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This paper describes the inhibitory activities of diacylglyceride phospholipids, such as phosphatidylcholine (lecithin), phosphatidylethanolamine (cephalin), phosphatidylserine, phosphatidylglycerol, bisphosphatidylglycerol (cardiolipin), phosphatidylinositol, and phosphatidic acid (phosphatidate) (compounds 1 - 7, respectively) against DNA polymerase (pol), DNA topoisomerase (topo), and human cancer cell growth. Among the compounds tested, compounds 3 - 7 were revealed to be potent inhibitors of animal pols: compound 4 was the strongest inhibitor, with IC(50) values for different pols of 1.7 - 15 mM. Compounds 4 - 7 also inhibited the activity of human topo II: compound 7 was the strongest inhibitor, with an IC50 value of 20 mM. The glycerophospholipids had no effect on the activities of plant (cauliflower) pol a, prokaryotic pols, or other DNA metabolic enzymes, such as calf primase of pol a, T7 RNA polymerase, T4 polynucleotide kinase, and bovine deoxyribonuclease I. These results suggest that compounds 3 - 7 are selective inhibitors of animal pols and human topos. Compounds 4 and 7 also suppressed the growth of a human colon carcinoma cell line that lacked p53 (HCT116 p53(-/-)); their LD(50) values were 63.6 and 51.1 mM, respectively, suggesting that cell growth inhibition by these compounds leads to the inhibition of pols and/or topos. From these findings, diacylglyceride phospholipids, which are present in various foods, might be effective nutrients for promoting human anti-cancer health promotion.

This paper describes the inhibitory activities of cholesterol derivatives such as cholesterol, sodium cholesteryl sulfate, cholesteryl-5alpha, 6alpha-epoxide, cholesteryl chloride, cholesteryl bromide, and cholesteryl hemisuccinate (compounds 1-6, respectively) against DNA polymerase (pol), DNA topoisomerase (topo), and human cancer cell growth. Among the compounds tested, compounds 2 and 6 revealed themselves to be potent inhibitors of animal pols, and the IC50 values for pols were 0.84-11.6 and 2.9-148 microM, respectively. Compounds 2, 3 and 6 inhibited the activity of human topo II, with IC50 values of 5.0, 12.5 and 120 microM, respectively. Compounds 2, 3 and 6 also suppressed human cancer cell (promyelocytic leukemia cell line, HL-60) growth, and LD50 values were 8.8, 20.2 and 72.3 microM, respectively, suggesting that cell growth inhibition had the same tendency as the inhibition of topos rather than pols. Compounds 2 and 6 arrested the cells in S and G2/M phases, compound 3 arrested the cells in the G2/M phase, and these compounds also increased sub-G1 phase in the cell cycle. These results suggested that the effect of cell cycle arrest might be effective on both pols and topos activities. From these findings, the action mode of cholesterol derivatives as anti-cancer compounds is discussed.

We screened the inhibitor of mouse inosine 5′-monophosphate dehydrogenase (IMPDH) type II from natural compounds, and found that a fatty acid, linoleic acid (C18:2), inhibited IMPDH activity. In the C18:2 fatty acid derivatives, all trans -configuration (i.e., linoelaidic acid), ester form, alcohol form, and addition of the hydroxyl group of linoleic acid had no effect on inhibitory activity. Therefore, both parts of a carboxylic acid and an alkyl chain containing cis -type double bonds of fatty acid might be essential for inhibition. Among the various carbon atom lengths and double bonds of fatty acids examined, the strongest inhibitor was C20:2-fatty acid, eicosadienoic acid, and 50% inhibition was observed at a concentration of 16.1 μM. Eicosadienoic acid induced the inhibition of IMPDH activity and was competitive with respect to IMP ( K i = 3.1 μM). For inhibitory effect, the C20-fatty acids ranked as follows: C20:2 > C20:3 > C20:1 > > C20:4 > C20:5, and C20:0 showed no inhibition. The energy-minimized three-dimensional structures of linear-chain C20-fatty acids were calculated, and it was found that a length of 20.7–22.5 A and width of 4.7–7.2 A in the fatty acid molecular structure was suggested to be important for IMPDH inhibition. Docking simulation of C20-fatty acids and mouse IMPDH type II, which was homology modeled from human IMPDH type II (PDB code: 1NF7), was performed, and the fatty acid could bind to Cys331, which is a amino acid residue of the active site, competitively with IMP. Based on these results, the IMPDH-inhibitory mechanism of fatty acids is discussed.

Cholesterol hemisuccinate (compound 5), which consists of succinic acid esterified to the beta-hydroxyl group of cholesterol, selectively and strongly inhibited the activities of mammalian DNA polymerases (pols) such as pol beta, pol lambda, and terminal deoxynucleotidyltransferase (TdT), which are family X pols, in vitro, and the IC50 values were 2.9, 6.3, and 6.5 microM, respectively. The compound moderately suppressed the activities of other mammalian pols such as pol A (i.e., pol gamma), pol B (i.e., pols alpha, delta, and epsilon), and pol Y (i.e., pols iota, eta, and kappa) with 50% inhibition observed at concentrations of 131, 89.2-98.0, and 120-125 microM, respectively. The compound had no influence on the activities of plant pols alpha and beta, prokaryotic pols and other DNA metabolic enzymes tested. Since other cholesterol-related compounds such as cholesterol, cholesteryl chloride, cholesteryl bromide, cholesteryl acetate, and cholesteryl-5alpha, 6alpha-epoxide (compounds 1-4 and 6, respectively) did not influence the activities of any enzymes tested, the hemisuccinate group of compound 5 could be important for inhibition of the pol X family. Surface plasmon resonance analysis demonstrated that compound 5 bound selectively to the C-terminal 31 kDa domain of pol beta and pol lambda containing a pol beta-like region. On the basis of these results, the inhibitory mechanism of compound 5 on the pol X family was discussed.

In this study, the chemical properties of organic acids as DNA polymerase inhibitors were examined. In total, we assayed the inhibitory activities of 23 compounds. We found that the DNA synthesis activity of DNA polymerase was usually reduced to less than 50% in the presence of 100 microM monoprotic acids, which have a Clog P value greater than 7.0 and a pK(a) value less than 5.4. With a minor modification these chemical properties applied to several organic fatty acids previously reported as DNA polymerase inhibitors. Moreover, we also examined the inhibitory activities of perfluorooctadecanoic acid (PFOdA) and perfluorooctanesulfonic acid (PFOS) against DNA polymerase beta in detail. These compounds inhibited the polymerase activity of pol beta competitively with template-primer DNA, and non-competitively with dNTPs. In addition, the 8 kDa domain-defective pol beta was also sensitive to these compounds. Our results suggest that the inhibitory mode of action of PFOdA and PFOS is different from that mediated by the classic fatty acid inhibitors against DNA polymerase beta.

We succeeded in purifying the fraction of monogalactosyl diacylglycerol (MGDG), digalactosyl diacylglycerol (DGDG), and sulfoquinovosyl diacylglycerol (SQDG) containing the major glycolipids from a green vegetable, spinach (Spinacia oleraceaL.). This glycolipids fraction inhibited the activities of replicative DNA polymerases (pols) such as alpha, delta, and epsilon, and mitochondrial pol gamma with IC50 values of 44.0-46.2 microg/ml, but had no influence on the activity of repair-related pol beta. The fraction also inhibited the proliferation of human cervix carcinoma (HeLa) cells with LD50 values of 57.2 microg/ml. In an in vivo anti-tumor assay on nude mice bearing solid tumors of HeLa cells, the fraction was shown to be a promising suppressor of solid tumors. Histopathological examination revealed that tumor necrosis with hemorrhage was significantly enhanced with the glycolipids fraction in vivo. The spinach glycolipids fraction might be a potent anti-tumor compound, and this fraction may be a healthy food substance with anti-tumor activity.

Tetralols 1 and 2, dihydroisocoumarins 3-6, and chromone 7 are natural compounds isolated from cultures of fungi, and their structures were determined by spectroscopic analyses. Compounds 1 and 2 from Nodulisporium sp. are novel tetralols, 1,2,3,4-tetrahydro-5-methoxynaphthalene-1,4-diol (nodulisporol) and 3,4-dihydro-4-hydroxy-8-methoxynaphthalen-1(2H)-one (nodulisporone), respectively. All isolated compounds selectively inhibited the activity of human DNA polymerase lambda (pol lambda), and compound 5 (3,5-dimethyl-8-methoxy-3,4-dihydroisocoumarin) was the strongest inhibitor of pol lambda in the tested compounds with an IC(50) value of 49 microM. New tetralols (1 and 2) are the third and second strongest inhibitors of pol lambda, but did not influence the activities of mammalian pols alpha to kappa, and showed no effect even on the activities of plant pols alpha and beta, prokaryotic pols, and other DNA metabolic enzymes such as calf terminal deoxynucleotidyl transferase, human immunodeficiency virus type-1 (HIV-1) reverse transcriptase, human telomerase, T7 RNA polymerase, and bovine deoxyribonuclease I. The structure-activity relationships of isolated compounds such as novel tetralols, dihydroisocoumarins, and chromone are discussed.