ANTI-NUTRITIONAL CONSTITUENT OF COLOCASIA ESCULENTA ...

However,ifsaponins have a triterpenoid aglycone with glucuronic acid, they may taste of
licorice, sweetened by the sugar moiety (Grenby, 1991). Saponins occur in a wide variety
ofplants such as peanuts, lentils, lupins, alfalfa, soybeans, peas, oats and spinach (Smartt,
1976; 0akenfulL 1981; Price et al. 1987; Cuadrado et al., 1995; Hubman and Sumner,
2002).
Saponins are attracting considerable interest as a result of their diverse properties, both
deleterious and beneficial (Cuadrado et al., 1995). One of the well-known biological
effects ofsaponins is their ability to split erythrocytes (Khalil and EI-Adaway, 1994) and
to make the intestinal mucous membrane permeable (Johnson et aI., 1986). Saponins are
amphiphilous compounds which interact with biomembranes of animals, fungi and even
bacteria. The hydrophobic part of the molecule forms a complex with cholesterol inside
the membrane and their hydrophilic sugar side chain binds to external membrane
proteins. Thus, the fluidity ofbiomembranes is disturbed, which leads to the formation of
holes and pores. As a consequence, cells become leaky and die (Oakst and Knowles,
1977).
Clinical reports have also shown that the immune system is affected by saponins in ways
that lower cholesterol levels and help to protect the human body against cancers
(pathirana et al., 1980). This hypocholesterolemic effect has been ascribed to a
complexation of the saponin with cholesterol and bile acids, which results in a decrease
in their absorption from the intestines (Matsuura, 200I). A saponin-rich diet can be used
for the treatment of hypercalcinria in humans, as an antidote against lead poisoning and
in the inlnbition ofdental caries and platelet aggregation (Shi et al. 2004). Saponins also
reduce blood lipids (Chunmei et al., 2006), lower the risks ofdeveloping cancer (Messina
and Bennik, 1998) and lower blood-glucose response (Sajadi Tabassi et al. 2007).
A.I.S Effect ofproeessing on nutrients and anti-nutrients
Several fuctors influence the nutritional content offood. These include the genetic make-up
ofthe plant, the soil in which it is grown, nse of fertilizer, prevailing weather, maturity at
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