Contact allergy due to colophony (VII), Sensitizing studies with oxidation products of abietic and related acids

9 oxidation products of abietic acid, dehydroabietic acid, and levopimaric acid were prepared synthetically to determine their sensitizing potential in guinea pigs. It was found that compounds with epoxy and peroxo groups in rings A and B had a notable sensitizing potential. The same result was found with 7-oxode-hydroabietic acid identified earlier in rosin (3) and a polar fraction obtained from commercial abietic acid, suggesting the presence of still unidentified oxidation products. Hydroxylation of rings A or B, or conversion to the methyl esters, considerably decreases the sensitizing potential. A model is presented underlining the importance of hydrophobic and polar domains addition to chemically reactive groupings, in the allergen. Insertion into the lipid bilayer may play an important role in contact sensitivity.