M. A. Radwan

Antibacterial screening of some essential oils, monoterpenoids and novel N-methyl carbamates based on monoterpenoids against Agrobacterium tumefaciens and Erwinia carotovora

Abstract A comprehensive evaluation of 13 plant essential oils namely: caraway, chenopodium, cinnamon, clove, eucalyptus, garlic, geranium, lemon, matrecary, peppermint, rose, rosemary and thyme and 14 of their monoterpenoidal constituents: borneol, camphor, carvacrol, carveol, carvone (R and S), chlorothymol, cineol, cinnamaldehyde, citronellol, eugenol, geraneol, menthol, and thymol was investigated for their antibacterial activity against the two phytopathogenic bacteria, Agrobacterium tumefaciens and Erwinia carotovora var carotovora. Trials for improving the antibacterial activity by either structure modification or mixing with the three synergists: piperonyl butoxide, Triton X-100 and Tween 20 were achieved. New N-methyl carbamate derivatives based on monoterpenoids were introduced. Cinnamon, clove, chenopodium, caraway, rosemary and thyme oils proved to possess good antibacterial activity. Thymol, chlorothymol, and carvacrol were potent against the tested bacteria and quite close to the effect of the standard. Conversion of menthol into its carbamate derivative gave good enhancement in the bactericidal activity at all concentrations compared to menthol itself. Also, the carbamate derivatives of β-citronellol and borneol improved the bactericidal activity against E. carotovora, but decreased it against A. tumefaciens. Synergistic antibacterial activity of the tested monoterpenoids was observed when combined with each of the three synergists particularly with Triton X-100.

Imidacloprid induced alterations in enzyme activities and energy reserves of the land snail, Helix aspersa

The in vivo sublethal toxic effects (0.2 and 0.6 LD50) of topically applied imidacloprid on biochemical biomarkers in the land snail, Helix aspersa was examined. Biochemical perturbations were assessed by measuring the three enzymatic (Acetylcholinesterase, AChE; catalase, CAT and glutathione-S-transferase, GST) activities and three energy reserves (protein, glycogen and lipids) in the snails. Snail samples were taken from each sublethal dose and control groups at 1, 3 and 7 days after treatment. The results revealed that there were overall decrease in AChE activity as well as depletion of lipids and glycogen contents in the imidacloprid-treated snails compared to control groups. The CAT and GST activities of treated snails with the sublethal doses of imidacloprid were significantly higher than those of untreated controls along the three times of exposure. Moreover, an increase in the level of total proteins was observed in animals treated with 0.6 LD50 imidacloprid compared to control groups. The alterations in all tested biochemical perturbations were most pronounced with the 0.6 LD50 than 0.2 LD50. This study suggests that alterations of the enzyme activities and energy reserves in this species that could be useful as biomarkers of imidacloprid exposure in the evaluation of terrestrial impacts of this insecticide.

Larvicidal activity of some essential oils, monoterpenoids and their corresponding N -methyl carbamate derivatives against Culex pipiens (Diptera: Culicidae)

The larvicidal activity of 13 essential oils, 14 major monoterpenoids and 9 N-methyl carbamates based on these monoterpenoids was tested according to the recommendations of the WHO against fourth instar larvae of Culex pipiens L. The results of the larvicidal assays after 24 hr revealed a high potential for the essential oils, such as cinnamon, chenopodium and eucalyptus. Of the monoterpenoids, chlorothymol was found to be the most effective followed by thymol, carvacrol and cinnamaldehyde. Conversion of the most active monoterpenoids into their N-methyl carbamate derivatives resulted in higher larvicidal activities than those of the corresponding monoterpenoids. The use of piperonyl butoxide (PBO) to improve the efficacy of the most active monoterpenoids resulted in higher larvicidal activity. Also, all N-methyl carbamate derivatives were synergized by PBO. Carvacrol derivative, which was strongly synergized by PBO, was comparable with the standard synthetic insecticide malathion.

Oil cakes soil amendment effects on Meloidogyne incognita, root-knot nematode infecting tomato.

Abstract In a pot experiment, oil cakes of cotton, flax, olive, sesame and soybean were mixed with soil at the rate of 5, 10, 15, 20 or 50 g/kg soil. We compared their nematicidal potential with carbofuran as a standard against the root-knot nematode, Meloidogyne incognita infecting tomato. Their effects on the growth parameters of tomato plants were also investigated. The results showed that M. incognita populations in the soil and root galling were significantly suppressed when the tested cakes, at all rates, were allowed to decompose in the soil. All oil cakes exhibited varying degrees of reduction compared to the control. The highest reduction in galls was noted in plants treated with sesame cake, whereas the lowest reduction was observed in plants treated with olive cake. On the other hand, the highest reduction in J2 was noticeable in the plants grown in olive-cake-amended soil followed by sesame, soybean, cotton and flax cake. In addition, employing a high rate of the tested cakes gave higher activity in suppressing the nematode both in the soil and in tomato roots than using low rate. The data also indicated that all cakes, at low rates, significantly increased growth indices of tomato over control treatment, except cotton cake which decreased it, particularly in the root system. Phytotoxicity was associated with the higher rates of oil cakes tested except sesame cake. These oil cake soil amendments could prove to be one component in integrated root-knot nematode management for tomato in conventional and organic production systems.

Synthesis and structure–activity relationships for anticipated molluscicidal activity of some 2-amino-5-substituted pyridine derivatives

A series of 2-amino-5-substituted pyridine derivatives was synthesized and their molluscicidal activity against white garden, Theba pisana (Muller), and brown garden, Helix aspersa (Muller), snails was investigated by two methods of application. Some of these compounds showed strong activity under laboratory conditions against the two types of snail. T pisana was more sensitive to the tested compounds than H aspersa. The most effective compounds were 2-amino-5-(benzo- triazole-1-ylmethyl)-3-methylpyridine, 2-amino-5-(1-(benzotriazole-1-yl)nonyl)-3-methylpyridine and 2-((1,2,4-triazole-1-ylmethyl)amino)-3-methylpyridine which exhibited high molluscicidal activ- ity. The toxicity results are discussed in relation to the chemical structures. # 1999 Society of Chemical Industry

Efficacy of dried seed powder of some plant species as soil amendment against Meloidogyne incognita (Tylenchida: Meloidogynidae) on tomato

The nematicidal activity of dried ground seeds of Ammi majus, Matricaria chamomilla, Ricinus communis, Brassica alba, B. oleracea, Peganum harmala, Solanum nigrum, Raphanus sativus and Eucalyptus sp. was assessed against the root-knot nematode, Meloidogyne incognita, infecting tomato in a glasshouse. The powdered seeds of the tested plants were incorporated into the soil at the rate of 5 g/kg and their nematicidal activity was compared with that of the synthetic nematicide carbofuran at the rate of 0.01 g a.i./kg. The effects of the treatments on the growth of tomato were also examined. The populations of M. incognita in the soil and root galling of tomato were significantly suppressed by the powdered seeds of all the plant species tested, with the greatest reduction occurring in soil amended with M. chamomilla, followed by soil treated with powdered seeds of A. majus, S. nigrum, R. communis and Eucalyptus sp. The efficacy of B. oleracea, B. alba, M. chamomilla and R. communis in reducing the number of J2 in the soil was similar to that of carbofuran. All amendments, except powdered seeds of M. chamomilla and A. majus significantly increased shoot length compared to the untreated inoculated plants. Shoot weight was significantly increased in soil amended with powdered seeds of B. oleracea, B. alba, R. communis, P. harmala and S. nigrum, but not in soil amended with the other seed powders when compared with untreated inoculated soil. Significant increases in root length occurred in pots amended with seed powder of B. alba, R. communis and Eucalyptus and in root weight for P. harmala. None of the tested dried seeds was phytotoxic to tomato plants at the applied rate.

Use of some emulsified plant seed oils as a safe alternative for the management of Meloidogyne incognita infecting tomato

Abstract The aim of the present study was to formulate six different plant seed oils namely canola, cotton, flax, olive, sesame and soybean as emulsifiable concentrates. The composition of the formulation comprises at least one organic solvent, one surfactant and one plant oil. Physico-chemical properties of the formulated oils (emulsion stability test, cold stability and heat stability tests) were measured. The successfully emulsified oils were evaluated for nematicidal activity against Meloidogyne incognita infecting tomato plants under greenhouse conditions. Emulsified canola oil proved to be the most effective oil as a protectant against M. incognita infection to tomatoes followed by soybean, cotton, flax and sesame oil. In addition, employing a high rate of the tested emulsified oils gave higher activity in suppressing nematodes both in the soil and in tomato roots than using a low rate. Moreover, all tested formulated oils at both rates of application had no adverse effect on the growth of tomato plants except sesame oil which significantly decreased the shoot length when compared to the control. The prepared plant oils might be used as potential sources for sustainable eco-friendly botanical nematicides to protect plants from nematode attack.