Characterization of Hypericum perforatum L. (St. John's wort) macerates prepared with different fatty oils upon processing and storage

Hypericum perforatum L. (St. John's wort, SJW) is a traditional medicinal plant with a long history of pharmaceutical application. Today, besides formulations based on hydro-alcoholic extracts, lipophilic SJW preparations are widely used in phytomedicine e.g. for the symptomatic treatment of minor inflammations of the skin and subcutaneous tissue disorders. In the present study, SJW extracts were obtained with twelve different fatty oils according to a standardized protocol. In order to evaluate and compare the resulting macerates, a set of analytical parameters was chosen: the phytochemical profile of SJW oil extracts comprising acylphloroglucinol derivatives, flavonols, biflavones and naphthodianthrones was assessed using UHPLC-DAD and UV/VIS-spectroscopic methods Furthermore, overall appearance was monitored applying the CIE L*a*b* color system. Depending on the type of oil applied for extraction, a*-values, which are a measure of red color hues, ranged from 50.3 +/- 0.2 (almond oil) to -3.8 +/- 0.3 (macadamia nut oil). Considering total hypericin contents, extraction with almond oil also brought about highest amounts (5.5 +/- 0.21 mg/100 g). In contrast, preparations with macadamia nut oil resulted in highest contents of hyperforin and adhyperforin, whereas a semi-synthetic extractant composed of medium-chain triglycerides (MCT) revealed highest yields of flavonoids, i.e. quercetin, kaempferol and I3, II8-biapigenin. Since the phytochemical composition and the corresponding specific characteristics of SJW oil preparations markedly differed, tailor-made SJW extracts may be prepared by systematic adaption of the manufacturing conditions, including the choice of a specific fatty oil. Additionally, SJW oil extracts were stored under different temperature (5 degrees C, 20 degrees C, 50 degrees C) and light (artificial light, darkness) regimes over a period of six months to evaluate their respective storage stability. For maximizing the retention of the investigated plant secondary metabolites in the corresponding oil extracts, cold storage (5 degrees C) under the exclusion of light is recommended. (C) 2017 Phytochemical Society of Europe. Published by Elsevier Ltd. All rights reserved.