Benzo[ b ]naphtho[2,1- d ]furans and 2-Phenylnaphthalenes from Streblus usambarensis .

Three new benzo[ b ]naphtho[2,1- d ]furans, usambarins A-C ( 1 - 3 ), five new 2-phenylnaphthalenes, usambarins D-H ( 4 - 8 ), a new flavan ( 9 ), and a new phenyl-1-benzoxepin ( 10 ) as well as two known compounds ( 11 and 12 ) were isolated from the extract of the stem and roots of Streblus usambarensis (Moraceae). The structures were deduced using NMR spectroscopic and mass spectrometric analyses, and those of compounds 1 and 4 were confirmed by X-ray crystallography. Usambarin D ( 4 ) demonstrated moderate antibacterial activity (MIC 9.0 μM) against Bacillus subtilis , while none of the tested compounds were effective against Escherichia coli .