25LAXATIVE ACTIVITIES OF AQUEOUS EXTRACT OF ALPHITONIA ZIZYPHOIDES (SPRENGER) A. GRAY (RHAMNACEAE) BARK IN RATSAlphitonia zizyphoides (Sprenger) A. Gray (Rhamnaceae) is a tree that is commonly used in Tonga for the treatment of constipation. The present study was carried out to investigate the laxative activity of Alphitonia zizyphoides in albino's Wistar rats. The laxative activity of aqueous extract of bark of Alphitonia zizyphoides was determined based on the weight of the faeces matter. The effects of the aqueous extract of bark of Alphitonia zizyphoides and castor oil were also evaluated on intestinal transit. The aqueous extract of bark of Alphitonia zizyphoides administered orally (200 and 400 mg/kg, p.o.), produced significant laxative activity and reduced loperamide induced constipation in dose dependent manner. The effect of the extract at 200 and 400 mg/kg (p.o.) was similar to that of reference drug sodium picosulfate (5 mg/kg, p.o). The same doses of the extract (200 and 400 mg/kg, p.o.) produced a significant increase (p < 0.01) of intestinal transit in comparison with castor oil (2 mL) (p < 0.01). The results showed that the aqueous extract of bark of Alphitonia zizyphoides has a significant laxative activity and supports its traditional use in herbal medicineb_venki22@yahoo.co.inResearch312013Alphitonia zizyphoides,Laxative,loperamide,gastro intestinal motility,intestinal transitB.Venkateswarlu,D. Senthil NagarajMadawalabu University, Faculty of Biochemistry, Bale Robe, Ethiopia.,Madawalabu University, Faculty of Biochemistry, Bale Robe, Ethiopia.