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

Abstract

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.

Repellency Potential, Chemical Constituents of Ocimum Plant Essential Oils, and Their Headspace Volatiles against Anopheles gambiae s. s., Malaria Vector

“…For example, plants such as Tephrosia vogelii and Lippia javanica (Burm. f.) exhibited an extreme variation of bioactive principles [56]. Also, the chemical variability in the essential oil composition of the T. vogelii plant sampled from diferent locations in eastern Uganda has been reported [56].…”

“…f.) exhibited an extreme variation of bioactive principles [56]. Also, the chemical variability in the essential oil composition of the T. vogelii plant sampled from diferent locations in eastern Uganda has been reported [56]. Te variation in the essential oils of the plants can be attributed to the extraction methods, seasonal variation, and chemotaxonomic factors [56,57].…”

“…Also, the chemical variability in the essential oil composition of the T. vogelii plant sampled from diferent locations in eastern Uganda has been reported [56]. Te variation in the essential oils of the plants can be attributed to the extraction methods, seasonal variation, and chemotaxonomic factors [56,57]. In the current study, the headspace volatiles of the three Ocimum plants were diverse, but mostly monoterpene and sesquiterpene hydrocarbons were common, as it has been in the case of many essential oil-bearing plants [29,30,32,58].…”

Transcriptomic analysis of Sitophilus zeamais in response to limonene fumigation

“…For example, cinnamon EO sterilizes Escherichia coli and Staphylococcus aureus with minimum bactericide concentrations of 4.0 and 2.0 mg mL −1 , respectively 13 . Furthermore, EOs isolated from Clinopodium tomentosum , Clinopodium nubigenum, 10 Croton rudolphianus , Tephrosia vogelii , Lippia graveolens , Cymbopogon citratus , and Mentha piperita L. have been shown to have repellent or insecticidal activities against Sitophilus granarius , Callosobruchus maculatus , Sitophilus oryzae , and Tribolium castaneum 14‐17 …”

“…13 Furthermore, EOs isolated from Clinopodium tomentosum, Clinopodium nubigenum, 10 Croton rudolphianus, Tephrosia vogelii, Lippia graveolens, Cymbopogon citratus, and Mentha piperita L. have been shown to have repellent or insecticidal activities against Sitophilus granarius, Callosobruchus maculatus, Sitophilus oryzae, and Tribolium castaneum. [14][15][16][17] Limonene, a terpene, is the main chemical constituent of many EOs including Mentha spicata and Anethum sowa, 18 and has many potential applications as an insecticide, repellent, and antimicrobial agent. 19 Although a previous study showed that CYP6MS1 may be associated with the metabolism of terpenes, 20 few studies have evaluated the mechanisms mediating the insecticidal activities of limonene.…”