nan Pankaj

Development of Poly(ethylene glycol) Based Amphiphilic Copolymers for Controlled Release Delivery of Carbofuran

The formation of micelles in a solvent that is selective for one of the blocks is one of the most important and useful properties of block copolymers. We had synthesized copolymers of polyethylene glycol and various dimethyl esters, which self assemble into nano micellar aggregates in aqueous media. In the present work, we have utilized these nano micelles for the encapsulation of carbofuran, [2,3–dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate], a systemic insecticide-nematicide, for the development of controlled release formulation.

Development of controlled release formulations of azadirachtin-A employing poly(ethylene glycol) based amphiphilic copolymers

Controlled release (CR) formulations of azadirachtin-A, a bioactive constituent derived from the seed of Azadirachta indica A. Juss (Meliaceae), have been prepared using commercially available polyvinyl chloride, polyethylene glycol (PEG) and laboratory synthesized poly ethylene glycol–based amphiphilic copolymers. Copolymers of polyethylene glycol and various dimethyl esters, which self assemble into nano micellar aggregates in aqueous media, have been synthesized. The kinetics of azadirachtin-A, release in water from the different formulations was studied. Release from the commercial polyethylene glycol (PEG) formulation was faster than the other CR formulations. The rate of release of encapsulated azadirachtin-A from nano micellar aggregates is reduced by increasing the molecular weight of PEG. The diffusion exponent (n value) of azadirachtin-A, in water ranged from 0.47 to 1.18 in the tested formulations. The release was diffusion controlled with a half release time (t1/2) of 3.05 to 42.80 days in water from different matrices. The results suggest that depending upon the polymer matrix used, the application rate of azadirachtin-A can be optimized to achieve insect control at the desired level and period.

Bioefficacy evaluation of controlled release formulations based on amphiphilic nano-polymer of carbofuran against Meloidogyne incognita infecting tomato.

In the present investigation, the bioefficacy of developed carbofuran formulations, with PEG-600 (7a, CP1) & PEG-900 (7b, CP2) @ 5, 10 and 20 ppm, along with commercial formulation of carbofuran 3G (CP0) were evaluated against the root-knot nematode, Meloidogyne incognita infecting tomato (cv. Pusa Ruby) in pot and field conditions. The bioefficacy data indicated that the formulations developed by utilizing polymers having PEG – 900 (7b) as hydrophilic segment were effective even at 14 days post inoculation (dpi) as evident from shoot and root length. Also, the reduction in penetration was found to be maximum with CP2 (3.6 – 4.6 J2s) at all concentrations compared to CP1 (6.6 – 16.4 J2s) and CP0 (29.3 – 32.6 J2s). Overall, CP2 was more effective in reducing the number of nematodes up to 14 days, compared to CP1 and CP0. Both the CR formulations (CP1 and CP2) in general significantly reduced the number of galls, when compared to CP0. However, under field conditions, lower concentrations (5, and 10 ppm) of CP2, were less effective in controlling the gall formation whereas, CP2 at 20 ppm, was most effective than other treatments. The study revealed that the developed CR formulations of carbofuran have the potential for effective management of M. incognita in tomato under field conditions.

Microwave assisted solvent-free synthesis and biological activities of novel imines (Schiff bases)

Twelve new ortho-Hydroxyketimines were synthesized by conventional as well as microwave method and evaluated for their antinemic activity against Meloidogyne incognita [(Kofoid and White) Chitwood]. Conventional methods for synthesis of Schiff bases require refluxing at 140°C of the reactants in different solvents for at least 24 h or more, where as the microwave-assisted synthesis has brought down the reaction time from 24 h to 1 minute. The procedure reported is simple as it does not require any organic solvents and the time has been reduced to only 1 minute. Comparative yields of all compounds by different methods revealed that the yield was low in conventional method (79–87%) as compared to microwave assisted synthesis (94–97%). The bioassay revealed that all the test compounds exhibited promising nematicidal activity; N-propyl-2-hydroxypropiophenonimine being the most effective with LC50 value of 74.46 mgL−1 followed by N-hexyl-2-hydroxyacetophenonimine with LC50 value of 99.60 mgL−1 after 72 h of exposure. The results obtained from bioassay indicated that this class of compounds has not only given a lead with regard to potential of Schiff bases in pest control, but has suggested that a carbon chain length of 6 atoms in the side chain is optimum on the basis of structure activity relationship (SAR).

Controlled release formulations of acephate: Water and soil release kinetics

Controlled release formulations of insecticide acephate (O,S-dimethyl acetylphosphoramidothioate) have been prepared using commercially available polyvinyl chloride, carboxy methyl cellulose and carboxy methyl cellulose with kaolinite. Kinetics of acephate release in soil and water from the different formulations was studied in comparison with the commercially available formulation 75 DF. Release from the commercial formulation was faster than the new controlled pesticide release (CR) formulations. Addition of clay in the carboxy methyl cellulose matrix reduced the rate of release. The diffusion exponent (n value) of acephate in water and soil ranged from 0.462 to 0.875 and 0.420 to 0.547 respectively in the tested formulations. The release was diffusion controlled with a half release time (T1/2) of 2.97 to 52.41 days in water and 2.98 to 76.38 days in soil from different matrices. The maximum release of acephate in water and soil from controlled released formulations occurred between 6.33 to 36.34 and 12.49 to 29.09 days respectively. The results suggest that depending upon the polymer matrix used, the application rate of acephate can be optimized to achieve insect control at the desired level and period.

Biocatalytic amidation of carboxylic acids and their antinemic activity

A series of novel N-alkyl substituted amides, synthesized by enzyme catalysis, were evaluated against root-knot nematode, Meloidogyne incognita and found to have potential antinemic activity. The corresponding amides were prepared by the condensation of equimolar amounts of carboxylic acids with different alkyl amines in the presence of Candida antarctica lipase at 60–90°C in 16–20 h. The reactions were carried out in a non - solvent system without the use of any activating agents. All the products were obtained in appreciable amounts and the yields for different compounds varied between 77.4–82.3%. The synthesized compounds were characterized using spectroscopy techniques namely Infra Red (IR) and Nuclear Magnetic Resonance (NMR) (1H and 13C). Nematicidal activity of synthesized amides was evaluated against J2s of Meloidogyne incognita at 500, 250, 125 and 62.5 ppm concentrations after 24 h, 48 h and 72 h of exposure. Among all the tested compounds, N-propyl-butyramide, N-propyl-pentanamide and N-propyl-hexanamide were found to possess significant activity with LC50 values of 67.46, 83.49 and 96.53 respectively. N-propyl-butyramide with LC50 value of 67.46 ppm was found to be most active amide against J2s of Meloidogyne incognita. The bioactivity study showed that an increase in alkyl chain significantly decreased the activity of amides against root-knot nematode.

Synthesis and bioefficacy evaluation of new 3-substituted-3,4-dihydro-1,3-benzoxazines

A new series of 1, 3-Benzoxazines were synthesized, characterized (1H NMR and 13C NMR) and evaluated for their pesticidal activity. Six new 3-alkyl-3, 4-dihydro-4-methyl-2H-1, 3-benzoxazines (1-6) were prepared by hydroxymethylation of secondary amines with formaldehyde in 65–68% yields. These compounds were screened for there IGR activity against Spodoptera litura and for antifungal fungal activity in vitro against Sclerotium rolfsii ITCC 6181 by poisoned food technique. Insect Growth Regulatory (IGR) activity against Spodoptera litura showed that compound 3-Nonyl-3,4-dihydro-4-methyl-2H-1,3-benzoxazines was most effective as IGR with larval GI50 of 1.863 μ g/Insect. Compounds 3-Octyl-3,4-dihydro-4-methyl-2H-1,3-benzoxazines and 3-Decyl-3,4-dihydro-4-methyl-2H-1,3-benzoxazines were effective IGRs. Antifungal screening revealed that compound 3-Dodecyl-3, 4-dihydro-4-methyl-2H-1,3-benzoxazines, was highly effective against Sclerotium rolfsii with LC50 value 31.7 mg L−1 comparable with commercial fungicide Hexaconazole (LC50 1.27 mg L−1). Also compounds 3-Nonyl-3, 4-dihydro-4-methyl-2H-1,3-benzoxazines and 3-Decyl-3,4-dihydro-4-methyl-2H-1,3-benzoxazines displayed promising fungitoxicity. The results described in this paper are promising and provides new array of synthetic chemicals to be utilized as pesticides.

Synthesis and pesticidal activity of new N-alkyl-N-[1-(2-hydroxyphenyl) ethyl]amines

A series of novel N-alkyl-N-[1-(2-hydroxyphenyl) ethyl]amines were synthesized as potential new agents to control pests. Their structures were confirmed on the basis of IR, NMR and elemental analyses. Six new N-alkyl-N-[1-(2-hydroxyphenyl) ethyl]amines were prepared by reduction of corresponding Schiff bases using sodium borohydride in 80–87 % yields. These compounds were tested for their antifungal activity against two pathogenic fungi viz., Rhizoctonia bataticola ITCC 0482 and Sclerotium rolfsii ITCC 5226 and for insecticidal activity against insects of stored grain pest Callosobruchus analis. Fungicidal bioassay revealed that compound N-Decyl-N-[1-(2-hydroxyphenyl)ethyl]amine, was highly effective against R. bataticola (ED50 6.86 mg L−1) which was comparable with that of commercial fungicide hexaconazole (ED50 6.35 mg L−1). Also compounds N-Heptyl-N-[1-(2-hydroxyphenyl)ethyl]amine, N-Octyl-N-[1-(2-hydroxyphenyl)ethyl]amine and N-Nonyl-N-[1-(2-hydroxyphenyl)ethyl]amine displayed promising fungitoxicity against same pathogen. However, compound N-Heptyl-N-[1-(2-hydroxyphenyl)ethyl]amine was also found to be effective against S. rolfsii (ED50 4.92 mg L−1 as against 1.27 mg L−1 for hexaconazole). Compound N-Hexyl-N-[1-(2-hydroxyphenyl)ethyl]amine was most effective as insecticide followed by compound N-Octyl-N-[1-(2-hydroxyphenyl)ethyl]amine. LC50 values for these compounds were 155.0 and 275.0 mg L−1 respectively as against 36.70 mg L−1 for commercial insecticide dichlorovos. The results obtained from bioassays indicate that this class of compounds can be utilized for the design of new substances endowed with pesticidal activities.

Expression analysis of defence related genes and histopathological changes in direct seeded rice genotypes (Oryza sativa L.) against root-knot nematode (Meloidogyne graminicola)

The root-knot nematodes, Meloidogyne spp. are one of the most important diseases causing organisms in direct seeded rice. In order to gain insight of differential response of susceptible and resistant rice cultivars upon nematode infection, expression of OsEDS1, OsPAD4 and OsWRKY genes involved in plant innate immunity was investigated. The expression analysis showed that EDS1-and PAD4mediated SA-upstream signaling triggered the induced defense at an the early stage of infection i.e., 2dpi and 6dpi in the resistant rice variety NDR-97, while it was negatively regulated in the susceptible genotype PB-1121. The histopathological studies of root galls of susceptible and resistant plants showed significant differences in the development of females, giant cells and egg production. The fecundity of the nematode was suppressed in the resistant cultivars.

Molecular mapping of rice root-knot nematode (Meloidogyne graminicola) resistance gene in Asian rice (Oryza sativa L.) using STMS markers

Rice root-knot nematode, Meloidogyne graminicola is one of the major pests of rice cropping system and is responsible for considerable yield reductions. Out of various management options tried so far, the resistance against M. graminicola in rice could be the most valuable in alleviating this problem. In present study a rice cultivar Abhishek exhibited a strong resistance with least number of galls (2galls/plant) and a kind of necrotic browning of roots which is typical of R-gene mediated resistance response. In order to map the gene governing resistance to root-knot nematode, the cultivar Abhishek was crossed with the Bangla Patni, a highly susceptible genotype to generate F2 mapping population. Using bulked segregant analysis, a marker HvSSR10–21 was identified to be putatively linked with the resistant locus in cv. Abhishek with significant LOD score. The significant LOD score value indicates the linkage between identified marker and the resistant locus against M. graminicola. We designate this gene as Mg1(t).