Gyula Oros

Biological activity and environmental impact of anionic surfactants.

The newest results concerning the biological activity and environmental fate of anionic surfactants are collected and critically evaluated. The chemical and physicochemical parameters related to the biological activity and the field of application are briefly discussed. Examples on the effect of anionic surfactants on the cell membranes, on the activity of enzymes, on the binding to various proteins and to other cell components and on their human toxicity are presented and the possible mode of action is elucidated. The sources of environmental pollution caused by anionic surfactants are listed and the methods developed for their removal from liquid, semiliquid and solid matrices are collected. Both the beneficial and adversary effects of anionic surfactants on the environment are reported and critically discussed. It was concluded that the role of anionic surfactants in the environment is ambiguous: they can cause serous environmental pollution with toxic effect on living organisms; otherwise, they can promote the decomposition and/or removal of other inorganic and organic pollutants from the environment. The relationship between their chemical structure, physicochemical parameters, biological activity and environmental impact is notwell understood. A considerable number of data are needed for the development of new anionic surfactants and for the successful application of the existing ones to reduce the adversary and to promote beneficial effects.

Separation of the strength and selectivity of the microbiological effect of synthetic dyes by spectral mapping technique.

The growth inhibitory effect of 30 synthetic dyes on 22 bacteria (test organisms) belonging to various taxonomic groups was determined. The strength (potency) and selectivity of the biological effect were separated by the spectral mapping technique, reducing the dimensionality of the selectivity maps to two by the nonlinear mapping technique. The relationship between biological effect and physicochemical parameters of dyes was elucidated by stepwise regression analysis. It has been established that the strength of the effect of anthracene and trityl derivatives was higher than that of azobenzene dyes and significantly depended on the hydrophobicity of the compound. The selectivity of the effect also depended on hydrophobicity and on the nonpolar unsaturated surface area of the dyes. Gram negative and Gram positive bacteria differed in the strength and selectivity of their response to dyes indicating the marked impact of the taxonomical position on the response. Contrary to other multivariate mathematical statistical methods biological activity may be divided by SPM into potency and selectivity values, therefore, application of the technique in future QSAR studies is highly recommended.

Inclusion complexing by water-soluble β-cyclodextrin polymers

Cross-linked β-cyclodextrin with a molecular weight of less than 10000 has good solubility in water, and it is a better inclusion complexing agent than the parent β-cyclodextrin. By including lipophilic guest molecules into the apolar cyclodextrin cavity, their apparent lipophilicity is reduced because the outer surface of the molecular ‘wrapping’ (the crosslinked β-CD) is highly hydrophilic. The relative stability of the inclusion complexes can be rapidly determined by reversed-phase thin-layer chromatography. The reversed-phase TLC behaviour of 25 triphenylmethane derivatives and analogues were studied in the presence of β-cyclodextrin polymers containing neutral and carboxyl groups. Increasing the molecular weight results in an increased complex-forming capacity. The carboxyl group modifies the accessibility of the CD cavity which in turn results in increased or decreased complex stability, depending on the guest molecule. The presence of organic solvents diminishes the stability of the CD complexes.

Use of spectral mapping and stepwise regression analysis for the assessment of the relationship between chemical structure and biological activity of surfactants

Abstract The biological activity of 27 nonionic surfactants with different hydrophobic moiety and with different length of ethylene oxide chain was determined on 10 microbiological objects. Spectral mapping technique and stepwise regression analysis were used for the separation of the strength and selectivity of the biological effect of surfactants, and for the elucidation of the relationship between molecular structure and activity. It was found that both the strength and selectivity of the biological effect of surfactants differ considerably from each other and considerably depend on the molecular structure. It was established that the strength of the effect mainly depends on the hydrophobicity of surfactants whereas both the hydrophobicity and the length of polar ethylene oxide chain exert a significant influence on the selectivity indicating the involvement of hydrophobic and hydrophilic forces in the surfactant-target interaction.

Botanical fungicides: natural and semi-synthetic ceveratrum alkaloids

The practical potential of the main bioactive principles of sabadilla, a botanical insecticide prepared from the seeds of Schoenocaulon officinale, and related semi-synthetic ceveratrum alkaloids in controlling phytopathogenic bacteria and fungi was explored. Evaluating 35 compounds belonging to this group of steroid alkaloids revealed antimicrobial effects against Erwinia, Corynebacterium, Fusarium, Glomerella and Plasmopara species. Significant activities were displayed against the sunflower downy mildew fungus, Plasmopara halstedii. The ceveratrum alkaloids are thought to interact with the cell membrane, disrupting its integrity and/or altering its function. In contrast to commercial fungicides affecting either the parasitising thallus or the asexual spores of P. halstedii, ie, only a single developmental stage, the alkaloids tested disrupt its life cycle at several points in host-dependent and host-independent stages. Among the natural alkaloids, cevacine and cevadine were the most effective against sunflower downy mildew and the activity of the semi-synthetic oleoyl veracevine and cevagenine was comparable to that of metalaxyl. Sunflowers showed good tolerance to these highly active natural and semi-synthetic ceveratrum alkaloids. Our results indicate that the modest anti-oomycete activity of the natural sabadilla components can be greatly improved by appropriate structural modifications and thus establish the ceveratrum alkaloids as potential antifungal agents with a novel mode of action.

Antimicrobial activity of o-carboranylalanine.

SummaryFunctionalized polyhedral carboranes, including amino acid analogs, have unique physicochemical properties and are used as experimental anticancer agents. However, our current knowledge on their effect in nonmammalian biological systems is limited. We investigated the activity spectrumin vitro ofo-carboranylalanine (o-Cba), considered to be a highly lipophilic analog of phenylalanine, against representative plant pathogenic bacteria and fungi of various taxonomic position. The antibacterial effect ofo-Cba against some species was comparable to that of the widely used agricultural antibiotic, streptomycin. The sensitivity of individual bacterial species too-Cba within the same genus varied to a greater extent than the average sensitivity of various genera. In general, this carborane-containing amino acid was more toxic to Gram positive bacteria (Bacillus, Corynebacterium, Curtobacterium, Micrococcus, Rhodococcus, and Staphylococcus) than to Gram negative ones (Agrobacterium, Erwinia, Escherichia, Pseudomonas, Rhizobium, and Xanthomonas). Compared to the commercial fungicide, prochloraz,o-Cba was weakly toxic against various fungi (Zygo- and Ascomycota). It was also inferior to the commercial fungicide metalaxyl in inhibiting the vegetative growth of oomyceteous plant pathogens (Pythium irregulare, Phytophthora cryptogea and Plasmopara halstedii). Against the asexual spores of P. halstedii,o-Cba, however, was over a thousandfold more active than tridemorph, a selective zoospore inhibitor fungicide. For all taxonomic groups, the observed antimicrobial effect ofo-Cba could be diminished with histidine, but not with phenylalanine. In studies on healthy and mildew-infected sunflower and tobacco plantso-Cba showed neither fungicidal nor phytotoxic effects at 500ppm. This is the first report on the biological activity spectrum of a carborane-containing amino acid.

Antisporulant activity of leaf extracts of Indian plants against Sclerospora graminicola causing downy mildew disease of pearl millet

Methanolic extracts of forty plant species commonly growing across India were collected and have been screened for antisporulant activity against Sclerospora graminicola (Sacc.) Schroet., the causative agent of pearl millet downy mildew. The collection represented 38 genera of 30 families. The methanolic extracts of nine species did not show any effect, whereas the activity of the extracts of Clematis gouriana, Evolvulus alsinoides, Mimusops elengi, Allium sativum and Piper nigrum were commensurable to that of the marketed botanical fungicides. The extracts of 11 species (Agave americana, Artemisia pallens, Citrus sinensis, Dalbergia latifolia, Helianthus annus, Murraya koenigii, Ocimum basilicum, Parthenium hysterophorus, Tagetes erecta, Thuja occidentalis and Zingiber offinale) exhibited remarkable antisporulant effect even after 10-fold dilution of the crude extracts while in the case of remaining 15 plants the crude extracts loosed activity after 10-fold dilution. The antisporulant activity of commercialised Azadirachta preparation (Nutri-Neem) was more pronounced than that of Reynutria based one (Milsana) and Sabadilla (veratrin), however, these botanical preparations held off the extracts of C. gouriana and E. alsinoides and synthetic fungicides.

Microbial decomposition of some cyclodextrin derivatives by bacteria associated with plants.

Abstract Bacteria associated with plants were examined for their ability to use cyclodextrins (CDs) as a unique carbon source. Among 24 strains from eight genera, Xanthomonas were the most active. The cyclodextrin decomposing ability of strains were not related to their taxonomic position. Chemical structure significantly influenced the degradability of cyclodextrins by bacteria. The less rigid ring structure of gamma-CD favoured utilization, whereas methylation led to reduced utilization.

INHIBITORY EFFECT OF NONIONIC SURFACTANTS ON SUNFLOWER DOWNY MILDEW. A QUANTITATIVE STRUCTURE-ACTIVITY RELATIONSHIP STUDY

Abstract The inhibitory effect of 21 nonionic surfactants (nonylphenyl and tributylphenyl ethylene oxide oligomers, sorbitan derivatives) on the ontogenetic life cycle of sunflower downy mildew fungus ( Plasmopara halstedii Farl. Berlese et de Toni) was determined and the strength and selectivity of the inhibitory effect was separated by using spectral mapping technique. It was established that surfactants exert no marked influence on living zoosporangia but inhibit the other forms. Calculations indicated that both the strength and selectivity of the effect of surfactants considerably depend on the length of the polar ethylene oxide chain and the hydrophobicity of the surfactant molecule has a secondary importance. Surfactants with medium length of ethylene oxide chain were more toxic than surfactants with very short or very long ethylene oxide chain.

Effects of phenylamide pesticides on the GSH-conjugation system of Phytophthora spp. fungi.

Abstract Phytophthora cactorum, Ph. cambivora, Ph. cinnamomi, Ph. citricola, Ph. cryptogea, Ph. drechsleri, Ph. infestans, Ph. megasperma, Ph. parasitica, and Ph. syringae contain GSH-conjugation systems as indicated by the presence of active GST enzyme in addition to GSH. Basal levels of both GSH and GST in the thalli of Phytophthora strains studied did not correlate with either fungal sensitivity to phenylamides (acetochlor, butachlor, metolachlor, dimethachlor, propachlor, ofurace, CGA-29212, metalaxyl, RE-26745, benalaxyl, furalaxyl, LAB-149202) or their acquired resistance to metalaxyl. Thalli of Phytophthora strains from axenic cultures ex posed to sublethal concentrations of the above pesticides contained significantly higher levels of both GSH and GST than the untreated controls. This response was independent of the sensitivity and tolerance of the strains to phenylamides. When the responses of Phytophthora strains to phenylamide chemicals were compared by means of principal component analysis, four independent components were detected account ing for 88% of the total variation. Biological properties (basal and induced levels of GST and GSH, growth intensity, degree of acquired resistance to metalaxyl, sensitivity to propiconazole and to cis-and trans-tridemorph) of the strains contributed differently to this variation. It was concluded that, in contrast to plants, sensitivity or tolerance of Phytophthora species to phenylamide pesticides is not regulated by the efficiency of the GSH-conjugation system. In addition, our data clearly indicate that the acetanilide pesticides have multiple sites of action in the Phytophthora genus.