Antimicrobial compounds isolated from Tropaeolum tuberosum.

Activity-guided fractionations of black tubers of Tropaeolum tuberosum led to the isolation of 3-[3-(3-pyridinyl)-1,2,4-oxadiazol-5-yl] benzonitrile (1) and [3,5-Bis (1,1-dimethylethyl)-4-hydroxyphenyl] ethenylidene] bis-phosphonic acid tetraethyl ester (2). Compounds 1 and 2 showed an antibacterial effect against almost all the strains assayed, especially compound 2, showing the same inhibition potential for Enterococcus faecalis and Salmonella enteritidis as the ampicillin (MIC = 1.5 µM) and a better potential than chloramphenicol which has a MIC of 3.5 µM. In addition, compounds 1 and 2 showed a relevant antifungal inhibition against Candida tropicalis with MICs of 100 µM and 50 µM, and against Saccharomyces kudriavzevii with MICs of 25 µM and 1.5 µM. This is in comparison to fluconazole which had MICs of 150 µM (against Candida tropicalis) and 3.5 µM (against Saccharomyces kudriavzevii). This is the first time that compounds 1 and 2 are reported as showing antimicrobial activities.

Antitumoral potential of carbamidocyclophanes and carbamidocylindrofridin A isolated from the cyanobacterium Cylindrospermum stagnale BEA 0605B.

Three carbamidocyclophanes, A, F and V, and carbamidocylindrofridin A were isolated from the cultured freshwater cyanobacterium Cylindrospermum stagnale, collected in the Canary Islands. The chemical structures of these compounds were elucidated through NMR, HRMS and ECD spectroscopy. The absolute configuration of carbamidocyclophane A was confirmed using X-ray-diffraction. All compounds showed apoptotic capacity against the SK-MEL-1, SK-MEL-28 and SK-MEL-31 tumour cells. Carbamidocylindrofridin A had the highest anti-tumour potential, with an IC50 of 1 ± 0.3 µM in the SK-MEL-1 cell line.