Protective effect of carboxyethylgermanium sesquioxide (Ge-132) on superoxide generation by60Co-irradiated leukocytes

The carboxyethylgermanium sesquioxide, Ge-132, is an organogermanium compound which has been shown to modulate leukocyte functions. In this study, we examined the effect of Ge-132 on the generation of superoxide radicals (O₂ ^–) either from leukocytes or in cell-free system, employing the highly sensitive 2-methyl-6-[p-methoxy-phenyl]-3,7-dihydroimidazo[1,2-alpha] pyrazin-3-one (MCLA) -dependent chemiluminescence method and the specific electron spin resonance/spin trapping method, respectively. In addition, thein vitro protective effect of Ge-132 on the leukocytes irradiated with⁶⁰Co was studied.The incubation with Ge-132 resulted in an increase in basal O₂ ^– release of intact leukocytes, but had no effect on OZ generation from leukocytes stimulated with phorbol myristate acetate (PMA). Irradiation with⁶⁰Co decreased the Oz generation from leukocytes in a dose-dependent manner. Ge-132 had no effect on basal O₂ ^– release from⁶⁰Co-irradiated leukocytes, but it prevented the decrease in PMA-stimulated O₂ ^– generation by irradiated leukocytes. Ge-132 itself had no superoxide scavenging activity in cell-free system. On the other hand, higher concentrations of Ge-132 had decreasing effects on both basal O₂ ^–1 release and PMA-stimulated O₂ ^– generation from leukocytes, but they did not affect leukocyte viability. Above results indicate that 1) Ge-132 can stimulate the basal O₂ ^– release from leukocytes, 2) Ge-132 can prevent the decrease of O₂ ^– generation by⁶⁰Co-irradiated leukocytes, 3) in higher concentrations, Ge-132 may have a membrane stabilizing effect.     

Inhibitory effects of the analgesic neuropeptides kyotorphin and neo-kyotorphin on enkephalin-degrading enzymes from monkey brain

The inhibitory effects of the analgesic neuropeptides kyotorphin (Tyr-Arg) and neo-kyotorphin (Thr-Ser-Lys-Tyr-Arg) on enkephalin-degrading enzymes were studied. The enzyme used were aminopeptidase (AP), dipeptidyl aminopeptidase (DPP), enkephalinase-A (ENK-A), and angiotensin-converting enzyme (ACE), which were prepared from the monkey brain membrane fraction. Kyotorphin inhibited only DPP (IC50, 18 microM), and the mode of inhibition was non-competitive (Ki, 6 microM). Neo-kyotorphin inhibited AP, DPP, and ACE with IC50 values of 131, 306, and 200 microM, respectively, but the inhibition of the enzyme activities were not effective. The selective inhibition by kyotorphin suggested that kyotorphin might protect the released Met-enkephalin against enzymatic degradation by DPP. Thus, kyotorphin may not only induce the release of Met-enkephalin but also stabilize the released neuropeptide.     

Inhibitory effects of N-(acryloyl)benzamide derivatives on tyrosinase and melanogenesis

Targeting of tyrosinase has proven to be the best means of identifying safe, efficacious, and potent tyrosinase inhibitors for whitening skin. We designed and synthesized ten NAB (N-(acryloyl)benzamide) derivatives (1a–1j) using the Horner-Wadsworth-Emmons olefination of diethyl (2-benzamido-2-oxoethyl)phosphonate and appropriate benzaldehydes. A mushroom tyrosinase inhibitory assay showed compounds 1a (36.71 ± 2.14% inhibition) and 1j (25.99 ± 2.77% inhibition) inhibited tyrosinase more than the other eight NAB derivatives and kojic acid (21.56 ± 2.93% inhibition), and docking studies indicated 1a (−6.9 kcal/mole) and 1j (−7.5 kcal/mole) had stronger binding affinities for tyrosinase than kojic acid (−5.7 kcal/mole). At a concentration of 25 μM, 1a and 1j were nontoxic in B16F10 melanoma cells and exhibited stronger tyrosinase inhibition (59.70% and 76.77%, respectively) than kojic acid (50.30% inhibition) or arbutin (41.78% inhibition at 400 μM). Similarly, in B16F10 melanoma cells, compounds 1a and 1j at 25 μM decreased total melanin content by 47.97% and 61.77%, respectively (kojic acid; 38.98%). Similarities between inhibitions of tyrosinase activity and melanin contents suggested the anti-melanogenic effects of 1a and 1j were due to tyrosinase inhibition. The excellent DPPH scavenging activity of 1j suggests it might enhance in vivo effect on melanin contents. The study suggests compound 1j offers a potential starting point for the development of safe, potent tyrosinase inhibitors.     

Induction of interferon and activation of NK cells and macrophages in mice by oral administration of Ge-132, an organic germanium compound

After oral administration of an organic germanium compound, Ge-132 (300 mg/kg), a significant level of interferon (IFN) activity was detected in the sera of mice at 20 hr and it reached a maximum of 320 U/ml at 24 hr. This IFN activity was lost after heat- or acid-treatment, suggesting that the induced IFN is of gamma-nature. The molecular weight of this IFN was estimated to be 50,000 daltons by gel filtration. The NK activity of spleen cells was increased 24 hr after the oral administration of Ge-132, and cytotoxic macrophages were induced in the peritoneal cavity by 48 hr. In the mice receiving an intraperitoneal (ip) injection of trypan blue or carrageenan 2 days before oral administration of Ge-132, neither induction of IFN nor augmentation of NK activity occurred, and X-ray irradiation of mice also rendered the mice incapable of producing IFN, all indicating that both macrophages and lymphocytes are required for this IFN induction. Both NK and cytotoxic macrophages appeared 18 hr after ip administration of the induced IFN with a titer as low as 20 U/ml. These facts suggest that both the augmentation of NK activity and activation of macrophages in mice after oral administration of Ge-132 are mediated by the induced IFN.     

Inhibitory effects of lapachol derivatives on epstein-barr virus activation

Sixteen derivatives (2-17) synthesized from the naphthoquinone lapachol (1), were tested for their inhibitory effects on Epstein-Barr virus early antigen (EBV-EA) activation induced by 12-O-tetradecanoylphorbol-13-acetate (TPA), as a test for potential cancer chemopreventive agents. They exhibited a variety of inhibitory activities from very high to moderate, which allow us to suggest structure-activity relationships. Ten of these derivatives are reported for the first time, their structures being thoroughly determined by spectroscopic methods.     

Inductive effects of enzymes of salicylic acid derivatives

In the series of salicylic acids derivatives investigated 3,5-DIS has a large inductive effect of enzymes with respect to the metabolism of xenobiotics: rise in the rate of Cyt. P 450; increase of ethoxycoumarin deethylase, bilirubin glucuronosyl transferase and benzphetamine-N-demethylase activities. This effect is comparable with that of phenobarbital.     

Inhibitory effects of resveratrol derivatives from dipterocarpaceae plants on tyrosinase activity

Stilbene derivatives, which are resveratrol (3,4',5-trihydroxy-trans-stilbene) oligomers ranging from monomer to tetramer, isolated from Dipterocarpaceae plants were tested for their inhibitory effects against murine tyrosinase activity. The structure-activity relationships obtained in this study suggest that the double bond in the stilbene skeleton is critical for the inhibition, and also that molecular size is important for inhibitory potency.     

Inhibitory effects on mitochondrial complex I of semisynthetic mono-tetrahydrofuran acetogenin derivatives

Modifications in the terminal alpha,beta-unsaturated gamma-methyl-gamma-lactone moiety or in the alkyl chain that links this terminal gamma-lactone with the alpha,alpha'-dihydroxylated THF system of the natural mono-tetrahydrofuranic acetogenins, annonacin and annonacinone, led to the preparation of eight semisynthetic derivatives. Their inhibitory effects on mitochondrial complex I is discussed and compared with that of the classical complex I inhibitor, rotenone.     

Inhibitory effects of stress-activated nitric oxide on antioxidant enzymes and testicular steroidogenesis

The messenger role of nitric oxide (NO) in immobilization stress-induced inhibition of testicular steroidogenesis has been previously suggested. In accord with this, here, we show that the intratesticular injection of isosorbide dinitrate (ISDN; 2x2.5 mg/testis), an NO donor, mimicked the action of stress on serum testosterone concentrations and hCG-stimulated testosterone production in rat testicular tissue. When added in vitro, ISDN inhibited testicular 3beta-hydroxysteroid dehydrogenase and 17alpha-hydroxylase/lyase. Immobilization stress and injections of ISDN also decreased the activity of catalase, glutathione peroxidase, glutathione transferase, and glutathione reductase in the interstitial compartment of testis. When stressed rats were treated concomitantly with bilateral intratesticular injections of N(omega)-nitro-L-arginine methyl ester, a non-selective NOS inhibitor (2x600 microg/testis), the activities of antioxidative enzymes, as well as serum testosterone concentration, were partially normalized. These results indicate that stress-induced stimulation of the testicular NO signalling pathway leads to inhibition of both steroidogenic and antioxidant enzymes.     

Inhibitory effects of novel synthetic methimazole derivatives on mushroom tyrosinase and melanogenesis

In this study, we synthesized 4 methimazole (2-mercapto-1-methylimidazole, MMI) derivatives. The kinetics of inhibition on mushroom tyrosinase by methimazole and its derivatives were investigated. The results indicated that tert-butyl 3-methyl-2-sulfanylidene-2,3-dihydro-1H-imidazole-1-carboxylate (compound 3; 3), 2-mercaptoimidazole (MI; compound 1; 1) and MMI (compound 2; 2) significantly inhibited tyrosinase activity in a dose-dependent manner, exhibiting an IC₅₀ value of 1.50 mM, 4.11 mM, and 1.43 mM. However, compound 4 (4), compound 5 (5), and compound 6 (6) exerted no inhibitory effect on mushroom tyrosinase activity. Kinetic analysis indicated that 3 was a noncompetitive tyrosinase inhibitor, whereas both 1 and 2 were exhibited as mixed-type tyrosinase inhibitors. Furthermore, 3 exerted a potent inhibitory effect on intracellular melanin formation in the B16/F10 murine melanoma cells and did not cause cytotoxicity, as 1 and 2 did.     

Inhibitory effects of benzyl benzoate and its derivatives on angiotensin II-induced hypertension

Hypertension is a lifestyle-related disease which often leads to serious conditions such as heart disease and cerebral hemorrhage. Angiotensin II (Ang II) plays an important role in regulating cardiovascular homeostasis. Consequently, antagonists that block the interaction of Ang II with its receptors are thought to be effective in the suppression of hypertension. In this study, we searched for plant compounds that had antagonist-like activity toward Ang II receptors. From among 435 plant samples, we found that EtOH extract from the resin of sweet gum Liquidambar styraciflua strongly inhibited Ang II signaling. We isolated benzyl benzoate and benzyl cinnamate from this extract and found that those compounds inhibited the function of Ang II in a dose-dependent manner without cytotoxicity. An in vivo study showed that benzyl benzoate significantly suppressed Ang II-induced hypertension in mice. In addition, we synthesized more than 40 derivatives of benzyl benzoate and found that the meta-methyl and 3-methylbenzyl 2'-nitrobenzoate derivatives showed about 10-fold higher activity than benzyl benzoate itself. Thus, benzyl benzoate, its derivatives, and benzyl cinnamate may be useful for reducing hypertension.     

Inhibitory effects of alkyl gallate and its derivatives on fatty acid desaturation

Alkyl gallate, which is known as an antioxidant, intensively inhibited Δ5 and Δ6 desaturation in both rat liver microsomes and an arachidonic acid-producing fungus Mortierella alpina 1S-4. The rat liver microsomal Δ5 and Δ6 desaturases were inhibited by gallic acid esterified with alcohols with various numbers of carbons, suggesting that the necessary structure in an esterified alcohol for the inhibition is not so strict. Among the three hydroxy groups in gallic acid, the m-hydroxy group was shown to be the necessary structure. Kinetic analyses revealed that propyl gallate is a noncompetitive inhibitor of Δ5 desaturase (K_i = 2.6 · 10⁻⁵ M) and Δ6 desaturase (K_i = 1.7 · 10⁻⁴ M). These data indicate that alkyl gallate is a new type of desaturase inhibitor and different from known natural inhibitors, i.e., sesamin and curcumin.     

Novel inhibitors of enkephalin-degrading enzymes. III: 4-Carboxymethylamino-4-oxo-3 (phenylamino) butanoic acids as enkephalinase inhibitors.

4-Carboxymethylamino-4-oxo-3-(4'-aminophenylamino) butanoic acid (25), its ethyl ester (26) and the corresponding unsubstituted-aryl analogues (17) and (16) are fairly potent inhibitors of enkephalinase (neutral endopeptidase; EC 3.4.24.11), Ki = 0.14-0.39 microM, with weak inhibitory potency, Ki = 15-75 microM, towards aminopeptidase MII. In the mouse abdominal constriction test, the esters (26) and (16) showed systemic inhibitory (antinociceptive) activity with ED50 values 62 +/- 3.05 and 81 +/- 1.74 mg/kg respectively. In the mouse tail immersion test, both (26) and (16) exhibited antinociceptive activity when administered intracerebroventricularly and (26) also exhibited a systemic effect which was only partially reversed by naltrexone. The antinociceptive effect seen with (26) reflects its ranking in vitro as an inhibitor of enkephalinase (Ki = 0.14 microM) but it is possible that this effect is not totally opioid-mediated. Compounds (26) and (16) represent the first combined inhibitors of enkephalinase and aminopeptidase MII.     

Inhibitory effect of polyelectrolytes on oligomeric enzymes

The effect of polyelectrolytes on the stability and catalytic characteristics of oligomeric enzymes--pig muscle lactate dehydrogenase (LDH) and bovine liver glutamate dehydrogenase (GDH)--was studied by fluorescent spectroscopic and steady state kinetic methods. It was shown that the binding of negatively charged polyelectrolytes--polystyrene sulfonate, polymethacrylate, and polyphosphate--destroys the tertiary and partially the secondary structure of LDH and GDH, resulting in their complete inactivation at pH < 7. The concentrations of polyelectrolytes needed for inhibition of the enzymes were in this case by two or more orders of magnitude lower than the corresponding concentrations for monomers--toluene sulfonate, methacrylate, and phosphate. The affinity of the substrate (pyruvate) for LDH did not vary in the presence of the polyelectrolytes, but the inhibition was removed by excess of substrate. We propose that the oligomeric state of enzymes causes polyelectrolytes to act on them in a special manner, this special effect differing significantly from the effect of polyelectrolytes on monomeric enzymes. The effect consists in that polyelectrolytes cleave the oligomeric structure of the enzymes, this "cleaving" effect being higher the greater the hydrophobicity of the polyelectrolyte chain.     

Inhibitory effects of phenol derivatives on bovine platelet aggregation and their effects on Ca2+ mobilization

The effects of phenol derivatives on aggregation of bovine platelets induced by ADP, thrombin, platelet activating factor, collagen and A23187 were investigated. The phenol derivatives inhibited all these induced aggregations except that by the calcium ionophore. The derivatives each inhibited the aggregations induced by ADP, thrombin, platelet activating factor and collagen, respectively, within a similar concentration range. A linear relation was found between the inhibitory potencies of the phenol derivatives and their partition coefficients between n-octanol and water (Poct values), suggesting that their interaction with hydrophobic regions of the cell was important for inhibition. Fluorescence analyses with fura-2-loaded platelets showed that in the concentration ranges in which the phenol derivatives inhibited aggregation, they also inhibited agonist-induced increases in Ca2+ both in the presence and absence of extracellular Ca2+. Moreover, a high correlation was found between the inhibitory effects of the derivatives on aggregation and their effects on Ca2+ mobilization. These results suggest that inhibition of platelet aggregation by phenol derivatives is mainly due to inhibition of the increase in cytoplasmic Ca2+ by inhibition of both intracellular Ca2+ mobilization and Ca2+ uptake.     

Inhibitory effects of 2-substituted-1-naphthol derivatives on cyclooxygenase I and II

Naphthol derivatives, 2-(3'-hydroxypropyl)-naphthalen-1-ol (2), 2-(3'-hydroxy-2'-methylpropyl)-naphthalen-1-ol (3) and 2-(3'-hydroxy-2',2'-dimethylpropyl)-naphthalen-1-ol (7) were synthesized and already reported by our group. Therefore in this paper we described further synthesis of their ether derivatives, 3-(1-methoxy-naphthalen-2-yl)-propan-1-ol (4), 3-(1-methoxy-naphthalen-2-yl)-2methyl-propan-1-ol (5), 3-(1-methoxy-naphthalen-2-yl)-2,2-dimethyl-propan-1-ol (8), 2-(3-methoxy-propyl)-naphthalen-1-ol (10) and 2-(3-methoxy-2,2-dimethyl-propyl)-naphthalen-1-ol (13). Compounds 4, 5 and 8 were prepared by methylation of compounds 2, 3 and 7, respectively while compounds 10 and 13 were prepared in good yield from naphthols 2 and 7, respectively. When tested for inhibitory activity, five compounds (2, 3, 7, 10 and 13) showed preferential inhibition of COX-2 over COX-1, while compounds 4, 5 and 8 lacked inhibitory effect on either the COX-1 or COX-2 isozyme. The structure-activity relationships of these naphthols analyzed by docking experiments, indicated that the presence of hydroxyl group at C-1 position on the naphthalene nucleus enhanced the anti-inflammatory activity towards COX-2 via hydrogen bonding to the COX-2 Val 523 side chain. When this hydroxyl group was replaced by methoxy group, there was no inhibition. C-2' Dimethyl substituents on the propyl chain also increased the inhibitory activity. All active compounds have the C-1 hydroxyl group aligned so as to form hydrogen bond with Val 523. The results provide a model for the binding of the naphthol derivatives to COX-2 and facilitate the design of more potent or selective analogs prior to synthesis.     

Inhibitory effects of pasuchaca (Geranium dielsiaum) extract on alpha-glucosidase in mouse

The methanolic extract of pasuchaca (Geranium dielsiaum) (PsEx) was found to suppress blood glucose elevation after oral administration of sucrose, maltose, and starch, but not after oral administration of glucose, in the mouse. In vitro examination of the inhibitory effect of PsEx on maltase activity revealed that PsEx strongly inhibited mouse small intestine maltase activity. Taken together, these results suggest that the inhibitory effect of PsEx on alpha-glucosidase activity might contribute to delay in carbohydrate digestion and subsequent lowering of the blood glucose level, thereby leading to prevention and cure of diabetes.