ANTI-NUTRITIONAL CONSTITUENT OF COLOCASIA ESCULENTA ...

A.1.4.8
coordination sides to inhibit OH radical production (Obata, 2003; Muraoka and Miura.
2004).
Indeed, it is possible to use phytic acid as an uncommon, versatile food preservative
because of its anti-oxidant or iron-chelating properties (Hix et al. 1997). Thompson
(1988) suggested that the interaction among phytate, dietary starch and protein could be
beneficially utilized in the treatment of diabetes and hyperglycemia. This apparent
discrepancy between unhealthy and healthy properties of phytate clearly calls for a re­
evaluation ofthis storage compound (Grases et al. 2001).
Cyanogens
Cyanogen molecules consist of two CN groups that are bonded together at their carbon
atoms: N=C-N=C. Cyanogens are glycosides of 2-hydroxynitriles aod are widely
distnbuted among plants (Rosenthal aod Berenbaum, 1991; Bisby et al., 1994). When
plaots are wounded by herbivores or other organisms, the cellular compartmentation breaks
down and cyaoogenic glycosides come into contact with an active l3-glucosidase, which
hydrolyses them to yield 2-hydroxynitrile (Vetter, 2000). This is further cleaved into the
corresponding aldehyde or ketone aod hydrogen cyanide (HeN) by hydroxynitrile lyase
(eq. AI-I) (Conn, 1981). It is the low pH in the stomach which deactivates the 13­
glucosidase. Because the environment of the gut is alkaline, reactivation of part of the
enzyme fraction is a possibility. The collective name given to glycosides, cyaoohydrins
aod hydrogen cyanide is cyanogens (M0l1er and Seigler, 1999).
26