline resolution of over 20 phenylpropanoid metabolites and 18 naturally occurring metabolites of indole-3-acetic acid can be obtained. The methods can be applied directly to whole tissue extracts without prepurification or enrichment. Moreover, the simplicity and sensitivity of the protocols allow their application to a large number of very small tissue samples, such as those encountered in research on host-microbe interactions. Such profiles allow one to monitor simultaneously the various alternative metabolic fates of a complex array of molecules. Examination of the profiles over time thus provides one with a powerful tool to correlate many concurrent molecular events that may relate to a given biological phenomenon. The final protocol requires as little as 1 milligram of tissue, which is extracted directly in a microfuge tube in 80% ethanol. With a variable wavelength detector, as little as 100 femtomoles of a given metabolite can be analyzed. Examples of the application of the protocols to a number of plant and microbial secondary product investigations and to screening for flavonoid mutants of Arabidopsis thaliana (L.) Heynh. are given.