GB2112286A

GB2112286A - Extracts of acacia as algicides and molluscicides

Info

Publication number: GB2112286A
Application number: GB08135676A
Authority: GB
Inventors: Saad Mohamed Hussein Ayoub
Original assignee: Ciba Geigy AG
Current assignee: Novartis AG
Priority date: 1981-11-26
Filing date: 1981-11-26
Publication date: 1983-07-20
Also published as: GB2112286B

Abstract

A composition having an algicidal and molluscicidal action, which composition contains as active ingredient an extract of Acacia nilotica.

Description

SPECIFICATION Extracts of acacia as algicides and molluscicides The present invention relates to a composition having an algicidal and molluscicidal action, to a process for producing the composition and to the use thereof.

The mass increase of algae, particularly in inland waters, including reservoirs and irrigation canals, creates serious problems. It leads to the clogging of pipe lines, filter plants, locks and sluiceways. The movement and thorough mixing of the water are considerably impaired by the mass population, in consequence of which the oxygen balance of the waters is disturbed and conditions for swamp formation are created; transport on the water and fishing are rendered more difficult by the excessive growth of algae; and disease-carrying insects and molluscs find in the vegetation shelter and protection from natural enemies, and are more easily able to survive measures to combat them.Mechanical removal of the algae from the water requires a great amount of labour and is therefore expensive, so that the control of algae populations by the use of chemical agents is thus becoming increasingly important. This applies also to the combating of molluscs, especially of those which act as carriers or intermediate hosts of pathogens. To be mentioned here in particular is bilharziosis (schistosomiasis), a group of frequent and dangerous helminthic diseases which are prevelant in hot countries and which affect humans and other mammals.The eggs of parasites of the genus Schistosoma (Bilharzia) are excreted with the urine or excreta of the final host, that is to say, a human or other mammal, and if the eggs get into water, there develop from them miracidia, which then penetrate into water snails, and can further develop and multiply in these intermediate hosts. The fork-tailed larvae formed in the snails subsequently bore, after leaving the intermediate host, into the skin of the final host, enter the blood stream and develop into worms. Known intermediate hosts are for example water snails of the genera Biomphalaria and Bulinus, such as Biomphalaria glabrate, Biomphalaria pfeifferi, Bulinus obtusispira and Bulinus truncatus.

It is known that within some genera of plants, specific species contain constituents which have a molluscicidal action. Thus, for example, there is described in Helvetica Chimica Acta, Vol. 61, Fasc. 6, No. 187 (1978), 1990--1995, a molluscicidal activity of a bark extract of Cornus florida, the active agents able to be isolated being saponins. From J. Am. Chem. Soc. 101:15, July 18, 1 979, pp.

4398-4400, are known molluscicidally effective sesquiterpenoids from Warburgia ugandensis and Warburgia stuhlmanii. The presence of molluscicidally acting constituents in Phytolacca dodecandra is disclosed in Bull. WHO 42, No. 4 (1970), pp. 597-612, and Bull. WHO 47, No. 3 (1972), pp.

422-425.

It is the object of the present invention to provide a composition having an algicidal and molluscicidal action, the active ingredient of the composition being obtainable from vegetable material which is available on a large scale over wide areas of vegetation.

A further object of the present invention is to make available a process which can be used for producing a composition of the type claimed by subjecting the vegetable material to extraction, and which can moreover be put into practice also in those countries over which the plants supplying the raw material of the composition are distributed.

The present invention also relates to a process for combating algae and molluscs by application of the extracted vegetable material.

It has now been found that in the plantAcacia nilotica, which is known also by the name Sunt or Sunot, there are contained substances which can be extracted from the vegetable material and used for combating algae and molluscs.

The composition according to the invention is characterised therefore in that it contains as active ingredient an extract of Acacia nilotica.

The composition can contain the extract as the sole constituent, or together with suitable additives, for example dispersing agents, wetting agents, stabilisers or fungicides.

The genus Acacia belongs to the order Leguminosae, family Mimosaceae, subfamily Mimosoideae. Synonyms forAcacia nilotica are:Acacia arabica,Acacia scorploides, Mimosa nilotica, Mimosa arabica and Mimosa scorpioides.

The fruits of Acacia nilotica are formed as pods consisting of two valves, which enclose the seeds and which have small grains in their tissues.

The pods of Acacia nilotica have been used for example in the Sudan, one of the large regions of distribution of these plants, for a long time for medicinal purposes and are considered to be harmless both for humans and for animals.

The composition according to the invention preferably contains an extract of pods or of constituents thereof, leaves or bark of Acacia nilotica, particularly of the pods of this plant. The extract can be in a solid or liquid form, especially in the form of a powder.

The production of the composition according to the invention is characterised in that raw material of Acacia nilotica is extracted, by a single- or multistage process, with water, with an organic solvent, or with a mixture thereof. The raw material used can consist of pods or constituents thereof, leaves or bark of Acacia nilotica. The use of the fruit, that is to say, of the pods, as raw material has the advantage that the donor plant is not harmed, and that the obtaining and processing of the raw material requires little expenditure. The individual constituents of the pods, that is, the shells, grains and seeds, can also be processed separately, the active agent being contained in particular in the grains and in the shells. This procedure increases however considerably the effort required and hence reduces the profitableness of the production process.With the use of whole pods, that is to say, including the seeds, it can under certain circumstances be of advantage to add to the vegetable material an agent preventing infestation of the material by mould fungi, since the sugar-containing material present in the seeds can act as a nutrient medium for these microorganisms. Suitable additives are for example 1% of sodium fluoride or 1 % of sodium bisulfite with 0.5% of oxalic acid.

To produce the composition according to the invention, the pods ofAcacia nilotica are advantageously coarsely ground or crushed, or preferably milled or pulverised into the form of fine powder, and then extracted with suitable extraction agents. The extracts have a high tannin content.

When extraction is performed with water, it proves advantageous to use the water at a temperature within the range of 30 to 70"C, especially at 300 C. To be mentioned as suitable organic solvents with which the extraction can be performed are in particular ether, alcohol and acetone. In the case where extraction is carried out with a sequence of solvents, it is advantageous to use one consisting of petroleum ether, benzene, acetone, alcohol and water. The process according to the invention can be performed for example by extracting alternately with stagnation and with circulation of the liquid. It is shown to be advantageous to concentrate the resulting extraction product, especially by drying, particularly by spray drying.The process according to the invention can be carried out either as a singlestage process or as a multistage process. It is possible for example to extract the raw material in the first stage and separate the extract, and in the second stage to charge the raw material with fresh extraction liquid and to extract again. This procedure can be carried out either once or repeatedly. The extraction liquid, that is, the washing liquid, resulting from the second and optionally subsequent further stages, can be used as the extraction medium for a new batch with fresh raw material. Each further batch can be extracted with the washing solution from a preceding batch.

The production of the compositions according to the invention is further illustrated by the Exampies which follow.

EXAMPLE 1 Pods ofAcacia nilotica (water content 3.9%) are ground to powder. 200 g of the powder obtained are extracted in a Soxhlet extractor with petroleum ether (fraction 60--800C) for about 1 5 hours. After the petroleum ether has been distilled off, the powder is dried at room temperature, and extracted in the Soxhlet extractor for 1 5 hours with benzene. The benzene is distilled off, the powder is dried at room temperature, and extracted in the Soxhlet extractor for 1 5 hours with acetone. The acetone is distilled off, and the powder is dried at room temperature and extracted in the Soxhlet extractor for 1 5 hours with ethyl alcohol (95%). The alcoholic extract is concentrated under vacuum to about 80 ml.The residue remaining after the alcoholic extraction is dried at room temperature, and transferred to a 1 litre flask; 600 ml of distilled water are added, the mixture is left to stand for 24 hours and is subsequently filtered.

The starting material produced 7.90% by weight of bound oil in petroleum ether, 1.40% by weight of the total content of solids in the benzene extract, 77.30% by weight of the total content of solids in the acetone extract, 3.70% by weight of the total content of solids in the alcoholic extract and 4.85% by weight of the total content of solids in the aqueous extract.

EXAMPLE 2 Batch 1 A sack containing 6 kg of crushedAcacia nilotica pods is placed into an extraction apparatus provided with a back-flow line. The extraction vessel containing the sack is filled with 24 litres of water at a temperature of 300 C. After an extraction time of 30 minutes (stagnant phase), the extract is maintained in circulation for 30 minutes (circulating phase) by means of a pump with connection to the back-flow line. The extract is then fed from the extraction vessel into a collecting vessel, and a further 24 litres of water at 300C are fed to the pods remaining in the extraction vessel. After an extraction time of 30 minutes (stagnant phase), the liquid is circulated by means of a pump with connection to the back-flow circuit (circulating phase).After a circulation time of 30 minutes, the washing liquid is fed into a further collecting vessel.

Batch 2 After removal of the extracted pods of Batch 1, the extraction apparatus is again charged with 6 kg of crushed Acacia nilotica pods,-and this material is extracted in the manner described in the foregoing, the washing solution collected from Batch 1 being used as the extracting agent for the first one-hour extraction stage. In each case, 7 litres of the extract obtained in this batch are concentrated in a climbing-film evaporator under a vacuum of 260 mm Hg and a vapour pressure of 1.65 bars (24 psi) at 290C to 4.5 litres.Immediately after removal from the evaporator, the concentrate is filtered, and 4.5 litres of the liquid obtained, with a specific weight of 1.014 and a concentration of 12.1 0%, are dried in a spray dryer at a constant flow rate of 30 ml/min. and at a temperature of 12100, the drying time being 1 50 minutes. The powder obtained is separated from the hot gas by means of a cyclone separator, and collected in the collecting vessel of the separator. Powder residues in the spray-drying chamber are likewise conveyed to the collecting vessel. The batch yields 390 g of powder, the composition of the powder being shown in the following Table I.

Batch 3 After removal of the extracted pods from Batch 2, the extraction apparatus is again charged with 6 kg of crushed Acacia nilotica pods, and this material is further processed as described for Batch 2, the washing solution of Batch 2 being used as the extracting agent for the first one-hour extraction stage.

The condensate taken from the evaporator has a specific weight of 1.016 and a concentration of 12.20%, and spray drying yields 420 g of powder, the composition of which is given in the following Table Batch 4 After removal of the leached pods from Batch 3, the extraction apparatus is again charged with 6 kg of crushed Acacia nilotica pods, and this material is further processed in the manner described for Batch 2, the washing solution of Batch 3 being used as extracting agent for the first one-hour extraction stage. The condensate removed from the evaporator has a specific weight of 1.015 and a concentration of 12%. Spray drying yields 400 g of powder, the composition of which is shown in Table I.

TABLE I Composition of the Powder

Charge 2 3 4 tannins 56.4% 57.1% 56.8% non-tannins 36.4% 36.2% 36.7% water content 3.1% 2.9% 2.9% insoluble material 4.1% 3.8% 3.6% 100% 100% 100% pH of the solution examined 4.5 4.4 4.4 ash 1.9 2.1 1.8 nature of tannins mixture mixture mixture The powder is amorphous and is yellowish-white to light-brown in colour. It has a slight smell and the sharp taste of astringents.The powder is soluble in water, methanol and ethanol, and insoluble in ether, chloroform and benzene.

The compositions according to the invention are suitable both for combating molluscs and for combating algae, the process according to the invention for combating these organisms consisting of bringing the organisms to be combated in contact with a composition of the invention.

The use of the compositions according to the invention is further illustrated by the tests which follow.

Test 1 Specimens of the extracts obtained according to Example 1 are tested for molluscicidal activity against Bulinus truncatus and Biomphalaria pfeifferi by application of the test method of WHO (1 961) for the evaluation of novel molluscicides. In this test, 5 healthy snails of uniform size are placed into beakers each containing 500 ml of test solution at room temperature (20-25 C). The exposure time is 24 hours, followed by a 24 hours' recovery phase in ordinary water. In the following Table II are summarised the mean values from four test runs, based on the number of snails destroyed.

TABLE II A) Bulinus truncatus B) Biomphalaria pfeitteri

Extract Test Acetone Alcohol Aqueous ppm snail extract extract extract 200 A - ~ 5 B - 5 180 A - - 5 B 4 160 A - - 5 B - 4 140 A 5 5 5 B 5 5 2 120 A 5 4 5 B 5 5 0 100 A 5 2 3 B 5 5 0 80 A 5 1 0 B 5 3 0 60 A 4 0 0 B 4 1 0 - - not tested.

The petroleum ether extract and the benzene extract exhibit no activity.

Test 2 Powder (Batch 4) produced by the process described in Example 2 is tested, with application of the test method explained in Test 1, at varying concentration for activity against Bulinus truncatus and Biomphalaria pfeifferi. The results are shown in Table Ill.

TABLE Ill A) Bulinus truncatus B) Biomphalaria pfeifferi

Concentration Number of snails ppm Test snail destroyed 120 A 5 B 5 100 A 5 B 5 80 A 5 B 5 60 A 5 B 5 40 A 5 B 0 30 A 2 B 0 Whereas with the use of an aqueous extract 200 ppm are required for a 100% mortality of the snails (Table II), this effect is achieved with 60 ppm with use of powder. Compared with the aqueous extract, the powder has therefore a more than threefold greater activity against molluscs.

Test 3 A 2% aqueous solution is prepared from powder produced by the process described in Example 2 (Batch 4), and is left to stand for 5 days. The solution is subsequently tested, in the manner described in Test 1, for its effectiveness. The results are summarised in Table IV.

TABLE IV A) Bulinus truncatus B) Biomphalaria pfeifferi

Concentration Number of snails ppm Test snail destroyed 120 A 5 B 5 100 A 5 B 5 80 A 5 B 5 60 A 4 B 3 40 A 3 B 0 20 A O B O The results show that after a standing time of 5 days 80 ppm are sufficient to achieve 100% mortality.

The activity of extracts of Acacia nilotica against algae is tested in a layout of 30 ponds, as shown in Figure 1. The trough-shaped ponds have an excavated depth of 60 cm and are lined with a layer of polyethylene and provided with a 10 cm deep layer of silt. The surface diameter is 150 cm and the volume of water is about 6 m3. The ponds are arranged in three rows, the ponds of row K acting as control ponds, and those of rows I and ll as test ponds are separated from the control row by a path.

The ponds of row K are numbered 1-10, and this enumeration appiies also to the ponds of the rows I and II. In order to maintain a uniform ievel of water in the ponds, these are supplied with water by means of a suitable supply arrangement, as shown schematically in Figure 2.

The algae which can be effectively controlled with extracts ofAcacia nilotica include for example those of the species: Rivularia, Spirogyra, Oscillatoria, Pediastrum, Coelastrum, Spirulina, Chroococcus, Microcystis, Cyclotella, Euglena, Cosmarium and Closterium.

After the formation of an algae population in the ponds, the ponds of rows I and II are treated with the extract to be tested.

Test 4 An aqueous extract of Acacia nilotica, produced by the process described in Example 1, is added at various concentrations to the ponds of the rows I and II, and the time elapsing before the disappearance, that is, the decomposition, of the algae population is determined. The concentrations used and the results are given in Table V.

TABLE V

Pond Decomposition of the Added extract algae population, Row No. ppm days I 1 20 4 2 40 4 3 60 3 4 80 3 5 100 3 6 120 2 7 140 2 8 160 2 9 180 2 10 200 2 II 2 20 4 3 40 4 4 60 3 5 80 3 6 100 3 7 120 2 8 140 2 9 160 2 10 180 2 1 200 2 Test 5 The powder (Batch 4) produced by the process described in Example 2 is added at varioius concentrations to ponds of rows I and II, and the time elapsing before the algae population has decomposed is determined. The concentrations used and the results obtained are shown in Table VI.

TABLE VI

Pond Decomposition of the Added extract algae population, Row No. ppm days 1 1 20 3 2 40 2 3 60 1 4 80 1 5 100 1 6 120 1 7 140 1 8 160 1 9 180 1 10 200 1 2 20 3 3 40 2 4 60 1 5 80 1 6 100 1 7 120 1 8 140 1 9 160 1 10 180 1 1 200 1 Test 6 The powder (Batch 4) produced by the process described in Example 2 is added at various concentrations to the ponds of rows I and II, and the time elapsing until the algae population is decomposed is determined. The concentrations used and the results obtained are given in Table VII.

TABLE VII

Pond Decomposition of the Added extract algae population, Row No. ppm days 1 1 5 6 2 10' 6 3 15 5 4 20 3 5 30 3 6 40 2 7 50 1 8 60 1 9 70 1 10 80 1 II 2 5 6 3 10 6 4 15 5 5 20 3 6 30 3 7 40 2 8 50 1 9 60 1 1 80 1 The results summarised in the Tables V to VII show that in the case of treatment with an aqueous pod extract the destruction of the algae occurs with a concentration of 120 ppm within two days. The algae in this period of time become discoloured and decompose until they are no longer visible. This result can be achieved with spray-dried powder at a concentration of 50 ppm within one day.

Claims

1. A composition having an algicidal and molluscicidal action, which composition contains as active ingredient an extract of Acacia nilotica.

2. A composition according to Claim 1, which contains an extract from pods or constituents thereof, leaves or bark of Acacia nilotica.

3. A composition according to Claim 2, which contains an extract from pods of Acacia nilotica.

4. A composition according to any preceding claim, which contains the extract in solid or liquid form.

5. A composition according to Claim 4, which contains the extract in the form of a powder.

6. A process for producing a composition according to Claim 1 , wherein raw material of Acacia nilotica is extracted, in a single stage or in several stages, with water, an organic solvent, or a mixture thereof.

7. A process according to Claim 6, wherein the raw material used comprises pods or constituents thereof, leaves or bark ofAcacia nilotica.

8. A process according to Claim 7, wherein Acacia nilotica pods are used as raw material.

9. A process according to any of Claims 6 to 8, wherein the raw material is extracted with water.

10. A process according to Claim 9, wherein extraction is performed with water having a temperature within the range of 30 to 70cm.

11. A process according to Claim 10, wherein extraction is performed with water at a temperature of300C.

12. A process according to any of Claims 6 to 8, wherein the raw material is extracted with an organic solvent.

13. A process according to Claim 12, wherein the raw material is extracted with ether, alcohol or acetone.

14. A process according to any of Claims 6 to 8, wherein the raw material is extracted with a sequence of solvents, consisting of petroleum ether, benzene, acetone, alcohol and water.

1 5. A process according to any of Claims 6 to 8, wherein extraction is performed alternately with stagnation and with circulation of the liquid.

1 6. A process according to any of Claims 6 to 15, wherein the extraction product obtained is concentrated.

1 7. A process according to Claim 16, wherein the extraction product obtained is dried.

1 8. A process according to Claim 17, wherein the extraction product obtained is spray dried.

1 9. A process for combating molluscs, which process comprises bringing the organisms in contact with a composition according to any one of Claims 1 to 5.

20. A process for combating algae, which process comprisesd bringing the organisms in contact with a composition according to any one of Claims 1 to 5.

21. A composition according to Claim 1 substantially as hereinbefore described with reference to any of the foregoing Examples.