RESUMEN
The unprecedented homolytic opening of ozonides promoted and catalyzed by titanocene(III) is reported. This novel reaction proceeds at room temperature under neutral, mild conditions compatible with many functional groups and provides carbon radicals suitable to form C-C bonds via both homocoupling and cross-coupling processes. The procedure has been advantageously exploited for the straightforward synthesis of the natural product brittonin A.
RESUMEN
Condensation of 2H-benzo[g][1,2]oxasilocines with aromatic aldehydes in the presence of boron trifluoride affords mixtures of cis/trans 2-phenyl-3-vinylchromans with moderate yields. These can be transformed into homopterocarpans, a synthetic group of substances homologous to the natural isoflavonoid pterocarpans.
RESUMEN
The cytotoxic effects of extracts of the tomato variety "Racimo" have been evaluated through the use of the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay at several concentrations. Three extracts-ethanol-water, petroleum ether, and in vitro digested tomato-exhibited in vitro cytotoxicity against the proliferation of the cultured cancer cell line HT-29. The concentration that caused 50% inhibition of cancer cell growth occurred (GI(50)) of the different extracts for HT-29 cells was 62.5 µg/mL for the petroleum ether extract and 87.0 µg/mL for the digested tomato extract. For the ethanol-water extract, it was not possible to determine this parameter at the assayed extract concentrations. These results clearly indicate that after the digestion process, the less polar substances, such as carotenoids and sterols, are bioavailable as active species against cancer cells. The GI(50) levels for tomato extracts are similar to those values reported for medicinal plants. The results of the MTT assay on nonmutagenic CCD-18 cells showed a lack of negative effect on cell growth, which indicates that tomato extracts act selectively on HT-29 tumor cells. (1)H-Nuclear magnetic resonance spectra confirmed the presence of known compounds with accepted cytotoxic activity against tumor lines (lycopene and ß-carotene). The high cytotoxicity for HT-29 cells showed by the petroleum ether extract might be due to the simultaneous presence in the extract of both carotenoids and glyceryl esters of fatty acids. The results of this work clearly indicate the importance of carotenoid consumption on colon tumor proliferation and prevention, and also the importance of the dietary fats in carotenoid bioavailability.