Abstract
The bioactivity of the aqueous extracts of the leaf and stem bark of the medicinal plant, Alstonia boonei De Wild (Apocyanaceae), against the pink stalk borer, Sesamia calamistis Hampson (Lepidoptera: Noctuidae) was studied in a laboratory bioassay. The extracts were incorporated into artificial diet at a rate of 0.0% (control), 1.0%, 2.5%, 5.0%, and 10.0% (w/w). Both extracts significantly (P<0.01) reduced larval survival and weight in a dose dependent manner. The concentrations that killed 50% of the larvae (LC50) for the stem bark extract were 2.8% and 2.1% at 10 and 20 DAI (days after introduction), respectively, while those for the leaves extract were 5.6% and 3.5%. The weights of the larvae also varied significantly (P<0.05) between the treatments in a dose dependent manner. We conclude that both leaf and stem bark extracts of A. boonei are toxic, used as growth inhibitors to S. calamistis larvae, and hold good promise for use as alternative crop protectants against S. calamistis.
Keywords: Alstonia boonei, Extract, Sesamia calamistis, Toxicity, Growth inhibitors
INTRODUCTION
Alstonia boonei De Wild (Apocyanaceae) is a medicinal plant used extensively in West and Central Africa for the treatment of malaria, fever, intestinal helminthes, rheumatism, hypertension, etc. (Terashima, 2003; Betti, 2004; Abel and Busia, 2005). The major phytochemicals in the stem bark are saponins, alkaloids, tannins and cardiac glycosides (Fasola and Egunyomi, 2005). Despite its popularity as an aromatic plant, the insecticidal potential of A. boonei has not been investigated as has been done for other medicinal plants like neem, Azadirachta indica A. Juss (Maala et al., 2000; James et al., 2003; Bruce et al., 2004). The objective of the present study was to examine the insecticidal properties of the aqueous extracts of the leaf and stem bark of A. boonei against the pink borer, Sesamia calamistis Hampson (Lepidoptera: Noctuidae), a major pest of maize and some other cereals in West and Central Africa (Bosque-Perez and Mareck, 1990; Kfir et al., 2002).
MATERIALS AND METHODS
Fresh leaves and stem bark were collected once from A. boonei trees (about 15~20 m tall) along the Akure-Ifon Road, Ondo State, Nigeria, between October and December, 2005. This is the beginning of the dry season when the plant flowers and produces seeds. It is expected to have high concentration of secondary metabolites during this period. The leaves and stem bark were sun dried and ground to powder with an electric blender (SuperMaster®, Model SMB 2977, Japan). About 250 g each of the powders were extracted in the cold with about 300 ml of water in 1 L Schott Duran bottles for 72 h. The extracts were filtered through Whatman No. 1 filter paper and the extraction was repeated twice for maximum yield. The extracts were evaporated to dryness in a Gallenkamp Hotbox oven at 40 °C and kept in sealed glass vials until needed. The bioassay was done in the Insect Rearing Unit of the International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria. The dry extracts were incorporated into artificial diet for S. calamistis, made from cowpea and wheat germ flours (Jackai and Raulston, 1988), at a rate of 0.0% (control), 1.0%, 2.5%, 5.0%, and 10.0% (w/w). The treatments were dispensed into wells of a plastic tray (Bioserv®) and allowed to cool down and solidify under a microflow workstation. S. calamistis larvae were obtained from the colony in the Insect Rearing Unit at the IITA, Ibadan, Nigeria. They were maintained on the artificial diet for two generations. Two larvae (<12 h old) were introduced into each well of the assay tray containing the treated diet. Each plastic had twenty four wells and represented a treatment. The plastic tray was sealed with a perforated nylon sheet to allow for ventilation. There were three replicates. The treatments were arranged randomly in trays in the laboratory maintained at a temperature of (26±2) °C, (80±5)% relative humidity and 14 h:10 h (light:dark) illumination. Larval survival and weight were recorded at 10 and 20 d after introduction (DAI) from twelve wells per treatment. The fresh weight of the larvae was taken immediately after removal from the diet while the dry weight was taken after drying in the oven for 7 d at 40 °C. The concentration that killed 50% of the larvae (LC50) was calculated at 10 and 20 DAI using probit analysis while data on survival and weight were analyzed using the analysis of variance (ANOVA) (SAS System for Windows, Version 8.2). Means were separated with the Student-Newman-Keuls’ test.
RESULTS
The percentage survival of S. calamistis larvae reared on the treatments is shown in Table 1. The stem bark was more toxic than the leaf extract against the S. calamistis larvae. The LC50 of the stem bark extract was 2.8% while that of the leaf extract was 5.6% at 10 DAI. Table 2 shows the fresh weight of the larvae reared on the different treatments. There was a significant reduction in the weight of the larvae in a dose dependent manner by both extracts.
Table 1.
Mean survival (%) of S. calamistis larvae reared on artificial diet incorporated with extracts of A. boonei
| Concentration (%) | Larval survival (%) |
|||
| Stem bark extract |
Leaf extract |
|||
| 10 DAI | 20 DAI | 10 DAI | 20 DAI | |
| 10.0 | 0.00e | 0.00d | 16.67d | 6.25d |
| 5.0 | 29.17d | 16.67c | 64.58c | 50.00c |
| 2.5 | 62.50c | 50.00b | 83.33b | 66.67b |
| 1.0 | 83.33b | 75.00a | 95.83ab | 79.17ab |
| 0.0 (control) |
100.00a |
87.50a |
100.00a |
87.50a |
| LC50 (%) | 2.8 | 2.1 | 5.6 | 3.5 |
| 95% CL | 2.3~3.4 | 1.7~2.5 | 4.7~6.8 | 2.7~4.4 |
DAI: Days after introduction; Means followed by the same letters in the same column are not significantly different (P<0.05; Student-Newman-Keuls’ test). CL: Confidence limits
Table 2.
Mean fresh weight of S. calamistis larvae reared on artificial diet incorporated with extracts of A. boonei
| Concentration (%) | Mean larval weight (mg) |
|||
| Stem bark extract |
Leaf extract |
|||
| 10 DAI | 20 DAI | 10 DAI | 20 DAI | |
| 10.0 | − | − | 0.00d (8) | 0.00e (3) |
| 5.0 | 1.43d (14)* | 2.40d (8) | 1.29cd (31) | 10.30d (24) |
| 2.5 | 2.60c (30) | 29.50c (24) | 3.73c (40) | 30.70c (32) |
| 1.0 | 5.73b (40) | 94.50b (36) | 7.23b (46) | 87.40b (38) |
| 0.0 (control) | 25.46a (48) | 214.80a (42) | 25.46a (48) | 214.80a (42) |
Means followed by the same letters in the same column are not significantly different (P<0.05; Student-Newman-Keuls’ test); DAI: Days after introduction
Figures in parenthesis indicate the number of larvae weighed
DISCUSSION
The results of our study show that the aqueous extracts of the stem bark and leaf of A. boonei adversely affected survival and growth of S. calamistis larvae. Growth inhibition may result from toxicity or feeding deterrent properties of the extracts (El-Lakwah et al., 1996; Akhtar and Isman, 2004; Erturk, 2006). Since larvae reared on the 10.0% stem bark extract suffered 100% mortality and other doses of this extract caused lower larval survival than the leaf extract, A. boonei stem bark likely contains more potent compounds than the leaves. These substances may be antibiotic or antifeedant in nature (Verkerk and Wright, 1993; Kabaru and Gichia, 2001; Sadek, 2003). The insecticidal activity of A. boonei extract against Maruca vitrata Fabricius was reported by Oigiangbe et al.(2007), while McLaughlin et al. (1980), Raju et al.(1990), El-Lakwah et al.(1996) and Jeong et al.(2001) observed the bioactivity of other species of the Family Apocyanaceae against different insect species. Some chemical compounds of the indole alkaloid group (alstonine, porphine and astonidine) and triterpenoids have been identified from the bark of A. boonei (Phillipson et al., 1987; Anonymous, 1992; 2001). The insecticidal potential of these compounds has not been investigated or reported in literature. A bioassay-guided fractionation of these extracts will help to identify the compounds responsible for the activity observed in this study.
We conclude that the stem bark and leaves of the medicinal plant, A. boonei, contain insecticidal substances that have potential for use as alternative crop protectants against S. calamistis and most likely other pest species.
Acknowledgments
We thank Mrs. Aanu Aderanti, International Institute of Tropical Agriculture, Ibadan, Nigeria, for insect rearing.
Footnotes
Project supported by the Research Grant Committee of the Ambrose Alli University, Ekpoma, Nigeria
References
- 1.Abel C, Busia K. Alternative Medicine Review. 2005. An Exploratory Ethnobotanical Study of the Practice of Herbal Medicine by the Akan Peoples of Ghana (Ethnobotanical Study: Herbal Medicine in Ghana) p. 42. [PubMed] [Google Scholar]
- 2.Akhtar Y, Isman MB. Comparative growth inhibitory and antifeedant effects of plant extracts and pure allelochemicals on four phytophagous insect species. Journal of Applied Entomology. 2004;128(1):32–38. doi: 10.1046/j.1439-0418.2003.00806.x. [DOI] [Google Scholar]
- 3.Anonymous . Ghana Herbal Pharmacopoeia. Accra Ghana: The Advent Press; 1992. Monograph of Alstonia Bark; pp. 10–12. [Google Scholar]
- 4.Anonymous Earthnotes Herb Library. 2001. Ernestinar Parziale CH.
- 5.Betti JL. An ethnobotanical study of medicinal plants among the Baka Pygmies in the dja biosphere reserve, Cameroon. African Study Monographs. 2004;25(1):1–27. [Google Scholar]
- 6.Bosque-Perez NA, Mareck ZT. Distribution and composition of Lepidopterous maize borers in southern Nigeria. Bulletin of Entomological Research. 1990;80:363–368. [Google Scholar]
- 7.Bruce YA, Gounou S, Chabi-Olaye A, Smith H, Schulthess F. The effect of neem (Azadirachta indica A Juss) oil on oviposition, development and reproductive potentials of Sesamia calamistis Hampson (Lepidoptera: Noctuidae) and Eldana saccharina Walker (Lepidoptera: Pyralidae) Agricultural and Forest Entomology. 2004;6(3):223–232. doi: 10.1111/j.1461-9555.2004.00218.x. [DOI] [Google Scholar]
- 8.El-Lakwah FA, Hamed MS, Abdel-Latif AM. Effectiveness of Lantana camera and Nerium oleander extracts alone and in mixtures with two insecticides against Rhizopertha dominica (F.) Annals of Agricultural Science Moshtohor. 1996;34:1879–1905. [Google Scholar]
- 9.Erturk O. Antifeedant and toxicity effects of some plant extract on Thaumetopoae solitaria Frey. (Lep.: Thaumetopoeidae) Turkish Journal of Biology. 2006;30:51–57. [Google Scholar]
- 10.Fasola TR, Egunyomi A. Nigerian usage of bark in phytomedicine. Ethnobotany Research and Applications. 2005;3:73–77. [Google Scholar]
- 11.Jackai LEN, Raulston JR. Rearing the legume pod borer, Maruca testulalis Geyer (Lepidoptera: Pyralidae) on artificial diet. Tropical Pest Management. 1988;34(2):168–172. [Google Scholar]
- 12.James B, Caulibaly O, Gbaguidi B. New solutions for cowpea production in Africa. Pesticide News. 2003;61:12–13. [Google Scholar]
- 13.Jeong SE, Lee Y, Hwang JH, Knipple DC. Effects of the sap of the common oleander Nerium indicum (Apocyanaceae) on male fertility and spermatogenesis in the oriental tobacco budworm Helicoverpa assulta (Lepidoptera: Noctuidae) The Journal of Experimental Biology. 2001;204:3935–3942. doi: 10.1242/jeb.204.22.3935. [DOI] [PubMed] [Google Scholar]
- 14.Kabaru JM, Gichia L. Insecticidal activity of extracts derived from different parts of the mangrove tree Rhizophora mucronata (Rhizophoraceae) Lam. against three arthropods. African Journal of Science and Technology: Science and Engineering Series. 2001;2(2):44–49. [Google Scholar]
- 15.Kfir R, Overholt WA, Khan ZA, Polaszek A. Biology and management of economically important lepidopteran cereal stem borers in Africa. Annual Review of Entomology. 2002;47(1):701–731. doi: 10.1146/annurev.ento.47.091201.145254. [DOI] [PubMed] [Google Scholar]
- 16.Maala E, Kiiya W, Omollo P, et al. Participatory Evaluation of the Effectiveness of Locally Known Plant Extracts and Insecticides in Controlling Maize Stalk Borer. 2000 (Available from: http://www.kari.org/Legume_Project/Legume2Conf_2000/44.pdf)
- 17.McLaughlin JL, Freedman B, Powel S, Smith CRJr. Neriifolin and 2′ acetyl neriifolin insecticidal and cytotoxic agents of Thevitia thevetoides seeds. Journal of Economic Entomology. 1980;73:398–402. [Google Scholar]
- 18.Oigiangbe ON, Igbinosa IB, Tamo M. Bioactivity of extracts of Alstonia boonei (Apocynaceae) De Wild Stem Bark against Maruca vitrata (Lepidoptera: Pyralidae) Fabricius. Advances in Science and Technology. 2007;1(1):67–70. [Google Scholar]
- 19.Phillipson JD, O′Neill MJ, Wright CW, Bray DH, Warhurst DC. Plants as Sources of Antimalarial and Amoebicidal Compounds; Medicinal and Poisonous Plants of the Tropics: Proceedings of Symposium 5~35 of the 14th International Botanical Congress; July 24~Aug. 1 1987; Berlin. 1987. pp. 70–78. [Google Scholar]
- 20.Raju M, Thakur K, Maruthi RG. Sterilizing activity of the flower extract of Thevitia neriifolia on the male fifth instar nymph of red cotton bug, Dysdercus similis F. (Heteroptera: Pyrrhocoridae) Journal of Animal Morphology and Physiology. 1990;37:77–78. [Google Scholar]
- 21.Sadek MM. Antifeedant and toxic activity of Adhatoda vasica leaf extract against Spodoptera littoralis (Lep.: Noctuidae) Journal of Applied Entomology. 2003;127(7):396–404. doi: 10.1046/j.1439-0418.2003.00775.x. [DOI] [Google Scholar]
- 22.Terashima H. Names, use and attributes of plants and animals among the Ituri forest foragers: a comparative ethnobotanical and ethnozoological study. African Study Monographs. 2003;28(Suppl.):7–24. [Google Scholar]
- 23.Verkerk RHJ, Wright DJ. Biological activity of neem seed kernel extracts and synthetic azadirachtin against larvae of Plutella xyllostella L. Pesticide Science. 1993;37(1):83–91. doi: 10.1002/ps.2780370113. [DOI] [Google Scholar]