Isolation and Structure of Cordifolin, A Novel Insecticidal Oxygenated Chalcone, from the Stem of Tinospora Cordifolia Miers

Cordifolin, a chalcone reported for the first time from a natural source, has been isolated from the ethanolic extract of the woody stem of Giloe (Tinospora cordifolia). The chemical structure was established as 1-(2′,3′,4′-trihydroxyphenyl)-3-(4′‘-methoxyphenyl)-propen-1-one by spectroscopic analysis. The compound exhibited good insect growth regulatory activity against larvae of Spodoptera litura.

Assessment of Phytotoxicity of Parthenin

Phytotoxicity of parthenin, a sesquiterpene lactone, was evaluated against four weedy species (Amaranthus viridis, Cassia occidentalis, Echinochloa crus-galli, and Phalaris minor) through a series of experiments conducted under laboratory or greenhouse conditions to assess its herbicidal potential. Under laboratory conditions, parthenin (0.5 - 2 mm) severely reduced seedling growth (root and shoot) and dry weight of test weeds. However, the effect was greater on root growth. Parthenin (1 mm) suppressed the mitotic activity in the onion root tip cells that could possibly be responsible for the reduction in seedling growth. Both pre- and post-emergent application of parthenin caused a significant loss of chlorophyll pigments and affected photosynthesis. Parthenin (≥1 mm) caused an excessive electrolyte leakage in the plant tissues which was light-dependent. The root inhibition was associated with swelling and blackening of the root tip, shriveling and damage to the epidermal tissue and non-formation of root hairs. The study concludes that parthenin possesses weed-suppressing potential (both pre- and post-).

Comparative study of allelopathy as exhibited byProsopis Juliflora swartz andProsopis cineraria (L) druce

The allelopathic effects ofProsopis juliflora were studied both in the laboratory and in nature and compared with that ofProsopis cineraria to understand the chemical nature of allelochemics. Both species occupy the same habitats butP. cineraria does not appear to have any toxic effect on other plants under its canopy.P. juliflora is highly allelopathic and does not allow the growth of any other species. Leaf extracts and leaf leachates ofP. juliflora were inhibitory. Decaying leaves were also inhibitory at early stages of decomposition. Live roots were not found to be inhibitory in cogermination and interplanting of seeds. Chemical investigation of the extracts showed the allelopathic compounds to be phenolic in nature in both the species. Slow decomposition and heavy accumulation of leaf litter belowP. juliflora may possibly result in accumulation of toxic substances in soil layers, inhibiting growth of other species.

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 degrees 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 LC(50) value of 74.46 mgL(-1) followed by N-hexyl-2-hydroxyacetophenonimine with LC(50) 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).

Nematicidal prenylated flavanones from Phyllanthus niruri

Two prenylated flavanones have been isolated from the hexane extract of Phyllanthus niruri plant. The structure of these flavanones were established as 8-(3-Methyl-but-2-enyl)-2-phenyl chroman-4-one (1) and 2-(4-hydroxyphenyl)-8-(3-methyl-but-2-enyl)-chroman-4-one (2) on the basis of spectral analysis. These were evaluated for nematicidal activity against root-knot, Meloidogyne incognita, and reniform, Rotylenchulus reniformis, nematodes. Compound 2 exhibited nematicidal activity at par with the standard carbofuran (LC50 3.3 and 3.1ppm, respectively) when tested against reniform nematode. The LC50 value against root-knot nematode was found to be 14.5ppm. Compound 1 however, showed moderate activity against both the test nematodes.

Effect of parthenin--a sesquiterpene lactone from Parthenium hysterophorus--on early growth and physiology of Ageratum conyzoides

A study was undertaken to assess the effect of parthenin--a sesquiterpene lactone from Parthenium hysterophorus--on the germination, growth, and some associated physiological changes in Ageratum conyzoides. The study reveals that germination and growth of A. conyzoides was severely reduced by parthenin in the concentration range of 50, 100, and 200 microM, while at 400 microM a complete inhibition of germination was observed. The radicle length of A. conyzoides was reduced more than the plumule length. Further, the content of the photosynthetic pigment chlorophyll was appreciably reduced in the leaves of test plants spray treated with parthenin at 200 microM concentration. However, this inhibitory effect declined with the passage of time and at 10 days after treatment only a 25% reduction in chlorophyll content was observed compared to 76% on the first day after spray. Likewise, the cellular respiration measured through 2,3,5-triphenyl tetrazolium chloride was found to be less in the treated leaves, and the inhibitory response also declined with time. The content of proteins and carbohydrates decreased with the passage of time after parthenin treatment. The specific activities of the enzymes protease and alpha- and beta-amylase were also adversely affected in the parthenin treated leaves. In the case of protease. the activity decreased with passage of time while those of the amylases increased. Thus, we conclude that parthenin affects the germination and growth of A. conyzoides by altering the contents of some macromolecules and the specific activities of some enzymes. Such observations may be helpful in further exploring parthenin's mode of action.

Pesticidal properties of parthenin (from Parthenium hysterophorus) and related compounds

Eleven sesquiterpene lactone derivatives of parthenin (1), obtained from wild feverfew, Parthenium hysterophorus, were prepared by chemical and photochemical transformations. The compounds tested were a pyrazoline adduct (2) of parthenin, its cyclopropyl (3) and propenyl (4) derivatives, anhydroparthenin (5), a dihydro-deoxygenated product (6), a formate (7) and its corresponding alcohol (8) and acetate (9), a rearranged product (10), lactone (11) and hemiacetal (12). All these derivatives, along with parthenin, were tried for their antifeedant action against sixth-instar larvae of Spodoptera litura, for insecticidal activity against the adults of store grain pest Callosobruchus maculatus, for phytotoxic activity against Cassia tora, and for nematicidal activity against the juvenile stage-II (J2) of the root knot nematode Meloidogyne incognita. Antifeedent bioassay revealed that parthenin is moderately antifeedant. Among the derivatives, the saturated lactone (11) was found to be about 2.25 times more active than parthenin. The pyrazoline adduct (2) was found to be the most effective as an insecticide, with LC50 values after 24, 48 and 72 h of 96, 43 and 32 mg litre-1, respectively, which are comparable with neem extract. Compound 4 was found to be the most effective inhibitor of germination and seedling growth of C tora, with ID50 values for germination, plumule length and radicle length of 136, 326 and 172 compared with 364, 738 and 427 mg litre-1, respectively, for parthenin. Compound 10 was found to be the most effective in terms of nematicidal activity. The LC50 values for this compound were 273 and 104 mg litre-1, respectively, after 48 and 72 h compared with 862 and 512 mg litre-1 observed for parthenin after 48 and 72 h.

Efficacy of some essential oils and their constituents on few ubiquitous molds

Six essential oils of Mentha arvensis, Mentha piperita, Anethum sowa, Cymbopogon winterianus, Nardostachys jatamansi, and Commiphora mukul were selected and tested for their efficacy against Aspergillus flavus, A. fumigatus, A. sulphureus, Mucor fragilis, and Rhizopus stolonifer. These oils were fungistatic or fungicidal to one or the other molds, depending upon the concentrations.