Identification of HSP70-inducing activity in Arnica montana extract and purification and characterization of HSP70-inducers

• We here searched for HSP70-inducers from a library of herbal extracts that have already been approved as quasi-pharmaceutical products in Japan.
• We selected an ethanol extract of Arnica montana and purified an HSP70-inducer, AM-2 (helenalin 2-methylbutyrate).
• Pre-treatment of cells with AM-2 or Arnica montana extract decreased melanin production.
• These results suggest that AM-2 and Arnica montana extract could be beneficial for use in hypopigmenting cosmetics as a consequence of their stimulatory effects on HSP70 expression.

BackgroundThe expression of heat shock proteins (HSPs), particularly HSP70, is receiving considerable attention in the field of cosmetics, particularly given our recent report that ultraviolet-induced melanin production, skin damage and wrinkle formation were all suppressed in transgenic mice expressing HSP70.ObjectiveIn the present study, we searched for HSP70-inducers from a library of herbal extracts that have already been approved as quasi-pharmaceutical products in Japan. We selected an ethanol extract of Arnica montana (A. montana), based on its high HSP70-inducing activity and low cytotoxicity.MethodsCell viability was determined by MTT method and expression of HPS70 was monitored by immunoblotting analysis.ResultsFrom the extract, we purified and identified eight sesquiterpene lactones (AM1–8) as HSP70-inducers, among which AM-2 (helenalin 2-methylbutyrate) was selected due to its good HSP70-inducing properties and low cytotoxicity. Treatment of cultured mouse melanoma cells with AM-2 or A. montana extract up-regulated the expression of HSP70 in a dose-dependent manner. This treatment also activated heat shock factor-1, a transcription factor for hsp genes. Furthermore, pre-treatment of cells with AM-2 or A. montana extract decreased melanin production and expression and activity of tyrosinase.ConclusionThese results suggest that AM-2 and A. montana extract could be beneficial for use in hypopigmenting cosmetics as a consequence of their stimulatory effects on HSP70 expression.