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Molluscicidal activity of some Solanum species extracts against the snail Biomphalaria alexandrina

Molluscicidal activity of some Solanum species extracts against the snail Biomphalaria alexandrina

 

 

Gehad T. El-Sherbini 1*$, Rawia M Zayed2*, Eman T. El Sherbini ,3*

 

 

 

1Department of Parasitology, Faculty of Pharmacy, October 6 University Cairo (Formerly Sinai University), El Arish, Egypt

 2Department of Zoology, El Nahda University, Beni Sweif. Egypt

3Department of Pharmacognosy, Faculty of Pharmacy, Zagazig University.  Egypt

 

 

 

*These authors contributed equally to this work

§Corresponding author

 

 

 

 

Email addresses:

gody_55@yahoo.com           GTS:

               ETS: emanelsherbiny55@yahoo.com

            RZ: rawiazayed@hotmail.com

 

 

 

 

 

 

 

 

 

 

 

 

Abstract

Background

Snails' species are associated with transmission schistosomiasia and fascioliasis, and other parasitic disease as intermediate host. Biological control alone as a part of integrated snail management stands to be a better alternative to the chemical controls aimed against snails. The search of herbal preparations that do not produce any adverse effects in the non- target organisms and are easily biodegradable remains a top research issue for scientists associated with alternative molluscicides control.

Method

Solvent extracts of fresh mature leaves of S.nigrum, S. villosum, and S. sinaicum were tested against Biomphalaria alexandrina, a common intermediate host of schistosoma mansoni. A phytochemical analysis of chloroform: ethanol extract was performed to search for active toxic ingredient. The lethal concentration was determined

Objective of the study

The present study was designed to screen the toxic effect of snail molluscicidal activity extract isolated from matured leaves of Solanum negrum, Solanum sinaicum, and Solanum villosum against Biomphlaria Alexandrina snails, which are an intermediate host of parasites causing human schistosomiasis.

Results

Extracts isolated from mature leaves of Solanum species were found to be having molluscicidal properties. S. nigrum extract was recorded as the highest mortality rate. When the mortality of different solvent extracts was compared, the maximum (p<0.05) mortality was recorded at a concentration of 90 ppm of ethanol extract of S. nigrum.

Conclusion

Extract of mature leaves of S. nigrum exhibited molluscicidal activity followed by S. sinaicum and the less one was S. villosum. The study provides considerable scope in exploiting local indigenous resources for snails' molluscicidal agents

Background

The snails have the potential and lethal capacity to harm more than million victims a year around the world. Exploitation of the snail host is effectively accomplished by dramatic and dynamic changes in host survival, behaviour, defence immune function, nutrition, metabolism and reproduction [1].  Schistosomiasis is a parasitic disease that affects 200 million people in different countries; and frequently referred to as the second most important parasitic disease after malaria among the infectious diseases of tropical and subtropical countries, and the third most prevalent parasitic disease in the world in terms of overall morbidity burden, socio- economic and public health importance and human impact. Use of molluscicides to eradicate the snail vector is considered the method of choice to eliminate schistosomiasis [2]. Several different strategies have been used to control snail populations. Although praziquantel is available and generally very effective, the treatment is expensive and not always successful. [3,4]. In poor countries where schist soma is common, biological control of the snails that serves as intermediate host for schist soma and Fasciola, appears feasible and cost effective. Control of the intermediate host disrupts the life cycle of the parasite, stopping the transmission of infection. Synthetic organic molluscicides have been widely used for the effective control of harmful snails [5]. Today, it has been realized that these molluscicides are toxic to non- target animals and have a long –term detrimental effect on the aquatic environment [3, 6]. Medicinal plants represent the oldest and most wide spread form of medication known to man, and have become the focus of attention since they are less expensive and less hazardous to the environment than their synthetic counterparts [3]. For many centuries people have been trying to alleviate and treat diseases with different plant extracts and formulations [2].  The cost and toxicity of synthetic molluscicides, used in the intermediate snail hosts of snail- borne diseases, resulted in renewing the interest in plant molluscicides [5, 6].

Tropical plants have a long history of use in traditional medicine in many parts of the world, and to improve the efficacy of modern medical practice, researchers are increasingly turning their attention to folk medicine as a source of new drugs.

The leaves of many species of Solanum have molluscicidal properties and relatively little work has been carried out on this possibility and much more is necessary especially field trials. Before field trials are started, more laboratory testing is also necessary to determine the MLC50 values for different species and study toxicity to non- target organisms. The Species S. nigrum, known as, black night shade. Herbs, shrubs, trees, or vines, with or without spines, leaves alternate or paired and frequently unequal in size. Flowers, white, green yellow, pink, or purple. Fruit a berry, usually fleshy but occasionally dry, usually many- seeded, the seeds often flattened. Egyptian S. nigrum extracts were very effective at controlling intermediate host of parasites causing human schistosomiasis and fascioliasis [7]

Solanum villosum is a common weed known as red- fruit night shade; this is Ayurvedic herb with multiple medicinal properties [8]. Solanum siniacum plants are isolated from high land of Tin (wilderness) desert of North Sinai, these mountains, besides being rather rich in plant diversity; include many interesting elements not known from Egyptian mainland, or even in other region of Sinai. The aim of this study was to screen for molluscicidal activity, of, Solanum species against adult Biomephlaria  alexandrina snails and comparative study of the different degrees of toxicity of each species of genus Solanum.

Materials and Methods

Test snails

Species of intermediate snail host of intestinal schistosomiasis, Biomphalaria alexandrina were used in this study. Adult snails were collected from some irrigation canals in Giza and Dakahlia Governorate, The canals had not been previously treated with molluscicides. Uninfected snails, that is, those that did not show patent trematode infections, were maintained in the laboratory conditions for seven days before being used in our molluscicidal tests. Ten snails were then allocated to each of the groups and immersed in either untreated; dechlorinated tap water (control) or aqueous extract treated dechlorinated water. Preparations of the plant extracts and toxicity test protocols were adapted from those described by Brackenbury and Appleton in 1997[9, 10]

Plant material

The plants examined in this study were selected on the basis of ethnopharmacological information indicating their medical uses in schistosomiasis control in the endemic areas. The plant species were collected locally from their natural habitat. Leaves of the plants (Sollanum nigrum S. villosum, and S. sinaicum) were collected from Faiyoum, Giza, and Sinai during the four seasons from March 2008 to February 2009, and identified by a plant taxonomist.

The molluuscicidal activity against the snails was assessed to determine the toxicity and the degree of toxicity of leaves collected at various seasons.

 

 

Preparation and preservation of plant extracts:

One kilogram me(1kg) each of the air- dried plant leaves were ground into fine particles with a warring blender, and Soxhlet extracted twice, on each occasion with 2.5 litres of distilled water at room temperature for 24 hrs with shaking. The aqueous extracts were filtered through Whatman No 1 filter paper, then concentrated to dryness in vacuo under reduced pressure in a rotary evaporator at 30 + 1oC and freeze-dried, finally yielding powdery, crude aqueous extract of the plant leaves.

Preparation of plant extracts in different solvent systems

The plant extracts were prepared using five solvents, namely petroleum ether, benzene, chloroform: methanol (1:1, v/v), acetone and absolute alcohol, applying one after another (extraction period 72 hour for each solvent a temperature was <40oC). The extracts were collected separately and the column of the Soxhlet apparatus was washed with 200 ml of water and 100 ml of a similar solvent as an eluent after each type of solvent extraction procedure. The eluted materials and each type of extract were concentrated in combination at 40oC to 100 ml of extract by evaporation in a rotary evaporator. Then each of the extracts was filtered, solvents were evaporated and the solid residues were weighed and then dissolved in a suitable amount of sterilized distilled water for the formulation of graded concentrations. The total yield of each extract from 25 g of leaves was as follows: petroleum ether extract, 1.26 g, benzene extract, 2.38 g, chloroform: methanol (1:1, v/v) extract, 4,33 g, acetone extract, 3.00 g; and absolute alcohol extract 2.36 g. From the crude extracts, stock solutions of concentration series in gram per litre of water (1000 mg/L) were freshly prepared in distilled water. Different test dilute solutions, ranging from 10 to 1000 mg/L, (i.e ppm) were prepared from the stock solutions, using deionized and dechlorinated water, to determine the LD50 and LD90 values.

Molluscicidal activity tests:

Molluscicidal evaluation of the plant extracts were performed according to WHO guidelines [11]. Groups of 10 uninfected snails were placed in glass tanks (containers) with some sand, snail food and 1000 ml of deionized and dechlorinated pond or tap water bubbled with atmospheric air. Tests were carried out at room temperature (26+ 1oC). In each set up, the snails were prevented from crawling out of the glass container by means of a fine stainless steel mesh placed above the water surface. The test snails were challenged with various doses of the plant extracts (10,20,30,40,50,60,70,80,90,100,200,400,800,and 1000 mg/l{ppm}. After 24 hours of exposure to the plant extracts, the snails were transferred to fresh dechlorinated and deionized water and maintained there for another 24 hours. Death of the snails was determined and confirmed by the absence of heartbeat and lack of reaction to irritation of the foot with a blunt wooden probe to elicit typical withdrawal movements. Control solutions were also made with deionized and dechlorinated tap water. Control experiments were performed with deionised and dechlorinated water alone (negative control) or with niclosamide (Baylucide) (positive control). Moulliscicidal test with each plant extract dose was separately repeated three times. The snails were neither fed nor disturbed during the exposure and recovery periods. LD 50 and LD90 ( referring to the plant extract doses in ppm, that kill b 50% and 90% of the test snails respectively) were determined by the methods of [12] with 95% confidence limit. Plant extracts that causes no mortality at 1000 ppm were considered inactive and were not investigated further.

Results and discussion

 

In the present study, a species of solanum were screened for its moulluscicidal activity. Successive extracts of leaves were evaluated for their molluscisidal activity against B. alexandrina adult snails. The LC50, LC90 are listed for different extracts of Solanum species leaves (Table 2).

The present data revealed that ethanol extract of S. nigrum leaves showed the highest molluscicidal activity (LC90= 5.95 mg/l), followed by S. sinaicum (6.04mg/l) and S. villosum (8.95 mg/l). This similar to other data [13]. The richness of the flora in most areas of the world where snail transmitted diseases are endemic, probably suggests that many plants with molluscicidal properties remain to be discovered. Several promising plant molluscicides have been identified. Previous studies have shown that potency levels of plant samples vary significantly according to season and geographical location of the plants, such unpredictable trends in the potency of plant molluscicides militate, against their selection of control programme [14]. Over 100 species of Solanum are indigenous to Africa and several of these have been developed there ( Davidson ,1972)[15]. Several Solanum species of the family Solanaceae are widely used as leafy vegetables as source of fruits and medicine in different countries, In this study, S, nigrum, S. villosum, and S, sinaicum which in its features like S. nigrum were tested against B. alexandrina snail, the intermediate host of Schistosma mansoni. The present investigation showed the effect of exposure of the different concentration of the three species of Solanum against the snails, and the results were agree with some other results recorded by [7, 16, 17, and 8].

After exposure to the active plant extracts examined in the present study, the snails showed several behavioural responses, including the "distress syndrome" described for other planorbid species by [18, 19, 20, and 21] indicative of intoxication. Swelling of the tissues was not restricted to the tentacles, but involved the whole cephalopedal mass. According to [21], the inference from this observation is that the tissue of the cephalopedal mass had accumulated water, which caused haemorrhage at lethal concentration of the active plant extracts. Nevertheless the observation made in this study suggest that the toxic principles in the active plant extracts disturbed the permeability of the foot- sole surface epithelium by preventing its normal osmo-regulatory function [21]. The toxic effect of the sub lethal doses of the plant extracts were, however, reversible after exposure if the snails were moved to toxic extract – free water for a recovery period. This observation is in agreement with the findings of Herry and Aldrich (1963) [18], and Van Aardi and Coertze (1981) [20] for Bulnius tropicus and Biomphalaria after exposure to copper.

 

Conclusion

As in general, the results of solanum species extracts indicates that the three species share in possessing a molluscicidal activity against the snail B. alexandrina. In conclusion, it appears that the ethanol extract of Solanum species has a strong mollscicidal activity and it is most suitable for biological application which offers a simple, available locally, cheap and environmental safe molluscicidal agent of plant origin for controlling human schistosomiasis by killing the intermediate host snails. Also the use of plant molluscicides may not only eliminate the economic burden of importing expensive synthetic molluscicides, but could also stimulate growth of small-scale industries in developing countries. More emphasis must, however, be placed on agronomic and organization aspects, including community participation. If plant molluscicides are to be applied successfully in long – term and self- sustained snail control programmes

.

Competing interests

The authors declare that they have no competing interests

 

Author's contributions

GS conceived the idea, designed the experiments, train assistants for sample collection, interpreted the experimental results, and critical revision of the manuscript.

RZ carried out the laboratory bioassay experimentation and phytochemical analysis of the extract.

ES carried out the data analysis and assisted in the planning of the study

All authors contributed to manuscript preparation and approved the final manuscript.

 

Acknowledgments

We thank all the participants who shared their time for working on this study.

 

References

1. El- Ansary A, Sammour EM, and Mohamed AM: Susceptibility of Biomphalaria alexanrina to infection with Schistosmoa mansoni : Correlation with activity levels of certain glycolytic enzymes. J Egypt Soc Parasitol 2000, 30(2): 547-650.
2. Cowan MM: Plant product as antimicrobial agent. Clin Microbiol Rev 1999, 12:564-582.
3. WHO: The control of Schstosomiasis. WHO Technical Report Series, 1985, N0. 728.
4. WHO: The control of Schistosomiasis. WHO Technical Report Series, 1993, N0 830.
5. Clark TE, Appleton C, and Drewes SE: A semi-quantitave approach to the selection of appropriate candidate plant molluscicides. A South African application. J Ethnopharmacol 1997, 56(1): 1-13.
6. Massoud AM, and Habib FSM: The effect of Myrrh Commiphora molmol on the infected snails of Schistosmoa sp and their egg masses: Effect on shedding of cercariae and on snail fecundity. J Egypt Soc Parasitol 2003, 33(2): 585-596
7. Ahmed AH,and Ramzy RM: Laboratory assessment of the molluscicidal and cercaricidal activities of the Egyptian weed, Solanum nigrum L. Ann Trop Med Parasitol. 1997, 91(8): 931-937.
8. Edmonds JM, Chweya JA: Promoting the conservation and use of underutilized and neglected crop; Black Night Shades ( Solanum nigrum L) and related species. Rom: International Plant Genetic Resources Institute; 1977:40-46.
9. Barbosa FS, Mello DA: Acao molluscicida de plantas. Revista Brasileira de Pesquisas Medica e Biologia 1969, 364-370.

10.  Brackenbury TD, Appleton CC: Acute toxicity evaluation of the plant molluscicide Apodytes dimidiate (lcachinaceae, to Eisenia fetida (Oligochaetae) and Oreochromis mossambicus ( Cichilidae) in South Africa. Acta Tropica 1997, 63:1-14.

11.  WHO: Molluscicide screening and evaluation. Bull Wld Hlth Org 1965, 33:567-581.

12.  Leitchfield JT, Wilcoxon F: A simplified method of evaluating dose- effect experiment. J Pharm Expt Ther 1949, 96:99-113.

13.  Ahmed AH, Kamal IH, and Ramzy RM: Studies on the molluscicidal and larvicidal properties of Solanum nigrum L. leaves ethanol extract. J Egypt Soc Parasitol 2001, 31(3): 843-852.

14.  Brackenbury TD, Appleton CC, Kayonga L: Use of a plant molluscicide, Apodytes dimidiate, in a preliminary field trial in Kwazulu- Natal, South Africa. South Afric J Sci 1997, 93: 303-306.

15.  Davidson B: Africa: History of a Continent. Hamlyn, London, 1972,    320 - 322.

16.  Amer HA, Manal MAR: Molluscicidal and cercaricidal efficacy of Acanthus mollis and Its binary and tertiary combinations with Solanum nigrum and Iris pseudacorus against Biomphalaria alexanrina . J Egypt Soc Parasitol 2004, 34(3): 1041-1050.

17.  Ahmed AH and Singab AB: The molluscicidal effect of the ethanol extracts of two Egyptian plants. Solanum nigrum and Iris pseudacorus in single and combined treatments J Egypt Ger Zool 2004, (in press).

18.  Harry HW, Aldrich DV: The distress reaction to toxic concentrations of inorganic ions. Malacologia 1963, 1: 283-287.

19.  Sullivvan J, Cheng T: Heavy metal toxicity to Biomphalaria glabrata (Mollusca: Pulmonata). Annals New York Acad Sci 1975, 266: 437-444.

20.  Van Aardt WJ, Coertze DJ: Influence of copper sulphate on the water and electrolyte balance of the fresh water snail Bulinus tropicus. South Afric J Zool 1981, 16: 193-199.

1.   Brackenbury TD, Appleton CC: Structural damage to the foot-sole epithelium of Bulinus africanus following exposure to a plant molluscicide. Malacologia 1999, 41: 393-401.

 

 

 

Figures

 

    

 

                                

Fig.1- S.nigrum                 Fig.2- S.villosum        Fig.3- S.sinaicum

 

Tables

Table 1- The results of molluscicidal evaluation of the 3 plants examined

 

Plants

LD90 values for the snail used

1. Solanum nigrum
2. Solanum Sinaicum
3. Solanum villosum
4. Positive control ( Aqueous solution)

100 – 200 ppm

100 – 200 ppm

200 – 400 PPm

0.20 – 0.8 ppm

 

Key: 0.1- 10 ppm = very strong molluscicidal activity

         50-100 ppm = Moderate to strong

         100- 200 ppm= Mild to moderate

         200-400 ppm = Weak to mild

 

Table 2- Efficacy of different concentration of solvent extracts of leaves of solanaceae family.

 

Type of solvent

Activity (mg/liter) 24 hour

S. nigrum

S. Villosum

S. sinaicum

LC50

LC90

LC50

LC90

LC50

LC90

Pet. Ether

Chloroform

Acetone

Methanol

4.2

70.75

6.55

6.9

8.62

142.7

11.7

16.2

6.33

90.0

9.67

8.4

11.02

175.7

12.9

18.3

5.8

82.5

8.7

7.8

9.94

164.7

11.2

17.5

 

Table 3: Moliscicidal activity of S. species leave extracts against B. alexandrina 24 hrs after exposure.

 

Plant species

Type of extract

Activity (mg/Liter)

LC50

LC90

S. nigrum

S.sinaicum

S. villosum

Ethanol

Ethanol

Ethanol

2.98

3.19

4.88

5.95

6.04

8.95

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