ANTI-NUTRITIONAL CONSTITUENT OF COLOCASIA ESCULENTA ...

B2.1.1
B2.1.2.1
Introduction
CHAPTER B2-1: SAPONIN
LITERATURE REVIEW
Many different secondary metabolites are synthesized collectively by plants. This can
either be as a response to pathogen attacks and stress or part ofthe plant's normal growth.
Although these secondary metabolites are not required for growth and reproduction, they
are important in that they offer the plant selective advantages: for example, restraining
the growth of neighboring plants or protecting the plant against pests, pathogens and
stress (Wink, 1999; Morrissey and Osbourn, 1999).
Saponin - chemistry
Saponins are a pharmacodynamic group of secondary metabolites with a wide spectrum
of biological activities. They are found in more than 90 plant families (Sondhia, 2005),
such as peanuts, lentils, lupins, alfalfa, oats and spinach (Fenwick and Oakenfull, 1983;
Huhman and Sunmer, 2002; Woldemichael et aI., 2003).
Saponins are characterized by surfactant properties because they contain both
hydrophobic and hydrophilic components and, in most cases, give stable, soap-like foams
in aqueous solutions. Saponins are glycosidic compounds containing a carbohydrate and
a non-carbohydrate unit in the same molecule. An acetal linkage joins the carbohydrate
residue to a non-earbohydrate residue or aglycone at carbon atom position 1. The sugar
component is called the glycone. Saponins are surface-active compounds because of a
lipid-soluble aglycone and water-soluble sugar chain(s) in their structure. This
aruphiphilic characteristic gives saponins detergent, wetting, emulsifying and foaming
properties (Ibanoglu and lbanoglu, 2000; Sarnthein-Graf and La Mesa, 2004; Wang et
aI., 2005)
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