Planta Med 2009; 75 - SL6
DOI: 10.1055/s-0029-1234261

Rapid and efficient purification of hypericin and pseudohypericin and inhibition of thioredoxin reductase

A Karioti 1, F Sorrentino 2, P Gratteri 1, MP Rigobello 2, G Scutari 2, L Messori 3, A Bindoli 4, MC Bergonzi 1, AR Bilia 1
  • 1Department of Pharmaceutical Sciences, University of Florence, via Ugo Schiff 6, Polo Scientifico, Sesto Fiorentino, 50019, Florence, Italy
  • 2Department of Biological Chemistry, University of Padua, Viale G. Colombo 3, 35121 Padua, Italy
  • 3Laboratory of Metals in Medicine, Department of Chemistry, Univ. of Florence, Via della Lastruccia 3, 50019 Sesto Fiorentino, Florence, Italy
  • 4Institute of Neurosciences (CNR), Section of Padua c/o Department of Biological Chemistry, Padua, Italy

Hypericins have many biological and pharmacological activities and in particular reported as potent anticancer molecules [1]. These molecules are widely distributed in plant kingdom but their availability is limited due to the low content in the plants. A rapid and efficient isolation of hypericin and pseudohypericin from H. perforatum hydro-alcoholic dried extracts has been developed. Briefly, the method consists of a partition of the extract between organic and aqueous layers, further purification with Sephadex LH-20 column chromatography and a final separation of constituents using Sephadex LH-60 column chromatography. The three-step fractionation resulted in 98% content in total naphthodianthrones. To the best of our knowledge this is the first report on the separation of hypericin from pseudohypericin using size exclusion chromatography [2]. Pure hypericin and pseudohypericin were tested on both cytosolic (TrxR1) and mitochondrial thioredoxin reductases (TrxR2). Hypericin and, particularly, pseudohypericin acted as strong inhibitors of thioredoxin reductases, both in the dark and in ambient light. Further, pseudohypericin, similarly to hypericin, also inhibits glutathione reductase. Pseudohypericin IC50 values for TrxR1 and TrxR2 were 4.6 and 7.9µM, respectively. Hypericin appeared to be more effective on mitochondrial thioredoxin reductase reaching an IC50 value of about 50µM, a value that is noticeably lower than that measured for TrxR1 (198µM). The inhibition profile was similar to that produced by hypericins on glutathione reductase. As the thioredoxin system is highly overexpressed in cancer cells, its inhibition by hypericins, natural compounds that are known to display appreciable anticancer properties, can offer new clues on their mechanism of action and may open interesting perspectives for future tumor therapy.

References: [1] Kubin, A. et al. (2005) Curr. Pharm. Design 11:233–253.

[2] Karioti, A. et al. (2009)J. Sep. Sci. in press.