Inhibitory effects of 3-nitro-2,4,6-trihydroxybenzamides on Epstein-Barr virus early antigen induction

Inhibitory effect of soybean hypocotyls on Epstein-Barr virus early antigen induction and skin tumor promotion

The in vitro anti-tumor promoting effect of hypocotyls from fresh soybeans was evaluated. The dimethyl sulfoxide extracts of hypocotyls showed a stronger inhibitory effect than that of soybeans on Epstein-Barr virus early antigen activation induced by 12-O-tetradecanoylphorbol-13-acetate. Daidzin, an isoflavone with the highest content of hypocotyls, was also inhibitory. An in vivo evaluation of anti-tumor promoting activity of hypocotyls against the skin of mice also revealed a significant inhibitory effect on tumor formation.

Anti-tumor promoting activity of Dryopteris phlorophenone derivatives

As a part of screening studies for cancer chemopreventive agents (anti-tumor promoters) 33 Dryopteris phlorophenone derivatives have been evaluated. The compounds tested comprised of monomeric acylphloroglucinols (e.g. desaspidinol, aspidinol) as well as dimeric (e.g. aspidin, desaspidin), trimeric (e.g. filixic acids), and tetrameric (e.g. dryocrassin) phlorophenone, wherein hexacyclic rings are bound together by a methylene bridge. These compounds were examined for their in vitro anti-tumor promoting effect on Epstein-Barr virus antigen activation induced by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). The two dimeric compounds aspidin and desaspidin, which were found to be the most active among the tested phlorophenones, were also examined in vivo on two stage mouse skin carcinogenesis, and found to show significant inhibitory effect on 7,12-dimethylbenz[alpha]anthracene (DMBA)-TPA tumor promotion.

Inhibitory effect of iridoids on Epstein-Barr virus activation by a short-term in vitro assay for anti-tumor promoters

The in vitro anti-tumor promoting effect of the methanolic extracts of iridoids containing three plants and several pure iridoids isolated from other plants, has been evaluated. The alcoholic extracts of Paederia scandens, P. scandens var. mairei and the Ayurvedic herbal remedy Picrorhiza kurrooa were tested against the Epstein-Barr virus. Among the 15 iridoids evaluated, the glycoside, paederoside, displayed the highest order of anti-tumor promoting activity.

Chemoprevention of lung and skin cancer by Beta vulgaris (beet) root extract

The in vitro inhibitory effect of Beta vulgaris (beet) root extract on Epstein-Barr virus early antigen (EBV-EA) induction using Raji cells revealed a high order of activity compared to capsanthin, cranberry, red onion skin and short and long red bell peppers. An in vivo anti-tumor promoting activity evaluation against the mice skin and lung bioassays also revealed a significant tumor inhibitory effect. The combined findings suggest that beetroot ingestion can be one of the useful means to prevent cancer.

Antipromoting effects of 5-lipoxygenase inhibitors, 3-nitro-2,4,6- trihydroxybenzamide derivatives, on TPA-promoted transformation in BALB 3T3 cells

In order to discover the role in the promotion process of 5-lipoxygenase (5-LO), a key enzyme in the arachidonate cascade, the antipromoting effects of the 5-LO inhibiting 3-nitro-2,4,6-trihydroxybenzamide (NTB) derivatives were studied in a two-stage transformation assay system using BALB 3T3 cells. All compounds inhibited TPA-promoted transformation in a dose-dependent manner. Most of them achieved a 70-80% inhibition. Good correlations were observed between the inhibition of TPA-promoted transformation and that of 5-LO. These results indicate that 5-LO plays an important role in the promotion stage of the transformation of BALB 3T3 cells.

Inhibitory effects of 3-nitrophloroglucinecarboxylic acid derivatives on Epstein-Barr virus early antigen induction

The inhibitory effects of two series of 3-nitrophloroglucinecarboxylic acid derivatives, 3-nitro-2,4,6-trihydroxythiobenzamides (II) and 3-nitro-phloroglucinecarboxylates (III), on Epstein-Barr virus early antigen (EBV-EA) induction were examined using Raji cells. Some of them strongly inhibited the induction, N-nonyl and O-decyl derivatives being the most potent inhibitors among the thioamides and esters, respectively. These results suggest the possibility that these two 3-nitrophloroglucinecarboxylic acid derivatives may be listed as novel inhibitors of tumor promotion.

Inhibitory effects of dihydroagarofuran sesquiterpenes on Epstein-Barr virus activation

To search for possible antitumor promoters, we carried out a primary screening of thirty-seven dihydroagarofuran sesquiterpenes from Tripterygium wilfordii Hook fil. var. regelii Makino and Euonymus sieboldianus Blume, using their possible inhibitory effects on the Epstein-Barr virus early antigen (EBV-EA) activation which is induced by 12-O-tetradecanoylphorbol-13-acetate (TPA) in Raji cells. Some of these sesquiterpenes, triptofordin F-2 (Takaishi et al., 1988), 1,2,6,8,15-pentaacetoxy-9-benzoyloxy-4-hydroxy-beta-dihydroagarofuran and triptogelin A-1 (Takaishi et al., 1990) were observed to significantly inhibit the EBV-EA activation at low doses. Based on the results, the structural requirements for the activity of these compounds were discussed [corrected].