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Open AccessArticle

Chemical Variation and Implications on Repellency Activity of Tephrosia vogelii (Hook f.) Essential Oils Against Sitophilus zeamais Motschulsky

1
Department of Chemistry, University of Fort Hare, P/BagX1314, Alice 5700, South Africa
2
Department of Chemical and Physical Sciences, Walter Sisulu University, P/BagX1, Mthatha 5117, South Africa
3
Department of Chemistry, Makerere University, Kampala P.O. Box 7062, Uganda
4
Department of Biological and Environmental Sciences, Walter Sisulu University, P/BagX1, Mthatha 5117, South Africa
*
Author to whom correspondence should be addressed.
Agriculture 2020, 10(5), 164; https://doi.org/10.3390/agriculture10050164
Received: 18 February 2020 / Revised: 13 March 2020 / Accepted: 26 March 2020 / Published: 12 May 2020
The aim of this research is to characterize the variation in the chemical composition of Tephrosia vogelii essential oils from different locations and to investigate the repellency of essential oils against Sitophilus zeamais. Chemical variability in the components of T. vogelii essential oils from eastern Uganda was identified using principal component analysis (PCA) and agglomerative hierarchical clustering (AHC). Based on the profiles of the compounds of the farnesene family, three chemotypes were found: farnesol (chemotype 1), springene (β-springene and α-springene) and β-farnesene were all distinctive in chemotype 2 and a mixed variety of farnesol and springene. In the three cases, alkyl benzenes (o-xylene, m-xylene and ethylbenzene) were significant components in the oil. The compounds 1,4-dihydroxy-p-menth-2-ene, 6,10-dimethyl-5,9-undecadien-2-one, and 3,4-dimethyl-3-cyclohexen-1-carboxaldehyde were other prominent constituents. The yields of the essential oils did not vary significantly, however the chemical composition varied with harvesting time during the rainy and dry seasons. In choice repellency tests, chemotype 1 and chemotype 2 were more active against Sitophilus zeamais than the mixed chemotype. Farnesol was found to be effective only at a higher concentration as a repellent against S. zeamais. We therefore hypothesize that farnesol is a key player in this and we demonstrated the weak repellency of this compound. However, further study that aims to optimize and standardize the varieties and harvesting period is needed for recommendation to smallhold farmers. View Full-Text
Keywords: chemotypes; Tephrosia vogelii; repellency activity; Sitophilus zeamais; essential oils chemotypes; Tephrosia vogelii; repellency activity; Sitophilus zeamais; essential oils
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MDPI and ACS Style

Kerebba, N.; Oyedeji, A.O.; Byamukama, R.; Kuria, S.K.; Oyedeji, O.O. Chemical Variation and Implications on Repellency Activity of Tephrosia vogelii (Hook f.) Essential Oils Against Sitophilus zeamais Motschulsky. Agriculture 2020, 10, 164.

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