Tropical Journal of Pharmaceutical Research Pharmacotherapy Group, Faculty of Pharmacy, University of Benin, Benin City, Nigeria ISSN: 1596-5996 EISSN: 1596-9827 Vol. 8, Num. 2, 2009, pp. 139-143

Tropical Journal of Pharmaceutical Research, Vol. 8, No. 2, June 2009, pp. 139-143

Research Article

Abiodun Falodun¹, R Siraj², Muhammad Iqbal Choudhary ²

¹ Department of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Benin, Benin City 300001, Nigeria,
² H.E.J. Research Institute of Chemistry, International Center for Chemical Sciences, University of Karachi, Karachi 75270, Pakistan
³ *Corresponding author: Email: faloabi25@yahoo.com; Tel: +234-(0)8073184488

Received: 20 September 2008 Revised accepted: 28 December 2008

Code Number: pr09019

Abstract

Purpose: Insecticides have been known to cause serious toxicological and environmental problems. Hence, the insecticidal activity and chemical composition of a local medicinal plant was investigated.
Methods: Steam distillation of P.staudtii leaves was carried out using a Clavenger apparatus in order to obtain the volatile oils. Gas chromatography/mass spectrometric (GC/MS) analyses (DB-5 Optima-5 column) of the essential oil were performed and its insecticidal activity determined.
Results: GC-MS spectrometry showed that the major chemical components of the oil were tetradecanoic acid (22 %), hexanoic acid, α-phellandrene (13 %), and citronellol sp. (7 %). The work also revealed significant insecticidal activity of 80 % and 60 % against Rhyzopertha dominica and Tribolium castaneum, respectively.
Conclusion: The study established the chemical composition and insecticidal activity of the essential oil of the plant leaf. Future formulation studies, toxicity profile and possible mechanism of action may lead to the development of a potential insecticidal product.

Keywords: Pyrenacantha stautii leaf, GC-MS, Leaf essential oils, Insecticidal.

Introduction

The tropical rainforests provide a lot of medicinal plants with potential medicinal properties but the ethno-and phytopharmaceuticals of these plants have not been fully exploited¹ . Their potential medicinal importance is due not only to the species richness of the tropical flora, but also to the diversity of pathogens, parasites and herbivores against which the plants must provide defensive mechanism. Many of the defense chemicals secreted, because of their metabolic precision, can be used to treat humans and prevent or eradicate other organisms²

The invasion of food products by insects and moulds contribute greatly to the loss of quality and quantity. Chemicals and fumigants play a vital role in controlling this problem but they have been known to cause serious toxicological and environmental problems, with the consequent carcinogenic effect on man³. The use of plants as an alternative in controlling insects is attracting attention from scientists’ worldwide probably due to the non toxicity, affordability and availability of the products³.

The plant Pyrencanatha staudtii belongs to the family Icacinaceae and it is a woody climber with green influorescent flowers. The leaves have various therapeutic uses in traditional medicine as a remedy against dysmenorrhoea, malaria, cancer, intestinal colic, miscarriage and ulcer^4-6. Scanty phytochemical information on this plant exists. However, extensive information about the morphology, ethnomedicine, karyology and ecogeographic differentiation of the genus has been accumulated^7-8.

The current study is aimed at characterizing the chemical components and insecticidal activity of the essential oil of P.staudtii leaf. Therefore, we report for the first time the separation and identification of the components of leaf essential oils with the aid of GC-MS and other spectroscopic techniques.

Experimental

The fresh leaves of the plant were collected in Benin City. Botanical authentification was done at the Forest Research Institute of Nigeria (F.R.I.N., Ibadan), where a herbarium specimen No. FHT 107624 was deposited.

Extraction and isolation of essential oil

Fresh leaves of Pyrenacantha staudtii were obtained in April, 2008. The plant was dried at room temperature, powdered and hydrodistilled for 6 h in a Clavenger apparatus. The oil was dried with anhydrous Na2SO4 to remove moisture. The fraction obtained was stored in a refrigerator at -4^oC until use.

Identification of the components

The identification of the chemical constituents was assigned on the basis of comparison of their retention indices and mass spectra with those given in the literature^9-12.

Gas chromatography

Quantitative and qualitative data were determined by GC and GC-MS, respectively. The oil was injected onto a Shimadzu GC-17A system, equipped with an AOC-20i autosampler and a split/ splitless injector. The column used was an DB-5 (Optima-5), 30 m, 0.25 mm i.d., 0.25 µm df, coated with 5 % diphenyl-95 % polydimethylsiloxane, operated with the following oven temperature programme: 50 °C, held for 1 min, rising at 3 °C/min to 250 °C, held for 5 min, rising at 2 °C/min to 280 °C, held for 3 min; injection temperature and volume, 250 °C and 1.0 µl, respectively; injection mode, split; split ratio, 30:1; carrier gas, nitrogen at 30 cm/s linear velocity and inlet pressure 99.8 KPa; detector temperature, 280 °C; hydrogen, flow rate, 50 ml/min; air flow rate, 400 ml/min; make-up (H2/air), flow rate, 50 ml/min; sampling rate, 40 ms. Data were acquired by means of GC solution software (Shimadzu).

Gas chromatography-mass spectrometry analysis

Agilent 6890N GC was interfaced with a VG Analytical 70-250s double -focusing mass spectrometer. Helium was used as the carrier gas. The MS operating conditions were: ionization voltage 70 eV, ion source 250 0C. The GC was fitted with a 30 m x 0.32 mm fused capillary silica column coated with DB-5. The GC operating parameters were identical with those of GC analysis described above.

Insecticidal activity

The materials used include test insects (Tribolium castaneum and Rhyzopertha dominica), ethanol (99%), standard insecticide (Permethrin), Petri dish (9 cm diameter), micropipette (1000 µl), growth chamber, test sample, filter paper, glass vials, brush.

The insecticidal property of P. staudtii essential oil was investigated against Rhyzopertha dominica and Tribolium castaneum in comparison with commercial insecticide Permethrin and ethanol (negative control). In evaluating the insecticidal activity of the volatile oils, a preliminary test was carried out in which several doses, ranging from those having no killing effect on the experiment population to those with a minimum of 100 % killing of this population, were assessed. Using a micropipette (Rainin magnetic assist), the precise volume (2 mL) of essential oil was added to ethanol (2 mL) (negative control) and diluted to 5 mL. From this, 0.5 mL of solution was uniformly applied to a 9 cm disk of filter paper (Whatman No.1) and placed in a Petri dish. Insects used for the test were reared in glass jars at 27 ± 1^oC and 60 ± 5% relative humidity (RH) at the laboratory of the H.E.J Research Institute of Chemistry in Karachi, Pakistan.

Statistical analysis

Data are expressed as means ± s.e.m. Statistical analysis was by one way analysis of variance (ANOVA) and Student’s t –test, using SAS 1994, Version 8.2 (SAS Institute, Inc., Cary, NC, USA). The statistical level of significance was p<0.05.

Twenty adult insects, less than 1 month old, were introduced into the dish 5 min later and the dish was covered. A control with ethanol alone (2 mL) was made. For each preparation, five replicates were made. The number of dead insects was determined 24 h after application. Mortality (%) was calculated as in Eq 1.

Results

The chemical composition of the leaf essential oil of P. staudtii is presented in Table 1. The yield of the essential oil was 1.40 (w/w) %. It was found to be a mixture of mono-and sesqui-terpenoids, and fatty acids. A total of 19 components were identified by their retention indices RI, as well as by GC-MS and other spectroscopic techniques, accounting for 95 % of the oil. Six (6) of the components accounted for the 80 % of the oil (Table 1). The oil comprised of fatty acid derivatives (52 %), sesquiterpene hydrocarbons (32 %) caroyphyllene (6 %), and oxygenated sequiterpenes such as carophylene oxide (5 %). Monoterpenes hydrocarbons such as phallenden (12 %), pinene (2 %), thujene sp. (2 %), terpinene (4 %) were also present in the essential oil. Hexadecanoic (30 %) and tetradecanoic (22 %) acids were major components. The essential oil showed 80 and 60 % insecticidal activity, respectively, (see Table 2) against Rhyzopertha dominica and Tribolium castaneum.

Discussion

The insecticidal activity of the essential oil would be dependent on the active chemical constituents and the gross sensitivity of the target pest to the active chemical principles¹³. The volatile oil of P. staudtii contains limonene which is reported to be an active insecticidal constituent, that exerts a toxic effect on Coleopterans¹⁴. The insecticidal activity can be explained, in part, by the high concentration of fatty acids and minor components such as limonene and phallendrene. Thus, the large proportion of fatty acids might have contributed to the activity of the oil against Rhizopertha dominica. This is because, hexadecanoic acid is known to possess a variety of medicinal and pharmacological properties, such as larvicidal effect, on Plasmodium falciparum¹⁵, and a sex pheromone¹⁶.

Pesticides are used extensively in agricultural farms, homes and other public places. Resistance to one or more pesiticides has occurred in most major pest species. Relentless development of resistance is a serious threat to the future use of these materials, and consequently, there is an urgent need to develop affordable, safe and sound pest control agents and techniques. The essential oil of P. staudtii demonstrated some potentials as a new plant insecticide.

Conclusion

We have determined the chemical composition of the essential oil of leaf of P. staudtii leaf by a GC-MS analysis, and have evaluated its insecticidal activity. The results showed that the essential oil was active against the two insects -Tribolium castaneum and Rhyzopertha dominica -tested. However, further studies will need to be undertaken to ascertain fully its bioactivity, toxicity profile, effect on the ecosystem and agricultural products. This will help to establish the synergistic effect of mono-and sesquiterpene hydrocarbon components of the essential oil and its suitability as an insecticide.

Acknowledgements

The authors are grateful to Third World Academy of Sciences (TWAS) and International Center for Chemical and Biological Sciences (ICCBS) for a Postdoctoral Fellowship Award to A.F. The interest and support of Professor E.O.P. Agbakwuru, formerly of the University of Benin, is gratefully acknowledged.

References

1. Baladrin MF, Kinghorn AD, Farnsworth NR. Plants derived natural products in drug discovery and Development. In Human medicinal Agents from Plants, Symposium Series 534, Baladrin MF (Ed.). American Chemical Society, Washington DC. 1993, pp 2-12.
2. Farnsworth NR. Screening Plants for New Medicines. In Biodiversity. Wilson EO, Peter FM (Eds.) National Academy Press, Washinghton DC 1988, pp 83 – 96.
3. Atta-ur-Rahman, Choudhary MI, William, JT. Bioassay techniques for drug development. Harward Academic Publisher, 1997, pp 67-68.
4. Aguwa CN, Okunji, CO. Gastrointestinal Studies of Pyrenacantha staudtii Leaf Extracts. Eur. J. Pharmacol. 1986; 15 : 45 -55.
5. Gill LS. In: Gills, L.S.(Ed.), Ethnomedical Uses of Plants in Nigeria. Uniben Press, 1992; p. 143.
6. Mesia Gk, Tona Gl Penge O, Lusakabanza M, Nanga TM, Cimanga RK, Apers S Van Miert S, Totte J, Rieters L, Vlietinck AJ. Antimalarial Activities and Toxicities of Three Plants Use in the Democratic Republic of Congo: Croton Mubango, Nauclea pobeguinii and Pyrenacantha staudtii. Ann. Trop. Med. Parasitol. 2005; 99(4): 345 -7.
7. Falodun A, Usifoh CO, Nworgu ZAM. Phytochemical and active column fractions of Pyrenacantha staudtii leaf extract on isolated rat uterus. Pak.J. Pharm. Sci. 2005; 18(4) 31 -35.
8. Falodun A, Usifoh CO. Isolation and Characterization of 3-carbomethoxypyridine from the leaves of Pyrenacantha staudtii (Hutch and Dalz). Act. Pol Pharm Drug Res. 2006; 63 (3) 235 -237.
9. Adams RP. Identification of Essential oils by Gas Chromatography Quadrupole Mass Spectrometry. Allured Publishing Corpoartion, Carol Stream, USA, 2001.
10. Adams RP. Identification of Essential oils by Ion Trap Mass Spectroscopy. Academic Press, New York, 1989.
11. British Pharmacopoeia. H.M. Stationary Office , London, II, P.A. 1980, p 109.
12. Julain D, Konig WA. The atlas of spectral data of sesquiterpene hydrocarbons. Verlag, Harburg, 1988.
13. Obeng OD, Reichmuth C, Bekele J, Hassanali A. Biological Activity of 1,8 cineole, a major component of essential oil of Ocimum kenyense (Ayobengina) against stored products beetles. J. Appl. Entomol. 1997; 121: 237 – 243.
14. Tanpojou LA, Adler C, Bouda H, Fountern DA. Efficacy of powder and essential oil from Chinopodium ambrossioides leaves as post harvest grain protectants against six stored product beetles. J. Stored Prods. Res. 2002; 38: 395 -402.
15. Guoqing L, Zhaojun H, Lili M, Xiaron Q, Changkun C, Yinchang W. Natural Oviposition-deterring chemicals in female cotton bollworm, Hellicoverpa armigera (Hubner). J. Insect Physiol.2001; 47: 951 -956.
16. Fu X, Fujuzawa M, Tabata J, Taksuki S, Ishikawa Y. Sex Pheromone biosynthesis in Ostrinia zaguliaevi, a congener of the European corn borer moth O. nubilalis. Insect Biochem. Mol. Biol. 2005; 35: 621 -956.

© Pharmacotherapy Group, Faculty of Pharmacy, University of Benin, Benin City, 300001 Nigeria.

The following images related to this document are available:

Photo images