ABSTRACT
Pausinystalia yohmibe is a member of thefamilyRubiaceae. It is a valuable medicinal tree, distributed in evergreen closed canopy forests in West Africa. It is traditionally used for treatment mostly on erectile dysfunction. This research was carried out to evaluate the immunomodulatory effect of (Pausinystalia yohmibe) stem bark methanolic extract. The yohimbe extract has been reported for its medicinal use for the treatment of impotence in men and for its anti-oxidants effects but have not be reported for any sign of immunomodulation or suppressive activity, which Is the basic aim for this research. This was achieved by assessments of the extract in the following parameters, using albino mice the phytochemical analysis which received the presence of alkaloids, flavonoids, tannnis . The acute toxicity effect of the extract which showed LD50 above 1000mg/kg and other signs of toxicity like dizziness and depression at dose 800mg/kg on a prolong administration . The animals were divided into four groups which received 100, 300 and 600 mg/kg , respectively while group four served as the control which revived a standard drug (levmisole) for the Delayed-type hypersensitivity response analysis while group four in the determination of humoral received distilled water .The extract significantly (p < 0.05) showed dose related stimulation of humoral immunity at 600mg/kg dose compared to the standard and also a significantly (p>0.05) anti-inflammatory activity at 300mg/kg compared with the control group. This result showed potential immunomodulatory effect because the immunomodulatory suppressed the antigenic response in system.