Synthesis,insecticidal activity and pyrethroidal mode of action of new tin ether derivatives

A novel range of trimethylstanniomethyl ethers of well known pyrethroid alcohols were synthesised, and their insecticidal activities and modes of action as insecticides were investigated. Among them, ethers from three types of alcohol (3-phenoxybenzyl, 4-fluoro-3-phenoxybenzyl and 6-phenoxy-2-pyridylmethyl) showed remarkable insecticidal activities against rice stem borers, houseflies and German cockroaches. According to electrophysiological studies on the abdominal nerve cords of German cockroaches, trimethylstanniomethyl 6-phenoxy-2-pyridylmethyl ether induced a rapid decline in spontaneous firing similar to that from tetramethrin. However, insecticidal trimethyltin chloride caused an entirely different response. These observations suggest that the present tin ether derivatives resemble pyrethroids, rather than the insecticidal tin compounds known so far.     

Neuropharmacological studies of an insecticidal trihaloimidazole derivative in the crayfish neuromuscular preparation

A trihaloimidazole derivative (S-377; 1-(4-chlorobutoxymethyl)-2,4,5-trichloroimidazole) caused giant excitatory junctional potentials by a single electrical stimulus to the excitatory nerves. Repetitive discharges were simultaneously induced in the nerve fibres. S-377 also caused repetitive firing in the inhibitory nerve fibres. Permethrin showed quite similar actions on both the junction and nerve fibres. It was supposed that S-377 inhibited the inactivating system of the sodium channel, like pyrethroids. However, S-377 reduced the number of spikes of the permethrin-induced repetitive discharges on the excitatory nerve fibres. These observations suggest that binding sites of S-377 on sodium channels are different from those of pyrethroids.     

A new pyrethroid-type ester with strong knockdown activity

Thirteen pyrethroid-type esters of substituted 1(or 3)-hydroxymethylimidazolidine-2, 4-dione were synthesised and their knockdown activities against houseflies, mosquitoes and cockroaches were examined. Knockdown activities of 2,4-dioxo-1-prop-2-ynylimidazolidin-3-ylmethyl esters in oil solutions were higher than those of known knockdown pyrethroids; three of the compounds also possessed strong knockdown and flushing-out activities against cockroaches.     

2-arylalkanoates,a new group of synthetic pyrethroid esters not containing cyclopropanecarboxylates

Although structure modifications of natural pyrethrin constituents have disclosed a variety of potent synthetic analogues, all known examples are cyclopropanecarboxylate esters, a grouping that appeared to be essential for insecticidal activity. Some new substituted 2-phenylalkanoates, whose biological activities are of a similar nature and potency to those of conventional pyrethroids, are now reported. 5-Benzyl-3-furylmethyl and 3-phenoxybenzyl 3-methyl-2-phenylbutyrates and their analogues are potent insecticides. Activity is increased on the introduction of appropriate groups into the 3 and/or 4-positions of the aryl ring and the (S)-2-phenylalkanoates are far more active than their (R)-enantiomorphs. Structure/activity relationships are compared with those for conventional pyrethroids. Some of the new series compare favourably with typical insecticides in tests against Musca domestica, Spodoptera litura and Plutella xylostella.     

Cytotoxic Effects of Fucoidan Nanoparticles against Osteosarcoma

In this study, we analyzed the size-dependent bioactivities of fucoidan by comparing the cytotoxic effects of native fucoidan and fucoidan lipid nanoparticles on osteosarcoma in vitro and in vivo. In vitro experiments indicated that nanoparticle fucoidan induced apoptosis of an osteosarcoma cell line more efficiently than native fucoidan. The more potent effects of nanoparticle fucoidan, relative to native fucoidan, were confirmed in vivo using a xenograft osteosarcoma model. Caco-2 cell transport studies showed that permeation of nanoparticle fucoidan was higher than native fucoidan. The higher bioactivity and superior bioavailability of nanoparticle fucoidan could potentially be utilized to develop novel therapies for osteosarcoma.     

A new pyrethroid of high insecticidal activity

New pyrethroids containing heterocyclic rings in the alcohol moieties were synthesised and their insecticidal activities were studied. Of these new pyrethroids, 3-benzylpyrrol-1-ylmethyl (1RS-cis, trans-3(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate was found to be the most effective, having higher activity than permethrin against Musca domestica by a topical application method. In addition, para-substituted analogues of the 3-benzylpyrrol-1-ylmethyl ester were also synthesised to study the substituent effects on insecticidal activities; the residual effects of these compounds against Blattella germanica were also examined.