Ent-Kaurene diterpenes and n-alkanes isolated from the leaves of Coespeletia thyrsiformis (A.C.SM.) CUATREC

摘要

Coespeletia thyrsiformis is a resinous plant characteristic of the Andean highlands of Venezuela. The present work describes the extraction, from the leaves of this plant, of several biologically active diterpene compounds. An extract obtained by shaking the leaves with a 3:1 mixture of n-hexane-diethyl ether was treated with a 0.5 N NaOH solution to separate the acidic fraction. An aliquot of this acid fraction was methylated with diazomethane to submit the mixture to GC-MS analysis, which permitted to identify the following kaurene derivatives: ent-kaur-9(11),16-dien-19-oic acid (6.9 %), ent-kaur-16-en-19-oic acid (17.0 %), 15a-hydroxy-ent-kaur-16-en-19-oic acid (29.3 %), 15 a-isovaleroxy-ent-kaur-16-en-19-oic acid (7.6 %), and 15 α-O-isobutyroxy-ent-kaur-16-en-19-oic acid (6.1 %), as major components. On the other hand nonacosane (26.2 %) and 16-β-hydroxy-ent-kaurane (14.1 %) were found as major components in the neutral fraction.