The only chemical thumbnail of radish I could find in popular scientific references, is this one:
"The raw flesh has a crisp texture and a pungent, peppery flavor, caused by glucosinolates and the enzyme myrosinase which combine when chewed to form allyl isothiocyanates, also present in mustard, horseradish, and wasabi."
Of which the
glucosinolates have possible pesticidal properties according to this citation:
"Besides being bitter tasted in cooking, plants producing large amounts of glucosinolates are also desirable, because substances derived from these can serve as natural pesticides and are under investigation in the prevention of cancer (with sulforaphane in broccoli being the best known example).
Structural formula of
glucosinolates is in '
Related links' just beneath this answer page