Evaluation of Insecticidal Activity of Pteris Ensiformis (burn.f.) Against Cowpea Weevii, Callosobruches Maculatus (Fabricius).
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Date
2023
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Department of Biochemistry and Molecular Biology, Faculty of Science, Obafemi Awolowo University.
Abstract
This study investigated the toxicity bioassay of Pteris ensiformis leaf extracts against Callosobruchus maculatus. It assessed the oviposition and adult emergency effect of the most potent extract; as well as the sublethal effect of the most potent extract on some biochemical metabolites and on the neurotransmitting, detoxifying and antioxidant enzymes in C. maculatus and profiling the constituents of the extract using spectroscopic technique. These were with a view to providing an information on the insecticidal potential of Pteris ensiformis leaf on C. maculatus and the constituents responsible for this property.
Fresh leaves of both sterile and fertile P. ensiformis were harvested and separately air-dried and milled into fine powder with the aid of an electrical grinder. The powdered samples (100 g) of sterile and fertile P. ensiformis leaves were soaked in 300 mL of 80% ethanol and n-hexane separately at room temperature for 72 h. Each sample was then filtered after 72 h through Whatman filter paper and the filtrates were concentrat(separately) on a rotary evaporator to give the fertile ethanolic (FE), fertile hexane (FH), sterile ethanolic (SE) and sterile hexane (SH) crude extracts of P. ensiformis leaf. Acute toxicity test was conducted by inhalation over a period of 24 h using five serial concentrations (0, 1.25, 2.5, 5 and 10 mg/mL) of each of the FE, FH, SE and SH extract on filter papers using standard method. Anti-oviposition test as well as repellency against the weevils were carried out on each of the extracts according to standard methods. Compared to others, FE showed highest mortality, anti-oviposition and repellency activities against
C. maculatus. Thus, FE LC50 was determined using probit analysis and its sub-acute toxicity study at 80%, 40% and 20% of the LC50 was conducted for 6, 12, 18 and 24 h exposure periods. The tested insects at each exposure period were homogenized inphosphate buffer and the homogenate was assayed for the following biochemical parameters: alkaline phosphatase (ALP), lactate dehydrogenase (LDH), reduced glutathione (GSH), glutathione transferase (GST), superoxide dismutase (SOD), acetylcholinesterase (AChE), acid phosphatase (ACP), glycogen and total protein. Also, the constituents of fertile P. ensiformis ethanolic leaf extract was profiled via GC-MS analysis. Analysis of data were carried out using GraphPad Prism, Statistical Analysis Software (SAS), Trimmed Spearman-Karber (TSK) program (Probit analysis), Turkey Post Test (GraphPad Software, San Diego, CA, USA). The difference weres considered to be significant if p ˂ 0.05.
The results indicated 11.14 mg/mL as the LC50 value for fertile P. ensiformis ethanolic leaf extract. The result further revealed different patterns of inhibition (6 and 12 hours; p ˂ 0.05) and increases (18 and 24 hours; p< 0.05) in the activities of C. maculatus ALP, LDH, GSH, and AChE (p ˂ 0.05). Additionally, at all the exposure periods, GST activity was significantly stimulated while SOD activity was inhibited. Moreover, ACP activity (p ˂ 0.05) was consistently inhibited while glycogen and protein levels increased significantly at all the exposure periods. A total of 21 compounds were identified in fertile ethanolic leaf extract of P. ensiformis with four of the components (Cis-11-Hexadecenal, Octadecanal, Ethyl 9-hexadecenoate and n-Hexadecanoic acid) constituting 69.17% of the total extract.
The study concluded that leaves of P. ensiformis (especially sporophylls) possess insecticidal properties that could be employed in the prevention of storage infestation of cowpeas.
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Citation
Obana, G. (2023). Evaluation of Insecticidal activity of pteris ensiformis (burn.f.) against cowpea weevii, callosobruches maculatus (fabricius). Department of Biochemistry and Molecular Biology, Faculty of Science, Obafemi Awolowo University.