Permethylation is a related term of permethylated.

In organic chemistry terms the difference between permethylated and permethylation

is that permethylated is modified by the addition of many (or as many as possible) methyl groups while permethylation is any methylation reaction in which very many, or all possible sites are methylated.

As an adjective permethylated

is modified by the addition of many (or as many as possible) methyl groups.

As a noun permethylation is

any methylation reaction in which very many, or all possible sites are methylated.