Micromorphological and phytochemical traits of four Clinopodium L. species (Lamiaceae)

Types and distribution of trichomes, chemical composition of the essential oil, as well as contents of phenolic compounds were studied in four Balcanic Clinopodium L. species (family Lamiaceae), namely C. dalmaticum (Benth.) Bräuchler et Heubl, C. pulegium (Rochel) Bräuchler, C. serpyllifolium (M. Bieb.) Kuntze, and C. thymifolium (Scop.) Kuntze. Non-glandular trichomes, peltate trichomes, and three types of capitate trichomes were observed on the leaves, calyces, and stems. In general, 62 different essential oil compounds were identified: 21 from C. dalmaticum, 31 from C. thymifolium, 36 from C. serpyllifolium, and 37 from C. pulegium. The essential oil of all species was characterized by the high content of oxygenated monoterpenes (66.2–79.6%), with dominant menthane type compounds, such as menthone, pulegone, piperitenone, and piperitenone oxide. Total polyphenols (TP), tannins (T), total flavonoids (TF), and total phenolic acids (TPA) were determined spectrophotometrically. The lowest levels of these compounds were found in C. serpyllifolium (3.83%, 0.88%, 0.39%, and 2.91%, respectivelly), and the highest in C. thymifolium (TP, 7.40%) and C. pulegium (T, 1.78%; TF, 0.57%; TPA, 6.59%).