Antibacterial activity of some natural products against bacteria expressing a multidrug-resistant phenotype.

The present study assessed the antimicrobial activities of various natural products belonging to the terpenoids, alkaloids and phenolics against a collection of Gram-negative multidrug-resistant (MDR) bacteria. The results demonstrated that most of the compounds were extruded by bacterial efflux pumps. In the presence of the efflux pump inhibitor phenylalanine arginine β-naphthylamide (PAβN), the activities of laurentixanthone B (xanthone), plumbagin (naphthoquinone), 4-hydroxylonchocarpin (flavonoid) and MAB3 (coumarin) increased significantly against all studied MDR bacteria.

Antimalarial activity of extract and norbergenin derivatives from the stem bark of Diospyros sanza-minika A. Chevalier (Ebenaceae).

The methanol extract from the stem bark of Diospyros sanza-minika as well as five norbergenin derivatives isolated from this crude extract were evaluated for their in vitro activity against Plasmodium falciparum K1 and cytotoxicity on MRC-5 cells. 4-O-(3'-methylgalloyl)norbergenin was found to be the most potent compound (IC(50) 0.6 μg/mL; CC(50) 24.

In vitro cytotoxic activity of isolated acridones alkaloids from Zanthoxylum leprieurii Guill. et Perr.

Chemical investigation of the roots and fruits of Zanthoxylumleprieurii Guill. et Perr. led to the isolation of three new alkaloids including two acridone derivatives, 3-hydroxy-1,4-dimethoxy-10-methyl-9-acridone (2) and 3-hydroxy-1,2-dimethoxy-10-methyl-9-acridone (3) named helebelicine A and B, respectively, and one secobenzo[c]phenantridine, 10-O-demethyl-12-O-methylarnottianamide (10), together with thirteen other compounds.

Cytotoxicity of natural compounds isolated from the seeds of Garcinia afzelii.

The new compounds guttiferone O ( 1) and 3-methoxycheffouxanthone ( 2) have been isolated from the seeds of Garcinia afzelii Engl., together with nine known compounds: 2-hydroxy-1,7-dimethoxyxanthone ( 3), smeathxanthone A ( 4), 1,5-dihydroxyxanthone ( 5), 1,6-dihydroxy-5-methoxyxanthone ( 6), cheffouxanthone ( 7), 1,3,5-trihydroxyxanthone ( 8), smeathxanthone B ( 9), isoxanthochymol ( 10) and guttiferone E ( 11). Their structures were elucidated by means of 1D and 2D-NMR techniques.

Polyanxanthone A, B and C, three xanthones from the wood trunk of Garcinia polyantha Oliv.

Three xanthones, polyanxanthone A (1), B (2) and C (3) have been isolated from the methanol extract of the wood trunk of Garcinia polyantha, along with five known xanthones: 1,3,5-trihydroxyxanthone (4); 1,5-dihydroxyxanthone (5); 1,3,6,7-tetrahydroxyxanthone (6); 1,6-dihydroxy-5-methoxyxanthone (7) and 1,3,5,6-tetrahydroxyxanthone (8). Their structures were determined by means of 1D- and 2D-NMR techniques. Some of the above compounds were screened for their anticholinesterase activity on acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes.