A bioassay-guided fractionation of a culture filtrate of Botryosphaeria obtusa led to the isolation of four dihydroisocoumarins, named mellein 1, 4-hydroxymellein 2, 7-hydroxymellein 3 and the new 4,7-dihydroxymellein 4. LC-UV-DAD-MS analysis of vine wood infected by B. obtusa revealed the presence of mellein (1). Botryosphaeria obtusa was also able to oxidise wood δ-resveratrol into the dimer delta-viniferin. The structures of isolated phytotoxins were established on the basis of IR, MS, 1D and 2D NMR.

Antibacterial bioassay-guided fractionation of Syzygium guineense leaf extracts afforded 10 triterpenes, namely betulinic acid 1, oleanolic acid 2, a mixture of 2-hydroxyoleanolic acid 3a, 2-hydroxyursolic acid 3b, arjunolic acid 4a, asiatic acid 4b, a mixture of terminolic acid 5a, 6-hydroxyasiatic acid 5b, and a mixture of arjunolic acid 28-␤-glucopyranosyl ester 6a and the asiatic acid 28-␤-glucopyranosyl ester 6b. Isolated compounds were submitted to an antibacterial assay system against gram-positive and -negative bacteria and human pathogen bacteria. Compounds 4a and 4b showed the most significant antibacterial activity against Escherichia coli, Bacillus subtilis and Shigella sonnei. The fraction 5a-5b was the least active, whereas compounds 1, 2 and the mixtures of 3a-3b and 6a-6b were inactive in the assays.

Two clerodane diterpenoids, Bafoudiosbulbins A 1, and B 2, together with five known compounds: tetracosanoic acid, 1-(tetracosanoyl)-glycerol, trans-tetracosanylferulate, b-sitosterol and 3-O-b-D-glucopyranosyl-b-sitosterol were isolated from the tubers of Dioscorea bulbifera L. var sativa. Their structures were established by spectroscopic methods (1D and 2D-NMR, MS) and X-ray crystallographic diffraction analysis of compound 1. The CH 2 Cl 2 -soluble portion of the crude extract and the two clerodanes were screened for anti-bacterial activity using both agar diffusion and broth dilution techniques against Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, Salmonella typhi, Salmonella paratyphi A and Salmonella paratyphi B. They both showed significant activities against P. aeruginosa, S. typhi, S. paratyphi A and S. paratyphi B.

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