GB2218337A - Stable acaricidal composition - Google Patents

Description

1 4 r? 221833, STABLE MITE KILLING PRODUCT This invention relates to a

new stable, amitrase containing product, that can be used to combat the bee parasite olte even after long storage.

Presently the bee-keepers use paper strips that contain the active ingredient (amitrase) adsorbed on the surface. Burning this strip the active ingredient will be released with the smoke and destroyes the mites. The problem is that the amitrase decomposes rapidly during the storage and the concentration of the released amitrase in the smoke is less than required. I'herefore these smoker-strips are useful only within a short time after of production. The shelf-life of the correctly dosed strips are very short. Also overdosing must be avoided, because it is noxious for the bees.

The mites are harmful parasites of plants, animals and humans. The mites belong to phillum Arthropodes, class Spiderformes and order Acarides. Their mass-population causes damage in plants or animals, but they are dangerous also to human 1 e.g. tick, ich-mitel.

The Varroa Jacobsoni fr-om lava causes presently heavy damage in honey-bee populations. This mite strongly reduces the number of bees in the colonies, or destroys theift totally resulting in a considerable loss in the honey production.

Amitrase ltriaside: C,.H..N,.1 is known as an excellent insecticide against mites. Its efficiency is generally over 90%. The bee-keepers use amitrase containing smoker-strips against Varroa Jacobsoni. The effective dose is around 15 mg amitrase on KNO, impregnated paper-strip per one colony of bees. Decreasing the dose decreases the effectiviy, increasing the dose of the amitrase results in noxious effect also to the bees. Therefore to ensure the exact dose is important.

The amitrase easily decomposes rapidly when distributed over a large surface on the paper-strip, its effectivity drops below the required level, therefore the shelf-life of the paper-strips marketed until now is less than the the acceptable minimum.

1 The process described in this invention aims to eliminate this problem: the amitrase 11,5-bis-(2,4-di-methyl-phenyl)-3-methyl-1,3,5-triaza-1,4.diene, a product of FBC Limited Hauxton, Cambridge/ is formulated with cyclodextrins. The formed crystalline inclusion complex, consisting of amitrase and cyclodextrin in molar ratio 1:2, is chemically stable and not sensitive to light and heat. The active ingredient content of the formulation is 14.0-14.3 % by weight (determined by UY-spectrophotometry). This product when distributed and fixed on the surface of paper-strips by any appropriate method results in long shelf-life, long stability without significant lost of biological effect.

Further details of the invention are illustrated by the following examples, without any limitation of our invention only to the given examples.

Example crP aqueous suspension of 22.7 g 10.02 moll 0-cyclodextrin was stirred at 22-C and 2.93 g 10.01 moll amitrase in 15 ciO ethanolic solution was added. The stiring of the suspension continued for 24 hours, then the product was filtered and dried. The yield was 25.0 g. The amitrase content was found to be 14..0-14.3 % in according to UV-spectrophotometry.

Example 2.

22.7 g /0.02 mol/ 0-cyclodextrin wetted with 3 cW3 of water was intensively mechanically ground with 2.93 g /0.01 moll amitrase for 30 min. The product is a fine white powder. The amitrase content is 12.0 Z. Heating the dry complex in a TAS pyrolytic equipment no amitrase release was detected below 160-C according to the TLC patterns.

Amitrase-lactose mixture was made of identical active ingredient content with that of the former two cyclodextrin complexes. All the three samples were stored in a thermostatate 60-C in open tubes over three weeks.

1 -11P The change of the active Ingredient content was determined by taking samples and analysing by HPLC method. The amitrase content of the amitrase 0-cyclodextrin complex showed no changes during the three weeks. The apparent amitrase content of' the amitrase-lactose mixture showed no significant drop during the first week, but after the tenth day a rapid active ingredient content loss was found. lliese results are summarized in Table 1.

Due to the presence of the diazapentadiene group the amitrase is sensible to UV light, but the cyclodextrin stabilizes the amitrase. AmitraseOcyclodextrin complex and amitrase-lactose mixture were stored wider 254 nm wave-length UW light and the decomposition of the acaricide was followed ill function of irradiation tire. The results are summarised in Table 2.

Example G,

5.0 g 0-eycl odext r Ln wat er soluble pol ymer (cross-linked wi t h epiclilorohydrin) was wetted with 5 cin3 water and 0.3 g CL mmol)anii'Lrase,&.n 2 em:' etlianolic solution was added, intensively mechanically grounded and dried. The amilrase content is 6%.

Example 4.

9.72 g (0.01 mol) a-cyclodextrin wetted with 2 em? of water was intensively mechanically ground with 1.47 g (5 mmol) amitrase I'or 30 min. The amitrase content is 15%.

Exerfsple 5.

2 x 9 em filter paper strips were impregnated with 10% sodium-n:ltrate solution and drLed. The amitrase-J3-cyclodextrin complex was suspended in an aqueous solution of appropriate adhesive materials le. g.dextrin, carboxymethyl-cellulose, polyvinyl-alcohol, polyvinyl pyrrolidone/ and this suspension was smeared on the surface of the impregnated filterpaper strips. After drying the strips each of them contained about 15 mg t 1 mg amitrase in molecularly encapsulated state, distributed uniformly over the full strip surface.

This amitrase containing smoker-strips were burnt in an about 2 dMP volume glass container, whose base was open, from the highest point smoke was continuously removed and bubbled through two ice cooled methanol filled gaswashing bottles to absorb the amitrase from the smoke. This methanolic soluzions were analysed by TLC, HPLC and UV spectrophotometry, respect ively. The ami trase was fdtrd to be complet ly released f rom t he complex containing smoker strips during the burning process.

The ainitrase-o-cyclodextrin inclusion complex can be used also in sprays. Adding 3% aerosil to the complex a microcrystalline, light. solid powder is formed that can be directly used as a dusting-powder.

By suspending in aqueous solution of nonionic tensides (surfactants) the amitrase-_cyclodextrin complex can be used as a wettable powder formulation.

i 1 i C 1 I i I i i L Table

The change of amitrase content of the amitrase-lactose mixture and amitrase-o-cyclodextrin complex upon storage at 60-C in open tubes.

Time Amitrase content lwlw41 /day/ in amitrase-lactose mixture in amitrase-o-cyclodextrin complex 0 14.26 14.14-14.30 3 14.80 15.09 13.93 14.96 7 16.10-10.02- 15.07 8. 24-'"1 15.20 14 4.8-6.2- 15.02 16 4.0--15.00 19 5.0-4.2-- 14.96 The high amitrase content is due to the inhomogeneity of the solid sample.

Thin-layer chromatography showed a series of decomposition products, and the color of samples turned from white to yellow.

Table 2.

The stability of amitrase-lactose mixture and amitrase-O-cyclodextrin complex upon storage under 254 nm wave-length UY light at 22-C.

Time Amitrase content lwlw%l /hour/ in amitrase-lactose mixture in amitrase-o-cyclodextrin complex 0 1 2 3 4 14.26 11.00 6.70 6.82 5.70 14.14 13.3 12.8 13.0 13.2

Claims (7)

1. The preparation of a stable amitrase formulation with cyclodextrin in aqueous solution or in an aqueous-organic solvent system.

2. Products which comprise ot--, or 0-cyclodextrin as host molecules.

Products which comprise water soluble 0-cyclodextrin polymer or ionic group containing water soluble 0-cyclodextrin polymer as cyclodextrin.

A product prepared according to claim 1. which comprise amitrasecyclodextrin inclusion complex, used in a smoke preparation by smearing the adhesive agent containing amitrase-cyclodextrin suspension onto material, e.g. filter-paper strips, impregnated with burning promoting materials.

S. Products according to claim 1. which comprise formulation of amitrase cyclodextrin inclusion complex inthe form of a wettable powder product.

6. Products according to claim 1. which comprise formulation of amitrasecyclodextrin inclusion complex used to a dusting powder product.

7. A^ amitrase - cyclodextrin formulation substanitally as hereinbefore described in any one of examples 1 to 5.

r"GUShOd 1989 atThe Patent Office, State House, 66/71 FEigh Holborn, LorLdonWCIR4TP. Further copies maybe Obtaloedftm The Patent oftice. Sales Branch, St Mary CrW Orpington, Kent BR5 3RD. Printed by Multiplex techniques ltd, St Mary Cray, Kent, Con_ 1187 i