Inhibition of 12-O-tetradecanoylphorbol-13-acetate induced Epstein-Barr virus early antigen activation by natural colorants.

Natural colorants such as anthocyanins, betalains, carotenoids, curcuminoids and chlorophylls have been widely used in the food processing industry and in beverages. Most of these colorants constitute part of human dietary components and are considered to be harmless and non-toxic. As a part of the study of natural products to identify non-toxic cancer chemopreventive agents, we have investigated several natural colorant extracts from vegetables and fruits of daily human consumption for their cancer chemopreventive action using the short-term in vitro assay which involves inhibition of Epstein-Barr virus early antigen activation (EBV-EA) induced by phorbol esters. Our study has identified several plant extracts that show profound activity in the EBA assay.

[Preliminary screening for antiviral AIDS drugs. VIII. Report for fiscal year 1995].

Preliminary screening of antiviral AIDS drugs has been carried out using three different in vitro assay systems. Among 96 samples of different origin tested, two were shown to inhibit the growth of HIV in vitro. One of the positive samples (plant origin) has hopeful signs, as the ranges of effective doses are wider than those of most of positive samples which had been found by us.

Inhibitory effects of lantadenes and related triterpenoids on Epstein-Barr virus activation.

To search for possible antitumor promoters, inhibitory effects of lantadenes and related triterpenoids from Lantana camara L. (Verbenaceae) on Epstein-Barr virus activation, were tested. The substitutions on the carboxylic acid through an ester bond might play an important role in the activity.

Inhibition of 1,2-dimethylhydrazine-induced oxidative DNA damage by green tea extract in rat.

Following subcutaneous injection of 1,2-dimethylhydrazine (DMH), which is carcinogenic to rat colon and liver, to Sprague-Dawley rats, a significant increase of 8-hydroxydeoxyguanosine (8-OHdG) was observed in the DNA of colonic mucosa and liver. The 8-OHdG formation reached the maximal level at about 24 h after the DMII injection. On the other hand, no increase of 8-OHdG was observed in the DNA of the kidney. Drinking green tea extract (GTE) for ten days prior to the DMH injection significantly inhibited the formation of 8-OHdG in the colon. These findings demonstrate that DMH causes oxidative damage to the DNA of its target organ, and that GTE protects colonic mucosa from this oxidative damage.

Inhibitory effects of quassinoids on Epstein-Barr virus activation.

Short-term in vitro assays for tumor promoters and anti-tumor promoters (Epstein-Barr virus activation test) were carried out for 45 quassinoids. As a result, some quassinoids showed potent activity, more than 50% inhibition at a molar ratio of 1:1 (TPA/quassinoids). These results led to the following structure-activity relationships: (1) a methyleneoxy bridge and side chain enhance the activity and (2) a sugar moiety reduces the activity.

Structures of new coumarins and antitumor-promoting activity of coumarins from Angelica edulis.

From the fruits of Angelica edulis Miyabe (Umbelliferae), three new angular furanocoumarins, edulisin III (1), edulisin IV (2), and edulisin V (3), were isolated along with three known coumarins, 2'(S), 3'(R)-3'-isobutyryloxy-4'-acetoxy-2',3'-dihydrooroselol (4), edultin (5), and 2'(S),3'(R)-3'-senecioyloxy-4'-acetoxy-2',3'-dihydrooroselol (6), respectively. The structures of 1 and 2 were established to be 2'(S),3'(R)-3'-(2-methylbutyryloxy)-4'-acetoxy-2',3'-dihydrooro selol and 2'-(S),3'(R)-3'-propyryloxy-4'-acetoxy-2',3'-dihydrooroselol by chemical studies and spectral analyses. Coumarin 3 was proved to be 3'-(2-methylbutyryl-oxy)-4'-angeloyloxy-2',3'-dihydrooroselol++ + by chemical and spectral analyses and H-C COLOC. Coumarins 1-6 were examined for the effects on tumor-promotor induced phenomena in vitro. Among these coumarins, 3 showed the most potent inhibitory activity on 12-O-tetradecanoylphorbol 13-acetate (TPA)-stimulated 32Pi incorporation into phospholipids of cultured cells.

Inhibitory effects of cucurbitane triterpenoids on Epstein-Barr virus activation and two-stage carcinogenesis of skin tumors.

To search for possible anti-tumor-promoters, we carried out a primary screening of 21 cucurbitane triterpenoids using an in vitro assay system. Of these triterpenoids, scandenoside R6 (6), 23,24-dihydrocucurbitacin F (14), 25-acetyl-23,24-dihydrocucurbitacin F (15), 2-O-beta-D-glucopyranosyl-23,24-dihydrocucurbitacin F (17) and cucurbitacin F (18) exhibited significant inhibitory effects on Epstein-Barr virus (EBV) activation induced by the tumor promoter, 12-O-tetradecanoyl-phorbol-13-acetate (TPA). Further, compounds 14 and 17 exhibited remarkable anti-tumor-promotion effects on mouse skin tumor promotion in an in vivo two-stage carcinogenesis test.

Antitumor-promoting activity of mallotojaponin, a major constituent of pericarps of Mallotus japonicus.

Mallotojaponin, a major constituent of the pericarps of Mallotus japonicus (Euphorbiaceae), inhibited the action of tumor promoter in vitro and in vivo; it inhibited tumor promoter-enhanced phospholipid metabolism in cultured cells, and also suppressed the promoting effect of 12-O-tetradecanoylphorbol-13-acetate on skin tumor formation in mice initiated with 7,12-dimethylbenz-[a]anthracene.

Structures of sesquiterpene polyol esters from Celastrus stephanotiifolius with potential tumor-promotion inhibitor activity.

Esters of eight new ([1],[4-6], and [8-11]) and five known sesquiterpenenoid polyalcohols have been isolated from Celastrus stephanotiifolius. Their structures were established on the basis of chemical reactions and spectral analysis. The structural elucidation indicated that the structures of some related compounds should be revised. The isolated sesquiterpenes were observed to inhibit Epstein-Barr virus early antigen activation significantly at low doses.

Antitumor-promoting activity of scopadulcic acid B, isolated from the medicinal plant Scoparia dulcis L.

Scopadulcic acid B (SDB), a tetracyclic diterpenoid isolated from a medicinal plant, Scoparia dulcis L., inhibited the effects of tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) in vitro and in vivo; SDB inhibited TPA-enhanced phospholipid synthesis in cultured cells, and also suppressed the promoting effect of TPA on skin tumor formation in mice initiated with 7,12-dimethylbenz[a]anthracene. The potency of SDB proved to be stronger than that of other natural antitumor-promoting terpenoids, such as glycyrrhetinic acid.

Anti-tumor-promoting activities of afromosin and soyasaponin I isolated from Wistaria brachybotrys.

Afromosin [1] and soyasaponin I [2] isolated from Wistaria brachybotrys exhibited remarkable inhibitory effects on mouse skin tumor promotion, and afromosin also exhibited a significant inhibitory effect on pulmonary tumor promotion. The combined effects of these compounds on the two-stage skin carcinogenesis were also examined, and it was concluded that the combination of 1 with 2 enhanced the inhibitory effect.

Potent preventive action of alpha-carotene against carcinogenesis: spontaneous liver carcinogenesis and promoting stage of lung and skin carcinogenesis in mice are suppressed more effectively by alpha-carotene than by beta-carotene.

Although beta-carotene has been considered to be a key cancer preventive agent in green and yellow vegetables, other types of carotenoids, such as alpha-carotene, may also contribute to anticarcinogenic action, since these carotenoids usually coexist with beta-carotene and are detectable in human blood and tissues. In this study, we compared the inhibitory effect of natural alpha-carotene, obtained from palm oil, with that of beta-carotene on spontaneous liver carcinogenesis in C3H/He male mice. The mean number of hepatomas per mouse was significantly decreased by alpha-carotene supplementation (per os administration in drinking water at a concentration of 0.05%, ad libitum) as compared with that in the control group (P < 0.001, Student's t test). On the other hand, beta-carotene, at the same dose as alpha-carotene, did not show any such significant difference from the control group. Furthermore, we also compared the antitumor-promoting activity of alpha-carotene with that of beta-carotene against two-stage mouse lung carcinogenesis (initiator, 4-nitroquinoline 1-oxide; promoter, glycerol). alpha-Carotene, but not beta-carotene, reduced the number of lung tumors per mouse to about 30% of that in the control group (P < 0.001, Student's t test). The higher potency of the antitumor-promoting action of alpha-carotene compared to beta-carotene was confirmed in other experimental systems; e.g., alpha-carotene was also found to have a stronger effect than beta-carotene in suppressing the promoting activity of 12-O-tetradecanoylphorbol-13-acetate on skin carcinogenesis in 7,12-dimethylbenz[a]anthracene-initiated mice. These results suggest that not only beta-carotene, but also other types of carotenoids, such as alpha-carotene, may play an important role in cancer prevention.

Anti-tumor-promotion by principles obtained from Angelica keiskei.

Potent anti-tumor promoter activity has been found in the nonpolar extracts of the root of "Ashita-Ba", Angelica keiskei Koidz. (Umbelliferae), which is eaten as a vegetable in Japan. From this active fraction, two angular furanocoumarins, archangelicin (1) and 8(S),9(R)-9-angeloyloxy-8,9-dihydrooroselol (2), three linear furanocoumarins, psoralen (3), bergapten (4) and xanthotoxin (5), and three chalcones, 4-hydroxyderricin (6), xanthoangelol (7) and a novel chalcone named ashitaba-chalcone (8), were isolated. Among these compounds, two angular type furanocoumarins, 1 and 2, and three chalcones, 6-8, suppressed 12-O-tetradecanoylphorbol-13-acetate (TPA)-stimulated 32Pi-incorporation into phospholipids of cultured cells, whereas coumarins 3-5 were less effective. In addition, chalcones 6 and 7 were proved to have anti-tumor-promoting activity in mouse skin carcinogenesis induced by 7,12-dimethylbenz[a]anthracene (DMBA) plus TPA. Since chalcones 6 and 7 showed calmodulin-interacting property, both chalcones may reveal anti-tumor-promoting activity via the modulation of calmodulin involved systems. These chalcones may be useful to develop the effective method for cancer prevention.

Studies on the anti-tumor-promoting activity of naturally occurring substances. IV. Pd-II [(+)anomalin, (+)praeruptorin B], a seselin-type coumarin, inhibits the promotion of skin tumor formation by 12-O-tetradecanoylphorbol-13-acetate in 7,12-dimethylbenz[a]anthracene-initiated mice.

Since Pd-II [(+)anomalin, (+)praeruptorin B], a seselin-type coumarin, was found to inhibit tumor promoter induced phenomenon in vitro, the effect of Pd-II on the in vivo tumor-promoting action of 12-O-tetradecanoylphorbol-13-acetate (TPA) in 7,12-dimethylbenz[a]anthracene-initiated mouse skin was investigated. Pd-II, applied 40 min before the TPA treatment, at a dose of 10 mumol/painting, completely suppressed tumor formation up to 20 weeks of tumor promotion, without any toxicity. Besides Pd-II, various anti-tumor-promoter coumarins were found in the traditional Chinese medicine Qian-Hu, from which Pd-II was obtained. These coumarins may be useful for the development of an effective method to prevent cancer.

Structures of euglobal-G1, -G2, and -G3 from Eucalyptus grandis, three new inhibitors of Epstein-Barr virus activation.

Three new euglobals with acylphloroglucinol-monoterpene structures, named euglobal -G1 (1), -G2 (2), and -G3 (3) were isolated from the chloroform extract of the juvenile leaves of Eucalyptus grandis (Myrtaceae). The structures of these new compounds were determined on the basis of their spectral data. The compounds strongly inhibited the Epstein-Barr virus activation.

Studies on the antitumor-promoting activity of naturally occurring substances. II. Inhibition of tumor-promoter-enhanced phospholipid metabolism by umbelliferous materials.

Ninety-five extracts prepared from 14 kinds of Umbelliferous materials were studied to determine their effects on tumor-promoter-induced phenomena in vitro. Of the materials, 5 Chinese crude drugs, two Bai-Hua Qian-Hu classified as Q-I and Q-II types, the root of Peucedanum praeruptorum Dunn., Zi-Hua Qian-Hu, the root of P. decursivum Maxim., Tang-Bai-Zhi, the root of Angelica dahurica Benth, et Hook. var. pai-chi Kimura, Hata et Yen., Dang-Gui, the root of A. acutiloba Kitagawa and 2 Umbelliferous plants, ashita-ba. A. keiskei Koidz., and ama-nyuu, A. edulis Miyabe, showed potent inhibitory effects on 12-O-tetradecanoylphorbol-13-acetate (TPA)-stimulated 32Pi incorporation into phospholipids of cultured cells. From the active fraction of the crude drug "Tang-Bai-Zhi," imperation (1), isoimperatoin (2), oxypeucedanin (3), pabulenol (4), neobyakangelicol (5) and byakangelicin (6) were identified as active or inactive principles. Compound 4 had not previously been isolated from Tang-Bai-Zhi, A. dahurica var. pai-chi. We also discuss the structure-activity relationship among the above 6 kinds of linear-type furanocoumarins, together with 3 kinds of antitumor-promoter coumarins having the same skeleton, psoralen (7), bergapten (8) and xanthotoxin (9), obtained from "ashita-ba" (eaten as a vegetable in Japan). Among the compounds in the present experiment, compounds 1 and 2 showed potent inhibitory activity at the concentration of 50 micrograms/ml and 3-9 were found to have less or no activity.

[Anticarcinogenesis activity of natural carotenes]. / Activité anticarcinogénétique des carotènes naturels.

Natural carotene sample obtained from palm oil was proved to suppress the promoting stage of two-stage carcinogenesis of mouse skin, and also inhibit the proliferation of human malignant tumor cells, such as neuroblastoma GOTO cells, stomach cancer HGC-27 cells, and pancreatic cancer PANC-I cells. Among the major constituents of palm carotene, alpha-carotene showed stronger anti-proliferative effect than beta-carotene. The present results indicate that further investigation for not only beta-carotene but also other kinds of natural carotenes, such as alpha-carotene, should be carried out.

Antitumor-promoting activity of garlic extracts.

Garlic extract was proved to inhibit one of the earliest phenomena caused by 12-O-tetradecanoyl-phorbol-13-acetate (TPA), a tumor promoter, in vitro; i.e., the enhancement of phospholipid metabolism. And also the first stage of tumor promotion in two-stage mouse skin carcinogenesis in vivo was suppressed by the treatment with garlic extract. Thus, garlic extract seems to be effective to inhibit initial events caused by TPA type tumor promoters in vitro and in vivo.