Laurene-type sesquiterpenes from the Red Sea red alga Laurencia obtusa as potential antitumor-antimicrobial agents.

Three new laurene-type sesquiterpenes, 12-hydroxy isolaurene (1), 8,11-dihydro-12-hydroxy isolaurene (2) and isolauraldehyde (3) were isolated from the organic extract of the red alga Laurencia obtusa. The chemical structures of isolates were determined by interpretation of their spectral data 1D and 2D NMR, UV, IR and MS. The newly isolated compounds were tested for their antimicrobial and antitumor activities. Compounds (1-3) exhibited potent activity against the gram-positive Bacillus subtilis and Staphylococcus aureus, where 3 proved to be the most active (MIC 35 and 27 μg/mL, respectively). Moreover, compound 3 exhibited a significant activity against Candida albicans (MIC of 70 μg/mL) and revealed to have very promising activity in an in vitro model of Ehrlich ascites Carcinoma.