Neuropharmacological profile of Mentha longifolia: Effects on convulsion, nociception and pentobarbitone-induced sleep in mice
Mentha longifolia Huds., subspecies, capensis Briq, a plant species used for the treatment of epilepsy, painful conditions such as headache and toothache, and insomnia amongst other ailments, was investigated for anticonvulsant, analgesic and central nervous system depressant activities using chemically-induced seizures, acetic acid-induced writhing and hot-plate thermal stimulation, and pentobarbitone sleeping tests respectively in mice. The parameters used for the measurement of the anticonwlsant activity included the onset of seizures and/or the incidence of the seizures. For the analgesic activities, the parameters of measurement were, the number of writhes for the acetic acid test and reaction time of animals to thermal stimulation for the hot-plate test. For the central nervous system depressant activity, akin to the anti-insomniac activity, the parameter of measurement was the duration of sleep elicited by pentobarbitone. All the data obtained were analysed using the paired Student's t-test with the exception of that on the incidence of seizures, which was analysed using Chi-squared test. Aqueous extract of M. longifolia significantly delayed the onset of pentylenetetrazoleinduced seizures, profoundly antagonised the seizures elicited by picrotoxin and had no effects against seizures induced by either bicuculline or N-methyl-Dl-aspartic acid. M. longifulia completely antagonised acetic acid-induced writhing and profoundly delayed the reaction times of the animals to hot-plate thermal stimulations in similar manner to the standard drugs, paracetamol and morphine respectively. Like the standard drug, diazeparn, M. longifolia significantly prolonged the duration of sleep induced by pentobarbitone. The phytochemical analysis carried out on the leaves of M. longifolia showed the presence ofsaponins, tannins, reducing sugars, cardiac glycosides, flavonoids and triterpene steroids. The HPLC spectrum of M. longifolia showed major peaks at the following retention times (minutes) : 20.52, 22.37, 23.1 5, 24.87 and 26.93. The data obtained show that M. longifoliahas anticonvulsant, analgesic and anti insomniac activities, thus justifying the claim by traditional health practitioners of its use in epilepsy, painful conditions and insomnia.