[en] A sensitive and accurate method, combining Soxhlet extraction, solid-phase extraction and capillary gas chromatography, is described for the quantitative determination of four new diterpenes (ent-trachyloban-3 beta-ol, ent-18-hydroxy-trachyloban-3-one, ent-trachyloban-3-one and isopimara-7,15-dien-3 beta-ol) from the leaves of Croton zambesicus. This is the first method describing the quantification of trachylobane diterpenes in a crude extract. It has been fully validated in order to be able to compare the diterpene composition in other samples of C. zambesicus, which is an important source of trachylobanes. Copyright (c) 2005 John Wiley