Aromatic ring structures are metabolized by:

i. Dehydroxylation

ii. Ring cleavage mechanism

But before this transformation take place substitution group present on the aromatic ring are completely or partially removed. Substitution groups which are uncommon in the natural compounds for e.g.:  halogens etc. hinder hydroxylation process resulting in the recalcitrant like DDT

• The aromatic ring is cleaved by highly specific oxygenase which is produced by a no. of micro-organisms.
• The cleavage occurs between 2-C atoms, each of which is linked to a hydroxyl group. This is called ortho-fission.
• The cleavage may occur between an-hydroxylated C-atom & a non-hydroxylated C-atom. This is called meta fission.