Essential Oil Composition and Allelopathic Effect of the Brazilian Lamiaceae <i>Hesperozygis ringens</i> (Benth.) Epling and <i>Hesperozygis rhododon</i> Epling

Abstract

Samples of Hesperozygis ringens (Benth.) Epling and Hesperozygis rhododon Epling essential oils were analyzed by a combination of analytical techniques: capillary gas chromatography, liquid/solid chromatography, GC/MS coupling, and NMR spectroscopy. Twenty-four components have been identified representing altogether more than 95% of the oil content. The oil of H. ringens is constituted mainly by pulegone (79.2%) accompanied by several oxygenated derivatives (pulegone oxides, 1.2%; 8-hydroxy-p-menth-3-one, 1.3%; and 8-hydroxy-p-menth-4-en-3-one, 3.7%); that of H. rhododon contains menthone and pulegone as main compounds in almost comparable amounts (43.4% and 29.6%, respectively). Tests carried out on lettuce seeds using alcoholic extracts of the two species showed significant antigerminating properties mainly for H. ringens. The same activity was observed with its essential oil. Keywords: Hesperozygis ringens (Benth.) Epling; Hesperozygis rhododon Epling; Lamiaceae; essential oil composition; pulegone; menthone