Field evaluations of systemic fungicides and derivatives of dithiocarbamic acid for the control of clubroot

Strains of Botrytis cinerea and Mucor mucedo germinated and grew over the range 0.25^°C. There were differences in germination rates and growth rates between strains of B. cinerea at any given temperature. Five of the benomyl-resistant strains germinated and grew more slowly than any of the other benomyl-resistant or benomyl-sensitive strains of B. cinerea tested. Strains of Rhizopus stolonifer and R. sexualis germinated and grew between 5 and 25^°C, and although some spores germinated at 2^°C, subsequent growth of the germ tubes and growth from a mycelial inoculum did not occur. Neither species germinated or grew at o^°C. The effect of temperature on mycelial growth in vitro was consistent with the ability of the strains of the four species to infect strawberry fruits.     

Glasshouse evaluation of some systemic fungicides for control of clubroot of brassicae

Of nine systemic fungicides screened as soil mixes against clubroot, only the precursors of methyl benzimidazol-2-ylcarbamate (MBC) or ethyl benzimidazol-2-ylcarbamate (EBC) gave promising results. Benomyl was the most effective, usually giving control at 250 mg/kg dry soil. Most fungicides were less effective against an isolate of Plasmodiophora brassicae from Brussels sprouts than against one from rape. Disease control was slightly better on cabbage than on a highly susceptible rape variety.     

Investigations on fungicides: The systemic fungicidal activity of certain N-carboxymethyl dithiocarbamic acid derivatives

The systemic activity of thirty-three N-substituted S-esters derived from dithiocarbamic acid was investigated by assessing their ability to reduce the infection of broad-bean seedlings by Botrytis fabae and of wheat seedlings by Erysiphe graminis, following application to the roots or cut shoots of the host. Marked systemic activity against mildews was shown by the N-carboxymethyl dithiocarbamates, by S-carboxymethyl-N, N-dimethyl-dithiocarbamate (G₃₃) and by procaine and 6-azauracil. The effect was not very host-specific since most compounds showing high activity in wheat also showed activity in pea, cucumber and, to a smaller extent, apple. All the materials tested showed a much lower level of systemic activity in broad-bean seedlings against B. fabae. Measurements were also made of the uptake, translocation, phytotoxicity and the stability within plant tissues of some of these compounds. The degree of systemic activity which they show is discussed in relation to these and other properties of the compounds.     

Glasshouse evaluation of fungicides for the control of sunflower downy mildew (Plasmopara halstedii)

A precise, reproducible and easy-to-handle glasshouse test is described for the evaluation of the systemic activity of chemicals for the control of Plasmopara halstedii, the downy mildew pathogen of sunflower. Four-day-old sunflower germlings were inoculated by immersing them in a zoosporangium suspension. Seedlings were then immersed in appropriate concentrations of the chemicals to be tested. Plants were grown in a glasshouse and assessed on three occasions to determine successively antisporulant, curative (systemic fungistatic), and eradicant effects. Sporulation in general was inhibited by lower concentrations than those required to exert an eradicant effect. There was a highly significant correlation between the ED₅₀ values for visually recognised disease symptoms (stunting, dampingsff and leaf chlorosis) and for both curative and eradicant effects. Among 13 compounds tested, metalaxyl, RE 26745, furalaxyl, LAB 149202F and cymoxanil showed sufficient eradicant activity, to justify field evaluation for eradication of seed infections.     

Distribution of quinic acid derivatives and other phenolic compounds in Brazilian propolis

The quinic acid derivatives (including 4-feruoyl quinic and 5-ferruoyl quinic acids characterized for first time in propolis samples) and other phenolic compounds were quantified in thirteen Brazilian propolis samples by HPLC analysis. For chemometrical analysis, the distribution of quinic acid derivatives and other phenolic compounds were considered. The results suggest that the Brazilian propolis with floral origin from Citrus sp. have the highest concentration of the quinic acid derivatives (between 11.0 to 58.4 mg/mg of the dried crude hydroalcoholic extract) and therefore would probably show a more effective hepatoprotective activity.     

Studies in the mechanism of fungicidal action: V. Non-metallic and sodium dithiocarbamic acid derivatives

This investigation has as its object the elucidation of the mode of action of dithiocarbamic acid derivatives as fungicides, with die help of the theory of variability, heavy metal salts being dealt with separately.
The experiments were carried out using Macrospcrium sarcinaeforme as the test organism; the chemical materials used are listed.
Deviations from the experimental and mathematical techniques described in previous papers of this series are explained.
From the results it is inferred that: ( a ) dithiocarbamates are decomposed by the spores to a greater or lesser degree into amine and carbon disulphide, both being toxic; ( b ) the amines can be absorbed only in a combined form, which may be the dithiccarbamate itself but is more probably a derivative, possibly an ester; ( c ) the carbon disulphide probably acts through the mediation of a thiocarbonate; ( d ) thiuramsulphides act through being decomposed to dithiocarbamates (or their derivatives mentioned above). The monosulphides are largely, and the disulphides slightly, decomposed; in the latter case with reduction.
It is suggested that the greater toxicity of the methyl-derivatives over all others tested is due to the shortness of the hydrocarbon chain.
It is concluded that the role of the carbon disulphide is chiefly that of a chemical carrier of the amino group, but that, owing to the negative index of variation of the spores to the latter, the carbon disulphide must play an essential part in completing the toxicity.
It is suggested that heavy-metal dimemyldithiocarbamates may show promise against M. sarcinaeforme, but that others may be effective against other fungi.     

Seed treatments with benomyl and other fungicides for the control of Ascochyta pisi on peas

In three experiments, using laboratory, glasshouse and field tests, seed dressings of benomyl-1½ (42.4 g) to 2 oz (56.6 g) Benlate 50% w.p. per 28 lb (12.7 kg) of seed-gave complete control of Ascochyta infection of pea seeds. Mixtures of benomyl and captan and benomyl and thiram were also effective. Carboxin, captan, and thiram used as seed dressings, either singly or in mixtures, did not eliminate the pathogen from peas. Germination, emergence and seedling vigour were not impaired by any dressing.     

Enzyme inhibition as a possible mechanism of the mutagenicity of dithiocarbamic acid derivatives in Salmonella typhimurium

In recent years data have accumulated regarding genotoxic properties of dithiocarbamic acid derivatives. The results from the present work indicate that the mutagenicity of these compounds depends on an indirect effect via oxygen radicals. Mutagenicity of tetramethylthiuram disulfide ( TMTD ), that was used as a model substance, was established with both frameshift and base substitution sensitive strains of Salmonella typhimurium. Addition of copper ions resulted in a decreased survival at low dithiocarbamate doses. The dose response curves seem to correlate with the formation of two types of metal dithiocarbamate complexes. At low doses charged complexes are formed, while the formation of uncharged complexes is favoured at higher dosages. The data suggest that this formation of uncharged metal complexes implies a decreased toxicity but at the same time an increased mutagenicity. The mutagenicity of both TMTD and its ethyl analogue TETD was enhanced by oxygen. Furthermore, TMTD potentiates the mutagenic action of menadione, a substance that produces O(2) and H2O2 by redox cycling with molecular oxygen. Interaction of uncharged metal dithiocarbamate complexes with both production and detoxification of reactive forms of oxygen is suggested to be responsible for the direct mutagenic effects via oxidative damage to DNA. A further enhancement of the oxygen radical content of the cells by adding microsomes that produce oxygen radicals via autoxidation of cytochrome P-450 is proposed as the mechanism for the 'metabolic activation of TMTD '.     

Some factors affecting the control of Rhizoctonia solani by systemic and non-systemic fungicides

In laboratory tests, Rhizoctonia solani grew best on agar at 30 ^oC and pH 5-5. Mycelial growth was strongly inhibited by benomyl, chloroneb and quintozene, less so by thiophanate-methyl. The optimum temperature for inhibition was 25 ^oC for quintozene; the other three fungicides gave greatest inhibition at the lowest temperature tested (20 ^oC). Benomyl and thiophanate-methyl were most inhibitory at pH 7–8, chloroneb and quintozene at pH 5–6. In pot trials using mung bean, long melon, egg-plant, common pea and sugar beet, R. solani caused maximum disease at 20 ^oC and in wet and alkaline soils. As seed treatments, benomyl and thiophanate-methyl gave optimum control at 20 ^oC and pH 7-6; chloroneb and quintozene were most effective at 30 ^oC and pH 5-4. All four fungicides gave maximum control on plants growing in wet sandy loam. Comparisons of host effects showed that, on all the four hosts tested, thiophanate-methyl wettable powder at 0.25% (0.175% a.i.) gave 90% control, chloroneb w.p. at 0.3% (0.195% a-i-) gave 80% control on mung bean and sugar beet, benomyl w.p. at 0.3% (0.15% a.i.) was satisfactory on mung bean, egg-plant and sugar beet but not on long melon, quintozene w.p. at 0.3 % (0.225 % a-i-) gave effective control on sugar beet only. The senior author is grateful to the Council of Scientific and Industrial Research, New Delhi, India, for the award of a Research Fellowship for undertaking these studies. Thanks are due to Dr S. D. Gupta and Mr S. L. Verma for determining the soil characteristics.     

Effect of surfactants and fungicides on clubroot (Plasmodiophora brassicae) of brassicas

Two formulations of the surfactant sodium dioctyl sulphosuccinate (Aerosol OT, Monawet MO70), one of alkyl phenyl ethylene oxide (Agral) and three fungicides (PP192, dichlorophen and a thiabendazole/iodophor complex -Byatran) were tested in field trials for control of clubroot (Plasmodiophora brassicae) on cabbage in 1988 and 1989. A standard mercurous chloride treatment (pre-sowing compost incorporation) was included in all experiments. Plants were raised in 64 cm³ blocks (1988) or 15 cm³ free-fill cells (1989). Mercurous chloride reduced disease severity and increased yield in both years. Byatran was ineffective. The surfactants and dichlorophen, applied as pre-planting soaks to the plant-raising compost, restricted disease development and increased yield in 1988 but not in 1989. A similar treatment with PP192 restricted disease severity and enhanced yield in both years. Pouring the surfactants and dichlorophen into the planting hole was more effective than using them to soak the compost. In 1989 pour treatments with Agral and a combined soak/pour treatment with dichlorophen reduced disease severity and increased yields by 250% and 97% respectively; compost treatment with PP192 gave a 150% increase.     

Glasshouse tests of quinones, polyhydroxybenzenes and related compounds against potato common scab

Forty quinones, polyhydroxybenzenes and related compounds were tested for possible control of potato common scab, caused by Streptomyces scabies. They were incorporated, at 50 μg/g or less, into scab-infected soil in which potato plants were then grown in the glasshouse. Quintozene at 50/μ g/g was used as standard. The chemicals varied very widely in their effects on scab, and in their phytotoxicity, as measured by decrease in yield of tubers. Corresponding 1,4-benzoquinones and hydroquinones behaved similarly. The unsubstituted and the phenyl-, chloro-,2,5- and 2,6-dichloro-com-pounds were as effective as quintozene; with the exception of chloro-hydroquinone, they did not decrease yield. Chloranil and chloroneb (the dimethylether of 2,5-dichlorohydroquinone) were much less effective, and chloroneb decreased yield as well. 4-terf-butyl catechol was more effective than any other compound tested, including quintozene, and at suitable rates (25 or 12-5 μg/g) did not decrease yield. Other hydroxybenzenes and some 1,4-naphthaquinones (including dichlone) and anthraquinones were almost ineffective.     

Glasshouse tests of chemicals for control of potato common scab

Quintozene is the only chemical used successfully in practice to control soil-borne Streptomyces scabies, the cause of potato common scab. However it may be carcinogenic, and the aim of this work was to find a substitute for it. About 100 chemicals, most of which had known fungitoxic action or were related to such chemicals, were tested in the glasshouse by growing potato plants in soil with which the chemicals had been mixed, usually at 50 ppm. Many of the chemicals failed to decrease the incidence of scab, or decreased the yield of tubers, or both. The most effective chemical was captafol, which was as effective as quintozene and, unlike quintozene, did not decrease yield. Captan and folpet, which are very closely related to captafol, were ineffective.     

Oleanolic acid and related derivatives as medicinally important compounds

Oleanolic acid has been isolated from chloroform extract of Olea ferruginea Royle after removal of organic bases and free acids. The literature survey revealed it to be biologically very important. In this review the biological significance of oleanolic acid and its derivatives has been discussed. The aim of this review is to update current knowledge on oleanolic acid and its natural and semisynthetic analogs, focussing on its cytotoxic, antitumer, antioxidant, anti-inflamatory, anti-HIV, acetyl cholinesterase, alpha-glucosidase, antimicrobial, hepatoprotective, anti-inflammatory, antipruritic, spasmolytic activity, anti-angiogenic, antiallergic, antiviral and immunomodulatory activities. We present in this review, for the first time, a compilation of the most relevant scientific papers and technical reports of the chemical, pre-clinical and clinical research on the properties of oleanolic acid and its derivatives.     

Synthesis and evaluation of novel spiro derivatives for pyrrolopyrimidines as anti-hyperglycemia promising compounds

Pyrrolopyrimidin-4-ylidene-malononitriles IIa–d were prepared as important intermediates for preparation of a new series of spiro-pyrrolopyrimidines. These intermediates undergo cyclisation via reaction with acetylacetone, guanidine hydrochloride or hydrazine hydrate. Elemental and spectroscopic evidences for the structures of these compounds are presented. The final compounds have been monitored for in vivo anti-hyperglycemic activity, compared with Amaryl as standard drug. Among 12 tested compounds, both spiro (pyrano IIIb and pyrazlo Va) derivatives exhibit promising anti-hyperglycemic activity.     

Synthesis and cytotoxicity evaluation of oleanolic acid derivatives

Twelve derivatives of oleanolic acid (1) have been synthesized and evaluated for their inhibitory activities against the growth of prostate PC3, breast MCF-7, lung A549, and gastric BGC-823 cancer cells by MTT assays. Within these series of derivatives, compound 17 exhibited the most potent cytotoxicity against PC3 cell line (IC₅₀ = 0.39 μM) and compound 28 displayed the best activity against A549 cell line (IC₅₀ = 0.22 μM). SAR analysis indicates that H-donor substitution at C-3 position of oleanolic acid may be advantageous for improvement of cytotoxicity against PC3, A549 and MCF-7 cell lines.