Helle Weber Ravn

Caffeic acid esters as in vitro inhibitors of plant pathogenic bacteria and fungi

Abstract Seven caffeic acid derivatives were tested for their activity against two plant-pathogenic fungi and seven plantpathogenic bacteria. A determination of minimum inhibitory concentration (MIC) in solid media was used for the fungi, and for the bacteria agar diffusion, as well as determintion of the MIC in liquid media, were used. A distinct concentration related activity was seen for most of the compounds. The molar activity of the caffeoyl esters against the bacteria was similar to that of tartaric acid, higher than that of phenol, but much lower than that of streptomycin. For most host plants, their ‘own’ compounds were less active against their pathogens than foreign ones. Of the tested compounds, ferulic acid, caffeic acid, esculine, esculetin and orobanchoside were the most active against the two fungi, and similarly, ferulic acid and esculetin were the most active against the bacteria.

Phenolic compounds from Plantago asiatica

Abstract The four known phenolic compounds, 3,4-dihydroxyphenethyl alcohol-6- O -caffeoyl-β- d -glucoside, acteoside (verbascoside), plantaginin and plantamajoside, and a new phenylpropanoid glycoside, hellicoside, were isolated from the aerial parts of Plantago asiatica , which is used in oriental medicine ‘Plantaginis Herba’. The structure of hellicoside was deduced from chemical and spectral evidence to be 3,4,7-trihydroxy-β-phenethyl- O -β- d -glucopyranosyl-(1 → 3)-4- O -caffeoyl-β- d -glucopyranoside. Plantamajoside and hellicoside showed high inhibition of cyclic AMP phosphodiesterase and 5-lipoxygenase. Acteoside showed high inhibition of lens aldose reductase.

Seasonal variation and distribution of two phenolic compounds, rosmarinic acid and caffeic acid, in leaves and roots-rhizomes of eelgrass (Zostera Marina L.)

Abstract The seasonal variation and distribution of rosmarinic acid and caffeic acid in leaves and roots-rhizomes of eelgrass (Zostera marina L.) were examined by using an isocratic high-performance liquid chromatography (HPLC) method developed for separation and quantification of the two phenolic compounds in crude plant extracts. The variation in phenolic content was compared to variations in tissue concentrations of nitrogen and phosphorus, in order to test a proposed relationship between nutrient status of the plant and biosynthesis of the secondary metabolites. The concentration of rosmarinic acid (not previously found in a monocotyledon) plus caffeic acid ranged from 0.4 to 19.2 mg (g dw)-1 with rosmarinic acid being the quantitatively most important component. The figures represent low estimates due to loss of phenolics during sample preparation. High phenolic concentrations occurred in spring and low concentrations during summer and fall, and the highest concentrations were most often found in the...

Crassifolioside, a caffeic acid glycoside ester from Plantago crassifolia

Abstract The structure of crassifolioside, a phenylpropanoid glycoside isolated from Plantago crassifolia was shown to be β-(3′,4′-dihydroxyphenyl)-ethyl-(2,3-α- l -dirhamnosyl)-(4-O-caffeoyl)-β- d -glucopyranoside.

ELICITATION OF ALEXANDRIUM OSTENFELDII (DINOPHYCEAE) AFFECTS THE TOXIN PROFILE

Abstract Batch cultures of the dinoflagellate Alexandrium ostenfeldii (Paulsen) Balech et Tangen were characterized by an exponential growth phase ending after 10 days. Three different paralytic shellfish poison (PSP) toxin patterns (A, B, and C) occurred at days 3, 6 and 10, respectively. The main toxins in pattern A were: 53% GTX6, 26% C4, 17% GTX5; B: 62% GTX4, 17% GTX6, 16% C3; C: 31% GTX4, 28% GTX6, 26% C4, 13% C3. Batch cultures (with identical pattern A) were challenged (elicted) on day 3 with various organic compounds and extracts of Alexandrium tamarense . After elicitation each toxin concentration changed on both day 6 and 10. A causal relation between properties of the elicitor and the resulting toxin pattern could not be established. It is proposed that toxins responding with small relative standard variations from the mean concentration (STX, neoSTX, GTX3, GTX4, GTX6 and C3) are characteristic for the batch culture. Toxins with high variability (GTX1, GTX2, GTX5, C2 and C4) change concentration as a result of stress provoked by the elicitors. The toxicity (estimated from standard values) of some elicited cultures had increased by a factor of 4 on day 10 indicating that stimulation of blooms of A. ostenfeldii may have substantial consequences regarding the problem of paralytic shellfish poisoning.