Although cosmetic and personal care product developers are seeing German chamomile grow in popularity, the topical application of this herbal ingredient has been reported to cause allergic skin reactions. However, it is still unknown which chemical elements are responsible for this outcome.
Therefore, researchers from the University of Mississippi and the U.S. Food and Drug Administration used activity-guided fractionation and isolated three potential sensitizers from German chamomile, which were tested in vitro using a skin sensitization assay.
The compounds identified included:
- Polyacetylene tonghaosu
- trans-Glucomethoxycinnamic acid
- cis-Glucomethoxycinnamic acid
In chemico techniques found these compounds were non- to weakly reactive; although interestingly, aged tonghaosu was more reactive than freshly isolated tonghaosu.
This polyacetylene constituent was determined to be chemically unstable, generating a fourth compound as it aged: a small electrophilic spirolactone, 1,6-dioxaspiro[4.4]non-3-en-2-one.
This lactone was strongly reactive in both in chemico high-throughput screening and nuclear magnetic resonance based on Dansyl CYsteAmine (NMR-DCYA). In addition, it was verified as a potential skin sensitizer by Local Lymph Node Assay (LLNA).