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We examined the inhibitory effects of aqueous ethanol extract from mulberry leaves (ME) on postprandial hyperglycemia in normal Wistar rats. ME dose-dependently suppressed the postprandial rise of blood glucose in rats, when ME (0.02-0.5 g/kg) was given 0.5 h before the administration of carbohydrates such as sucrose, maltose and starch. The ME dose showing 50% inhibition of the increment of blood glucose (ED50) was 0.11 g/kg for sucrose, 0.44 g/kg for maltose, and 0.38 g/kg for starch. ME and its basic fraction (MB) containing 1-deoxynojirimycin were assayed for their inhibitory effects (IC50) on disaccharidase derived from the small intestine of rats. The IC50 value of ME was 3.2 microg/mL for sucrase, 10 microg/mL for isomaltase, and 51 microg/mL for maltase. The IC50 value of MB was 0.36 microg/mL for sucrase, 1.1 microg/mL for isomaltase, and 6.2 microg/mL for maltase. The IC50 value of 1-deoxynojirimycin as the principle component in ME was 0.015 microg/mL for sucrase and 0.21 microg/mL for maltase, and this value was comparable to the IC50 of voglibose. The inhibitory activity of ME in a-amylase was weak. These results suggest that ME strongly suppresses postprandial hyperglycemia after carbohydrate loading by inhibiting the activity of disaccharidases in the small intestine of rats.

Mutation enhancing activity of the mutagenicity of 2-acetylaminofluorene (AAF) in the fractions of cellulose pyrolysate toward Salmonella typhimurium TA98 was determined.The eluate with 50% benzene in hexane from silica gel column showed the highest activity, and this portion was further fractionated by Sephadex LH-20 column, thin layer and gas chromatography to separate the active components.Results indicated that some of polycyclic aromatic hydrocarbons, such as anthracene, phenanthrene and pyrene, and their derivatives in the pyrolysate might contribute to enhancement of the mutagenicity of AAF.

Reduction of aldehydes and ketones with 2-propanol was found to proceed efficiently in the presence of hydrous zirconium oxide. The reaction is performed simply and the products are easily isolated in the pure state by filtering off the hydrous zirconium oxide, followed by evaporation of solvents.

Retinol, 5 flavonoids, 3 steroids and 7 sweetening agents were studied for their effects on 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced early antigen (EA) of Epstein-Barr virus (EBV) in Raji cells. Concomitant treatment of Raji cells with TPA and retinol showed inhibition of EA induction. Among flavonoids, quercetin resulted in effective inhibition of EA induction by TPA and alpha-naphthoflavone showed the weakly inhibitory effect. None of the other flavonoids such as rutin, catechin and beta-naphthoflavone affected the induction of EBV-EA by TPA. beta-Estradiol obviously inhibited EBV-EA induction by TPA, but hydrocortisone did not show any inhibitory effect on it. Glycyrrhetinic acid, steviol, phyllodulcin and perrillartine also showed the remarkable inhibition of EBV-EA induction. On the other hand, glycyrrhizin and stevioside, glycosides of glycyrrhetinic acid and steviol, did not inhibit the induction of EBV-EA by TPA. Some of the inhibitors reported here may be effective on the inhibition of the in vivo tumor promotion by TPA.

The effects of some compounds, which have been reported to inhibit tumor promotion in vivo, on the induction of the early antigen (EA) of Epstein-Barr virus (EBV) by 12-O-tetradecanoylphorbol-13-acetate (TPA) in Raji cells were examined. The inhibitors of the cascade process involving arachidonic acid, indomethacin, nordihydroguaiaretic acid, phenidone and p-bromophenacyl bromide, effectively inhibited EBV-EA induction by TPA. Two flavonoids, morin and kaempferol also inhibited EA induction. Among antioxidants, butylated hydroxytoluene effectively inhibited EA induction, though alpha-tocopherol did not show any inhibition of EA induction at concentrations of up to 150 micrograms/ml. N-(6-Aminohexyl)-5-chloro-1-naphthalenesulfonamide, a calmodulin antagonist, and esculetin showed inhibitory effects on EA induction, though slight cytotoxicity was observed. L-1-p-Tosylamino-2-phenylethyl chloromethyl ketone, a protease inhibitor, showed cytotoxicity and no specific inhibition of EA induction. Five kinds of steroids, cortisone, hydrocortisone, prednisolone, dexamethasone and fluocinolone acetonide showed no inhibitory effect on EA induction at concentrations of up to 100 micrograms/ml. In addition, the relationship between the inhibition of EBV-EA induction and that of tumor promotion is discussed.

The mutagenic activities of quinoline, isoquinoline, phenanthridine, benzo(f)quinoline, benzo(h)quinoline and their α-amino derivatives were compared in relation to the effect of structural changes using the Salmonella typhimurium test system. All mutagenic compounds tested require the liver microsomal fraction for their mutagenic activity. Phenanthridine, two benzoquinolines and quinoline were mutagenic. α-Amination of two benzoquinolines and quinoline resulted to increase their mutagenic activity intensively. Addition of a benzene ring to the benzene moiety of 2-aminoquinoline, so that two carbon atoms are shared, affected distinctly the increase in the mutagenic activity. The co-existence of benzoquinoline series with 2-aminobenzo(f)quinoline showed the clear synergistic action.

Smoke condensates from Burley tobacco, bright-type tobacco and various brands of commercial cigarettes were tested for mutagenicity by using a microsomal test system with Salmonella typhimurium TA 1538. Smoke condensate from Burley tobacco had much higher mutagenic activity than that from bright-type tobacco. Increased mutagenic activity was observed with smoke condensates from Burley tobacco grown with increasing amounts of nitrogen fertilizer, and from commercial cigarettes blended with Burley tobacco. There was a significant correlation between nitrate content of cigarette and mutagenic activity of the resulting smoke condensate. The results suggest that nitrate in cigarettes may influence the formation of potential mutagens during the burning of a cigarette.

18 polycyclic aromatic hydrocarbons (PAHs) and 7 quinones were tested for mutagenicity using Salmonella typhimurium TA97, TA98 and TA100 with or without metabolic activation. In the presence of metabolic activation, TA97 was more susceptible to mutation than either TA98 or TA100 by many of PAHs tested. PAHs such as 1-methylphenanthrene, fluoranthene, pyrene, benzo[a]pyrene, benzo[e]pyrene and perylene had high mutagenic effects on TA97 in the presence of metabolic activation. 1,6- and 1,8-pyrenequinones were also highly mutagenic on TA97 in the presence or absence of metabolic activation. It appears that pyrene is mutagenic through its metabolic conversion to pyrenequinones.

Carbohydrate pyrolysates obtained at 700°C intensively enhanced mutagenicities of several mutagenic agents on Salmonella typhimurium. The pyrolysates obtained by heating from 1 to 15 min had an enhancing effect on the mutagenicity of a similar level. Of the 8 kinds of carbohydrates tested, sucrose pyrolysate showed the highest enhancing effect. The enhancement of mutagenicity by sucrose pyrolysate was much more effective on aromatic amines such as 2-aminofiuorene and 2-aminoanthracene than on polycyclic aromatic hydrocarbons. The enhancing effect of sucrose pyrolysate was exhibited in the presence of a metabolic activation system.

The cytotoxic effect of 4-nitroquinoline-1-oxide (4NQO) on cultured Chinese hamster cells was drastically reduced by the presence of caffeine (0.2-1 mM). Caffeine, however, did not reduce the cytotoxicity of 4-hydroxyaminoquinoline-1-oxide (4HAQO), an active metabolite of 4NQO. The 105 000 g supernatant from the cell homogenate could catalyze the conversion of 4NQO to 4HAQO in the presence of NADPH or NADH as a hydrogen donor. This enzyme activity was strongly inhibited by caffeine (0.1-10 mM) or dicumarol (10(-8)-10(-6) M), an inhibitor of DT diaphorase (E.C.1.6.99.2). Dicumarol also reduced the cytotoxicity of 4NQO. These results clearly suggest that caffeine inhibits the conversion step of 4NQO to 4HAQO, resulting in a decrease in the cytotoxicity of 4NQO. Furthermore, the frequency of 6-thioguanine-resistant mutation by 4NQO was also strongly reduced by the presence of caffeine (1 mM) in cultured Chinese hamster cells, being consistent with the results of cytotoxicity.

dl-Ornithine-2-14C, dl-methionine-14CH3 and partially racemized l-nornicotine-2, 5-14C, were administered to aseptically grown excised roots (N. rustica var. Brasilia). Incorporation of their radioactivity to nicotine was compared. The extent of their radioactive incorpo-ration to nicotine was high in the order of ornithine, methionine and nornicotine; incorpo-ration of radioactivity of nornicotine to nicotine was extraordinarily low. 15N-Labeled nornicotine was also fed to the same materials and 15N distribution was examined. Most of 15N still remained in the nornicotine reisolated. Marked amounts of 15N were located in the ethanol-insoluble fraction, the amino acid fraction and the substances having chro-matographic RF value close to that of nicotine. Only small amount of 15N was incorpo-rated to the isolated nicotine. Nornicotine is generally accepted to be a direct precursor of nicotine in tobacco plants. From these findings, however, it can be said that the biosynthesis of nicotine can occur through other routes without going through nornicotine.

N -Methylputrescine oxidase, catalyzing the oxidative deamination of the primary amino group of N -methylputrescine, was demonstrated in roots of tobacco plants, and purified 150-fold. N -Methylpyrrolinium salt was identified as the reaction product by comparison with the authentic compound. The enzyme had a pH optimum at 8·0 and the K m value for N -methylputrescine was 4·5 × 10 −4 M. Putrescine and cadaverine were also oxidized. Activity of the enzyme was strongly inhibited by carbonyl reagents, thiol inhibitors and diethyldithiocarbamate, but hydrazine derivatives were without significant effect on the enzyme activity. The enzyme was localized exclusively in the roots and its activity markedly increased on decapitation of the shoots. The demonstration of N -methylputrescine oxidase, in addition to putrescine N -methyltransferase, provides evidence that the biosynthetic route of nicotine involves N -methylputrescine and 4-methylaminobutanal ( N -methylpyrrolinium salt) as intermediates.

gamma-Methylaminobutyraldehyde (N-methylpyrroline) labeled with (14)C was isolated from tobacco roots which had metabolized ornithine-2-(14)C. It was labeled most strongly 4 hours after adding ornithine-2-(14)C to the root, also labeled by putrescine-1,4-(14)C and methionine-(14)CH(3), and observed in the root but not in the aerial portions of tobacco plants. gamma-Methyl-aminobutyraldehyde when added back to the root was an efficient precursor of nicotine. Identity of gamma-methylaminobutyraldehyde from tobacco roots was confirmed by comparison with the authentic compound.The existence of gamma-methylaminobutyraldehyde (N-methylpyrroline) in the biosynthetic pathway of nicotine indicates that the methyl group must be introduced before condensation of the pyridine moiety with the pyrrolidine moiety.

Duplicate feeding experiments of dl-ornithine-2-14C to the excised tobacco root culture were made, and the radioactive nornicotine was isolated. Approximately two thirds of the radioactivity was located in the 2-position of the pyrrolidine of the nornicotine in these experiments. This fact indicates that there are two modes in nornicotine biosynthesis: exclusive incorporation to the C-2 and equal incorporation to C-2 and C-5 from C-2 of ornithine.On the basis of this finding, biosynthetic route was discussed.dl-Ornithine-2-14C, dl-methionine-14CH3 and partially racemized l-nornicotine-2,5-14C were administered to aseptically grown excised roots (N. rustica var. Brasilia). Incorporation of their radioactivity to nicotine was compared. The extent of their radioactive incorporation to nicotine was high in the order of ornithine, methionine and nornicotine; incorporation of radioactivity of nornicotine to nicotine was extraordinarily low. 15N-Labeled nornicotine was also fed to the same materials and 15N dist...

14C from nicotinic acid-6-14C which was administered to tobacco plants was incorporated into nine pyridine compounds during 3 hr incubation; two of these were identified as nicotinic acid-N-glucoside and 6-hydroxynicotinic acid. Nicotinic acid was only incorporated into intermediates of the pyridine nucleotide cycle to a limited extent the main product being the glucoside. Nicotinic acid glucoside was incorporated into nicotine with the same efficiency as nicotinic acid, but the rate of the incorporation was markedly reduced when unlabelled nicotinic acid was also fed, suggesting that the glucoside is not involved in the direct route of nicotine biosynthesis.

(1985). Mutagenicity of Pyrolyzates of Natural Substances toward Salmonella typhimurium TA97. Agricultural and Biological Chemistry: Vol. 49, No. 6, pp. 1893-1895.

(1984). Isolation of 2-Amino-3-methyl-imidazo- [4,5-f]quinoline as Mutagen from the Heated Product of a Mixture of Creatine and Proline. Agricultural and Biological Chemistry: Vol. 48, No. 1, pp. 241-243.

The effects of naturally occurring sweetening agents, which inhibited the induction of Epstein-Barr virus-associated early antigen (EBV-EA) induced by 12- O -tetradecanoylphorbol-13-acetate (TPA), and related compounds on the induction of ornithine decarboxylase (ODC) by TPA is examined. Application of glycyrrhetinic acid or steviol to mouse skin 1 h before TPA treatment showed a remarkable decrease in TPA-induced ODC activity. Post-treatment with glycyrrhetinic acid or steviol 1 h after application of TPA also resulted in a considerable depression in the induction of ODC activity. Neither glycyrrhetinic acid nor steviol alone induced epidermal ODC activity. These results suggest that glycyrrhetinic acid and steviol interfere with the process of induction of epidermal ODC by TPA treatment of mouse skin. cis -Abienol, frullanolide and norambreinolide, which have a partially similar structure in the moiety with glycyrrhetinic acid or steviol, were tested. cis -Abienol and frullanolide showed an inhibitory effect when applied 1 h before TPA treatment, but norambreinolide was not effective. A relationship between suppression of ODC activity and inhibition of EBV-EA induction is discussed.

Pyrolyzates of 25 amino acids and 5 indole derivatives were tested for mutagenicity in the histidine-requiring mutant Salmonella typhimurium TA 98. Significant mutagenic activity was detected with pyrolyzates of most of the amino acids. These pyrolyzates required a liver microsomal fraction, as representative of mammalian metabolism, to be detected as mutagens. Among the pyrolyzates tested, the highest mutagenic activity was observed with that of L-tryptophan. As little as 10 microgram of the pyrolyzate of L-tryptophan had detectable mutagenic activity toward TA 98. The optimal pyrolysis temperatures for the formation of mutagenic products were shown to be 500 degrees C for L-tryptophan and 600 degrees C for the other amino acids. The results from pyrolyses of some indole derivatives suggest that an amino group at the alpha-position to the carboxyl group of L-tryptophan plays an important role in the formation of mutagens.

Reduction of aldehydes and ketones with 2-propanol was found to proceed efficiently in the presence of hydrous zirconium oxide. The reaction is performed simply and the products are easily isolated in the pure state by filtering off the hydrous zirconium oxide, followed by evaporation of solvents.

Cigarette smoke condensate (CSC) was separated into several fractions and each was tested for an inhibitory effect on the early antigen (EA) of Epstein-Barr virus (EBV) which can be induced by 12-O-tetradecanoylphorbol-13-acetate (TPA) in Raji cells. Two diastereoisomers of 2,7,11-cembratriene-4,6-diol (alpha- and beta-CBT) were isolated from the neutral fractions of CSC and these showed potent inhibitory effects on the induction of EBV-EA by TPA. The doses of alpha- and beta-CBT required for 50% inhibition of EBV-EA induction by TPA were 7.7 and 6.7 micrograms/ml, respectively, which are comparable with those of retinoic acid, a potent inhibitor of induction of epidermal ornithine decarboxylase (ODC) activity and tumor promotion by TPA in mice. Application of alpha- and beta-CBT to mouse skin prior to treatment with TPA inhibited TPA-induced ODC activity. The degree of inhibition was dependent on the dose and application of 16.5 mumol/mouse of alpha- and beta-CBT resulted in a 50 and 40% reduction, respectively, of the maximum of the ODC activity induced as a result of treatment with TPA. In initiation-promotion experiments, alpha-CBT markedly inhibited the promoting effect of TPA on skin tumor formation in mice which were initiated with 7,12-dimethylbenz[a]anthracene, but beta-CBT was found to be less effective. Application of 3.3 mumol of alpha-CBT 40 min prior to treatment with TPA (1 microgram) resulted in a 53% reduction in the number of papillomas per mouse. Our present data suggest that EBV-EA inhibition assay using Raji cells is effective for the first screening of inhibitors of tumor promotion, and provide evidence that CSC contains antitumor-promoting agents in addition to carcinogenic and tumor-promoting agents already reported.

(1965). Transformation of Nicotine to Nornicotine in Excised Tobacco Root Culture. Agricultural and Biological Chemistry: Vol. 29, No. 1, pp. 78-79.