Essential oil of Lippia alba and its main constituent citral block the excitability of rat sciatic nerves

Abstract

Lippia alba is empirically used for infusions, teas, macerates, and hydroalcoholic extracts because of its antispasmodic, analgesic, sedative, and anxiolytic effects. Citral is a mixture of trans-geranial and cis-neral and is the main constituent of L. alba essential oil and possesses analgesic, anxiolytic, anticonvulsant, and sedative effects. The present study evaluated the effects of the essential oil of L. alba (EOLa) and citral on compound action potentials (CAPs) in Wistar rat sciatic nerves. Both drugs inhibited CAP in a concentration-dependent manner. The calculated half-maximal inhibitory concentrations (IC50) of peak-to-peak amplitude were 53.2 µg/mL and 35.00 µg/mL (or 230 µM) for EOLa and citral, respectively. Peak-to-peak amplitude of the CAP was significantly reduced by 30 µg/mL EOLa and 10 µg/mL citral. EOLa and citral (at 60 and 30 µg/mL, values close to their respective IC50 for CAP blockade) significantly increased chronaxy and rheobase. The conduction velocity of the first and second CAP components was statistically reduced to ∼86% of control with 10 µg/mL EOLa and ∼90% of control with 3 µg/mL citral. This study showed that EOLa inhibited nerve excitability and this effect can be explained by the presence of citral in its composition. Both EOLa and citral showed inhibitory actions at lower concentrations compared with other essential oils and constituents with local anesthetic activity. In conclusion, these data demonstrate that EOLa and citral are promising agents in the development of new drugs with local anesthetic activity.

Anesthetic activity of plant essential oils on <i>Cyprinus carpio</i> (koi carp)

“…Even though, eugenol and its derivatives were not found, OCO showed the anesthetic activity in the fish. It was previously reported that E-citral and Z-citral had the anesthetic activity on white shrimps (Litopenaeus vannamei) (43) and Wistar rats (Rattus norvegicus) (44). Therefore, the fish anesthetic activity of OCO as found in the current study is considered to be due to these two isomers of citral.…”

Physiological responses of Rhamdia quelen (Siluriformes: Heptapteridae) to anesthesia with essential oils from two different chemotypes of Lippia alba

“…The anesthetic effect of EO-L in silver catfish involves the modulation of the benzodiazepine (BDZ) site of the GABAergic system . The EO-C blocks the excitability of rat sciatic nerves (Sousa et al, 2015), but the anesthetic effect of the EO from Aloysia triphylla (which has citral as its major compound) in silver catfish is not related to a modulation of the BDZ site of the GABAA receptor (Santos et al, in press). …”

Essential oils from Citrus x aurantium and Citrus x latifolia (Rutaceae) have anesthetic activity and are effective in reducing ion loss in silver catfish ( Rhamdia quelen )

“…Additionally, linalool, found in EOCA, has anesthetic effects in silver catfish (both S-(+) and R-(−) linalool isomers) and common carp, Cyprinus carpio Linnaeus (Mirghaed et al, 2016), though its mechanism of action seems not to involve the benzodiazepine site of the GABAergic system (Heldwein et al, 2014). Citral, another major component of EOCL, increased barbituric sleeping time of mice (Vale et al, 2002) and blocks the excitability of rat sciatic nerves (Sousa et al, 2015). Citral is also the main component of other EOs that have anesthetic effects in fish: Aloysia triphylla (Gressler et al, 2012;Parodi et al, 2014;Santos et al, 2017 Cymbopogon flexuosus (Limma-Neto et al, 2016) and L. alba citral chemotype (Souza et al, 2017).…”