Acid facilitates the digestion of protein and absorption of iron, calcium, and vitamin B-12 as well as preventsbacterial overgrowth and enteric infection (Schubert and Shamburek, 1990). However,when levels of acid (and pepsin) overwhelm mucosaldefense mechanisms ulcers occur.Peptic ulcer disease occurs mainly due to consumption of NSAIDS, infection by H. pylori, stress or due to pathological condition such as Zollinger-Ellison Syndrome (Mohammed et al., 2008).It has been shown that long term use ofulcer drugs may be associated with ineffectiveness ofdifferent drug regimens and even resistance to drugs isemerging (Al-Mofleh et al., 2007). Thus, there is anurgent need to identify more effective and safe anti-ulceragents. In the scientific literature, a large number of medicinal plants with gastric anti-ulcer potential have been reported(Ketuly et al., 2011). Plant extracts are some of the most attractive sources of new drugs and have been shown to produce promising results for the treatment of gastric ulcer (Schmeda-Hirschmann and Yesilada, 2005). One such medicinal plant is Cyperus esculentus (Borges et al., 2008).
1.1 Cyperus esculentus
Cyperus esculentus (Tigernut) is an underutilized plant of the family Cyperaceae, which produces tubers from the base that are somewhat spherical (Cortes et al., 2005). The plant is not really a nut but a tuber first discovered some 4000 years ago (Lowe and Whitewell, 2000). It has other names like yellow nutsedge, chufa, flatsedge, rush nut, water grass, earth almond, northern nut grass and nut grass (Shilenko etal., 1979). Cyperus esculentus is known in Nigeria as aya in Hausa, ofio in Yoruba and akihausa in Igbo. Cyperus esculentus grows mainly in the middle belt and northern regions of Nigeria (Okafor et al., 2003), where three varieties (black, brown and yellow) are cultivated (Umerie et al., 1997). Among these, onlytwo varieties, yellow and brown are readily available in the market. The yellow variety is preferred to all other varieties because of its inherent properties like its bigger size, attractive colour and fleshier body (Belewu and Abodurin, 2006). Cyperus esculentus can be eaten raw, roasted, dried, baked or be made into a refreshing beverage called kuunu (Oladele and Aina, 2007).
1.1.1 Biochemical and Pharmacological benefits of Cyperus esculentus
Cyperus esculentus was reported as healthy food and helps in preventing heart failures, thrombosis and poor blood circulation. It helps in preventing cancer, due to high content of soluble glucose. It was also found to assist in reducing the risk of colon cancer (Adejuyitan et al., 2009). Cyperus esculentus is rich in energy content (starch, fat, sugars and protein), mineral (phosphorus, potassium) and vitamins E and C (Belewu and Belewu, 2007). Cyperus esculentus is suitable for diabetic persons and also helps in weight loss (Borges et al., 2008). Its tubers are said to be aphrodisiac, carninative, diuretic, emmanagogue and stimulant (Chevallier, 1996). In addition, it has been demonstrated to contain very high essential amino acids than those proposed in the protein standard by FAO/WHO/UNU (1985) for satisfying adult needs (Bosch et al., 2005). Cyperus esculentus milk has been found to be good for artherosclerosis. It contains arginine, a precursor of nitric oxide that helps the vein to relax and dilate. Its milk without sugar can be drunk by diabetics for its content in carbohydrates which is a base for sucrose and starch (without glucose) and due to its content of arginine which liberates the hormone that produces insulin (Adejuyitan, 2010).
Table 1: Proximate composition of Cyperus esculentus tuber