Controlled silylation of friedelin (1) from cork smoker wash solids, a byproduct generated during processing of corkboard by steam baking, gave 3-trimethylsiloxyfriedel-2-ene (3) in high yields. Oxidation of 3 with OsO(4)/NMMO produced 2alpha-hydroxyfriedelan-3-one (cerin) (5), from which the new 2,3-secofriedelan-2-al-3-oic acid (6) was obtained quantitatively by periodic acid oxidation. Oxidation of 3 with DDQ afforded friedel-1-en-3-one (8). Reductive ozonolysis of 3 gave 2alpha,3beta-dihydroxyfriedelane, pachysandiol A (7). Compound 6 proved to be a potent inhibitor of human lymphocyte proliferation (IC(50) = 10.7 microM) and of the growth of a human cancer cell line (GI(50) = 5.4-17.2 microM). (13)C NMR data for compounds (3, 4, 5, 6a,7, and 8) are described for the first time.

Seco acids 7 and 9 and hydroxylated analogues 5 and 6 derived from friedelane triterpenes were synthesized stereoselectively in high yields. Compounds 5-9 were evaluated for their ability to inhibit in vitro the growth of three human tumor cell lines, MCF-7 (breast adenocarcinoma), NCI-H460 (non-small cell lung cancer), and SF-268 (CNS cancer). Only compounds 7 and 9 were found to possess significant growth inhibitory effects, exhibiting GI(50) values that range from 24.6 to 32.8 microM and 10.9 to 17.6 microM, respectively.

The genus Asparagopsis is a prolific source of halogenated metabolites. Due to its commercial applications, it has been intensively cultivated in southern Portugal. In the present study, we assess if the internal levels of the major halogenated metabolites (bromoform and dibromoacetic acid) in Asparagopsis taxiformis can be increased with hydrogen peroxide (H 2 O 2 ) addition. Previous studies with red algae showed that the production/release of bromoform can be enhanced by exogenously supplying H 2 O 2 . However, no study has assessed if H 2 O 2 supply enhances the content of secondary metabolites within the biomass. This detail is important as the objective of the proposed research is to enhance the content of these valuable metabolites in the produced biomass. Both the activity of the haloperoxidase enzyme and the metabolite content were assessed on shortterm and long-term incubation periods to H 2 O 2 . To determine the susceptibility of A. taxiformis photosynthetic performance to the imposed oxidative stress, the in vivo fluorescence of photosystem II was monitored. A. taxiformis was shown to be physiologically vulnerable to H 2 O 2 , given the observed decrease of the maximum quantum yield of photosynthesis (F v /F m ). Contrary to what was expected, the presence of H 2 O 2 inhibited the activity of the iodoperoxidase enzyme. Nevertheless, the extracted halogenated metabolites were higher over the first hours of exposure to H 2 O 2 , decreasing after 48 h. These results are probably related to the prosthetic group of the halogenated enzyme in A. taxiformis and the long-term oxidative stress damage of H 2 O 2 exposure. Considering the objective of the proposed research, addition of H 2 O 2 to the cultures, prior (3 h) to biomass harvesting, increases the metabolite content.