Toxicity of Some Essential Plant Oils. Clinical and Experimental Study

Abstract

Commercial preparations of essences of sage, hyssop, thuja, and cedar have caused human intoxication in eight cases, from which tonico-clonic convulsions were the major symptom. The experimental study of the toxic properties of commercialized essential oils of sage and hyssop has revealed that their convulsant action was of central nervous system origin in unanesthetized rats, as proven by electrocortical records. The toxicity of the hyssop oil seems to be more powerful than that of sage, since the dose limit from which the cortical events are only subclinical is 0.08 g/kg for hyssop oil and 0.3 g/kg for sage oil. Above 0.13 g/kg for hyssop oil and 0.50 g/kg for sage oil, the convulsions appeared and became lethal above 1.25 g/kg with hyssop oil and 3.2 g/kg with sage oil. The daily repeated injection of subclinical doses revealed the cumulative toxic effect of hyssop oil, since the same low dose induced electrocortical clonic seizures. The toxicity of each oil appeared to be related to the presence of terpenic ketones, camphor in sage commercial oil, camphor and thujone in sage Dalmatian oil, thujone in thuja and cedar oils, and pinocamphone in hyssop oil. The convulsant properties of camphor are well known. The neurotoxicity of thujone and pinocamphone is demonstrated in rats for the first time.

Plant-induced seizures: reappearance of an old problem

“…Increasing the dose to 1.25 g/kg leads to rhythmic myoclonus, subsequently to one or several tonic, clonic, or tonic-clonic seizures, and eventually lethal convulsive status. Similar results have been obtained with half these doses of pinocamphone, the main component of hyssop [13]. Furthermore it has been demonstrated using the same experimental model that the kindling effect is facilitated by previous exposure to very small doses of sage EO [15].…”

“…The epileptogenic properties of these compounds have been well established and studied in animals both in vivo [3,13] and in vitro [14]. In fact, it has been shown by electrocorticographic records that Wistar rats, after intraperitoneal injection of 80 mg/kg hyssop EO, develop subclinical generalized sustained high-voltage spikes.…”

“…Compilation of published case reports and experimental data over more than a century results in a list of 11 EOs whose toxicity may be manifested in convulsive events (Table 1). References are scanty in the recent medical literature [9,13], the majority of cases having been reported before medical data banks became available [3,7,8,10,11,17].…”

Effects of the essential oils of Lippia turbinata and Lippia polystachya (Verbenaceae) on the temporal pattern of locomotion of the mosquito Culex quinquefasciatus (Diptera: Culicidae) larvae

“…extract decreased total motility, locomotor activity and rearing behaviour and showed sedative, anxiolitic and antidepressant effects in rats (Mora et al 2005). Individually, the compound α-Thujone has been found to have antinociceptive activity (Rice and Wilson 1976) and convulsionant activity in mice (Hold et al 2000) and neurotoxicity in rats (Millet et al 1981). In addition, it has been classified as a neurotoxic insecticide (Hold et al 2001; and pesticide (Duke 2004).…”

α-Thujone (the active component of absinthe): γ-Aminobutyric acid type A receptor modulation and metabolic detoxification

“…It is porphyrogenic, possibly thereby contributing to the absintheinduced illness of Vincent van Gogh (5,16). ␣-Thujone is neurotoxic in rats (17), and ingestion of wormwood oil containing ␣-thujone recently resulted in human poisoning (18). The hypothesis that ␣-thujone activates the CB 1 cannabinoid receptor, based on the structural similarity of thujone enol with tetrahydrocannabinol (19), was not supported experimentally (20).…”