Unusual Isomerisation of Cubebene
Keywords:
Microwave, soxhlet extraction, isomerisation of sesquiterpene, cubebenes, Solidago canadensis, NMR, tricyclic terpenesAbstract
Abstract. Some sesquiterpenes extracted from Solidago canadensis L. in methanol underwent apparent isomerisation and the addition of water or methanol when the Soxhlet extraction was replaced by a microwave heating method in polar solvents. The quantity of α-cubebene, one of these sesquiterpenes, during microwave extraction, was dramatically increased. In this study, we present the detailed comparison of two cubebenes subjected to this isomerisation, 6-epi-α-cubebene and α-cubebene, as well as their solvent microwave induced addition products obtained under microwave irradiation in polar solvents. The analysis is supported by high resolution bidimensional NMR (1H, 13C), mass spectroscopy and selected isotopic labelling experiments.
Resumen. Algunos sesquiterpenos extraidos de Solidago canadensis L. con metanol sufrieron aparente isomerización y la adición de agua o metanol cuando la extracción con soxhlet fue reemplazada por la extracción con disolventes polares en caliente usando microondas. La cantidad de α-cubebeno, uno de estos sesquiterpenos, se incrementó dramáticamente. En este estudio presentamos la comparación detallada de dos cubebenos sometidos a esta isomerización, 6-epi-α-cubebeno y α-cubebeno, así como sus productos de adición de disolvente obtenidos a partir de la irradiación con microondas en disolventes polares. El análisis se encuentra sustentado por evidencias de RMN bidimensional de alta resolución (1H y 13C), espectrometría de masas y experimentos selectos de marcaje isotópico.
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