A potent contact allergen of Phacelia (Hydrophyllaceae)

Abstract

The major contact allergen of Phacelia crenulata (Hydrophyllaceae) has been identified as geranylhydroquinone. A maximization test of geranylhydroquinone showed this to be a potent sensitizer comparable in degree to poison oak/ivy urushiol. Comparative patch testing on humans with urushiol established that the phacelia allergen does not cross-react with poison oak or ivy.

Synthesis and NMR Structure Determination of New Linear Geranylphenols by Direct Geranylation of Activated Phenols

“…The subgroups of linear geranylquinones or geranylhydroquinones are represented by an important number of compounds, for example 2-geranylbenzoquinone (1) isolated from Ascindian Synoicum castellatum [1] and 2-geranylhydroquinone (2) isolated from tree Cordia alliodora [2], Phacelia crenulata [3][4][5], Aplidium antillense [6] and the tunicate Amaroucium multiplicatum [7]. Both natural products are present in higher plants, but also have been reported in marine urochordates [8].…”

Contact allergens of an urban shrub Wigandia caracasana

“…We have conducted a human maximization test of geranylhydroquinone ( Fig. 1), isolated from arelated plant genus Phacelia (9). Although geranylhydroquinone is a relatively weak elicitor in guinea pig tests, compared to the compounds from Wigandia, it proved to be a potent sensitizer of humans, sensitizing all of 21 subjects tested and eliciting 2 + to 4 + reactions with a 5 j.lg unoccluded application on 14 of these subjects.…”

Human maximization test of falcarinol, the principal contact allergen of English ivy and Algerian ivy (Hedera helix, H. canariensis)

“…With geranylhydroqumone from the Califorma wildflower Phacelia, 19 of 21 subjects were sensitized With a 0.5% applicatiOn (7). However, numerous maximizatiOn studies have been conducted With plant products used m fragrances and cosmetics (8) and few approach the sensitiZing potential of falcannol or elicit such severe bullous reactwns m those sensitized.…”