Topical application of St Johnʼs wort (Hypericum perforatum L.) and of its metabolite hyperforin inhibits the allostimulatory capacity of epidermal cells - Schempp, C M; Winghofer, B; Lüdtke, R; Simon-Haarhaus, B; Schöpf, E; Simon, J C (Br J Dermatol, 2000)