Insecticidal Activity And Phytochemical Analysis Of Six Medicinal Plants Extracts Against Tribolium Castaneum

Background:The present study was carried out under laboratory conditions,at the Institute of Resources and Environmental Engineering,Shanxi University,China.The main objectives were to evaluate the mortality and repellent effects of various organic and water extracts from four Chinese medicinal plants,namely Amur honeysuckle(Lonicera maackii Maximowicz),oriental arborvitae(Platycladus orientalis(L.)Franco),European cranberry bush(Viburnum opulus L.)and Chinese hawthorn(Crataegus pinnatifida Bunge)and two Sudanese medicinal plants,viz.Mahogany(Khaya senegalensis Desrousseaux A.Juss.)and desert date(Balanites aegyptiaca(L.)Delile),in consecutive experiments against adults of the red flour beetle(Tribolium castaneum Herbst).The research also aimed to analyze the oils of B.aegyptiaca seeds by gas chromatography-mass spectrometry(GC-MS),to carry out phytochemical screening on Chinese plants and to compare the percent chemical materials extracted from each plant samples as pre-step for bioassays.Materials and methods:The maceration extraction method was used to extract the fixed oils of B.aegyptiaca seeds with three different extraction solvents namely hexane,chloroform and ethanol,the seed powders were macerated in the solvent at room temperature for 7 days.After that,the mixture was filtered and the solvent was evaporated.The obtained oils were kept in a refrigerator until use in biological bioassays and chemical analysis.The oils were investigated for insecticidal effect by contact toxicity on the red flour beetle(Tribolium castaneum)using the film residue method at different doses(1.131,0.566,0.283 and 0.142 mg/cm²)after 12,24,36,48,72 and 96 hours of exposure time.While essential oil of the plant was extracted by steam distillation method using steam distillation apparatus for 3 hours and evaluated by contact and fumigant toxicity at 8,4,2 and 1%w/v concentrations.Correspondingly,Soxhlet extraction was used to extract the leaves of Chinese plants and mahogany with ethyl acetate and methanol solvents at 60°C and55°C for 9 hours,respectively.These extracts were tested further along with the water extract from the plants at 5%,2.5%and 1.25%w/v concentrations against the pest by using grinds treatment method after 2,4,6,8,10,14 and 21days from treatment.Besides the insecticidal test,some extracts of the studied plants were selected for the repellency effect test,locally made repellency equipment was used for that.Results:The results for insecticidal activity revealed the presence of significant mortality actions in most extracts of B.aegyptiaca,V.opulus and C.pinnatifida,whereas all extracts of L.maackii,P.orientalis and K.senegalensis were not significantly different from the control.Considering B.aegyptiaca oils,the results showed that the highest dose of chloroform(1.131 mg/cm²)achieved 100%mortality rate of the pests after 12 h and the medium dose(0.566 mg/cm²)after 36 h of exposure time,while hexane extract caused a similar effect after 24 h and 48 h at the same doses,respectively.However,the ethanol extract showed the lowest mortality compared to the other extracts.The extract scored 60%of the pest mortality until the end of the experiment time,after 96 hours.The median lethal dose(LD₅₀)values demonstrated that the chloroform extract was the most toxic to T.castaneum followed by the hexane extract and lastly the ethanol extract.Moreover,the result detected that the LD₅₀ values of chloroform after 12,24,36,48 and 72 h(0.347,0.285,0.251,0.239 and 0.224 mg/cm²)were similar to LD₅₀ values of hexane extract after24,36,48,72 and 96 h(0.327,0.271,0.251,229 and 0.214 mg/cm²)respectively.On the other hand,the insecticidal efficacy of leaves extracts from the Chinese plants and mahogany showed that the ethyl acetate extract at 5%w/v concentration of V.opulus and C.pinnatifida were the best treatments,compared to the other treatments,but without significant differences from the middle concentration(2.5%w/v)of both extracts.However,all tested extracts of L.maackii,P.orientalis and K.senegalensis were very poor mortality effects on the T.castaneum compared with the control.Regarding the repellency test of the leaves extracts from the Chinese plants,most extracts of L.maackii and p.orientalis reflected highly significant repellency compared to the control.The methanol extract of L.maackii was the best repellent effect(91.38%)against T.castaneum.On the contrary,a majority of V.opulus and C.pinnatifida extracts showed attractant activities or low repellency effect.Correspondently,all tested concentrations of B.aegyptiaca essential oil and water extract causing repellant actions on the insects ranged between 52.01-89.95%and 79.56-76.00%,respectively.The highest concentration(8%)of essential scored the highest percentage of the repellency effect(89.95%).Concerning the gas chromatography/mass spectrometric analysis of B.aegyptiaca oils,the results revealed that 9,12-Octadecadienoic acid z,z,n-Hexadecanoic acid,Oleic acid and 6-Octadecenoic acid were the main components,but the concentration differs from extract to another.Similarly,the phytochemical screening of Chinese plants has revealed the presence of all tested secondary compounds,viz.alkaloids,saponins,tannins,flavonoid and terpenoids in C.pinnatifida,but the other plants contain some of these compounds.Conclusion:It is concluded that B.aegyptiaca seed oils possess strong insecticidal activities against T.castaneum,in particular,chloroform and hexane extracts,which caused 100%mortality rate of the pest after 12 and 24hours of exposure time,respectively.The present study determined that more than fifteen phytoconstituents were identified from the oils.The main components were 9,12-Octadecadienoic acid z,z,n-Hexadecanoic acid,Oleic acid and 6-Octadecenoic acid,the biological activities may be due to these compounds.Therefore,further studies are required to isolate,identify and characterize the active ingredients responsible for the biological activies and its evaluation on the pest and test for safety on humans.Moreover,leaves ethyl acetate extracts of V.opulus and C.pinnatifida at 5%and 2.5%w/v concentrations were the best toxicant treatments against the tested store pest species compared to Chinese plants.So these plants were recommended for additional studies so as to be utilized for pest control.On the other hand,the essential oil of B.aegyptiaca and methanol extract of L.maackii were the best treatments for repellency test,but more researches are needed to prove the presence of antifeedant besides the repellent compounds in these plants and their importance in protecting storage grains.