ANALYSIS OF NATURALLY OCCURRING PHENOLIC COMPOUNDS IN AROMATIC PLANTS BY RP‐HPLC AND GC‐MS AFTER SILYLATION

ABSTRACT Aromatic plants of Greek origin, Origanum dictamnus (dictamus), Eucalyptus globulus (eucalyptus), Origanum vulgare L. (oregano), Mellisa officinalis L. (balm mint) and Sideritis cretica (mountain tea) were examined for the content of phenolic substances. Reversed phase high performance liquid chromatography was used for the analysis of the plant extracts. Gas chromatography–mass spectrometry method was also used for identification of phenolic compounds after silylation. The most abundant phenolic acids were gallic acid (1.5–2.6 mg 100 g−1 dry sample), ferulic acid (0.34–6.9 mg 100 g−1 dry sample) and caffeic acid (1.0–13.8 mg 100 g−1 dry sample). (+)-Catechin and (−)-epicatechin were the main flavonoids identified in oregano and mountain tea. Quercetin was detected only in eucalyptus and mountain tea. PRACTICAL APPLICATIONS Plant-derived polyphenols receive considerable interest because of their potential antioxidant and antimicrobial properties. Undoubtedly, it is very important not only to determine those properties but also to determine each and every phenol in aromatic plants both qualitatively and quantitatively. A number of analytical methods have been proposed for the separation and determination of these compounds. Most of these protocols are based on a high performance liquid chromatography technique with ultraviolet spectrophotometry. Gas chromatography–mass spectrometry after silylation of the phenolic compounds is used in this research together with the aforementioned technique as an alternative and more sensitive method to detect and understand the compositional profile of the extracts as well as the structure and functional relationship of the components in the extracts, based on MS spectra.