PHARMACOGNOSTIC AND ANTICONVULSANT STUDIES ON GLOSSONEMA BOVEANUM DECNE (APOCYNACEAE)

ABSTRACT

 Glossonema boveanum Decne is a hairy canescent perennial herb belonging to the Apocynaceae. Traditionally, the powdered whole plant is use for the treatment of many illnesses including epilepsy. This study is aimed at establishing some of the pharmacognostic features of the powdered whole plant; investigating the phytochemical compounds of the plant and evaluating the anticonvulsant property of its aqueous ethanol extract. The powdered whole plant material was examined by microscopy and its physicochemical parameters such as: Moisture content, extractive values and ash values were also determined. Thin layer chromatographic technique was used for the phytochemical screening of the various fractions of the aqueous ethanol extract of the plant. Using silica gel column chromatography and preparative thin layer chromatography, a more detailed phytochemical screening was carried out on the n-Hexane fraction of the extract. Maximal electroshock-induced seizure model in chicks and Pentylenetetrazole (PTZ)-induced seizure model in mice were used for the anticonvulsant studies. The intra-peritoneal median lethal dose (LD50) of the extract on mice and chicks was also determined. Microscopical examination of the powdered whole plant of G. boveanum identified the presence of polygonal epidermal cells, anisocytic stomatal cells, covering trichomes with cystolith incrusted in them, Starch grains, suberins, lignins and aleurone grains were also found to be present. Thin layer chromatographic analysis on the various fractions of aqueous ethanol extract revealed the presence of phenolic compounds, triterpenoids, flavonoids, and anthracene derivatives. Column chromatography and Preparative thin layer chromatography carried out on the n-Hexane fraction of the extract led to the isolation of two pentacyclic triterpenoids; Compound SAL1 and compound SAL2 which were later identified using NMR spectroscopic analysis as α-amyrin acetate and lupeol respectively. At the highest dose used (140 mg/kg), the extract conferred 40% protection against maximal electroshock induce seizure in chicks with no significant decrease in

recovery period against it. Phenytoin (20 mg/kg), the standard anticonvulsant employed conferred 90% protection against maximal electroshock-induced seizure. The extract did not exhibit any significant effect against pentelenetetrazole induced seizure in mice. The intraperitonial median lethal dose of the extract on mice and chicks was determined to be 1246 mg/kg and 471 mg/kg respectively. All these findings on G. boveanum are being reported for the first time. The result suggests that the aqueous ethanol extract of the plant contains pharmacologically active compound(s) that may be valuable in management of generalized tonic-clonic and or partial seizures.