Tetradenia riparia (Lamiaceae) essential oil: an alternative to Rhipicephalus sanguineus

Abstract

In Brazil, Rhipicephalus sanguineus resistance to some pyrethroids have been detected, motivating research on new phyto-insecticides such as essential oil from Tetradenia riparia leaves (EOL) and flower buds (EOFB). The essential oils were obtained by hydrodistillation (3h) and identified by GC/MS. In addition, a multivariate exploratory analysis was done to determine the analysis of the major compounds (PCA). The bioassays on R. sanguineus larvae were done by immersion test at different EO concentrations which ranged from 50,000 to 0.47 mg/mL (v/v). The action mechanism of EOs were determined by bioautographic method evaluating the inhibitory potential on the acetylcholinesterase enzyme. The EO yield in leaves was 0.29±0.22 (%) and in flower buds 0.38±0.17 (%). The class projections showed oxygenated sesquiterpenes (43.62%) and diterpenes (15.60%) in EOFB, and hydrocarbon sesquiterpenes (26.44%) and oxygenated monoterpenes (16.44%) in EOL. Four components presented a greater distancing of mass flow: fenchone (11.57 and 6.01 %), α-cadinol (12.21 and 13.69 %), 14-hidroxy-9-epi-caryophyllene (8.56 and 15.38 %), and caryophyllene oxide (1.32 and 4.50 %) in EOL and EOFB, respectively. The lethal concentrations (LCs) to kill R. sanguineus larvae were (LC50: 2.18±0.24 and LC99.9: 9.98±0.10 mg/mL) for EOL, and (LC50: 5.36±2.50 and LC99.9: 20.12±0.54 mg/mL) for EOFB. The action mechanism of EOs by bioautographic methods indicated an inhibition of 0.70 mg/mL (EOL) and 1.40 mg/mL (EOFB) on the acetylcholinesterase enzyme (AChE). Therefore, this species can be considered promising to be part of the chemical larvicides to control this ectoparasite

Ethnomedicinal, Phytochemical and Pharmacological Investigations of Tetradenia riparia (Hochst.) Codd (Lamiaceae)

“…The flower buds ( Figure 1B ) begin to appear in winter (June in the Southern hemisphere), with opening of the flowers in July. The inflorescences appear in large, branched terminal panicles ( Figure 1C ) that are white to pale mauve in color ( Zardeto-Sabec et al, 2020 ). T. riparia has eight synonyms: Basilicum myriostachyum (Benth.)…”

“… Zardeto-Sabec et al (2020) evaluated the essential oil of T. riparia leaves or flower buds against Rhipicephalus sanguineus tick larvae. Larvae were exposed for 24 h to concentrations ranging from 50,000–0.47 mg/ml, and the larvicidal activity was measured by calculating lethal concentration (LC) using the Probit test.…”

“…The essential oil produced from its leaves and flower buds has an orange color and consists mostly of terpenoid compounds such as monoterpenes, sesquiterpenes, and diterpenes (in each case as hydrocarbons or oxygenated), whose concentration varies with the seasons ( Gazim et al, 2010 ; Zardeto-Sabec et al, 2020 ).…”

“…Studies with T. riparia have demonstrated many biological activities, such as antimicrobial ( Gazim et al, 2010 ; York et al, 2012 ; Elaka et al, 2020 ; Scanavacca et al, In Press ), antioxidant ( Fernandez et al, 2017 ), antitumor ( Gazim et al, 2014 ), analgesic ( Gazim et al, 2010 ), anti-leishmania ( Cardoso et al, 2015 ; Demarchi et al, 2015 ; Leitão et al, 2020 ), antituberculosis ( Baldin et al, 2018 ), antiparasitic ( de Melo et al, 2015 ), as well as acaricidal and larvicidal ( Lorenzi and Matos, 2008 ; Gazim et al, 2011 ; Fernandez et al, 2014 ; Zardeto-Sabec et al, 2020 ).…”