Synthesis and inhibitory activity of acyl-peptidyl-pyrrolidine derivatives toward post-proline cleaving enzyme; a study of subsite specificity.

Several pyrrolidine derivatives have been synthesized and examined for their inhibitory activity on post-proline cleaving enzymes from Flavobacterium meningosepticum and bovine brain. Almost all the compounds tested in this study inhibited the activity of both enzymes at low IC50 values (from nM to microM) but a specificity difference was observed with alkylacyl-peptidyl-pyrrolidine derivatives which strongly inhibited only the bacterial enzyme. The most effective inhibitors have a proline residue on their P2 sites and a substituted or unsubstituted phenoxybutyryl moiety on their P3 sites. Thus phenoxybutyryl-prolyl-pyrrolidine is the most effective partial structure of the inhibitors. The best inhibitors found were: 4-(4-benzylphenoxy)butyryl-prolyl-pyrrolidine for bacterial enzyme (IC50 1.4 nM) and 4-phenylbutyryl-thioprolyl-pyrrolidine for bovine brain enzyme (IC50 67 nM). In the passive avoidance test, using amnesic rats experimentally induced with scopolamine, the pyrrolidine derivatives which had potent inhibitory activity toward post-proline cleaving enzymes also showed strong anti-amnesic activities at doses of 1-5 mg/kg, i.p.     

Aminothiol multidentate chelators against Chagas disease

Three compounds of an aminothiol family of iron chelators were examined for activity against trypomastigote (human) and epimastigote (vector) forms of Trypanosoma cruzi: tetraethyl and tetramethyl derivatives of ethane-1,2-bis (N-1-amino-3-ethyl butyl-3-thiol) (BAT-TE and BAT-TM) and N',N',N'-tris-(2-methyl-2-mercaptopriopyl)- 1,4,7-triazacyclonane (TAT). BAT-TE at 270 microM completely arrested the growth of trypomastigote forms in mouse blood stored at 4 degrees C for 24 h (IC(50) 67.7+/-7 microM), while BAT-TM arrested growth at 630 microM (IC(50) 158+/-17 microM) and TAT at concentrations >800 microM (IC(50) 415+/-55 microM). In T. cruzi-infected mice, BAT-TE and BAT-TM had no anti-trypanosomal activity in doses up to 200 mg/kg, whether the route of administration was intraperitoneal or oral, and TAT was not tested due to insufficient quantity. TAT had an IC(50) of 52+/-7 microM against the epimastigote forms while BAT-TM and BAT-TE were inhibitory only at concentrations >250 microM. The trypanocidal activity of BAT derivatives in blood stored at 4 degrees C makes these compounds potential candidates for the purpose of clearing donated blood of trypomastigotes.     

Characterization of CGS 8515 as a selective 5-lipoxygenase inhibitor using in vitro and in vivo models

CGS 8515 inhibited 5-hydroxyeicosatetraenoic acid (5-HETE) and leukotriene B4 synthesis in guinea pig leukocytes (IC50 = 0.1 microM). The compound did not appreciably affect cyclooxygenase (sheep seminal vesicles), 12-lipoxygenase (human platelets), 15-lipoxygenase (human leukocytes) and thromboxane synthetase (human platelets) at concentrations up to 100 microM. CGS 8515 inhibited A23187-induced formation of leukotriene products in whole blood (IC50 values of 0.8 and 4 microM, respectively, for human and rat) and in isolated rat lung (IC50 less than 1 microM) in vitro. The selectivity of the compound as a 5-lipoxygenase inhibitor was confirmed in rat whole blood by the 20-70-fold separation of inhibitory effects on the formation of leukotriene from prostaglandin products. Ex vivo and in vivo studies with rats showed that CGS 8515, at an oral dose of 2-50 mg/kg, significantly inhibited A23187-induced production of leukotrienes in whole blood and in the lung. The effect persisted for at least 6 h in the ex vivo whole blood model. CGS 8515, at oral doses as low as 5 mg/kg, significantly suppressed exudate volume and leukocyte migration in the carrageenan-induced pleurisy and sponge models in the rat. Inhibitory effects of the compound on inflammatory responses and leukotriene production in leukocytes and target organs are important parameters suggestive of its therapeutic potential in asthma, psoriasis and inflammatory conditions.     

New antihypertensive peptides isolated from rapeseed

Four potent angiotensin converting enzyme (ACE) inhibitory peptides, IY, RIY, VW and VWIS, were isolated from subtilisin digest of rapeseed protein. Among them RIY and VWIS are new peptides with IC(50) 28 and 30 microM, respectively. All isolated peptides lowered blood pressure of spontaneously hypertensive rats (SHR) following oral administration. The maximum effect in the case of RIY was observed 4h after administration, while maximum effect of other peptides on blood pressure occurred 2h after administration. Furthermore, the antihypertensive effect of RIY was observed even in old rats, in which ACE inhibitors become less effective, suggesting that a different mechanism other than ACE inhibition is also involved in lowering blood pressure by this peptide. Subtilisin digest of rapeseed protein also significantly lowered blood pressure of SHR after oral administration of a single dosage 0.15 g/kg, exerting maximum antihypertensive effect 4h after administration. This digest appears promising as a functional food, which may be useful in the prevention and treatment of hypertension.     

Design, synthesis, and biological evaluation of N-acetyl-2-(or 3-)carboxymethylbenzenesulfonamides as cyclooxygenase isozyme inhibitors

A group of N-acetyl-2-(or 3-)carboxymethylbenzenesulfonamides, possessing either a F or a substituted-phenyl ring substituent (4-F, 2,4-F2, 4-SO2Me, 4-OCHMe2) attached to its C-4 or C-6 position, was prepared using a palladium-catalyzed Suzuki cross-coupling reaction for evaluation as selective cyclooxygenase-2 (COX-2) inhibitors. Although N-acetyl-3-carboxymethyl-6-fluorobenzenesulfonamide [14, COX-1 IC50 = 2.26 microM; COX-2 IC50 = 0.012 microM; COX-2 selectivity index (SI) = 188] and N-acetyl-3-carboxymethyl-6-(4-isopropoxyphenyl)benzenesulfonamide (20c, COX-1 IC50 >100 microM; COX-2 IC50 = 0.15 microM; COX-2 SI >667) exhibited potent in vitro COX-2 inhibitory activity and high COX-2 selectivity, both compounds were inactive anti-inflammatory agents in a carrageenan-induced rat paw edema assay. In contrast, the less potent and less selective COX-2 inhibitors N-acetyl-2-carboxymethyl-4-fluorobenzenesulfonamide (12, COX-1 IC50 = 4.25 microM; COX-2 IC50 = 0.978 microM; COX-2 SI = 4.3), N-acetyl-2-carboxymethyl-4-(2,4-difluorophenyl)benzenesulfonamide (17c, COX-1 IC50 = 1.02 microM; COX-2 IC50 = 1.00 microM; COX-2 SI = 1.02), and N-acetyl-3-carboxymethyl-6-(4-methanesulfonylphenyl)benzenesulfonamide (20e, COX-1 IC50 = 0.109 microM; COX-2 IC50 = 1.14 microM; COX-2 SI = 0.095) exhibited moderate anti-inflammatory activity where a 75 mg/kg oral dose reduced inflammation 26%, 14%, and 20%, respectively, at 3 h postdrug administration relative to the reference drug aspirin where a 50 mg/kg oral dose reduced inflammation by 25% at 3 h postdrug administration.     

Synthesis, anti-inflammatory, analgesic and kinase (CDK-1, CDK-5 and GSK-3) inhibition activity evaluation of benzimidazole/benzoxazole derivatives and some Schiff's bases

A series of N-(acridin-9-yl)-4-(benzo[d]imidazol/oxazol-2-yl) benzamides has been synthesized by the condensation of 9-aminoacridine derivatives with benzimidazole or benzoxazole derivatives. Condensation of 2-hydroxy naphthaldehyde with functionalized diamines leads to the formation of Schiff's bases and not imidazole derivatives. All these compounds were characterized by correct FT-IR, (1)H NMR, MS and elemental analyses. These compounds were screened for anti-inflammatory, analgesic and kinase (CDK-1, CDK-5 and GSK-3) inhibition activities. Compounds 11 and 7e(f) showed good anti-inflammatory (35.8% at 50 mg/kg po) activity and good analgesic activity (60% at 50 mg/kg po), respectively. Compound 3b showed significant in vitro activity against CDK-5 (IC(50)=4.6 microM) and CDK-1(IC(50)=7.4 microM) and compound 3a showed moderate CDK-5 inhibitory activity (IC(50)=7.5 microM). The other compounds showed moderate anti-inflammatory and analgesic activities.     

Type III phosphodiesterase plays a necessary role in the growth-promoting actions of insulin, insulin-like growth factor-I, and Ha p21ras in Xenopus laevis oocytes.

Three phosphodiesterase (PDE) type III inhibitors were tested and found to inhibit Xenopus oocyte maturation induced by insulin with apparent IC50 values of 2.2 +/- 0.2 microM Cl-930, 25 +/- 3 microM imazodan (Cl-914), and 786 +/- 237 microM piroximone (MDL 19,205). The same rank order of potencies was observed for inhibition of insulin-like growth factor-I (IGF-I)-induced oocyte maturation, with IC50 values of 5.5 +/- 0.9 microM Cl-930, 54 +/- 4 microM imazodan, and 1190 +/- 395 microM piroximone. Oocyte maturation induced by microinjection of Ha p21ras was also inhibited by pretreatment of oocytes with Cl-930 or imazodan, with IC50 values of 4.3 +/- 1.2 and 59 +/- 4 microM, respectively. Progesterone-induced maturation was not affected by PDE III inhibitor action; and, neither type IV PDE inhibitors (Ro 20, 1724 or rolipram) nor dipyridamole (a type V PDE inhibitor) inhibited cell division induced by IGF-I or microinjected Ha p21ras. In addition, while insulin-stimulated oocyte PDE activity measured in vivo after microinjection of 200 microM [3H] cAMP was inhibited by nonselective and type III-specific drugs (with IC50 values of 4.2 +/- 1.8 microM Cl-930 and 26 +/- 6 microM imazodan), type IV and type V inhibitors did not inhibit hormone-stimulated enzyme activity. This pharmacological evidence demonstrates a necessary role for PDE III in insulin-, IGF-I-, and p21ras-induced meiotic cell division in Xenopus laevis oocytes.     

Influence on Turnover and Level of Hypothalamic Noradrenaline by a New Antihypertensive Agent (GYKI 11679)

Abstract— In an attempt to delineate the possible importance of the concentration of noradrenaline at hypothalamic noradrenergic receptor sites in a hypotensive response to a drug, the action of a new antihypertensive agent, 1-(6-morpholino-3-pyridazynyi)-2-(1-[tert-butoxycarbonyi]-2-propylidene)-diazane (GYKI 11679), on the turnover rate and the endogenous level of noradrenaline (NA) in rat hypothalamus was examined. An effective, antihypertensive i.p. dose of the compound (10 mg/kg) produced a significant but relatively short-lasting reduction in the hypothalamic noradrenaline content, whereas no change was observed in the cardiac catecholamine level. The NA turnover determinations, carried out in GYKI 11679-pretreated rats by measuring the disappearance of labeled NA at 1, 2, 3, and 5 h after the injection of the radioactive amine, showed that a 10 mg/kg i.p. dose of the compound, given 1 h prior to the i.c.v. administration of the labeled NA, increased the turnover rate of noradrenaline to a great extent. The estimated half-lives of NA in the hypothalamus of the treated and of the non-treated animals were calculated as 1.72 and 3.62 h, respectively. In vitro studies showed that the spontaneous outflow of noradrenaline from hypothalamic slices was accelerated by GYKI 11679 in a dose-dependent manner in a concentration range of 10^?5 to 10^?7m . In a 10-fold higher range, GYKI 11679 produced inhibition of both the hypothalamic and the adrenal tyrosine hydroxylase activity but did not alter DOPA-decarboxylase, dopamine-β-hydroxylase, or monoamine oxidase activities. Direct in vivo measurements of catecholamine synthesis by determining the ³H-catecholamines (CA) formed from [³H]tyrosine in the hypothalamus after an i.c.v. administration of the labeled precursor showed a moderate increase in [³H]CA formation following a 10 mg/kg dose of the compound. When GYKI 11679 was administered in a 75 mg/kg i.p. dose to rats, the transformation was reduced by –50%. Adenylate cyclase activity measurements did not show stimulatory or inhibitory actions of the drug on the NA-stimulated adenylate cyclase of the rat hypothalamus, in accordance with previous results. This suggests that the increased NA turnover (utilization) caused by an effective, antihypertensive dose of GYKI 11679 is the direct consequence of an increased outflow, which occurs primarily in the hypothalamus. The increased activity of the noradrenergic neurons in this brain region might lead to a reduced sympathetic activity in the periphery and thus to a significant decrease in blood pressure.     

The human renin infused rat: use as an in vivo model for the biological evaluation of human renin inhibitors

The human renin infused rat model (HRIRM) was used as an in vivo small-animal model for evaluating the efficacy of a collection of inhibitors of human renin. The intravenous infusion of recombinant human renin (2.4 microg x kg(-1) x min(-1)) in the ganglion-blocked, nephrectomized rat produced a mean blood pressor response of 47+/-3 mm Hg (1 mm Hg = 133.3 Pa), which was reduced by captopril, enalkiren, and losartan in a dose-dependent manner following oral administration, with ED50 values of 0.3+/-0.1, 2.5+/-0.9, and 5.2+/-1.6 mg/kg, respectively. A series of peptidomimetic P2-P3 butanediamide renin inhibitors inhibited purified recombinant human renin in vitro in a concentration-dependent manner, with IC50 values ranging from 0.4 to 20 nM at pH 6.0, with a higher range of IC50 values (0.8-80 nM) observed at pH 7.4. Following i.v. administration of renin inhibitors, the pressor response to infused human renin in the HRIRM was inhibited in a dose-dependent manner, with ED50 values ranging from 4 to 600 microg/kg. The in vivo inhibition of human renin following i.v. administration in the rat correlated significantly better with the in vitro inhibition of human renin at pH 7.4 (r = 0.8) compared with pH 6.0 (r = 0.5). Oral administration of renin inhibitors also resulted in a dose-dependent inhibition of the pressor response to infused human renin, with ED50 values ranging from 0.4 to 6.0 mg/kg and the identification of six renin inhibitors with an oral potency of <1 mg/kg. The ED50 of renin inhibitors for inhibition of angiotensin I formation in vivo was highly correlated (r = 0.9) with the ED50 for inhibition of the pressor response. These results demonstrate the high potency, dose dependence, and availability following oral administration of the butanediamide series of renin inhibitors.     

Biochemical and pharmacological characteristics of a newly synthesized H+-K+ ATPase inhibitor, YJA20379-1, 2-amino-4,5-dihydro-8-phenylimidazole[2,1-b]thiazolo[5,4-g]benzothiazol e.

The biochemical and pharmacological characteristics of a newly synthesized H+-K+ ATPase inhibitor, 2-amino-4,5-dihydro-8-phenylimidazole[2,1-b]thiazolo[5,4-g]benzothiazole (YJA20379-1), were investigated. In the pig gastric microsomes, YJA20379-1 inhibited the gastric H+-K+ ATPase regardless of pH condition, IC50 values being 21 and 24 microM at pH 6.4 and 7.4, respectively. The inhibitory activity of YJA20379-1 was antagonized by dithiothreitol treatment but could not be reversed by dilution and washing of the enzyme preparation. In Sprague-Dawley rats, YJA20379-1, administered i.d., p.o, i.v., or s.c., significantly inhibited basal gastric acid secretion, with ED50 values of 4.7, 20.2, 6.3, and 13.4 mg/kg, respectively. The antisecretory action of YJA20379-1 was short lasting (less than 7 h at an oral dosing of 30 mg/kg). Oral administration of YJA20379-1 also prevented the formation of ethanol, indomethacin, and water immersion stress induced gastric lesions and mepirizole-induced duodenal ulcers in rats. Furthermore, YJA20379-1 accelerated the healing of acetic acid induced chronic gastric ulcers in rats. In conclusion, these results suggest that YJA20379-1 has a potent inhibitory activity on the gastric H+-K+ ATPase but much shorter duration of antisecretory action than omeprazole, thereby exerting its anti-ulcer effects partly with cytoprotective activity.     

A novel nonpeptidic, orally active renin inhibitor

BW-175 is a newly synthesized renin inhibitor which is a nonpeptidic, norleucine analog. Its IC50 values for renin activity in human, squirrel monkey, marmoset, dog, hog, rabbit and rat plasma were 3.3, 6.6, 2.4, 42, 110, 86 and 3500 nM, respectively, and 26 microM for cathepsin D. Pepsin and angiotensin converting enzyme were hardly inhibited at 10(-4) M. BW-175 showed an oral bioavailability of 2.8% at 10 mg/kg and 9.7% at 30 mg/kg in rats. In normotensive, furosemide-treated high-renin marmosets, BW-175 (30 mg/kg p.o.) caused an intensive reduction in plasma renin activity and plasma angiotensin I formation, associated with a reduction in systolic blood pressure of 10-20 mm Hg for 2 hours.     

Synthesis of celecoxib analogs that possess a N-hydroxypyrid-2(1H)one 5-lipoxygenase pharmacophore: biological evaluation as dual inhibitors of cyclooxygenases and 5-lipoxygenase with anti-inflammatory activity

A hitherto unknown class of celecoxib analogs was designed for evaluation as dual inhibitors of the 5-lipoxygenase/cyclooxygenase-2 (5-LOX/COX-2) enzymes. These compounds possess a SO(2)Me (11a), or SO(2)NH(2) (11b) COX-2 pharmacophore at the para-position of the N(1)-phenyl ring in conjunction with a 5-LOX N-hydroxypyrid-2(1H)one iron-chelating moiety in place of the celecoxib C-5 tolyl group. The title compounds 11a-b are weak inhibitors of the COX-1 and COX-2 isozymes (IC(50)=7.5-13.2 microM range). In contrast, the SO(2)Me (11a, IC(50)=0.35 microM), and SO(2)NH(2) (11b, IC(50)=4.9 microM), compounds are potent inhibitors of the 5-LOX enzyme comparing favorably with the reference drug caffeic acid (5-LOX IC(50)=3.47 microM). The SO(2)Me (11a, ED(50)=66.9 mg/kg po), and SO(2)NH(2) (11b, ED(50)=99.8 mg/kg po) compounds exhibited excellent oral anti-inflammatory (AI) activities being more potent than the non-selective COX-1/COX-2 inhibitor drug aspirin (ED(50)=128.9 mg/kg po) and less potent than the selective COX-2 inhibitor celecoxib (ED(50)=10.8 mg/kg po). The N-hydroxypyridin-2(1H)one moiety constitutes a novel pharmacophore for the design of cyclic hydroxamic mimetics capable of chelating 5-LOX iron for exploitation in the design of 5-LOX inhibitory AI drugs.     

Solid phase combinatorial synthesis of benzothiazoles and evaluation of topoisomerase II inhibitory activity

To investigate one possible mechanism of action of the cytotoxic activity of benzothiazoles, we synthesized 2-(substituted-phenyl)benzothiazoles and evaluated their ability to inhibit topoisomerase II activities. Solid phase combinatorial method using trityl resin was employed and benzothiazole derivatives with various substitution on 2'-, 3'-, or 4'-position of phenyl group were obtained in ca. 30 mg scale (7-96% yield). Most of the compounds synthesized exhibited topoisomerase II inhibitory activity at 100 microM. 2-(3-Amino-4-methylphenyl)benzothiazole showed high activity (IC(50) = 71.7 microM), comparable to etoposide (IC(50) = 78.4 microM).     

In vitro and in vivo antileishmanial activity of 2-amino-4,6-dimethylpyridine derivatives against Leishmania mexicana

Leishmania mexicana promastigote and intracellular amastigote growths were inhibited by the water-soluble furan-2-carboxamide issued from the pharmacophore 2-amino-4,6-dimethylpyridine with IC50 values of 69 +/- 2 and 89 +/- 9 microM, respectively. This compound was also tested against established L. mexicana infection in susceptible BALB/c mice; an intraperitoneal administration of 10 mg/Kg/day during five consecutive days induced a high reduction in the amastigote burden of the poplitea lymph node (81 +/- 6.4%), the spleen (80 +/- 1.6%) and the liver (73 +/- 9%). Approach of the mechanism of antileishmanial activity of this compound, assessed by the flow cytometry, showed a reduction in the protein and DNA synthesis. Finally, an actual increase of the in vitro antileishmanial activity was obtained by replacement of the amidic function by an imidazolidin-2-one moiety. In this new series, two of the N-substituted derivatives showed IC50 values of 13 +/- 0.5 and 7 +/- 3 microM in intracellular amastigotes constituting new promising compounds for further studies.     

Analgesic effect of actinonin, a new potent inhibitor of multiple enkephalin degrading enzymes

Actinonin, previously isolated as an antibiotic and shown to be an inhibitor of aminopeptidase M (EC 3.4.11.2), has now been shown to inhibit three enkephalin-degrading enzymes from guinea-pig striatum. The values of IC50 were 0.39 microM for striatal membrane aminopeptidase ("enkephalin-aminopeptidase") and 5.6 microM striatal membrane neutral endopeptidase ("enkephalinase A"). Furthermore, soluble dipeptidylaminopeptidase in a rat whole brain homogenate was also inhibited by actinonin with the IC50 value of 1.1 microM. Actinonin administered intracisternally (i.cist., 50 micrograms) or intraperitoneally (i.p., 100 mg/kg), potentiated the analgesic action of met-enkephalin (50 micrograms i.cist.). analgesia by a tail-flick test. The potentiating activity of actinonin i.p. to met-enkephalin analgesia was almost the same potency as that of thiorphan, whereas the inhibitory activity of actinonin against enkephalinase A was 1/1000 that of thiorphan. Actinonin alone, administered either i.cist. or i.p., showed an analgesic action as estimated by the tail-flick test.     

Pharmacological actions of Y-24180, a new specific antagonist of platelet activating factor (PAF): II. Interactions with PAF and benzodiazepine receptors

The inhibitory effect of Y-24180, 4-(2-chlorophenyl)-2-[2-(4-isobutylphenyl)ethyl]-6,9-dimethyl-6H-t hieno [3,2-f][1,2,4]triazolo [4,3-a][1,4]diazepine, on platelet activating factor (PAF)-induced platelet aggregation and the specific binding of 3H-PAF to platelets was compared with other thienodiazepine derivatives, WEB 2086 and etizolam. Y-24180 inhibited PAF-induced rabbit platelet aggregation in vitro (IC50 3.84 nM), but had little effect on adenosine diphosphate- or arachidonic acid-induced aggregation. WEB 2086 and etizolam also showed an inhibitory effect of PAF-induced aggregation (IC50 values are 456 and 6730 nM, respectively). In PAF-induced human platelet aggregation, Y-24180 (IC50 0.84 nM) was more potent than WEB 2086 (IC50 4.21 nM) and etizolam (IC50 998 nM). Y-24180, WEB 2086 and etizolam displaced 3H-PAF binding from the washed-platelets of rabbits with an IC50 value of 3.50, 9.35 and 29.5 nM, respectively. In rabbits, pretreatment with Y-24180 and WEB 2086 antagonized PAF-induced platelet aggregation dose-dependently. The significant inhibitory effect of Y-24180 (1 mg/kg, p.o.) lasted 72 hr after a single dose oral administration. WEB 2086 (10 mg/kg, p.o.) also antagonized the ex vivo response induced by PAF 1 hr after administration, but no significant effect was observed 3 hr after administration. Y-24180 displaced 3H-diazepam binding from the synaptosomal membranes of rat cerebral cortex with a Ki value of 3.68 microM. The affinity of Y-24180 for benzodiazepine(BZP) receptors was lower than those of WEB 2086 and etizolam and was about 1000 times lower than that for PAF receptors in platelets.     

A novel anti-hypertensive peptide derived from ovalbumin induces nitric oxide-mediated vasorelaxation in an isolated SHR mesenteric artery.

In this report, we deal with the isolation of a novel vasorelaxing peptide from a chymotryptic digest of ovalbumin and its vasorelaxing activities. This peptide is composed of Arg-Ala-Asp-His-Pro-Phe (RADHPF) in its sequence, corresponding to residues 359-364 of ovalbumin. This peptide (30-300 microM) exerted a dose-dependent vasodilation in an isolated mesenteric artery from a spontaneously hypertensive rat which was pre-constricted by phenylephrine, besides the relaxation being endothelium-dependent. It is noteworthy that the nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester inhibited this relaxation, implying involvement of nitric oxide in its mechanism of action. Following oral administration of RADHPF at a dose of 10 mg/kg, the systolic blood pressure in a spontaneously hypertensive rat was significantly lowered.     

Alpha-glucosidase inhibitory activity of a 70% methanol extract from ezoishige (Pelvetia babingtonii de Toni) and its effect on the elevation of blood glucose level in rats

The 70% methanol extract from ezoishige (Pelvetia babingtonii de Toni) inhibited the rat-intestinal alpha-glucosidase, sucrase and maltase activities, with IC50 values of 2.24 and 2.84 mg/ml. Sucrose was orally administered with or without the extract to rats at 1000 mg/kg. The postprandial elevation in the blood glucose level at 15 and 30 min after the administration of sucrose with the extract was significantly suppressed when compared with the control. These results suggest that the extract from ezoishige has potent alpha-glucosidase inhibitors and would be effective for suppressing postprandial hyperglycemia.     

Triphenyltin and Tributyltin inhibit pig testicular 17beta-hydroxysteroid dehydrogenase activity and suppress testicular testosterone biosynthesis

We previously reported that tributyltin chloride (TBT) and triphenyltin chloride (TPT) powerfully suppressed human chorionic gonadotropin- and 8-bromo-cAMP-stimulated testosterone production in pig Leydig cells at concentrations that were not cytotoxic [Nakajima Y, Sato Q, Ohno S, Nakajin S. Organotin compounds suppress testosterone production in Leydig cells from neonatal pig testes. J Health Sci 2003;49:514-9]. This study investigated the effects of these organotin compounds on the activity of enzymes involved in testosterone biosynthesis in pig testis. At relatively low concentrations of TPT, 17beta-hydroxysteroid dehydrogenase (17beta-HSD; IC(50)=2.6microM) and cytochrome P450 17alpha-hydroxylase/C(17-20) lyase (IC(50)=117microM) activities were inhibited, whereas cholesterol side-chain cleavage cytochrome P450 and 3beta-HSD/Delta(4)-Delta(5) isomerase activities were less sensitive. Overall, TPT was more effective than TBT. TPT also inhibited both ferredoxin reductase and P450 reductase activities at concentrations over 30microM; however, TBT had no effect, even at 100microM. The IC(50) values of TPT were estimated to be 25.7 and 22.8microM for ferredoxin reductase and P450 reductase, respectively. The inhibitory effect of TPT (30microM) on microsomal 17beta-HSD activity from pig testis was eliminated by pretreatment with the reducing agents dithiothreitol (1mM) and dithioerythritol (1mM). On the other hand, TPT (0.03microM) or TBT (0.1microM) exposure suppressed the testosterone production from androstenedione in pig Leydig cells indicating that these organotins inhibit 17beta-HSD activity in vivo as well as in vitro, and the IC(50) values of TPT and TBT for 17beta-HSD activity were estimated to be 48 and 114nM, respectively. Based on these results, it appears possible that the effects of TBT and TPT are largely due to direct inhibition of 17beta-HSD activity in vivo.