Echinacea angustifolia DC is among the top-selling medicinal plants, whose pharmacological activity is due to several active principles, including caffeic acid derivatives (CAD). Plants grown under controlled conditions exhibit a large variability in composition, which may result from inadequate processing prior to HPLC analysis. Moreover, commercial preparations of E. angustifolia are normally obtained from dried roots and limited information is available on the extraction of fresh material, which may be required in research work. The paper shows how the post-harvest handling (i.e. storage temperature, drying conditions and extraction protocol) influenced the content of two main components, echinacoside and cynarin, in E. angustifolia roots. The two marker compounds were identified by means of LC-MS and quantified by HPLC with UV detection. A pooled sample of roots was prepared with plants from a controlled greenhouse hydroponic cultivation and six homogeneous aliquots were subjected to the following treatments: storage at -80°C (FR-80) or -20°C (FR-20), freeze-drying (FD), air- drying at room temperature (AD25), oven-drying at 50°C (AD50) or 75°C (AD75). Subsequently the samples were extracted according to a protocol reported in the literature. With the air- or oven-drying treatments, the concentrations of the marker compounds exhibited opposite dependence on temperature. Moreover, both echinacoside and cynarin were absent or scarce in FR-80, FR-20 and FD root samples. Some modifications of the original extraction method were therefore tested, aimed at improving the extraction efficiency. The final protocol that was developed consisted in the addition of acidified methanol 70% to the sample prior to grinding, to reduce the risk of air and enzymatic oxidation. No loss of metabolites, as determined through an internal standard (gallic acid), was observed with this method. Compared to the original extraction protocol, the modified one improved the extraction efficiency in AD50 roots and, above all, allowed the recovery of both echinacoside and cynarin in FR-80, FR-20 and FS samples. Despite the substantial improvement, in the latter samples the contents of the two marker compounds remained significantly lower than those found in oven-dried roots. These findings suggest that metabolite degradation may occur in roots which do not undergo dehydration, and the best post-handling process is oven-drying at 50°C or higher temperature.
|Autori:||MAGGINI R; RAFFAELLI A; ANNAHEIM K.E; TOZZINI L; PACIFICI S; GUIDI L; PARDOSSI A|
|Titolo:||Effect of post-harvest handling and extraction on the content on echinacoside and cynarin in the root tissues of Echinacea angustifolia DC|
|Anno del prodotto:||2010|
|Appare nelle tipologie:||1.1 Articolo in rivista|