Effect of Light on Hypericins Contents in Fresh Flowering Top Parts and in an Extract of St. John's Wort (Hypericum perforatum)

Abstract

St. John's Wort is a medicinal plant increasingly used for its antidepressive activity. Hypericins are considered as one of the compounds contributing to the activity of the extract. These naphthodianthrones exist in various forms in Hyperici herba. Protopseudohypericin and protohypericin (protopigments) are converted into pseudohypericin and hypericin (pigments) under the action of light. The aim of this work is to study the influence of light on the phototransformation of protopigments into pigments. Two experiments were carried out. The studies were performed on one hand, on plant material in order to know the proportion of these substances in various plant parts and the possibility of transforming the protopigments into pigments under the action of sunlight; on the other hand, in the extract to determine the optimal wavelength allowing this transformation. Three parts of the fresh plant (buds, flowers, leaves) were treated with sunlight on three levels of exposure. Liquid extracts were exposed to various types of light with wavelengths ranging between 480 and 660 nm by means of diodes. The flowering tops of St. John's Wort contain a share of approximately 30 % hypericins in the form of protopseudohypericin and protohypericin: buds (48 %), flowers (30 %), leaves (17 %). After an exposure of fresh buds to sunlight for 16 hours the share of protopigments was then 32 %. In the extract, the transformation of the protopigments is total and requires less energy than in the plant material. The optimal wavelength for the transformation of the protopigments in the extract is around 515 nm (green), close to the optimum absorption level of protopigments.

Protohypericins - hypericins - phototransformation - Hypericum perforatum L. - Clusiaceae

References

• 1 Bombardelli E, Morazonni P. Hypericum perforatum .  Fitoterapia. 1995;  116 43-67
• 2 Bennett D A, Polk L JF, Voglino S A, Zlotnik V, Raffa R B. Neurophamacology of St. John's Wort (Hypericum).  Psychiatry. 1998;  32 1201-8
• 3 Hölzl J, Ostrowski E. Johanniskraut (Hypericum perforatum L.). HPLC-Analyse der wichtigen Inhaltsstoffe und deren Variabilität in einer Population.  Deutsche Apotheker Zeitung. 1987;  23 1227-30
• 4 Nahrstedt A, Butterweck V. Biologically active and other chemical constituents of the herb of Hypericum perforatum L.  Pharmacopsychiatry. 1997;  30 129-34
• 5 Cellarova E, Kimakova G M, Brutovska R. Multiple shoot formation and phenotypic changes of ro regenerants in Hypericum perforatum L.  Acta Biotechnologica. 1992;  12 445-52
• 6 Southwell I A, Campbell M H. Hypericin content variation in Hypericum perforatum in Australia.  Phytochemistry. 1991;  30 475-8
• 7 Büter B, Orlacchio C, Soldati A, Berger K. Significance of genetic and environmental aspects in the field cultivation of Hypericum perforatum .  Planta Medica. 1998;  64 431-7
• 8 Duran N, Song P S. Hypericin and its photodynamic action.  Photochemistry and Photobiology. 1986;  43 477-80
• 9 Butterweck V, Petereit F, Winterhoff H, Nahrstedt A. Solubilized hypericin and pseudohypericin from Hypericum perforatum exert antidepressant activity in the forced swimming test.  Planta Medica. 1998;  64 291-4
• 10 Singer A, Wonnemann M, Muller W E. Hyperforin, a major antidepressant constituent of St. John's Wort, inhibits serotonin uptake by elevating free intracellular Na⁺ .  The Journal of Pharmacology and Experimental Therapeutics. 1999;  290 1363-8
• 11 Delaey M, Kamuhabwa R, Vandenbogaerde A L, Witte P A. Phototoxicity of protohypericin after photoconversion to hypericin.  Planta Medica. 1999;  65 719-22
• 12 Freytag W E. Bestimmung von Hypericin und Nachweis von Pseudohypericin in Hypericum perforatum L. durch HPLC.  Deutsche Apotheker Zeitung. 1984;  124 2383-6
• 13 Krämer W, Wiartalla R. Bestimmung von Naphthodianthronen (Gesamthypericin) in Johanniskraut (Hypericum perforatum L.)  Pharmazeutische Zeitung der Wissenschaft. 1992;  137 202-7
• 14 Gaedcke F. Johanniskraut und dessen Zubereitungen, Qualitätsbeurteilung über ein selektives reproduzierbares HPLC Verfahren.  Deutsche Apotheker Zeitung. 1997;  137 117-21
• 15 Gaedcke F. Herstellung, Qualität, Analytik und Anwendung von Johanniskraut-Extrakten.  Zeitschrift für Arzneimittel und Gewürzpflanzen. 1997;  2 63-72
• 16 Kurth H, Spreemann R. Phytochemical characterization of various St. John's Wort extracts.  Advances in Therapy. 1998;  15 1117-28
• 17 Häberlein H, Tschiersch K P, Stock S, Hölzl J. St. John's Wort (Hypericum perforatum L.) Part 1: Identification of an additional naphthodianthrone.  Pharmazeutische Zeitung Wissenschaft. 1992;  137 169-74
• 18 Upton R E. St. John's Wort Quality Control Analytical and Therapeutic Monograph.  HerbalGram. 1997;  40 1-32
• 19 Hahlbrock K, Scheel D. Physiology and molecular biology of the phenylpropenoid metabolism.  Annual Review of Plant Physiology and Plant Molecular Biology. 1989;  40 347-69
• 20 Falk H, Schmitzberger W. On the nature of “soluble” hypericin in Hypericum species.  Monatshefte für Chemie. 1992;  123 731-9