A

cysteine

n ii ch pyridoxal phosphate r-c=n n=c-

o nh cooh cyanoalanine asparagine rhodanese r-s-c=n

Figure 10.10 The release of cyanide from linamarin and the detoxification of cyanide either by conversion of cysteine to asparagine or by oxidation to thiocyanate internal and water soluble, not on the cuticular surface, which is hydrophobic. He suggests the whole concept needs to be re-thought.

Some of the primitive cycad plants produce the highly toxic glycoside cycasin (Figure 10.11). Yet some butterflies and moths can feed on the plants and sequester the cycasin. The hairstreak butterfly Eumaeus atala florida absorbs the toxic glucoside, so that larvae contain 0.02% and adults 1.0 to 1.8% cycasin by weight. When the moth Seirarctia echo was fed on the aglycone, methylazoxymethanol, they stored cycasin. They probably hydrolyze cycasin in their gut and then re-glycosylate it again to store it. Cycasin and methylazoxymethanol are carcinogenic, hepato-toxic, mutagenic and radiomimetic, all of which can be summarized by saying that they are active alkylating agents.

ho ho oh

oh cycasin ch3 O

ho-c v h? o methylazoxymethanol Figure 10.11 Cycasin and its aglycone methylazoxymethanol

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