Analysis and stability of the constituents of St. John's wort oils prepared with different methods

St John's wort (SJW) is one of the most interesting medicinal plants with a long history of use in traditional medicine all over Europe [1]. Traditional preparations and in particular the oil from SJW flowers [3] remain one of the most popular and curative topical remedy against ulcerations and burns. In this study we tried to rationalize the production system of the oily preparation in order to obtain the highest concentration and stability of phloroglucinols. Five different samples of SJW oils were evaluated to verify the variability and stability of the constituents according to the following factors: different harvesting time, fresh or dried plant material, use of sunlight or heating during extraction. The stability of these oils during was tested over one year. Only constituents can be extracted during maceration and their variability, especially phoroglucinol content in the various oils is great. Extractability of hyperforin ranged from 19.5 to 2.4% and maximum extraction was obtained with fresh plant material exposed to sunlight during maceration. The drying process and the use of artificial light during maceration affected the extraction of hyperforin, producing a very low percentage of this compound. Adhyperforin showed a better extractability if fresh plant material was used. Furohyperforin was identified only in one sample (12%), probably as oxidation product derived from the phoroglucinol under heat. No naphthodianthrones neither flavonoids, with the exception of I3, II8-biapigenin were found in the oils. However, its content had a wide variability: the highest content was 3.51 ppm, while it was not detected in the samples stressed with heat and/or light. Concerning the stability study during one year, the results evidenced that the traditional oil and the oil obtained by extraction of fresh material represent the best procedures to obtain high phloroglucinol contents which seems to be responsible for the oil's activity.

References: [1] Bradley P. St. John's wort. British Herbal Compendium (2006) 363–368. vol. 2. British Herbal Medicine Association. Bournemouth UK. [2] ESCOP ''Hyperici Herba'' Monographs on the Medicinal Uses of Plant Drugs. Exeter, U.K.: European Scientific Cooperative on Phytotherapy, 1997. [3] DAB6, EB 6, 1941.