Prebiotics are non-digestible food substances that when consumed provide a beneficial physiological effect on the host, by selectively stimulating the favourable growth or activity of a limited number of indigenous bacteria. Most known prebiotics are complex carbohydrates commonly found in fruits, vegetables and plant products. Vernonia amygdalina, commonly called bitter leaf is widely consumed in Africa especially in Nigeria. The leaf extract has been reported to contain some prebiotic potential. This study was aimed at identifying and evaluating immuno-modulatory properties of prebiotics extracted from the leaf. The aqueous extract was separated into fractions by Liquid-liquid fractionation and the prebiotic compounds were identified through Thin Layer Chromatography (TLC).The evaluation of immuno-modulatory effects was conducted by monitoring the effects of oral administration of the aqueous extract on the haematological and lipid profiles of Rattus norvegicus. The animals were distributed into six groups with six animals in each group. One group was designated control while the other five groups were administered different concentrations of the extract. The control group was administered distilled water and the other groups 50, 100, 200, 400 and 800 mg/kg of the extract respectively, twice daily for three weeks. Blood was collected through the orbital-plexus of the rats to evaluate the effect of the extract on CD4 cells, packed cell volume (PCV), white blood cell count (WBC), haemoglobin (Hb) levels and lipid profile. Five fractions designated E1 to E5, were obtained from the extract. Thin Layer Chromatography analysis of these fractions revealed the presence of fructo-oligosaccharides namely D-fructose, D-arabinose, D-glucose, D-xylose, D-mannose and D-galactose suggesting that these are the prebiotic compounds of the plant extract. The aqueous extract of the plant showed a significant (p<0 .05="" and="" blood="" cd4="" cells="" cholesterol="" density="" effect="" high="" increased="" lipid-="" lipid-cholesterol="" low="" no="" on="" p="" reduction="" significant="" there="" total="" was="" white="">0.05) increased effect on haemoglobin (Hb) and packed cell volume (PCV) levels. The results of this study show that Vernonia amygdalina leaf extracts contain fructo-oligosaccharides and other prebiotic compounds and can play important roles in the modulation of the immune system.

Vernonia amygdalina, a member of the Asteraceae family, is a widely used local vegetable inNigeria, Uganda and other African countries. It grows in a range of ecological zones in Africa and the Arabian Peninsula (Bonsi et al., 1995). The leaf is commonly called “bitter leaf” in English, “Olubu or Onugbo” in Igbo, “Ityuna” in Tiv , “Oriwo” in Edo, “Ewuro” in Yoruba, “Chusar-doki” in Hausa, “Etidot” in Efik, “Omubiriz i” or “Omululuza” in West and Central Uganda; “Olusia” in Luo, Kenya. It is used in vario us food preparations and in ethnomedicine for the treatment of malaria and gastrointestinal infections. It is a shrub of 2-5 m tall with petiolate leaves of about 6.0mm wide (Ojiako and Nwanjo, 2006). It is up to 20 cm long and its bark is rough. The bitter taste of the leaf has been attributed to the presence of anti-nutritive principles like saponins, alkaloids, tannins and glycosides (Buttler and Bailey, 1973). There have been several reports on its antimicrobial, antiplasmodial, antitumor, antioxidant and antihelminthic properties (Jisaka et al., 1993; Izevbigie, 2003; Farombi, 2003; Ehiagbonare, 2007). Aqueous leaf extracts of V. amygdalina have been previously reported to have prebiotic properties (Ukwah and Ezeonu, 2008; Ezeonu and Ukwah, 2009; Ezeonu et al., 2012).

For many years, medicine depended exclusively on leaves, flowers and barks of plants, until the 1970s when synthetic drugs came into use (Conway, 1973). In orthodox medicine, a plant may be subjected to several chemical processes before its active ingredients are extracted, while in traditional medicine, a plant is simply eaten raw, cooked or infused in water or native wine or even prepared as food (Sofowora, 1992; Jones, 1996; Reynolds, 1996).