Insecticidal Ability of Essential Oil Content of Eucalyptus camaldulensis from Onigambari Forest Reserve, South West, Nigeria

Insecticidal Ability of Essential Oil Content of Eucalyptus camaldulensis from Onigambari Forest Reserve, South West, Nigeria

Adetola, O.O.*, Bakpolor, V.R, Yusuf, A.S., Onafurume, O.M., Oyedeji, O.T., Murtala, M.O., Ayanniyi, O.A., Adekoya, O.O

 Forestry Research Institute of Nigeria PMB 5054 Ibadan, Nigeria.

*Corresponding Author’s

DOI: https://doi.org/10.47772/IJRISS.2023.70569

 Received: 15 April 2023; Revised: 05 May 2023; Accepted: 09 May 2023; Published: 09 June 2023

ABSTRACT

Biodegradable and ecologically natural products such as essential oils are emerging candidates for the replacement of usually applied chemical pesticides. This work reported the chemical composition and effects caused by leaves essential oils (EOs) from Eucalyptus camaldulensis. Leaves of Eucalyptus camaldulensis gave 1.36 % w/w oil dried weight basis. GC-MS analysis of the oils resulted in the identification of 15 constituents, representing 96.24% of the oil.  1,8-cineole (CIN) (65.26%), γ-terpinene (18.45%), o-cymene (13.55%) and terpinen-4-ol (7.01%) were the major components of E. camaldulensis. From the results; E. camaldulensis leaf oils have great potential and can be utilized as cheap sources for the commercial isolation of 1,8-cineole.

Keywords: Eucalyptus camaldulensis, Essential oil composition, Nigeria, 1,8- cineole, Insecticidal properties, Secondary metabolite.

INTRODUCTION

Among the families of plants investigated to date, the one that shows great potential is the Myrtaceae family. Myrtaceae family or the myrtle family is made up of more than 3,800 species of trees and shrubs that are present in temperate, subtropical, and tropical regions of the world.

The main genera are Eucalyptus, Eugenia, Melaleuca, Leptospermum, Myrtus, Pimenta, Psidium, and Syzygium. Species of the Myrtaceae family provide many useful products, including timber and essential oils, and contain a number of economically important species. They’re also rich sources of essential oils containing bioactive constituents [2].  The Myrtaceae family contains volatile compounds of great economic importance. The leaves and the stems of several species are sources of essential oils used for medicinal purposes, food, perfume, cosmetic and pharmaceutical industries [6].  The volatile oil of the Eucalyptus has a number of constituents (terpenes) such as cineole, phellandrene, and globular, which occur in different proportions depending on the species and can vary within species depending on many factors including subspecies and specific environmental conditions. Less than 20 of the over 700 species of Eucalyptus appear to have been used for the commercial extraction of oil [4].

Several storage systems utilize chemical pesticides and fumigants as the most economical and common practice [1]. Insect strains are resistant to pesticides, toxic residues for human consumption, acute and chronic toxicity for workers, and adverse effects on the environment have been reported in, other countries [7].

 Studies indicate that essential oils (EOs), plant secondary metabolites, may affect significantly the plant resistance to parasites and microorganisms. The active components are monoterpenes and sesquiterpenes (hydrocarbon and oxygenated terpenoid derivatives), and aliphatic compounds such as alkanes, alkenes, ketones, aldehydes, acids, and alcohols.

Secondary metabolites play an important role in the adaptation of plants to the environment and in overcoming stress conditions. Biotic and abiotic factors may alter plant growth and the production and composition of secondary metabolites. Also, in previous work, we describe the effect of drought stress on the EO composition in leaves from E. camaldulensis Dehnh.. Another factor that can modify the composition of EOs is the ontogenetic stage of plants, so in this paper, we check the EO content of Eucalyptus camaldulensis from Nigeria to see the secondary metabolites that may be responsible for their insecticidal abilities.

MATERIALS AND METHOD

2.1 Extraction of Essential Oils and chemical analysis

Essential oils were extracted from Eucalyptus camaldulensis collected in June 2020 from Onigambari Forest Reserve (7°51’9.25″ N 3° 55′ 52.50″ E) Oyo State, Nigeria. The essential oils were extracted from freshly collected leaves (100 g) by hydrodistillation using a modified Clevenger steam distillation apparatus for 2 hours. EO was stored at – 18 °C, in an amber bottle with anhydrous sodium sulfate, until chromatographic analysis. Essential oil content was calculated for each repetition (n = 4) and expressed as a percentage (v/w, fresh weight). Gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) were performed to evaluate qualitative and quantitative changes in composition in EOs.

A volume of 1µL of each sample, dissolved in CH2Cl2 (1:100 v/v), was injected. Relative abundances of EO-type components were determined by GC by means of a gas chromatograph (7890A, Agilent Technologies, Santa Clara, California, USA) equipped with a flame ionization detector (FID) using an HP-5 (phenyl methyl siloxane, 30 m × 250 µm id × 0.25 µm) capillary column. Nitrogen was used as carrier gas and hexadecane as the internal standard. Temperature program: Initial temperature 60 °C (2 min), 60 °C to 280 °C with a ramp of 8 °C min-1; injector and detector temperature 250 °C. Qualitative identification of the different terpenes was based on a comparison of their retention times to n-alkanes, compared to published data, and confirmed by co-chromatography with authentic samples. Response factors were determined for standard commercial samples, and as expected when FID is used, they did not differ significantly from unity. Determination of individual compounds was achieved by capillary GC electron impact mass spectrometry (GC-MS; GC-6890, Agilent Technologies) coupled to a mass spectrometer (MSD 5973, Agilent Technologies) with the same characteristics column and identical operating conditions to those previously used for GC. Helium was used as a carrier gas, and the ionization voltage applied was 70 eV, mass ranges m/z 40-400 Da.

RESULTS AND DISCUSSION

The chemical composition of E. camaldulensis leaf oils from the Onigambari forest reserve was investigated for essential oils composition. The total yield of leaf essential oils of the Myrtaceae species; E. camaldulensis was 1.36 % w/w based on the dried weight. This is in slight contrast to the works of [3], which got a total yield of 1.4% from the study conducted in Malaysia. It can be suggested that the differences in the yield and constituents of the oils could be attributed to the differences in location, genetic, geographical, and environmental conditions.

The chemical composition of the leaf essential oils described above was assessed using the GC-MS technique and resulted in the identification of 15 compounds of essential oil components from E. camaldulensis representing 96.24% of the essential oil. E. camaldulensis oil main components are 1,8-cineole (CIN) (65.26%),γ-terpinene (18.45%), o-cymene (13.55%) and terpinen-4-ol (7.01%). In addition, components such as Linalool (0.06) and Cis-Sabinol (0.01) were identified in trace amounts in E. camaldulensis oils in this study (Table 1).

The chemical composition of E. camaldulensis and E. viminalis essential oils investigated in some previous studies have obvious differences from the present findings. For example, γ-terpinene (42.5%), 1,8-cineole (33.6%), p-cymene (17.5%), and terpinene-4-ol (3.9%) were determined as the main components of E. camaldulensis essential oil in the study of Siramon et al [5],

In the study of [2], it was concluded that 1,8-cineole (CIN) was largely responsible for the pesticidal properties of Eucalyptus spp. Recent studies have also shown that the toxicity of several constituents of EOs such as 1,8-cineole, chavacol, p-cymene, limonene, linalool, myrcene, α-pinene, γ-terpinene, terpinene-4-ol, and α-terpineol can be considered as the main reasons for the insecticidal activities from the Myrtaceae family on insect pests [3].

Regarding the toxicity of eucalyptus oils, not much is known; but EOs is considered to reduce the harmful effect of conventional insecticides on humans and the environment. However, several works have been conducted to prove the toxicity of the EO of this plant species for instance 1,8-Cineole have proven toxicity against the larvae of Culex quinquefasciatus Say. Fumigant toxicity against the adults of S. oryzae [1].

Table 1: Composition of Essential Oil from the leaf of E. camaldulensis.

RI=Retention Index is relative to C8-C20 n-alkanes on the HP-5MS column.

CONCLUSION

The higher percentage of   1,8-cineole (65.26%) and γ-terpinene (18.45%) in E. camaldulensis leaf oils from Onigambari forest reserve have great potential and can be useful for insect control, hence, the leaves of this plant species could be utilized as potential sources for the commercial isolation of 1,8-cineole, O-Cymene, and γ-terpinene.

ACKNOWLEDGMENT

The authors acknowledge the contribution of Mr. Olumide for proofreading this article.

REFERENCES

1. Andrade-Ochoa S., Correa-Basurto J., Rodríguez-Valdez LM., Sánchez-Torres LE., Nogueda-Torres B., Nevárez-Moorillón GV.(2018). In vitro and in silico studies of terpenes, terpenoids and related compounds with larvicidal and pupaecidal activity against Culex quinquefasciatus say (Diptera: Culicidae). Chem Cent J;12(1):53 doi:10.1186/s13065-018-0425-2
2. Boyer, S., H. Zhang, and G. Lempérière. (2012). A review of control methods and resistance mechanisms in stored-product insects. Bulletin of Entomological Research 102:213-229.
3. Ebadollahi, A. (2011). Antifeedant activity of essential oils from Eucalyptus globulus Labill and Lavandula stoechas L. on Tribolium castaneum Herbst (Coleoptera: Tenebrionidae). Biharean Biologist 5:8-10
4. Ebadollahi, A. (2013). Essential oils isolated from the Myrtaceae family as natural insecticides. Annual Review & Research in Biology 3(3):148-175.
5. Pearson, M. (1993). Eucalyptus Oil Distilleries in Australia. Australasian Historical Archaeology.  1993, 11, 99.
6. Siramon P., Ohtani Y., Ichiura H. Chemical composition and antifungal property of Eucalyptus camaldulensis leaf oils from Thailand. Rec Nat Prod. 2013;7:49-53.
7. Silva, C.J, Barbosa, L.C, Demuner, A.J, Montanari, R.M, Pinheiro,A.L,  Dias, I,  Andrade,N.J. (2010). Chemical composition and antibacterial activities from the essential oils of Myrtaceae species planted in Brazil. Quim. Nova. 2010, 33(Suppl1), 104-108.
8. Vinayachandra, S.R., and K.R. Chandrashekar. (2011). Larvicidal activities of Knema attenuate (Hook. f. & Thomson) Warb. (Myristicaceae) extracts against Aedes albopictus Skuse and Anopheles stephensi Liston. Parasitology.