The dried root or rhizome of Goldenseal (Hydrastis canadensis L.) contains several
alkaloids including
berberine,
hydrastine,
palmatine and lesser amounts of
canadine and
hydrastinine. Preparations derived from Goldenseal have been used to treat skin and eye ailments.
Berberine, the major
alkaloid in Goldenseal root
powder, has been used in
eye drops to treat
trachoma, a disease characterized by
keratoconjunctivitis.
Berberine and
palmatine are also present in extracts from Berberis amurensis Ruprecht (Berberidaceae) which are used to treat ocular disorders. We have previously shown that Goldenseal
alkaloids are phototoxic to keratinocytes (Chem Res Toxicol. 14, 1529, 2001; ibid 19, 739, 2006) and now report their effect on human lens and
retinal pigment epithelial cells. Human lens epithelial cells (HLE-B3) were severely damaged when incubated with
berberine (25 microM) and exposed to UVA (5 J cm(-2)). Under the same conditions,
palmatine was less phototoxic and
hydrastine,
canadine and
hydrastinine were inactive. Moderate protection against
berberine phototoxicity was afforded by the
antioxidants ascorbate (2 mM) and
N-acetylcysteine (5 mM). When exposed to UVA (5 J cm(-2)) both
berberine (10 microM) and
palmatine (10 microM) caused mild DNA damage as determined by the alkaline comet assay which measures single strand breaks.
Berberine and
palmatine are the only Goldenseal
alkaloids with appreciable absorption above 400 nm. Because light at wavelengths below 400 nm is cut off by the anterior portion of the adult human eye only
berberine and
palmatine were tested for
phototoxicity to human
retinal pigment epithelial (hRPE) cells. Although
berberine did damage hRPE cells when irradiated with visible light (lambda > 400 nm) approximately 10 times higher concentrations were required to produce the same amount of damage as seen in lens cells.
Palmatine was not phototoxic to hRPE cells. Neither
berberine nor
palmatine photodamaged
DNA in hRPE. Infusions of Goldenseal are estimated to contain approximately 1 mM
berberine, while in tinctures the
alkaloid concentration may be more than 10 times higher. Our findings show that eyewashes and lotions derived from Goldenseal or containing
berberine must be used with caution when the eyes are exposed to bright sunlight but that oral preparations are not likely to cause ocular
phototoxicity.