Antimicrobial and antileishmanial xanthones from the stem bark of Allanblackia gabonensis (Guttiferae).

The phytochemical study of stem bark of Allanblackia gabonensis has resulted in the isolation and characterisation of one new xanthone derivative, named allanxanthone D, together with 10 known compounds, including 6 xanthones derivatives, allanxanthone A, 1,5-dihydroxyxanthone, 1,7-dihydroxyxanthone and 1,3,6,7-tetrahydroxy-2-(3-methylbut-2-enyl)xanthone, forbexanthone, 6-deoxyisojacareubin, one polyisoprenylated benzophenone, guttiferone F, one flavanol, epicathechin, two phytosterols, beta-sitosterol and campesterol. The structures of these compounds were established on the basis of one- and two-dimensional NMR homo- and hetero-nuclear evidence. These compounds were evaluated for their activity against Leishmania amazonensis in vitro and antimicrobial activities against a range of Gram negative and Gram positive bacteria.