Genus Ocimum belonging to the Lamiaceae family consists of 64 members that occur naturally in tropical and subtropical America, Africa and Asia (Paton et al., 1994). Members of this genus find wide applications in traditional medicine systems (Paton et al., 1994; Mwangi et al., 2012). Ocimum sanctum L, Mant. (Holy Tulsi) which is widely used in Ayurvedic medicine is a salutary example (Gupta et al., 2006; Mondal et al., 2009). The pharmacological and chemical properties of species this genus have been intensively studied; indeed a Pubmed search for this plant species yields over 233 publications. In contrast, there has been a relative paucity of studies on Ocimum species endemic to Africa, despite the fact that they are used medicinally to a comparative extent. Ocimum lamiifolium Hochst ex Benth is one of the most widely used medicinal plant species in Ethiopia (Demissew and Asfaw, 1994). It finds wide application in the management of fever, pain and other inflammatory conditions (Makonnen et al., 2003; Mequanint et al., 2010). Ocimum masaiense Ayobangira ex Paton is a perennial Ocimum species closely related to Ocimum lamiifolium that is endemic to Kenya (Paton et al., 1994). However the pain alleviating properties of this Ocimum species have not been explored. The aims of this study were twofold; to screen Chloroform/ethanol extracts of Ocimum masaiense roots for antinociceptive activity and the determination of the possible mechanisms of action for the antinociceptive activity.
Peter Waweru Mwangi1 , Stanley Nderitu Wambugu2 , David Kinuthia Kariuki3 , Paul Mungai Mbugua1 , Titus Ikusyia Kanui
The members of genus Ocimum find wide application in traditional medicine. The current study was undertaken to evaluate the probable mechanisms of antinociceptive action of chloroform/ethanol extracts of Ocimum masaiense roots. The extract was prepared by soxhlet extraction. The mechanism of action experiments involved administration of various blockers along with the extract in the formalin test. Data was analyzed using Kruksal Wallis test. The extract possessed significant antiknociceptive activity in the formalin test. Atropine, enhanced while Ketamine, Capsaicin and Naloxone significantly inhibited the antinociceptive activity in the early phase. Only capsaicin had a significant inhibitory effect on the antinociceptive activity of the extract in the late phase among the substances tested. Based on the findings it is postulated that the extract mediates its antinociceptive activity via a complex interplay of various neurotransmitter syste-ms which may be mediated both centrally and peripherally. Key words: Ocimum masaiense; Pain; Mechanism of action; Antinociception; Medicinal plants; Kruksal Wallis test; Ketamine; Capsaicin; Naloxone; late phase; formalin test; nociception; Ocimum lamiifolium Hochst; Ocimum sanctum; International Association for the Study of Pain; IASP; formalin test; pull-up test; antinociceptive; Atropine; M2 receptor; M4 receptor; GABAergic; interneurons; pronociceptive; NMDA; N-Methyl-D-Aspartate receptor; TRPV1; Transient Receptor Potential Vanilloid 1 receptor; AMG-517; AMG-9810; NSAID; endocannabinoid; neurotransmitter;