Goldenseal is an herb that is widely used in dietary supplements, eye washes, and
skin lotions. The presence of Goldenseal root
powder in dietary supplements and the topical application of Goldenseal preparations raise the possibility that an adverse phototoxic reaction may result from an interaction between its constituent
alkaloids and light in exposed tissues. We have previously shown that
berberine, the major
alkaloid in Goldenseal
powder, in combination with UVA causes DNA damage and cell death in HaCaT keratinocytes [(2001) Chem. Res. Toxicol. 14, 1529]. We have studied the photochemical and photobiological properties of four minor
alkaloids found in Goldenseal, namely,
hydrastine,
palmatine,
canadine, and
hydrastinine. UVA radiation of
palmatine in aqueous solutions generated no (1)O(2), but in CH(2)Cl(2), copious amounts of (1)O(2) were detected (Phi = 0.2).
Palmatine also photogenerated
oxygen-centered radicals, (*)
OH and O(2)(*)(-) in aerated aqueous
buffer and
acetonitrile, respectively, as detected by the spin trap 5,5-dimethyl-1-pyrroline N-
oxide (DMPO). In
nitrogen-sparged
acetonitrile containing DMPO, we observed the neutral
palmatine radical formed by one-electron reduction. UVA irradiation (4 J/cm(2)) of HaCaT keratinocytes in the presence of
palmatine (50 microM) resulted in a 50% decrease in cell viability but no DNA damage as measured by the comet assay. UVA irradiation of
hydrastine,
hydrastinine, or
canadine (50 microM) did not cause DNA damage or cell death in keratinocytes. Although
palmatine is photoactive, it is present in such small amounts in Goldenseal root
powder that the
phototoxicity of the herb is most likely due to
berberine, the major constituent
alkaloid.