Anticonvulsant agents from Boswellia sacra identified by zebrafish bioassay-guided fractionation

Epilepsy is a chronic CNS disorder characterised by recurrent seizures. It is the most prevalent neurological disease worldwide, with over 70 million people afflicted [1]. Despite the availability of over 30 approved anti-epileptic drugs (AEDs), a third of treated epilepsy patients experience serious side effects to these medications, and another third do not respond at all and are referred to as being “pharmacoresistant”. Thus, there is a clear need for new AEDs. Towards this end, we investigated the sacred frankincense from Boswellia sacra Flueck. [Burseraceae], which has been used as a medicinal drug in many parts of the world for thousands of years. The hexane extract of the resin of this plant exhibited significant anticonvulsant activity in zebrafish larvae with seizures induced by the GABA_A antagonist pentylenetetrazol (PTZ) [2]. In order to easily isolate and identify the active compounds, the analytical HPLC-PDA-ELSD conditions were transferred geometrically to a preparative medium-pressure liquid chromatography column (MPLC-UV-ELSD) using chromatographic calculations [3]. This gradient transfer ensured that the same selectivity and elution order was kept between the analytical and the preparative scale and provided an efficient isolation of the active compounds at the milligram scale. The hexane extract was fractionated in 33 fractions and eight major compounds were isolated and characterized as terpenes, including a new diterpene. Incensole and β-boswellic acid showed significant in vivo anticonvulsant activity and decreased respectively 31% (10 µg/ml) and 90% (100 µg/ml) of the induced seizures. The present work reports for the first time the anticonvulsant activity of isolated compounds from B. sacra and confirmed the anti-epileptic activity of Boswellia species, validating their use in traditional medicine to treat epileptic seizures.