Assessment of toxicity and biochemical mechanisms underlying the insecticidal activity of chemically characterized Boswellia carterii essential oil against insect pest of legume seeds

https://doi.org/10.1016/j.pestbp.2017.04.004Get rights and content

Highlights

  • Insecticidal potential of Boswellia carterii EO against legume pest

  • Chemical composition of Boswellia carterii essential oil (EO) was identified by GC–MS.

  • Elucidate biochemical mechanisms underlying the insecticidal activity of EO

  • Recommends test EO as an eco-friendly alternative to synthetic insecticides

Abstract

The present study was undertaken to investigate the insecticidal activity of chemically characterized Boswellia carterii essential oil (EO) and its mode of action against the pulse beetle Callosobruchus chinensis and C. maculatus. GC–MS analysis depicted α-thujene (69.16%), α-Pinene (7.20) and α-Phellandrene (6.78%) as the major components of test EO. EO exhibited absolute toxicity at 0.10 μl/ml air against both C. chinensis and C. maculatus following 24 h exposure. EO caused a significant reduction in oviposition and further reproductive development at LC50 doses (0.050 μl/ml to 0.066 μl/ml in air). Compared to control, a significant elevation in ROS level accompanied with impairment in enzymatic (SOD and CAT) and non-enzymatic (GSH/GSSH) antioxidant defense system has been observed in EO exposed insect pest. However, EO has no significant effect on in vivo AChE activity. An absolute protection of Vigna radiata seeds samples exposed to EO at LC90 doses was observed without affecting seed germination. The findings revealed that the B. carterii EO has strong insecticidal potential, hence, it could be recommended as a biorational alternative to synthetic insecticides.

Introduction

Legume grains (beans, peas, lentils and chickpea) occupy an important place in human nutrition throughout the world with special significance to the low-income groups of people in developing countries [1]. Legumes are generally rich sources of proteins, calories, dietary fibres, minerals and vitamins, hence, considered as poor man's meat [2]. The pulse beetle Callosobruchus spp. (Coleoptera: Bruchidae) viz., C. chinensis and C. maculatus are the two foremost serious insect pest of legume seeds in many countries, especially in the tropics and subtropics. Callosobruchus spp. adults are compatible to mate and oviposit as soon as their emergence from infected seeds even in the absence of food or water resources [3]. The entire immature stages such as eggs, larvae, and pupae is spent in a single legume grain causing huge damages in term of loss in the quantity, nutritional quality and germination potential of seeds [4], [5].

Since 1930, synthetic insecticides and fumigants have been used to prevent the insect pest infestation in stored food commodities. Currently, phosphine gas and organophosphate insecticides (OPs) are widely been used for the control of stored product insect pest. There are several reports that the toxicity of OPs, carbamates and phosphine were accompanied by the inhibition of acetylcholinesterase enzyme (AChE) and impairment in antioxidant defense system [6], [7], [8], [9]. However, in consideration of the recent report on the resistant development and adverse effect on the health and environment many insecticides have been replaced/restricted in their use [10]. Risks associated with the synthetic insecticides compelled industries and scientific communities to search and explore rational alternatives to synthetic ones. In past few years, the use of plant essential oils and their constituents have been well explored as low-risk insecticides owing to their popularity with organic growers and environmentally conscious consumers. Some of the plant essential oils and their constituents are kept in GRAS category and meet the criteria of reduced risk pesticides [11]. In general, EOs and their constituents exert their insecticidal activity through neurotoxic effects such as octopamine synapses, GABA and inhibition of acetylcholinesterase activity. However, little is known about the influence of EO on antioxidative defense systems of stored product insect pest.

Previously we have reported that bark essential oil of B. carterii had potent fumigant toxicity against storage fungi, aflatoxin secretion and oxidative deterioration [12]. Some of the earlier studied exhibited the insecticidal activity of B. carterii EO against the Sitophilus oryzae, Reticulitermes speratus; Lycoriella ingenua [6], [13], [14]. The present study is the first report on the effect of B. carterii EO on Callosobruchus spp. mortality, reproductive behavior and some biochemical parameter such as in vivo acetylcholinesterase enzyme activity and antioxidative defense systems of test insect pest.

This study was aimed to explore the insecticidal potential of B. carterii EO against C. chinensis and C. maculatus adults, their egg hatchability, post-embryonic mortality and antifeedant activity. Further, effects of EO on in vivo acetylcholinesterase enzyme activity, antioxidative defense systems and its efficacy as a shelf-life enhancer of V. radiata seed has been studied so as to recommends it as a potential candidate for insecticide formulation against Callosobruchus spp.

Section snippets

Chemicals and equipment's

All the chemicals and reagents used in the study were procured from Sigma Chemical Co. (St. Louis, MO, USA), Hi-Media Laboratories Pvt. Ltd., Mumbai, India, and Sisco Research Lab, (Mumbai, India). Tissue grinder (P/XX/81/1 - 220 V) Yorco Instruments Delhi, India, GC–MS (Perkin Elmer Turbomass Gold MA, USA), ELISA Plate Reader (Spectromax - SPX340), Spectrophotometer (UV-1800-Shimadzu, Japan), Spectrofluorometer RF5301, Shimadzu, Japan.

Rearing of test insect

Callosobruchus chinensis and C. maculatus were reared on

Chemical profile of EO

The extraction yield of B. carterii EO was 0.52%. A total of nine compounds constituting > 90% of EO was identified by the GC–MS analysis where α-thujene (69.16%), α-Pinene (7.20%) and α-Phellandrene (6.78%) were identified as major ones while remaining compounds were ranged between (0.58–3.99) (Table 1).

Toxicity of essential oil

Results showed C. maculatus (LC50 = 0.050 μl/ml in air) adults were more susceptible to test EO than the C. chinensis (LC50 = 0.066 μl/ml in air). Following 24 h exposure, EO caused 100% mortality of

Discussion

The finding of present investigation explored the insecticidal activity (fumigant toxicity, oviposition deterrence, ovicidal, larvicidal and pupaecidal activities) of chemically characterized B. carterii EO as well as its effect on the biochemical parameter of insect pest. GC–MS results depicted α-thujene (69.16%), α-Pinene (7.20%) and α-Phellandrene (6.78%) as the major compounds of test EO (Fig. 5). The chemical profile of EO studied herein was similar to the previous reports with slight

Conclusion

The findings revealed that Boswellia carterii EO exhibited considerable fumigant toxicity against Callosobruchus chinensis and C. maculatus without affecting seed germination. As a fumigant, EO causes a significant elevation in cellular ROS level accompanied by impairment in antioxidant defense system suggested that the toxicity of EO might be associated with oxidative damages. Although, EO exhibited significant insecticidal activity, future research needed to design and develop an appropriate

Conflict of interest

The authors declare that there are no conflicts of interest.

Acknowledgements

Authors wish to thank Prof. Ram Rajasekharan, Director, CSIR-CFTRI, Mysore, India for his encouragement and support. We also thank to the Head, Department of Food Protectants and Infestation Control, for providing necessary facilities and Prof. N. K. Dubey, Banaras Hindu University, Varanasi for providing EO sample and his valuable suggestion. The research work is financially supported by Science and Engineering Research Board (SERB) New Delhi under Young Scientist Scheme No. SB/YS/LS-313/2013.

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