Histamine H2 receptor gene variants: lack of association with schizophrenia

A role of histaminergic neuronal systems in schizophrenia was suggested by an association with several polymorphisms located in the coding region of the histamine H2-receptor (H2R) gene (Orange et al, Mol Psychiatry 1996; 1: 466-469). Using either the reference method of direct sequencing or restriction endonuclease digestion of PCR products amplified from DNA, we could not confirm the existence of these polymorphisms in 53 Swedish controls, 52 French controls and 88 French schizophrenics. In contrast, we detected a G543A transition in the coding region of the gene that was not found in the British population. This allelic variation, which was observed in 15% of the controls with no homozygotes, did not change the amino acid sequence of the receptor. We also analyzed a 1.8-kb nucleotide sequence of the promoter region in which we detected two additional polymorphisms that may modulate the expression of the H2R gene. The first one was a A-592G transition located in the minimal promoter of the gene and found in;10% of controls with no homozygotes. The second one was a G-1018A transition located in an enhancer element of the promoter and was found in;20-30% of controls (with;2-4% homozygotes). DNA analysis of the 88 French schizophrenic subjects revealed that the incidence of the three polymorphisms was not significantly different in this population. In conclusion, the present findings may suggest a surprisingly high variability of the H2R gene polymorphisms in different geographical areas but do not support an association of these allelic variations with schizophrenia.

Chemical constituents of Micromelum minutum. Isolation and structural elucidation of new coumarins

The chemical constituents of an acetone extract of the stems of Micromelum minutum Wight et Arn (Rutaceae), collected at Nakorn-Rachasima province in Thailand, were studied. Six new coumarins, named micromarin-A (1), -B (2), -C (3), -F (4), -G (5), and -H (6), were isolated along with six known coumarins, and their structures were elucidated by chemical and spectroscopic methods.

Chemical constituents of Avicennia alba. Isolation and structural elucidation of new naphthoquinones and their analogues

Three new naphthoquinones and their analogues, named avicequinone-A (1), -B (2), -C (3), and avicenol-A (4), -B (5), -C (6), respectively, were isolated from the stem bark of Avicennia alba (Avicenniaceae) collected in Singapore, and their structures were elucidated by means of spectral methods. Gillan and co-workers have proposed that the structures of the new phytoalexins isolated from Avicennia marina are 1,2-naphthoquinones 8 and 9. Our synthetic and spectrometric studies showed that these structures should be revised respectively to 1,4-naphthoquinones 2 and 3, named avicequinone-B and -C by us.

1,1-Dimethylallylcoumarins potently suppress both lipopolysaccharide- and interferon-gamma-induced nitric oxide generation in mouse macrophage RAW 264.7 cells

We investigated the suppressive effects of 16 coumarin-related compounds on both lipopolysaccharide (LPS)- and interferon (IFN)-gamma-induced nitric oxide (NO) generation in a mouse macrophage cell line, RAW 264.7. Notably, coumarins possessing prenyl unit(s) were found to be highly active, a tendency consistent with our previous study. Among the coumarins tested, 1,1-dimethylallylcoumarins showed the highest inhibitory activity. Western blotting analysis revealed that they inhibited NO generation by suppressing inducible NO synthase (iNOS) protein expression. Our ongoing studies suggest that coumarins are prominent natural compounds that attenuate excessive and prolonged NO generation at inflammatory sites.

Chemical constituents of Glycosmis citrifolia (Willd.) Lindl. Structures of four new acridones and three new quinolone alkaloids

The structures of two new dimeric acridone alkaloids, glycobismine-D (1) and -E (2), having a novel linkage as binary acridones, three monomeric acridones, glycocitrine-IV (3), -V (4), and -VI (5), and three quinolone alkaloids, glycocitlone-A (6), -B (7), and -C (8) from Glycosmis citrifolia (Willd.) Lindl. (Rutaceae) have been elucidated by spectrometric studies.

New carbazole alkaloids from Clausena anisata with antitumor promoting activity

Four new carbazole alkaloids, named clausamine D (1), E (2), F (3), and G (4), were isolated from Clausena anisata as inhibitors of Epstein-Barr virus early antigen activation induced by 12-O-tetradecanoylphorbol-13-acetate in Raji cells.

A new biflavonoid from Calophyllum panciflorum with antitumor-promoting activity

A new biflavonoid named pancibiflavonol (1) was isolated from an EtOH extract of the stem bark of Calophyllum panciflorum, along with six known biflavonoids, and its structure was elucidated by spectroscopic methods. These biflavonoids all exhibited significant inhibitory activity against 12-O-tetradecanoylphorbol-13-acetate-induced Epstein-Barr virus early antigen activation in Raji cells.

Transient increases of histamine H1 and H2 receptor mRNA levels in the rat striatum after the chronic administration of methamphetamine

In our previous studies, we found that behavioral sensitization evoked by repeated administration of methamphetamine (METH) was suppressed by the activation of the histaminergic neuron system in the brain. In continuation of these studies, we measured the levels of H1 and H2 receptor mRNAs in the rat striatum by semi-quantitative reverse transcription-polymerase chain reaction. Seven days after the 21 consecutive administrations of METH (4 mg/kg, i.p.), the levels of both H1 and H2 receptor mRNAs in the rat striatum increased significantly. However, 1 and 14 days after the last administration, there were no significant changes in levels of either H1 or H2 receptor mRNA in the rat striatum. These transient increases of H1 and H2 receptor mRNAs may have some relation to chronic METH abuse and its withdrawal.

Accelerated proliferation of epidermal keratinocytes by the transgenic expression of the platelet-activating factor receptor

Transgenic mice overexpressing platelet-activating factor receptor (PAFR) have abnormal pigmentation of the ear and the tail, which can progress to melanocytic tumors as the mice age. Histologically, epidermal hyperproliferation and increases in dermal melanocytes are evident. Examination of these transgenic mice at various ages revealed hyperproliferation of the epidermis even 2 weeks after birth which developed as the mice aged. Dermal melanocytes also increased in number with growth. Expression of the PAFR transgene was found in keratinocytes and not in melanocytes, thereby suggesting that PAF does not play a direct role in proliferation of melanocytes. Topical application of a cream containing WEB2086, a specific PAFR antagonist, to the ear and the dorsal skin significantly suppressed the number of BrdU-positive cells in PAFR transgenic mice. These results suggest that PAF plays a modulatory role in the growth of epidermal keratinocytes. PAFR transgenic mice would be a useful model for investigations of skin diseases related to altered proliferation of epidermal keratinocytes including psoriasis.

A prospective survey on drug choice for prescriptions for admitted patients with schizophrenia

A survey on psychotropic drugs prescribed for the treatment of schizophrenia was implemented in order to obtain basic data required for revision of the Japanese Psychopharmacology Algorithm (1998). The subjects comprised 94 inpatients with schizophrenia (ICD-10) in seven public hospitals. A questionnaire was conducted to record age, gender, age at start of treatment, treatment period, compliance, frequency of admission and diagnostic classification. A mean dose of chlorpromazine base at 420 mg/day was prescribed to the subjects (six men vs four women; mean age: 32.4 years). The average number of psychotropic drugs prescribed together is 4.0 (1.8 for neuroleptics). The mean treatment period is 5.9 weeks. Antiparkinson drugs, hypnotics, anxiolytics, antimanics/antidepressants and antiepileptics are concurrently used in 92, 85, 25, 6.8 and 2.1% of cases, respectively. Prescriptions are changed 1.8 times on the average. In 84% of the patients, good response to the overall treatment is observed. Polypharmacy is carried out in more than 90% of the patients, although clinical psychopharmacological evidence for the benefits or disadvantages of polypharmacy are insufficient. A large-scale survey is required to revise the algorithm for treatment-refractory schizophrenia, because treatment-refractory and long-term hospitalized patients are rarely included in this survey. False intractable cases due to inadequate treatment such as long-term polypharmacy at a high dose may be included when the scope of subjects is enlarged.

Effect of plasmapheresis as initial monotherapy in a case of anti-neutrophil cytoplasmic autoantibody positive crescentic glomerulonephritis

The effect of plasmapheresis (PP) monotherapy was evaluated in a 77 year old man with crescentic glomerulonephritis (CrGN). Because both anti-neutrophil cytoplasmic myeloperoxidase autoantibody (MPO-ANCA) and circulating immune complex (IC) were positive, removal of these substances was expected to be beneficial. Thus, the treatment was started with PP alone. During 2 month's time, three series of PP monotherapy were performed: three sessions of plasma exchange (PEX) with fresh frozen plasma (FFP); two sessions of double filtration plasmapheresis (DFPP); followed by another two sessions of PEX. The ANCA remained suppressed for 4 weeks after the first PEX, and increased thereafter. Subsequent DFPP caused a rebound in ANCA titer, whereas the second PEX suppressed ANCA for 1 week. Although creatinine clearance (Ccr) improved from 9.3 to 15 ml/min after the first PEX, and this level was maintained, ANCA increased again after the second PEX. Therefore, the patient was treated with methylprednisolone semi-pulse therapy (500 mg/day for 3 days), followed by mild "cocktail" therapy. In 2 weeks ANCA and IC became negative, and Ccr further improved to 20 ml/min. Thus, PP, when performed alone, was shown to be partially effective, arresting the progression of renal damage in the present case. These observations also argue for the advantage of PP, especially PEX, as an adjunct therapy to immunosuppressive therapy in CrGN.

Anti-tumor-promoting effects of phenylpropanoids on Epstein-Barr virus activation and two-stage mouse skin carcinogenesis

In our joint project in the search for anti-tumor promoters from natural plant sources, we carried out a primary screening of 12 phenylpropanoids isolated from Boronia pinnata Sm. (Rutaceae) by examining their possible inhibitory effects on Epstein-Barr virus early antigen (EBV-EA) activation induced by 12-O-tetradecanoylphorbol-13-acetate in Raji cells. All tested compounds in this study showed inhibitory activity against the EBV activation even at 1 x 10 mol ratio without any cytotoxicity. Among 12 phenylpropanoids tested, boropinal-C (1), boropinol-A (5), boropinol-C (9) and 3-(3'-methoxy-4'-prenyloxy)phenyl-1-propene (10), all having a 4'-(3-methylbut-2-enyloxy) group, a so-called prenyloxy group, showed more potent activities. Furthermore, 3-(3'-methoxy-4'-prenyloxy)phenyl-1-propene (10) also exhibited remarkable inhibitory effects on mouse skin tumor promotion in an in vivo two-stage carcinogenesis test. This investigation indicated that certain phenylpropanoids might be valuable anti-tumor promoters.

Steroids from the roots of Nerium oleander

Two new cardenolides, 3beta-hydroxy-5alpha-carda-14(15), 20(22)-dienolide (beta-anhydroepidigitoxigenin) (1) and 3beta-O-(D-digitalosyl)-21-hydroxy-5beta-carda-8,14,16 , 20(22)-tetraenolide (neriumogenin-A-3beta-D-digitaloside) (2), and two known compounds, proceragenin and neridienone A (3), have been isolated from the roots of Nerium oleander. The structures of 1 and 2 were elucidated on the basis of spectral data interpretation.

Structure-activity relationship of cardiotonic flavonoids in guinea-pig papillary muscle

Sixteen flavonoids were tested for a positive inotropic effect (PIE) on guinea-pig papillary muscle paced at 0.2 Hz in a Krebs-Henseleit solution at 30 degrees C. The structure-activity relationship was investigated by determining both the pD2 value and the intrinsic activity in the case of ten flavonols, three flavones, one flavanone and two catechins. Quercetin showed the most potent intrinsic activity, and produced the strongest inotropic responses among the 16 compounds. The relative order of potency of the tested flavonoids was quercetin > morin = kaempferol = HEPTA > luteolin = apigenin > natsudaidain = fisetin = galangin. Those that did not produce any PIE were 3-hydroxyflavone, flavone, glycosides of quercetin (rutin and hyperin), flavanones (naringenin) and catechins. With respect to the essential flavonoid nucleus for PIE development, the presence of a hydroxy group at C-4', an alpha, beta-unsaturated ketone on the C-ring and a reasonable lipophilic moiety in the molecule are required. Pharmacological analyses suggest that there is a common mechanism for the PIE and it is cyclic AMP dependent.

Histamine H1 receptor binding capacities in the amygdalas of the amygdaloid kindled rat

The histamine H1 receptor binding capacity of the amygdalas of amygdaloid kindled rats was studied. In the kindled nonstimulated amygdala, significant decreases in K(D) and B(max) values compared with those of control amygdala were found 1 week after the last kindled seizure. One month after the last kindled seizure, the decreased K(D) value was sustained in the kindled nonstimulated amygdala. This decreased Bmax value 1 week after the last kindled seizure in nonstimulated amygdala may partly and transiently contribute to kindled seizure susceptibility. The decreased K(D) value in nonstimulated amygdala observed until 1 month after the last kindled seizure indicates the long-lasting increment of binding affinity of the pyrilamine binding site of the histamine H1 receptor in the steady state of kindled seizure susceptibility.

[Susceptibilities of bacteria isolated from patients with lower respiratory infectious diseases to antibiotics (1997)]

The bacteria isolated from the patients with lower respiratory tract infections were collected by institutions located throughout Japan, since 1981. Ikemoto et al. have been investigating susceptibilities of these isolates to various antibacterial agents and antibiotics, and analyzed some characteristics of the patients and isolates from them each year. Results obtained from these investigations are discussed. In these 17 institutions around the entire Japan, 512 strains of presumably etiological bacteria were isolated mainly from the sputa of 440 patients with lower respiratory tract infections during the period from October in 1997 to September in 1998. MICs of various antibacterial agents and antibiotics were determined against 100 strains of Staphylococcus aureus, 81 strains of Streptococcus pneumoniae, 85 strains of Haemophilus influenzae. 71 strains of Pseudomonas aeruginosa (non-mucoid strains), 27 strains of Pseudomonas aeruginosa (mucoid strains), 33 strains of Moraxella subgenus Branhamella catarrhalis, 17 strains of Klebsiella pneumoniae etc., and the susceptibilities of these strains were assessed except for those strains that died during transportation. S. aureus strains for which MICs of oxacillin (MPIPC) were higher than 4 micrograms/ml (methicillin-resistant S. aureus: MRSA) accounted for 55.0%. The frequency of the drug resistant bacteria decreased comparing to the previous year's 67.3%. Arbekacin (ABK) and vancomycin (VCM) showed the most potent activities against MRSA. Imipenem (IPM) and panipenem (PAPM) of carbapenems showed the most potent activities with MIC80S of 0.063 microgram/ml against S. pneumoniae. The frequency of penicillin (PC)-intermediate S. pneumoniae (PISP)+PC-resistant S. pneumoniae (PRSP) had decreased gradually, that is, in 1995 the frequency of it was 40.3%, but that was 30.9% in 1997. Against H. influenzae and M.(B.) catarrhalis, all the drugs showed good activities. But the sensitive strains of them against ceftazidime (CAZ) had decreased in 1997, compared those in 1995 and 1996. Meropenem (MEPM), IPM and tobramycin (TOB) showed the most potent activity against P. aeruginosa (mucoid strains). And TOB and ciprofloxacin (CPFX) showed the most potent activities against P. aeruginosa (non-mucoid strains). All drugs except ampicillin (ABPC) were more active against K. pneumoniae in 1997 than that in 1996. Also, we investigated year to year changes in the characteristics of patients, their respiratory infectious diseases, and the etiology. The examination of age distribution indicated that the proportion of patients with ages over 70 years was 45.5% of all the patients showing a slight increase year by year. About the proportion of diagnosed diseases, not so particular changes were recognized as follows: Bacterial pneumonia and chronic bronchitis were the most frequent with 33.6% and 29.1%, respectively. Number of strains isolated from patients before administration of antibiotics were more than those after administration of them in chronic bronchitis, but these had reversed in bacterial pneumonia. The tendency in bacterial pneumonia had been acknowledged since 1995. The increase of S. aureus and P. aeruginosa (both mucoid and non-mucoid strains) isolated after administration of antibiotics, has suggested the decrease of the susceptibility of these strains against antibiotics. Administration of antibiotics has changed the results of the frequency of isolation of bacterial species. Bacterial isolations before administration of antibiotics were as follows: S. pneumoniae 24.5%, H. influenzae 21.4%, S. aureus 18.4% and P. aeruginosa 12.2%. The frequencies of S. aureus decreased after antibiotics administration over 15 days, but the frequencies of P. aeruginosa was not affected. The frequencies of P. aeruginosa was 47.8% after administration over 15 days. From patients administered antibiotics of penicillins and cephems. S. aureus was mainly detected with 31.7-58.3%, and from patients administere

Anti-tumor-promoting effects of 8-substituted 7-methoxycoumarins on Epstein-Barr virus activation assay

In a search for anti-tumor-promoting agents, we carried out a primary screening of twenty-nine 8-substituted and four 6-substituted derivatives of 7-methoxycoumarins isolated from plants of the Murraya and/or Citrus species (Rutaceae), examining their possible inhibitory effects on Epstein-Barr virus early antigen (EBV-EA) activation induced by 12-O-tetradecanoylphorbol-13-acetate (TPA) in Raji cells. This investigation indicated that the prenyl (3-methyl-2-butenyl) or 2-hydroxy-3-methylbutyl (or butenyl) unit as an isoprenoid moiety at C-8 on the 7-methoxycoumarin nucleus plays an important role in the anti-tumor-promoting activity. Some of the 8-substituted 7-methoxycoumarins isolated from Murraya species, murrangatin (7), minumicrolin (10) and chloticol (18), were found to significantly inhibit EBV-EA activation, and preserved the high viability of Raji cells, suggesting that 7, 10 and 18 might be valuable anti-tumor-promoting agents.

The antiproliferative effect of acridone alkaloids on several cancer cell lines

Fifteen acridone alkaloids were examined for their antiproliferative activity toward monolayers and suspension of several types of cancer and normal human cell lines. As a result, atalaphyllidine (9), 5-hydroxy-N-methylseverifoline (11), atalaphyllinine (12), and des-N-methylnoracronycine (13) showed potent antiproliferative activity against tumor cell lines, whereas they have weak cytotoxicity on normal human cell lines. The structure-activity relationship established from the results revealed that a secondary amine, hydroxyl groups at C-1 and C-5, and a prenyl group at C-2 played an important role for antiproliferative activities of the tetracyclic acridones.

Effects of the acute and chronic restraint stresses on the central histaminergic neuron system of Fischer rat

The effects of acute and chronic restraint stresses on the brain histamine level and histamine N-methyltransferase activity in Fischer rat brain were studied. The acute restraint stress increased the histamine levels in the diencephalon and nucleus accumbens, and increased the histamine N-methyltransferase activities in the nucleus accumbens and striatum. The chronic restraint stress also increased histamine N-methyltransferase activities in the nucleus accumbens and striatum. These results indicate that the acute and chronic restraint stresses increase the brain histamine turnover, which may partly relate to the vulnerability for stress-induced anxiety and depression.

Acridones as inducers of HL-60 cell differentiation

Fifteen acridone alkaloids were examined for their activity of induction of human promyelocytic leukemia cell (HL-60) differentiation. HL-60 cells were differentiated into mature monocyte/macrophage by atalaphyllidine (9), atalaphyllinine (12), and des-N-methylnoracronycine (13). The activities of NBT reduction, nonspecific esterase, and phagocytosis, were induced by 2.5 microM of 9, 12, and 13. After a 4-day treatment, 9, 12, and 13 at 10 microM inhibited clonal proliferation of HL-60 cells by 28, 96, and 63%, respectively. The structure-activity relationship established from the results revealed that hydroxyl group at C-1 and prenyl group at C-2 had an important role.

CD38-mediated signaling events in murine pro-B cells expressing human CD38 with or without its cytoplasmic domain

To elucidate the signaling mechanism of CD38 (a transmembrane molecule highly expressed in immature hemopoietic cells), we transfected Ba/F3 murine pro-B cells with a cDNA encoding human CD38. CD38 ligation with anti-CD38 Abs caused rapid, transient, dose-dependent tyrosine phosphorylation of several proteins, including the tyrosine kinase TEC and the adaptor molecule CBL, and association of tyrosine-phosphorylated proteins with phosphatidylinositol 3-kinase p85. Exposure to anti-CD38 Abs or their F(ab')2 and Fab also induced tight aggregation of CD38-transfected Ba/F3 cells, which appeared to be Ca2+ and Mg2+ independent and did not involved LFA-1. Aggregation was abrogated by addition of the tyrosine kinase inhibitor herbimycin A and was delayed by the phosphatidylinositol 3-kinase inhibitor wortmannin, suggesting a link between biochemical events and cellular effects induced by CD38. Cell aggregation was accompanied by a decrease in cell recovery. After 3 days of culture on bone marrow-derived stroma, the mean (+/-SD) cell recovery in the presence of anti-CD38 (T16) was 10.5 +/- 9.2% (n = 7) of that in parallel cultures with an isotype-matched nonreactive Ab. Finally, CD38 ligation in Ba/F3 cells expressing a mutant human CD38 lacking the cytoplasmic domain induced tyrosine phosphorylation with intensity and kinetics similar to those seen with the entire protein. It also induced cell aggregation and decreased cell recovery. We conclude that CD38 triggers remarkably similar signaling pathways in human and murine immature B cells. This signaling is independent of the CD38 cytoplasmic domain, suggesting the existence of accessory transmembrane molecules associated with CD38.

Substituted 7H-pyrido[4,3-c]carbazoles with potent anti-HIV activity

Several substituted 7H-pyrido[4,3-c]carbazoles were synthesized from the natural product mukonal and tested for inhibition of HIV replication in H9 lymphocytes. 5-Methoxy-7-methyl-7H-pyrido[4,3-c]carbazole (7) had an EC50 value of 0.0054 microgram/mL and the highest therapeutic index (TI = 503) in the series.

Hyperdiploid acute lymphoblastic leukemia with 51 to 65 chromosomes: a distinct biological entity with a marked propensity to undergo apoptosis

To determine the cellular basis for the excellent clinical outcome of hyperdiploid acute lymphoblastic leukemia (ALL), defined by a modal chromosome number of 51 to 65, we assessed the growth potential of leukemic cells from 129 children with newly diagnosed ALL. Flow cytometric analysis was used to compare leukemic cell recoveries at the beginning and at the end of 7-day cultures on allogeneic bone marrow-derived stromal layers. The median percentage of cell recovery after culture was 91% (range, <1% to 550%). Among the 25 hyperdiploid cases, only two had cell recoveries above the median value, compared with 63 of 104 cases with different ploidies (P <.001); 21 had recoveries within the first quartile, in contrast to only 12 of the 104 other cases. Cell recoveries in the 16 cases with duplications of chromosomes 4 and 10, a feature previously associated with a superior outcome, were all within the first quartile. Flow cytometric studies indicated that rapid induction of apoptosis was the underlying cause of low cell recoveries in cases with hyperdiploidy. The demise of hyperdiploid cells on stroma was not due to failure to adhere with stromal elements (as shown by electron microscopy) or to deficiencies of interleukin-1 (IL-1), IL-2, IL-3, IL-4, IL-6, IL-7, IL-11, stem-cell factor, interferon- (IFN-), tumor necrosis factor- (TNF-), or to combinations of these cytokines. Inactivation of IL-4, IFN- and TNF-, which if secreted by stromal layers could be toxic to ALL cells, failed to improve the survival of hyperdiploid blasts. We conclude that leukemic cells bearing 51 to 65 chromosomes have a marked propensity to undergo apoptosis. The stringent survival requirements of these cells, together with their potentially higher sensitivity to antileukemic drugs, may well account for the high cure rates achieved in patients with this form of ALL.

Algorithm for the treatment of schizophrenia in Japan

Evidence-based psychopharmacological algorithms for the treatment of patients with schizophrenia have been developed in many countries in the last decade. While it would be of interest to consider a common algorithm based on international consensus, algorithms and information on antipsychotics available in each country are limited. Inspired by the algorithm generated by the International Psychopharmacology Algorithm (IPA) Project, this algorithm for the treatment of schizophrenia has been developed by the Japan Psychophamacology Algorithm (JPA) Project. New antipsychotics, such as clozapine, olanzapine and quetiapine, are excluded from this algorithm, being currently unavailable in Japan. In the end there was no essential difference between the algorithms for the treatment of acute schizophrenic episodes. However, combined use of antipsychotics appears to be more common in Japan and the adjunctive use of L-DOPS or thyrotropin-releasing hormone is included in the JPA algorithm for the treatment of drug-refractory schizophrenia.

Identification of coumarins from the fruit of Citrus hystrix DC as inhibitors of nitric oxide generation in mouse macrophage RAW 264.7 cells

Three known coumarins have been isolated from Citrus hystrix DC as inhibitors of both lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma)-induced nitric oxide (NO) generation in RAW 264.7 cells. The inhibitory activity of bergamottin (IC(50) = 14 microM) was comparable to that of N-(iminoethyl)-L-ornithine (L-NIO) (IC(50) = 7. 9 microM), whereas oxypeucedanin and 5-[(6',7'-dihydroxy-3', 7'-dimethyl-2-octenyl)oxy]psoralen, structurally different from bergamottin only in their side-chain moieties, were notably less active. Using 21 coumarins, we structurally classified various types of coumarins into groups A-C: (A) bearing an isoprenyl (IP) or a geranyl (GR) group, highly active; (B) bearing an IP group cyclized to a coumarin ring, moderately active; (C) bearing an IP group modified with hydroxyl group(s) and/or having other functional groups except for the IP, completely inactive. Cellular uptake studies suggested that coumarins in group C are inactive because of poor permeability to the cell membrane.