Prenylated Phenols that Cause Contact Dermatitis from Trichomes of Phacelia ixodes

Abstract

The principal phenolic constituents were isolated from the exudate of the glandular trichomes of Phacelia ixodes KELLOGG (Hydrophyllaceae), a Mexican plant that causes allergic contact dermatitis. These are, in decreasing order of the amount in the trichomes: geranylhydroquinone (I), 3-geranyl-2,5-dihydroxyphenyl acetate (II), geranylbenzoquinone (III), 2-geranyl-6-hydroxy-4-methoxyphenyl acetate (IV), 2-geranyl-4-hydroxyphenyl acetate (V), 6-hydroxy-2-methyl-2-(4-methyl-3-pentenyl)-chromene (VI), and 6,7-dimethoxyapigenin. Compounds II, IV, and V are new natural products. Geranylbenzoquinone was the principal contact allergen in testing with guinea pigs.

Key Word Index

Phacelia ixodes - Hydrophyllaceae - Contact Dermatitis - Trichomes - Prenylated Phenol Derivatives - 4′,5-dihydroxy-6,7-dimethoxyflavone