Activity-based fractionation of Eriodictyon californicum resulted in the isolation of 12 flavonoids that inhibit the metabolism of the carcinogen benzo[a]pyrene by hamster embryo cells in tissue culture. One was identified as a new flavanone, 3'-methyl-4'-isobutyryleriodictoyol [1], on the basis of spectroscopic analysis and alkaline hydrolysis. The seven other active flavanones were identified as eriodictyol [2], homoeriodictyol [3], 5,4'-dihydroxy-6,7-dimethoxyflavanone [4], pinocembrin [5], sakuranetin [6], 5,7,4'-trihydroxy-6,3'-dimethoxyflavanone [7], and naringenin 4'-methyl ether [8]. Four active flavones were also isolated: cirsimaritin [9], chrysoeriol [10], hispidulin [11], and chrysin [12]. The high inhibition of benzo[a]pyrene metabolism and the activation of benzo[a]pyrene to ultimate carcinogenic DNA-binding metabolites by cirsimaritin and chrysoeriol at a concentration of only 10 micrograms/ml indicates that these flavones warrant further investigation in vivo as potential chemopreventive agents.

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01) in EtOH (50 mL) under stirring. The solution was refluxed for 24 h, then a second portion of KOH (0.26 g, 4 mmol) was added, and the mixture was refluxed for additional 2 h. The mixture was filtered until hot to remove crude 34 (ca. 5%), and the filtrate was kept overnight in a refrigerator. The crystalline precipitate that deposited was collected by filtration, washed with water, and recrystallized from DMF to give 36 in 15% yield.Reaction of 7 with 1,3-Dibromopropane. The general procedure was followed except for the substitution of 1,3-dibromopropane (10 mol). After removal of ca. 500 mL of solvent from the reaction mixture, the residue was kept overnight in a refrigerator. The crystalline material that precipitated was collected by filtration and recrystallized from DMF to give l, lO-dithia[4.4 ] (3,5)-1,3,4-thiadiazolinophane-6,15-dithione (37) as yellowish prisms: 0.85 g, 45%; mp 210-212 "C; 'H NMR (Me2SO-d,) 6 2.44 (m, SCH2CH2CH2N, 4 H), 3.39 (dd, J = 5.5 13C NMR (Me2SO-d6) 6 thiazino[2,3-b ][ 1,3,4]thiadiazolium Bromide (40).Solutions of 2-mercapto-5-(methylthio)-1,3,4-thiadiazole sodium salt (0.31 g, 1.68 mmol), generated from 3 by treatment with 1 equiv of EtONa, and 1,3-dibromopropane (0.34

Bioassay-directed fractionation of an EtOH extract of the moss Polytrichum pallidisetum (Polytrichaceae) led to the isolation of three novel benzonaphthoxanthenones, 1-O-methylohioensin B [6], 1-O-methyldihydroohioensin B [7] and 1,14-di-O-methyldihydroohioensin B [8], and two novel cinnamoyl bibenzyls, pallidisetin A [9] and pallidisetin B [10]. Their structures and relative stereochemistry were established by spectral analyses and chemical correlation. Compounds 6-10 exhibited cytotoxic activity against the human tumor cell lines RPMI-7951 melanoma and U-251 glioblastoma multiforme. These two types of compounds could hypothetically be derived from cinnamic acid and bibenzyls through different biogenetic pathways.

Our findings suggest that conjugating GA to internalizing MAbs enhances the inhibitory effect of the MAbs. This approach might also be applied in cellular targeting via growth factors and may be of clinical interest.