Besides making a significant nutritional contribution to human diet, onions also have medicinal and functional properties (Lanzotti, 2006).
It has been used as a medicinal agent for thousands of years. Its tuber is used as tonic, aphrodisiac, stimulant, diuretic, antidiabetic, expectorant, emmenagogue, carminative, antispasmodic, anthelmintic, stomachic, anti-infective agent, against tumours, vomiting, pain and bleeding piles. Externally, it has been used as a rubefacient and poultice, giving relief in skin diseases and insect bites. Also, it increases fibrinolysis and lower blood pressure (Kirtikar and Basu, 1984; Al-Bekairi et al., 1991; Saleheen et al., 2004).
Jacob and Anwar (2009) reviewed the range of garlic- and onion-derived substances capable of preventing the formation of cancer cells, preventing cancer cell proliferation, and killing cancer cells (e.g., by induction of apoptosis).