Phytochemical investigation of Datura quercifolia (Solanaceae) plant yielded a new datura lactone, 1beta,5alpha,12alpha-trihydroxy-6alpha,7alpha,24alpha,25alpha-diepoxy-20S,22R with-2-enolide (1), along with two known compounds, 2 and 3. The structure of 1 was established on the basis of spectral