Two new antimicrobial dimeric compounds: febrifuquinone, a vismione-anthraquinone coupled pigment and adamabianthrone, from two Psorospermum species.

Febrifuquinone (1), a new vismione-anthraquinone coupled pigment and a new bianthrone named adamabianthrone (2), were isolated respectively, from the roots of Psorospermum febrifugum and from the bark of Psorospermum adamauense along with eight known compounds including: two bianthrones [(bianthrone A(1) (3) and bianthrone A(2b)], one vismione [(vismione D (4)], one anthrone (3-geranyloxyemodin anthrone) and four anthraquinones [(1,8-dihydroxy-3-isoprenyloxy-6-methylanthraquinone, emodin (5), 3-geranyloxy-1,8-dihydroxy-6-methylanthraquinone and 2-geranyl-1,8-dihydroxy-6-methylanthraquinone]. Their structures were determined using modern spectroscopic methods including one and two dimensional-NMR techniques as well as MS. Compounds 1 and 2 showed significant antimicrobial activities against a wide range of bacteria and fungi.

Antimicrobial activity of the methanolic extracts and compounds from Vismia laurentii De Wild (Guttiferae).

Methanolic extracts prepared from the leaves, twigs and the roots of Vismia laurentii De Wild as well as nine compounds isolated from these crude extracts, were tested for their antimicrobial activity against Gram-positive bacteria (six species), Gram-negative bacteria (12 species) and two Candida species using disc diffusion and well micro-dilution methods. The disc diffusion assay indicated that the crude extract was active against all the pathogens tested, whereas isolated compounds showed selective activities. The degree of sensitivity of the test organisms to purified compounds varied from 25 to 90%. Fridelin (8) was found to be the most active compound, while Bivismiaquinone (3) was the least active. The lowest minimum inhibition concentration (MIC) values as obtained by the micro-dilution assays were 19.53 and 1.22 microg/ml for the crude extracts and purified compounds, respectively. The lowest value for the purified compounds (1.22 microg/ml) was obtained with O(1)-demethyl-3',4'-deoxypsorospermin-3',4'-diol (6) on Candida gabrata and Bacillus subtilis; 1,8-dihydroxy-6-methoxy-3-methylanthraquinone (5) on Bacillus subtilis and 6-deoxyisojacareubin (7) on Bacillus stearothermophilus. These results provide promising baseline information for the potential use of these crude extracts as well as some of the isolated compounds in the treatment of bacterial and fungal infections.

Laurentixanthones A and B, antimicrobial xanthones from Vismia laurentii.

A phytochemical investigation of the constituents of the roots of Vismia laurentii has resulted in the isolation of two xanthone derivatives named laurentixanthone A (1) (6-hydroxy-3,3-dimethyl-11-(3-methylbut-2-enyl)pyrano[2,3-c]xanthen-7(3H)-one) and laurentixanthone B (2) (1-hydroxy-5,6,7,8-tetramethoxyxanthone), along with 11 known compounds: 1,7-dihydroxyxanthone, vismiaquinone, vismiaquinone B, bivismiaquinone, 3-geranyloxy-6-methyl-1,8-dihydroxyanthraquinone, O(1)-demethyl-3',4'-deoxypsorospermin-3',4'-diol, 6-deoxyisojacareubin, 1,8-dihydroxy-6-methoxy-3-methylanthraquinone, kaempferol, friedelin and stigmasterol. The structures of compounds were established by means of spectroscopic methods. Furthermore, the compounds were screened for antimicrobial activities in vitro.