Argentine plants as potential source of insecticidal compounds

Journal of Ethnopharmacology 67 (1999) 219 – 223 www.elsevier.com/locate/jethpharm

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Argentine plants as potential source of insecticidal compounds Adriana M. Broussalis a, Graciela E. Ferraro a, Virginia S. Martino a,*, Roberto Pinzo´n b, Jorge D. Coussio a, Jairo Calle Alvarez b a

Ca´tedra de Farmacognosia, IQUIMEFA (UBA-CONICET) Facultad de Farmacia y Bioquı´mica, Uni6ersidad de Buenos Aires, Junı´n 956, 1113, Buenos Aires, Argentina b Facultad de Quı´mica y Farmacia, Uni6ersidad Nacional de Santa Fe de Bogota´, Bogota, Colombia Received 12 May 1998; accepted 18 November 1998

Abstract CH2Cl2 and MeOH extracts of 15 Argentine plants used locally as insecticides, were evaluated for their insecticidal activity. Chenopodium multifidum L. (Chenopodiaceae); Fla6eria bidentis (L.) O.K. (Compositae); Aristolochia argentina Gris. (Aristolochiaceae) and Tagetes erecta L. (Compositae) showed a significant activity against Sitophilus oryzae. © 1999 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Insecticidal activity; Argentine plants; Potential source

1. Introduction Plants would already be extinct if they had no defence against insects. Secondary metabolites are an important part of the defence barriers against insects (Luthria et al., 1993) Over 2000 species of plants are known to possess some insecticidal activity (Klocke, 1989). In many cases the plants have a history of usage as folk remedies and are still used to kill or repel insects.

* Corresponding author.

Extensive surveys on plants used as insecticides can be found in the literature. For example, Secoy and Smith (1983) made a compilation of plants used for control of various agricultural and household pests. Jacobson (1982) in his extensive discussion about plants, insects, man and their interrelationships classified physiologically active plant compounds into six groups; attracting, repelling, killing, sterilising, inhibiting insect growth or development and antifeedants. Oil extracted from various parts of Tagetes minuta L. (Mexican marigold) (Asteraceae) are used in the Tropics as a dressing for livestock to control blowfly. The ( terthienyl (2,2%:5%,2%%-terthio-

0378-8741/99/$ - see front matter © 1999 Elsevier Science Ireland Ltd. All rights reserved. PII: S 0 3 7 8 - 8 7 4 1 ( 9 8 ) 0 0 2 1 6 - 5

A.M. Broussalis et al. / Journal of Ethnopharmacology 67 (1999) 219–223

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Table 1 Plants tested for toxicity against S. oryzae Number

Scientific name

Common name

Plant part

1 2 3

C. multifidum L. (Chenopodiaceae) S. pinnata (Lam.) O.K. (Compositae) F. bidentis (L.) O.K. (Compositae)

Aerial part Aerial part Aerial part

4 5 6

A. argentina Gris. (Aristolochiaceae) Eupatorium buniifolium H. et A. (Compositae) Wedelia glauca (Ort.) Hoffm. (Compositae)

7 8 9

Porophylum obscurum (Spr.) D.C. (Compositae) Ipomoea descolei O’ Donell (Convolvulaceae) Heliotropium curassa6icum L. (Boraginaceae)

Paico, paiquillo Matapulga, canchalagua Contrayerba, matagusanos, baldal Charruga, charrua Romero, romerillo Asolador, matasapo, clavel amarillo Yerba del venado, cominillo Zapallo´n de Misiones Cola de gama

10 11 12 13 14 15 16

Pterocaulon purpurascens Malme´ (Compositae) Acanthospermum australe (Loef) O. Kzc (Compositae) Spilanthes stolonifera D.C. (Compositae) Gamochaeta simplicicaulis (Willd.) Cabr (Compositae) B. orellana L. (Bixaceae) T. erecta L. (Compositae) V. baccifera a (Guttiferae)

Moo maaning aawa Naitu´, tapecue´, yerba de la oveja Umpe´ sanesanelet Plan kachu´ Orucu´, axiote, bicha Virreina Lancillo

a

Aerial part Aerial part Aerial part Aerial part Aerial part Leaves and flowering parts Aerial part Aerial part Aerial part Aerial part Aerial part Aerial part Aerial part

Used as positive control.

phene) present in the oil has been identified as the active phototoxic compound against mosquitoes. Its high level of activity makes possible its commercialisation as a mosquito larvicide (Klocke, 1989). Some Aristolochia species have been reported to possess insecticidal and repellent activity. For example A. clematitis, used as insect repellent, A. grandiflora used against flies and maggots (Secoy and Smith 1983) and A. bracteata, the extracts of which showed a clear activity against mosquitoes (Anopheles arabinensis, Culex quinquefasciatus and Aedes aegypti ) (Zarroug et al., 1988). Phytochemical studies have been reported for A. argentina (Priestap 1969). Aristolochic acid present in all these species has been reported to produce sterility in Triboleum castaneum (Jacobson, 1982). The finding of new insecticides is of great economic interest both from the agronomic and preventive medicine point of view and the renewed interest in natural products as source or models of new insect controlling agents led us to investigate the insecticidal activity of 15 plants growing in Argentina (Table 1). For the present study plants were selected according to their local use as insect

controller or insecticide. Ten of the plants belong to the Compositae family, which has been repeatedly reported as containing insecticidal compounds. Pyrethrins, isolated from the dried flowers of Chrysanthemum cinerariaefolium (Compositae) is a good example (Secoy and Smith 1983). Some other native species of the genus Tagetes and Aristolochia have been included in this screening based in the previous finding of insecticidal activity in other members of this genus. Fla6eria bidentis (L.) O.K. commonly known as ‘matagusanos’ or ‘contrayerba’ or ‘baldal’ by the Araucan Indians is used as external insecticide. Schkurhia pinnata (Lam.) O.K. twigs are put below beds or among clothes for repelling insects, particularly fleas. Bixa orellana L. ‘orucu´’, ‘axiote’ or ‘bixa’ provides a colouring matter that was used by Nature Americans of Peru´, Brazil and Venezuela, not only for colouring their faces and bodies but also as a protection against mosquito bites (Ricciardi and Esquivel, 1986). Taking into account that the number of insect species in the world is about 3 000 000, selection of appropriate insect species for screening assay must be established on a good basis (Kubo, 1991).

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Table 2 ANOVA MeOH 1%

MeOH 5%

CH2Cl2 5%

CH2Cl2 1%

df

MS

F

df

MS

F

df

MS

F

df

MS

F

Between plants Within replics

15 16

1037 48.81

21.24

15 16

716.4 14.54

49.28

14 15

2022 34.12

59.27

15 16

1603 24.38

65.76

Total

31

31

The reason of the selection of S. oryzae for the present screening is based on its economic importance. S. oryzae is a serious pest in South America which destroys stored wheat, rice and sorghum grains, producing a rise in the temperature and the humidity intergrains, that quickens the propagation of moulds and bacteria with the consequent contamination with metabolic products (King and Sannders, 1984). In the present study dichloromethane and methanol extracts of 15 Argentine plants (Table 1) were tested at two different concentrations, (1 and 5 % P/V), for their insecticidal activity on S. oryzae.

29

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2.3. Assayed extracts The extracts were dissolved in acetone at two different concentrations (5 and 1% P/V) for application in the contact test.

2.4. Insect assayed Insects (S. oryzae L.) were provided by Laboratorio de Fitoquı´mica, Departamento de Farmacia, Universidad Nacional de Santa Fe de Bogota´. Young adult insects were used for the assays. Insects were fed with maize (Zea mays) var. porva yellow and incubated under controlled conditions of temperature (25°C) and humidity (75%).

2. Materials and methods

2.5. Contact bioassay 2.1. Plant material The plant material was collected in different regions of Argentina and was identified by Ing. Agr. Gustavo Giberti. Voucher specimens are deposited in the Herbario del Museo de Farmacobota´nica, Facultad de Farmacia y Bioquı´mica, Universidad de Buenos Aires.

2.2. Preparation of the extracts Powdered aerial parts of each plants (11 g) were successively extracted three times by maceration, with CH2Cl2 and MeOH for 24 h. The extracts were taken to dryness under vacuum.

A contact bioassay was used to test the toxicity of the plant extracts. Each concentration of the extracts was applied on the bottom of a glass Petri dish (9 cm diameter). After evaporation of the solvent, 15 young adults of S. oryzae were introduced into the dish. Two replicates for each concentration were made. Observations of the assay were made at 8, 10, 24, 36, 60 and 95–100 h since the beginning of the experiment. Mortality was calculated by counting the number of dead beetles between 95–100 h which marks the end of it, with exception of methanolic and dichloromethane extracts of A. argentina. Insects were observed under an optical microscope and mortality was determined

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Fig. 1. Mortality produced by extracts of argentine plants on S. oryzae in the contact bioassay.

when they did not respond to mechanical stimulation. Control dishes with CH2Cl2, MeOH, acetone and without solvent were used.

2.6. Statistics The ANOVA followed by Dunnet test for statistical analysis of data were used. Percentage of mortality values were submitted to angular transformation (y=arc sen x %) before ANOVA test (Table 2)

3. Results and discussion Data of % of mortality for different extracts of 15 medicinal selected Argentine plants are given in Fig. 1. No statistically significant difference was found between positive control (Vismia baccifera ) and A. argentina CH2CI2 extracts (1 and 5%). These extracts were the most active and produced mortality at 60 h from the beginning of the experiment. A. argentina’s activity is consistent with data in the literature reporting insecticidal activity in other species of the same genus. On the other hand a value over 50% of mortality

.

has been considered promising in studies of insecticidal activity of plant extracts .Taking in account this value, CH2Cl2 extracts of Chenopodium multifidum (5%), Tagetes erecta (5%) and MeOH extracts of F. bidentis (5%), A. argentina (5%), can be considered promising for further studies on the insecticidal activity. Values just below the lower limit of significant activity were obtained in the following extracts: A. argentina MeOH 1%, C. multifidum MeOH 5%, B. orellana MeOH 5% and CH2Cl2 5% and F. bidentis CH2Cl2 1%. The reason of using new natural pesticides is that these are active at highly acceptable levels, biodegradable and do not leave toxic residues while the commonly phosphorous and chlorinated insecticides contaminate the environment. Besides, both organic and familiary subsistence farming, this last a common practice of far rural population in our country could be greatly benefited with the use of plant extracts for the insect control. This preliminary screening is a good mean of evaluation of the potential insecticidal activity of plants popularly used for this purpose. The results obtained in it indicate that further assays are worthwhile. Phytochemical analysis on the active extracts is also in progress.

A.M. Broussalis et al. / Journal of Ethnopharmacology 67 (1999) 219–223

Acknowledgements The authors would like to tank the Programa Iberoamericano de Ciencia y Tecnologı´a para el Desarrollo (CYTED) for granting the support of this work and Ing. Agr. Gustavo Giberti for collection and classification of plant material.

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