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DOI: 10.1055/s-0033-1352166
Anticonvulsant effects of kaurenoic acid isolated from the root bark of Annona senegalensis
The herbal preparations of Annona senegalensis Pers. (Annonaceae) root bark are used in Nigerian ethnomedicine for the treatment of epilepsy and febrile seizures. The scientific evidence to this effect has been reported [1]. This study aims to identify and characterize the active constituent(s) responsible for the anticonvulsant effect. Bioactive-guided fractionation of the methanol-methylene chloride root bark extract (MME) of A. senegalensis using pentylenetetrazole (PTZ)-induced seizures in mice, afforded a potent anticonvulsant ethyl-acetate fraction (EF). Further fractionation of the EF yielded eight sub-fractions (F1-F8) which were tested for anticonvulsant activity. The sub fraction F2 yielded whitish crystals that were purified to obtain A. senegalensis crystals, AS2. The AS2, which exhibited potent anticonvulsant effects, was characterized by 1D and 2D NMR spectroscopy, mass spectroscopy and X-ray crystallography. The AS2 was characterized as kaur-16-en-19-oic acid (KA), a diterpenoid phytoconstituent and exhibited the most potent anticonvulsant effect. The AS2 indicated an estimated LD50 of 3800 mg/kg. The results showed that the MME, EF and AS2 significantly (P < 0.05) and dose dependently delayed the onset of myoclonic spasms and tonic-clonic phases of seizures induced by PTZ and maximal electroshock seizure (MES). The anticonvulsant effects of the MME, EF and AS2 indicated the possible mediation of the anticonvulsant activity through central inhibitory mechanisms. Kaurenoic acid was identified as the anticonvulsant principle in the root bark extract of A. senegalensis.
Reference:
[1] Okoye TC and Akah PA. (2010). Anticonvulsant and sedative effects of root bark extract and fractions of Annona senegalensis. Inventi Impact: Ethnopharmacology. 1(2): 100 – 103.
Acknowledgement: The authors are grateful to Step-B Project of the Federal Government of Nigeria for the Innovators of Tomorrow (IOT) Award grant.