Diterpenquinones derivatives of the roots of Horminum pyrenaicum

Horminum pyrenaicum L. is the only representative of the monophyletic genus Horminum (Lamiaceae) and occurs in the south Alps as well as the Pyrenees. Previous phytochemical studies [1] revealed the presence of horminone and 7-O-acetylhorminone in the aerial plant parts as well as agastaquinone, 3-deoxyagastaquinone and coleon U 12-methylether in the sub aerial plant parts. Reinvestigation of the DCM extract of the root material carried out by means of silica gel and Sephadex LH 20 column chromatography as well as semi-preparative HPLC and LC-SPE-NMR enabled the identification of four abietane-diterpenquinone derivatives, two nor-abietane diterpenquinones and two abeo 18 (4→3) abietane diterpenequinones. The compounds were identified by mass spectrometry and 1- and 2-D NMR as horminone, 7-O-acetylhorminone, inuroyleanol and its 15,16-dehydro-derivative, representing a new natural product. Additionally, the nor-abietanes agastaquinone and 3-deoxyagastaquinone and the abeo 18 (4→3) abietanes agastol and its 15,16-dehydro-derivative were identified.

Fig.1: 15,16-Dehydroinuroyleanol

References: 1. Arnold, U. (2003) Ph.D. thesis at the University of Innsbruck, 154 pp.