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Reduction in hypericin-induced phototoxicity by Hypericum perforatum extracts and pure compounds.

Schmitt LA, Liu Y, Murphy PA, Petrich JW, Dixon PM, Birt DF

The Center for Research on Dietary Botanical Supplements, Iowa State University, 215 MacKay Building, Ames, IA 50011-1120, USA.

Clinical evidence suggests that administration of Hypericum perforatum (Hp) extracts containing the photo-activated hypericin compounds may cause fewer skin photosensitization reactions than administration of pure hypericin. This study was conducted to determine whether the phototoxicity of hypericin in HaCaT keratinocytes could be attenuated by H. perforatum extracts and constituents. Two extracts, when supplemented with 20 microM hypericin: (1) an ethanol re-extraction of residue following a chloroform extraction (denoted ethanol(-chloroform)) (3.35 microM hypericin and 124.0 microM total flavonoids); and (2) a chloroform extract (hypericin and flavonoids not detected), showed 25% and 50% (p<0.0001) less phototoxicity than 20 microM hypericin alone. Two H. perforatum constituents, when supplemented with 20 microM hypericin: (1) 10 microM chlorogenic acid; and (2) 0.25 microM pyropheophorbide, exhibited 24% (p<0.05) and 40% (p<0.05) less phototoxicity than 20 microM hypericin alone. The peroxidation of arachidonic acid was assessed as a measure of oxidative damage by photo-activated hypericin, but this parameter of lipid peroxidation was not influenced by the extracts or constituents. However alpha-tocopherol, a known antioxidant also did not influence the amount of lipid peroxidation induced in this system. These observations indicate that hypericin combined with H. perforatum extracts or constituents may exert less phototoxicity than pure hypericin, but possibly not through a reduction in arachidonic acid peroxidation.

Published 18 October 2006 in J Photochem Photobiol B, 85(2): 118-30.
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