Isoamyl methoxycinnamates

Isoamyl-p-methoxycinnamate is a natural compound found in the roots of the Indian galangal plant, a member of the ginger family. Industrially it can be produced from cinnamic acid.

Isoamyl-p-methoxycinnamate is a soluble organic UV-B filter. It absorbs UV-B rays in the range from 280 to 320 nm (UVB spectrum). The maximum concentration of isoamyl-p-methoxycinnamate in cosmetic applications is 10 %.

Isoamyl methoxycinnamate has a significant allergenic potential (Ghazavi MK et al. 2011; Monzón S et al. 2009)

Organic light protection filters are all those UV filters whose effect is not exclusively based on the inorganic, physically active substances titanium dioxide or zinc oxide. Organic, also known as chemical UV filters, are photoactive substances that are able to absorb light quanta in a certain wavelength range (ultraviolet radiation in the range of about 280 to 400 nm = ultraviolet radiation = UVB/UVA spectrum). The absorbed UV is then released as thermal energy without penetrating the skin. In this reversible photoisomerization, the energy of the absorbed photon must correspond to the energy required to lift an electron in the molecule of the filter substance from a lower to a higher orbit. In order to protect over the entire width of the wavelengths relevant to humans from 290 to 400 nm, several chemical filters with different absorption maxima are usually combined. With a suitable combination of organic and physical filters, the content of organic filters can also be reduced with the same UV protection. This is desirable, since especially photounstable organic UV filters can cause phototoxic and photoallergic reactions depending on their concentration in the finished product.

1. Ghazavi MK et al (2011) Photo-allergic contact dermatitis caused by isoamyl p-methoxycinnamate in an 'organic' sunscreen. Contact dermatitis 64:115-116.
2. Monzón S et al (2009) Photoallergic contact dermatitis due to isoamyl p-methoxycinnamate. J Investig Allergol Clin Immunol 19:415-416.
3. Schauder S et al. (1997) Contact and photocontact sensitivity to sunscreens. Review of a 15-year experience and of the literature. Contact dermatitis 37:221-232.