Lycosides, Unusual Carotenoid-Derived Terpenoid Glycosides from a Vegetable Juice, Inhibit Asexual Reproduction of the Plant Pathogen Phytophthora.

Vegetable juices, typical culture media for the plant pathogen Phytophthora, effectively induce its asexual reproduction (zoosporangia formation). However, some chromatographic fractions from a vegetable juice were found to inhibit asexual reproduction. Bioassay-guided chromatographic steps led to the isolation of four novel compounds, named lycosides A-D, 1-4, that could be metabolic products from a carotenoid. They showed 50% inhibitory activity against the asexual reproduction of P. capsici at 2.1-7.6 µM. The structure-activity relationship and the universality of the inhibitory activity within the Phytophthora genus were also investigated. In addition, the quantitative analysis of lycosides in fresh vegetables and vegetable juices revealed that tomato is the source of these active substances. These food-derived chemicals could help provide safe agents to control the outbreak of the agricultural pest Phytophthora in fields.

Novel cytotoxic polyoxygenated steroids from an Okinawan sponge Dysidea sp.

A library of extracts established from hundreds of marine organisms was screened by a cytotoxicity test. The active organic extract of an Okinawan marine sponge of the genus Dysidea was subjected to bioassay-guided fractionation to give three new polyoxygenated steroids dysideasterols F-H (1-3), together with two known related compounds (4 and 5). Their structures were confirmed by NMR and mass spectroscopic analyses. A characteristic structural feature of 2, 4 and 5 is an allylic epoxide, whereas this epoxide undergoes ring-opening by a neighbouring hydroxyl group to give a tetrahydrofuran ring in 1 and 3. All compounds 1-5 exhibited a similar cytotoxic effect with IC50 values of 0.15-0.3 µM against human epidermoid carcinoma A431 cells, demonstrating that the allylic epoxide moiety was not responsible for this cytotoxic effect.

Cyclolobatriene, a novel prenylated germacrene diterpene, from the soft coral Lobophytum pauciflorum.

A new 10-membered-ring diterpene, cyclolobatriene (1), along with three other known diterpenes, lobatriene (2), eunicol (3), and fuscol (4), were isolated from the Okinawan soft coral Lobophytum pauciflorum. Their structures were established by extensive NMR spectroscopic analyses. Cyclolobatriene (1) is an additional example of rare prenylated germacrenes. Although 1, due to a 10-membered-ring structure, exists as an equilibrium mixture of three conformers, the NMR measurement in CDCl(3) at 7°C enabled us to assign the NMR signals of the three, which is the first example of the complete NMR assignment of all the existing conformers of germacrene-type compounds. Cyclolobatriene (1) was thermally unstable and converted into 2 through Cope rearrangement upon heating at 70°C. Eunicol (3) also possesses the same prenylated germacrene structure as 1, showing similar physico-chemical properties to 1. All four compounds 1-4 showed cytotoxic effect with IC(50)'s of 0.64, 0.41, 0.35 and 0.52 µM, respectively, against human epidermoid carcinoma A431 cells.