Albert Kollmann

Biotransformation of bezo[a]pyrene in bench scale reactor using laccase of Pycnoporus cinnabarinus

The biotransformation of benzo[a]pyrene by purified extracellular laccase of Pycnoporus cinnabarinus was investigated in bench scale reactors. The reaction required the presence of exogenous mediator ABTS. Most of 95% of the substrate was converted within 24 hours. The enzyme preparation oxidised the substrate mainly to benzo[a]pyrene 1,6- 3,6- and 6,12-quinones in a 2/1/1 ratio after 24 h incubation.

Abiotic elicitation of indole phytoalexins and resistance to Leptosphaeria maculans within Brassiceae.

Forty three accessions of Brassica species and one each of Sinapis and Raphanus were assessed for (i) resistance to Leptosphaeria maculans according to a coty-ledon-inoculation test and (ii) indole phytoalexin accumulation following abiotic elicitation with CuCl2. Five indole phytoalexins were determined in the lines following elicitation. Brassilexin, cyclobrassinin and cyclobrassinin sulphoxide were found within at least some lines of all species, whereas brassinin was only detected in B. oleracea and B. napus and methoxybrassinin within these two species and B. rapa and B. carinata. None of the five indole phytoalexins could be found in Raphanus sativus or Sinapis alba. The accumulation of large amounts of specific phytoalexins could be correlated with the presence of the different Brassica genomes. Lines possessing the B genome (B. nigra, B. juncea and B. carinata) which accumulated high amounts of brassilexin, displayed a hypersensitive resistance to infection whereas the majority of lines of B. oleracea, B. napus and B. rapa which did not accumulate large amounts of brassilexin, were susceptible. However, a B. nigra and a B. rapa line which only accumulated low amounts of brassilexin were highly resistant to the pathogen. Neither the accumulation of the other phytoalexins nor the total accumulation of indole phytoalexins could be related to resistance to L. maculans.

Brassilexin, a novel sulphur-containing phytoalexin from Brassica juncea L., (Cruciferae)

Structure 1 is established for brassilexin, a new sulphur-containing phytoalexin isolated from the leaves of Brassica juncea (Cruciferae), on the basis of spectrographical data (UV, IR, high resolution MS, 13C and 1H NMR).

Accumulation of a phytoalexin in Brassica spp in relation to a hypersensitive reaction to Leptosphaeria maculans

A phytoalexin was isolated from the leaves of Brassica juncea cv. Aurea inoculated with Leptosphaeria maculans. Its purification and quantification were carried out by reversed-phase and silica HPLC. The molecular formula of this phytoalexin is C9H6N2S. It prevented spore germination and hyphal growth of L. maculans at 12 μg ml−1 in water. Accumulation of this phytoalexin was also obtained with sprays of AgNO3 or CuCl2 solutions. It was not detected in healthy plant tissues, and the effect of cycloheximide suggests that its accumulation is associated with induced plant metabolism. Kinetics of phytoalexin accumulation were compared in B. juncea cv. Aurea (hypersensitive to L. maculans) and B. napus cv. Brutor (susceptible to L. maculans) with CuCl2 as a non-specific elicitor. The phytoalexin was detected in B. juncea 6 h after challenge and in B. napus 18 h after challenge. Moreover, B. juncea always accumulated more phytoalexin than did B. napus (4 to 10 times more 48 h after elicitation).

Biological effects of sirodesmin PL, a phytotoxin produced by Leptosphaeria maculans

Abstract The phytotoxic effect of sirodesmin PL on cotyledons or leaves of Brassica napus consisted of chlorotic and collapsed lesions. Little differences in sensitivity to the toxin was observed between Brassica species or non-host plants. The toxin alone cannot produce the specificity of the disease. Using B. napus embryogenic tissue cultures, the toxic effects of sirodesmin PL were investigated with respect to several biological parameters: membrane alterations, cell respiration, DNA, RNA and protein synthesis. Only the incorporation of [14C]uridine in RNAs was strongly and rapidly inhibited by 5.2 μM toxin in liquid medium. The toxic activity of sirodesmin PL was attributed to the reactivity of its disulphide bridge. The metals of the II B series (Zn, Hg and Cd) reversed this toxicity. These results suggest an interaction of sirodesmin PL with essential Zn from Zn-containing metalloenzymes such as RNA polymerases.

Oligomeric compounds formed from 2,5-xylidine (2,5-dimethylaniline) are potent enhancers of laccase production in Trametes versicolor ATCC 32745

Numerous chemicals, including the xenobiotic 2,5-xylidine, are known to induce laccase production in fungi. The present study was conducted to determine whether the metabolites formed from 2,5-xylidine by fungi could enhance laccase activity. We used purified laccases to transform the chemical and then we separated the metabolites, identified their chemical structure and assayed their effect on enzyme activity in liquid cultures of Trametes. versicolor. We identified 13 oligomers formed from 2,5-xylidine. (4E)-4-(2,5-dimethylphenylimino)-2,5-dimethylcyclohexa-2,5-dienone at 1.25×10−5 M was an efficient inducer, resulting in a nine-fold increase of laccase activity after 3 days of culture. Easily synthesized in one step (67% yield), this compound could be used in fungal bioreactors to obtain a great amount of laccases for biochemical or biotechnological purposes, with a low amount of inducer.

Cyphostemmins A-B, two new antifungal oligostilbenes from Cyphostemma crotalarioides (Vitaceae)

Abstract Two new antifungal resveratrol dimers, cyphostemmins A-B (1–2), have isolated from the roots of Cyphostemma crotalarioides planch (Vitaceae) together with resveratrol 3 and previously known reseveratrol dimers (4–7). Structures of these new compounds have been established on the basis of their MS and 1H and 13C NMR spectroscopic data.

Cyclobrassinin sulphoxide, a sulphur-containing phytoalexin from Brassica juncea

Abstract Cyclobrassinin sulphoxide, a new sulphur-containing phytoalexin, was isolated from elicited leaves of Brassica juncea , and identified on the basis of physico-chemical data (IR, high resolution MS and 1 H NMR). The results so far obtained within this series of natural compounds are discussed in relationship with their possible biosynthesis.

Structure and biosynthesis of phomenoic acid, an antifungal compound isolated from Phoma lingam Tode

On the basis of 1H and 13C n.m.r. studies, ozonolysis, and biosyntheses from [13C]acetates and [methyl-13C]methionine, structure (1) is proposed for phomenoic acid, an antifungal compound isolated from the mycelium of the fungus Phoma lingam Tode.

Septorine and N-methoxy septorine, substituted pyrazines from the fungus Septoria nodorum berk

Abstract On the basis of 1 H nmr correlations with synthetic analogs, structures 1 and 2 are proposed for septorine and N-methoxy septorine, two p-hydroxybenzoyl 1-isobutyl substituted pyrazines obtained from the fungus Septoria nodorum Berk, a parasite of wheat.