Role of flavonoids in controlling the phototoxicity of Hypericum perforatum extracts

K. P. Wilhelm, K. P. Wilhelm, S. Biel, C. P. Siegers*

*Corresponding author for this work
27 Citations (Scopus)


Hypericum perforatum extracts are used mainly as oral antidepressants. Depending on source the extracts contain various amounts of phenylpropanes, flavonol derivates, biflavones, proathocyanidines, xanthones, phloroglucinoles, some amino acids, naphtodianthrones (hypericines) and essential oil constituents. The therapeutic use of Hypericum perforatum extracts however is limited by their phototoxic potential. It was the aim of the present study to investigate the phototoxic potential of 3 Hypericum perforatum extracts from different sources as well as some of its main constituents. In order to systematically study the phototoxic potential we established a modified neutral red assay utilizing an immortalized human keratinocyte cell line (HaCaT cells) as substrate and UVA irradiation. This modified neutral red assay was found to be a simple and reliable method for detecting phototoxic effects of reference agents and plant extracts. The validity of this method was demonstrated with known phototoxic compounds like chloropromazine and psoralenes like 5-MOP. Hypericum perforatum extracts demonstrated cytotoxicity and photocytotoxicity in a dose and UVA-dose dependent manner. Hypericine itself also evoked severe phototoxic effects and was thus identified as the main phototoxic constituent. Among the tested flavonoids quercitrin was found to be cytotoxic, while rutin unexpectedly demonstrated phototoxicity whereas quercitrin was effective to control the phototoxic activity of Hypericum perforatum extracts.

Original languageEnglish
Issue number4
Pages (from-to)306-309
Number of pages4
Publication statusPublished - 01.01.2001
Externally publishedYes

Research Areas and Centers

  • Academic Focus: Center for Brain, Behavior and Metabolism (CBBM)


Dive into the research topics of 'Role of flavonoids in controlling the phototoxicity of Hypericum perforatum extracts'. Together they form a unique fingerprint.

Cite this