Electronic absorption spectra of symmetrical cyanine dyes show vibronic sub-bands, attributed to the symmetric C-C valence vibration of the polymethine chain in the electronic excited state. Displacements in the equilibrium configuration between electronic ground and excited states of cyanine dyes lead to longer C-C bonds in the excited state. Additionally, in the electronic ground state, a small degree of bond localisation always remains in the chain depending on the different heterocyclic terminal groups. Our investigations suggest that we can use (3)J(H,H) coupling constants in the polymethine chain to characterise the bond localisation within the chain. Based on these values and the Franck-Condon principle, the intensity distribution among the vibrational sub-bands can be explained.
The results indicate that CYP1A2-catalyzed N-dealkylation and gamma hydroxylation are the major routes for BM phase I metabolism producing two metabolites less or similarly toxic than the parent compound. In contrast to the metabolic pathways of the structurally related chlorambucil, no beta-oxidation of the butanoic acid side chain leading to enhanced toxicity was detected for BM.
The ability of phytopathogenic fungi to overcome the chemical defense barriers of their host plants is of great importance for fungal pathogenicity. We studied the role of cyclic hydroxamic acids and their related benzoxazolinones in plant interactions with pathogenic fungi. We identified species-dependent differences in the abilities of Gaeumannomyces graminis var.tritici, Gaeumannomyces graminis var.graminis, Gaeumannomyces graminis var.avenae, and Fusarium culmorum to detoxify these allelochemicals of gramineous plants. The G. graminisvar. graminis isolate degraded benzoxazolin-2(3H)-one (BOA) and 6-methoxy-benzoxazolin-2(3H)-one (MBOA) more efficiently than did G. graminis var.tritici and G. graminis var. avenae. F. culmorum degraded BOA but not MBOA.N-(2-Hydroxyphenyl)-malonamic acid andN-(2-hydroxy-4-methoxyphenyl)-malonamic acid were the primary G. graminis var. graminis andG. graminis var. tritici metabolites of BOA and MBOA, respectively, as well as of the related cyclic hydroxamic acids. 2-Amino-3H-phenoxazin-3-one was identified as an additional G. graminis var. triticimetabolite of BOA. No metabolite accumulation was detected forG. graminis var. avenae and F. culmorum by high-pressure liquid chromatography. The mycelial growth of the pathogenic fungi was inhibited more by BOA and MBOA than by their related fungal metabolites. The tolerance ofGaeumannomyces spp. for benzoxazolinone compounds is correlated with their detoxification ability. The ability ofGaeumannomyces isolates to cause root rot symptoms in wheat (cultivars Rektor and Astron) parallels their potential to degrade wheat allelochemicals to nontoxic compounds.
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