Abstract:
This study aimed to profle the phytochemical profling constituents, characterize the
functional groups spectroscopically, and evaluate the acaricidal activity of Tephrosia
vogelii leaf extract from Laikipia County, Kenya. Ultrasound assisted sequential extraction
using n-hexane, chloroform, and ethanol was employed to obtain crude leaf extracts,
followed by qualitative phytochemical screening, FTIR and GC–MS analysis, and AAS
based heavy metal quantifcation. The ethanol extract was further tested for acaricidal
activity against Rhipicephalus sanguineus using adult and larval immersion tests. Results
revealed a rich spectrum of bioactive compounds, including favonoids and rotenoids,
saponins, alkaloids, terpenoids, phenols, and glycosides, with deguelin and tephrosin
identifed as key acaricidal agents. FTIR and GC–MS showed characteristic peaks at
3446.79 cm⁻
1
(O–H/N–H), 1743.65 cm⁻
1
(C=O lactone), and 1535.34 cm⁻
1
(aromatic
C=C), consistent with rotenoid and favonoid structures. AAS detected elevated levels of
heavy metals such as Fe, Mn, and Hg, exceeding WHO limits. Biologically, the ethanol
extract produced up to 99.74% larval mortality at 40–50 mg/mL (LC₅₀=8.58 mg/mL) and
strongly inhibited egg laying (20.03% at 40 mg/mL). The study concludes that Tephrosia
vogelii from Laikipia is a promising natural source of bioactive phytochemicals with potent
acaricidal activity against Rhipicephalus sanguineus (R. sanguineus). It is recommended
that future work focus on purifcation and fractionation of the ethanol extract to isolate key
rotenoids and favonoids and develop standardized, environmentally safe formulations for
tick control in livestock and integrated pest-management programs.
