Phenolics in Moroccan medicinal plant species as studied by electron spin resonance spectroscopy

A chemical survey of 49 Moroccan medicinal plant species comprising 45 genera of 27 families was performed by electron spin resonance spectroscopy (ESR). 3,4-Dihydroxyphenylethanoid glycosides were especially evident as strong chemotaxonomic markers for the subfamily Lamioideae of the Lamiaceae, being observed in Marrubium vulgare, Aloysia triphylla and possibly recorded here for the first time in Oxyris quadripartita (Santalaceae). Chlorogenic acid was observed in Artemisia herba-alba but not in A. absinthium or in two other Asteraceae species. Rosmarinic acid was observed in Mentha spicata, Nepeta apulaei, Nepeta sp., Thymus maroccanus and T saturoides, all belonging to subfamily Nepetoideae of Lamiaceae. However, the acid was not observed in four other species of the subfamily. Thymoquinol was observed in Curcubita pepo, Crotalaria saharae, Nigella sativa (seed) and Piper longum but not in P Cubeba. The compound was also found in Thymus maroccanus but not in T saturoides. A strong signal of lawsone was observed with Lawsonia inermis. A naphthohydroquinone of unknown structure as well as juglone were observed from the stem bark of Juglans regia. Protocatechuic and caffeic acids were observed in the seeds of Ricinus communis, Aloysia triphylla and in Nepeta sp. Gallic acid and/or its esters were observed in six species of six families and often observed together, e.g., in the leaves of Euphorbia falcata. 6-Hydroxydopamine was identified in Piper long-uni. No ESR detectable phenolics were observed in nearly 20 species.