IOSR Journal of Pharmacy and Biological Sciences (IOSR-JPBS) e-ISSN: 2278-3008, p-ISSN:2319-7676. Volume 9, Issue 2 Ver. IV (Mar-Apr. 2014), PP 26-31 www.iosrjournals.org www.iosrjournals.org 26 | Page Analgesic and toxicological evaluation of the stem bark of Albizia zygia Benth (Mimosoideae). Tavs A. Abere 1 , Profit Ibanishuka 2 , Rose I. Jesuorobo 3 1, 3 Department of Pharmacognosy, Faculty of Pharmacy, University of Benin, Benin City, PMB 1154, Nigeria 2 Department of Pharmacy, University of Benin Teaching Hospital, Benin City, PMB 1154, Nigeria. Abstract: Background: Albizia zygia Benth is used in ethnomedicine in West Africa for the management of painful conditions associated with tropical diseases. In the present study, the analgesic activity as well as the toxicological profile of the aqueous methanol stem bark extract was evaluated to confirm traditional usage and justify continuous usage. Method: The analgesic activity was evaluated using acetic acid-induced writhing response and hot plate model in Swiss albino mice. Acute toxicological evaluation was carried out in mice while 28-day assessment was done in rats. Results: Phytochemical screening revealed the presence of alkaloids, tannins, saponins, flavonoids and cardiac glycosides. The aqueous methanol extract (20-80 mgkg -1 body weight) significantly (p <0.01) inhibited acetic acid-induced abdominal constriction and also significantly (p <0.05) prolonged the reaction latency to pain thermally-induced in mice by the hot plate. The activity of the extract at 80 mgkg -1 was comparable to the reference standards Aspirin (Acetic acid-induced writhing) and Morphine (Hot plate model). Oral doses as high as 5 gkg -1 did not cause death or toxicological symptoms in mice. There were no marked adverse alterations or degeneration of tissues of the major organs during acute toxicity test. Conclusion: The present study indicates that the stem back of A. zygia possesses analgesic properties which lend credence to its use in ethnomedicine in the treatment of waist pain, arthritis, sprains and in feverish conditions, but its overall safety profile needs to be further evaluated. Keywords: Albizia zygia; analgesic; writhing; toxicological profile. I. Introduction Albizia zygia Benth belongs to the Mimosoideae family, one of the three subfamilies of Leguminosae. It is a deciduous tree 9-30m tall with a spreading crown and graceful architectural form. Its leaves are pinnate and broadening towards the apex. Flowers are subsessile and calyx is puberulous, white or pink in colour. The seeds are smaller and flatter compared to seeds of other Albizia species, but have the characteristic round shape, with a slightly swollen [1]. A. zygia, commonly known as red nango in English, Ayinre-weere (Yoruba) and Nyie-avu (Igbo) is mainly used in ethnomedicine for the treatment of fever and waist pain [2]. Extracts have been shown to be molluscicidal and the roots have been reported to be used in the treatment of tuberculosis in Lake Victoria region in Kenya. The methanol extract of the stem bark has been shown to have in-vitro antitrypanosomal activity against Trypanosoma brucei [3]. Also, when the cytotoxic effects of some selected Camerounian plants with efficacy against T. cruzi and T. brucei rhodesiense were evaluated, cytotoxicity and selectivity index was high with the methanol extract of A. zygia. Traditional plant medicines including preparations from A. zygia are used throughout Africa in the treatment of malaria and trypanosomiasis. Although, a number of research studies have been carried out on this plant, there is no scientific evidence on the analgesic activity of A. zygia. Scientific evaluation of toxicity by determining lethal dose (LD 50) and sub-acute toxicity effects on major organs will aid its continous usage. The present study was designed to investigate A. zygia for its analgesic activity as well as establish its toxicological profile II. Materials and Methods Preparation of plant extract The stem barks of Albizia zygia Benth (Mimosoideae) were collected in Ugbowo area of Benin City, Edo State, Nigeria. The plants were authenticated by the curator at the Department of Pharmacognosy Herbarium, University of Benin, Benin City, where voucher specimens were deposited. The stem barks were air–dried for 7days. Further drying was carried out in the oven at 40 o C for 8h, crushed with a mortar and pistle and powdered using an electric mill. The powder was extracted with 50 % aqueous methanol and concentrated in vacuo.