Aromatase inhibition by synthetic lactones and flavonoids in human placental microsomes and breast fibroblasts--a comparative study.

Interference of exogenous chemicals with the aromatase enzyme can be useful as a tool to identify chemicals that could act either chemopreventive for hormone-dependent cancer or adverse endocrine disruptive. Aromatase is the key enzyme in the biosynthesis of steroids, as it converts androgens to estrogens. Certain flavonoids, plant derived chemicals, are known catalytic aromatase inhibitors. Various systems are in use to test aromatase inhibitory properties of compounds. Commonly used are microsomes derived from ovary or placental tissue characterized by high aromatase activity. To a lesser extent whole cell systems are used and specifically cell systems that are potential target tissue in breast cancer development. In this study aromatase inhibitory properties of fadrozole, 8-prenylnaringenin and a synthetic lactone (TM-7) were determined in human placental microsomes and in human primary breast fibroblasts. In addition, apigenin, chrysin, naringenin and two synthetic lactones (TM-8 and TM-9) were tested in human microsomes only. Comparison of the aromatase inhibitory potencies of these compounds between the two test systems showed that the measurement of aromatase inhibition in human placental microsomes is a good predictor of aromatase inhibition in human breast fibroblasts.

Cuneatoside, a new megastigmane diglycoside from Erythroxylum cuneatum Blume.

A new megastigmane diglycoside, inamoside 6'-O-L-alpha-arabinofuranoside (cuneatoside), was isolated from the leaves and branches of Erythroxylum cuneatum together with seven known compounds, (+)-catechin, quercetin 3-O-alpha-L-rhamnoside, apocynol B, (6S,9R)-roseoside, vomifoliol 9-O-alpha-L-arabinofuranosyl (1-->6)-beta-D-glucopyranoside, inamoside, and citroside A The structural elucidations were based on analyses of physical and spectroscopic data.

Labdane and pimarane diterpenes from Croton joufra.

From the chloroform extract of the leaves of Croton joufra, the diterpenes 2alpha,3alpha-dihydroxy-labda-8(17),12(13),14(15)-triene and 3beta-hydroxy-19-O-acetyl-pimara-8(9),15-dien-7-one, were isolated. Their structures were established by spectroscopic methods. One of the compounds showed weak lethality in the brine shrimp assay.

Cytotoxic natural products from thai plants: a recent study.

Natural products will continue to be the most prolific source of bioactive compounds. Natural products exhibiting antitumor activity continue to be the subject of extensive research aimed at the development of drugs for the treatment of different human tumors. It is generally accepted that natural products offer a diversity and complexity of structure unmatched by even the most active imaginations of synthetic organic chemists. This paper reviews the research of selected Thai plants for the discovery of therapeutic agents. Attention will be focused on our recent research on Thai plants that possess cytotoxic properties. Synthetic modification and reaction of some of these compounds aimed at enhancing their potency will also be presented.

Chemical investigation of mammea siamensis.

A new 4-alkylcoumarin, mammea B/AC cyclo D ( 1 ), together with a 4-phenylcoumarin, mammea A/AC cyclo D ( 2 ), were isolated from the hexane extract of the dried flower of Mammea siamensis . Their structures were determined on the basis of spectroscopic evidence.

NMR study of seven coumarins from mammea siamensis.

Seven known mammea coumarins, mammea A/AA cyclo D ( 1 ), mammea A/AD cyclo D ( 2 ), mammea A/AB cyclo D ( 3 ), mammea A/AC cyclo F ( 4 ), mam-mea A/AB cyclo F ( 5 ), mammea A/AA cyclo F ( 6 ), mammea B/AC cyclo F ( 7 ), were isolated for the first time from the hexane extract of Mammea siamensis . A detailed analysis of both 1D and 2D NMR spectral data of these compounds was made.

Reinvestigation of derris reticulata.

The novel compound 1'''-hydroxy-2''',3'''-epoxylupinifolin ( 1 ), together with three known prenylated flavanones were identified from the stem of Derris reticulata during our reinvestigation of the plant. The structures were determined by spectroscopic methods including detailed study of NMR spectral data (DEPT, 2D-COSY, HMQC and HMBC) as well as by chemical derivatizations.

Cyanogenic and non-cyanogenic glycosides from Manihot esculenta.

In addition to lotaustralin and linamarin, a novel cyanogenic glycoside, 2-((6-O-(beta-D-apiofuranosyl)-beta-D-glucopyranosyl)oxy)-2-met hylbutanenitrile , two novel non-cyanogenic glycosides, (2S)-((6-O-(beta-D-apiofuranosyl)-beta-D- glucopyranosyl)oxy)butane and 2-((6-O-(beta-D-apiofuranosyl)-beta-D-glucopyranosyl)oxy)propane, and a simple non-cyanogenic glycoside, ethyl beta-D-glucopyranoside, were isolated from an ethanolic extract of the fresh root cortex of Manihot esculenta. From a methanolic extract of the fresh leaves of this species lotaustralin and linamarin, and two flavonoid glycosides, kaempferol-3-O-rutinoside and quercetin-3-O-rutinoside were isolated.

Mutagenic activity of newly synthesized sulfa drugs to Salmonella typhimurium.

The mutagenic activity of seven newly synthesized sulfa drugs was studied in Salmonella typhimurium, using forward mutation to 8-azaguanine (8-AG) resistance and reversion mutation assays (Ames test) both in the absence and presence of Aroclor induced rat liver S9. In forward mutation assays, N1-methylsulfanilamide, N4-acetyl-N1-methylsulfanilamide and N4-acetyl-N1-diethylsulfanilamide were mutagenic to S. typhimurium TM677 both in the presence and absence of metabolic activation while N4-acetylsulfanilamide, N1-diethylsulfanilamide and 4-nitro-N-2-pyridinylbenzenesulfonamide [2-(p-nitrobenzenesulfonamido)pyridine] were mutagenic only in the presence of metabolic activation. But 2-(N4-acetylsulfanilamido)pyridine was mutagenic in neither the presence nor the absence of metabolic activation. However, none of the seven compounds had any mutagenic effect on S. typhimurium TA98 or TA100 in the absence or presence of metabolic activation, by the Ames test preincubation method. The relationship between the structure of the compounds and their mutagenic activity is also discussed.

1H- and 13C-nmr assignments of phyllanthin and hypophyllanthin: lignans that enhance cytotoxic responses with cultured multidrug-resistant cells.

Complete 1H-nmr data and unambiguous assignments of the 13C-nmr spectra of phyllanthin [1] and hypophyllanthin [2] were obtained through extensive nmr studies, including homonuclear COSY, homonuclear decoupling, APT, HETCOR, nOe difference, selective INEPT, and COLOC experiments. The absolute configuration of hypophyllanthin [2] was determined by cd. Neither of these lignans demonstrated significant cytotoxic activity when evaluated with a battery of cultured mammalian cells, but both were found to enhance the cytotoxic response mediated by vinblastine with multidrug-resistant KB cells. In addition, 1 was found to displace the binding of vinblastine with membrane vesicles derived from this cell line, suggesting an interaction with the P-glycoprotein.

Repeated exposure to Opisthorchis viverrini and treatment with the antihelminthic Praziquantel lacks carcinogenic potential.

The effects of repeated Praziquantel administration, subsequent to infection and reinfection with Opisthorchis viverrini (OV), on lesion development in the Syrian hamster liver were investigated. Five applications of the antihelminthic drug were made (300 mg/kg body wt, i.g.), each time approximately 5 weeks after dosing with 60-80 OV metacercariae at weeks 0, 8, 16, 24 and 32. The animals were then maintained until week 40 when they were killed; histopathological investigation revealed no significant development of either hepatocellular of cholangiocellular preneoplastic/neoplastic lesions. The results indicate that repeated exposure to Praziquantel at levels sufficient for successful removal of parasite infestation does not itself carry carcinogenic risk.

Lack of modulation effects of praziquantel on DMN-induced lesion development in the Syrian hamster liver.

The effects of repeated praziquantel administration subsequent to dimethylnitrosamine (DMN) treatment of Syrian hamsters were investigated. The antihelminthic drug was given (200 mg/kg body wt. as a suspension in corn oil, by i.g. intubation) 11 times at 2 week intervals starting at week 4 after initial 20 mg/kg DMN i.p. injections at weeks 0 and 2. Sacrifice at week 28 revealed no differences in either hepatocellular or cholangiocellular lesion development between carcinogen-initiated groups with or without antihelminthic treatment. No lesions were observed in the praziquantel alone or untreated groups. The results thus indicate no promotion potential for praziquantel on nitrosamine-induced lesions in the hamster liver.

Structural requirements of some sulphonamides that possess an antifertility activity in male rats.

Sulphonamides with different chemical structures were synthesized and these 13 compounds together with 7 commercially available sulpha drugs were tested for antifertility activity by natural mating in male rats. All compounds were given daily by gastric intubation at doses of 125, 150, 250 or 450 mg/kg for 6 weeks. Sulphapyridine caused a dose-related and reversible reduction in fertility at doses between 125 and 450 mg/kg. At the high dose, fertility was reduced to 25.9% of control at 5 weeks after treatment, and complete recovery occurred by 3 weeks after drug withdrawal. This activity was abolished when the pyridine ring was substituted by other heterocyclic rings, except sulphachloropyridazine which had only weak activity. Replacement of the pyridine ring by a hydrogen atom or short aliphatic chains preserved or even enhanced the potency. Thus, sulphanilamide, N1-methylsulphanilamide or N1-diethylsulphanilamide produced a marked but reversible reduction in fertility. Removal or substitution of the N4-amino group on the benzene ring of sulphapyridine with a methyl group destroyed the activity. However, the bromo or nitro analogue (at the para- but not the meta-position of the benzene ring) still possessed some activity. N4-Acetyl derivatives of sulphapyridine, sulphanilamide, and N1-diethylsulphanilamide were as potent as their parent compounds. These results suggest that the presence of pyridine or other heterocyclic rings is not necessary for the antifertility activity of sulphonamide compounds. However, the N4-amino group is indispensable. In addition, acetylation of this amino group does not change the potency. The prototype of the antifertility sulphonamides therefore seems to be sulphanilamide.

Mode of action of the antifertility sulphonamides: lack of effects on folate metabolism.

The effects of some antifertility sulphonamides on folate metabolism were investigated in the male rat. Subcutaneous injections of sulphanilamide at a dose of 150 mg/kg/day for 6 weeks produced a marked reduction in fertility of the treated animals. This effect was rapidly recovered by one week after drug withdrawal. Similar treatments with trimethoprim (30 mg/kg/day) or pyrimethamine (8 mg/kg/day) had virtually no effect on fertility. The synergistic effect of trimethoprim or pyrimethamine on the antifertility activity of sulphanilamide was not observed when the drugs were administered in combinations. Treatment with sulphapyridine (450 mg/kg/day for 6 weeks) failed to alter the levels of folate in the blood and the reproductive organs except the testes in which accumulation of folic acid occurred. The results suggest that the antifertility activity of sulphanilamide, sulphapyridine and perhaps some other sulphonamides is not associated with the inhibition of folate metabolism.

Regioselective O-methylation of tetrahydropapaveroline and tetrahydroxyberbine in vivo in rat brain.

Enzymatic O-methylation is a primary pathway for the metabolism of catecholamines in mammals and of isoquinoline alkaloids in plants. This report describes the differential O-methylation patterns of the racemates and enantiomers of two catecholamine-derived alkaloids, tetrahydropapaveroline (THP) and 2,3,10,11-tetrahydroxyberbine (THB), in the brain of the rat. One hour after intracerebroventricular administration of a specific isomeric form of each alkaloid, the O-methylated metabolites were isolated from the rat brain and subsequently quantified using high performance liquid chromatography. The isomeric form of THP or THB which was administered markedly influenced the pattern of O-methylation. The racemate and R-(+)-enantiomer of THP were mono-O-methylated predominantly at the 7 and 3' positions, while the S-(-)-enantiomer of THP was mono-O-methylated to an essentially equal degree at the 6, 7 and 3' positions. Minimal mono-O-methylation at the 4' position was detectable only with the racemate and (-)-enantiomer of THP. The racemate and enantiomers of THB were mono-O-methylated predominantly at the 2 and 11 positions and to a lesser extent at the 3 and 10 positions. Although minimal with the R-(+)-enantiomer, the 3 and the 10-O-methylation pathways were enhanced significantly with the S-(-)-enantiomer of THB. These results demonstrate that both enantiomers of THP and THB are O-methylated in vivo in rat brain and that the chiral centers of these alkaloids influence the position of O-methylation, thereby dictating the relative amounts of specific products formed.

Interaction of catecholamine-derived alkaloids with central neurotransmitter receptors.

Catecholamine-derived alkaloids of the simple tetrahydroisoquinoline, 1-benzyl-tetrahydroisoquinoline and tetrahydroprotoberberine classes have been tested for their ability to inhibit the binding of seven different radioligands to neurotransmitter receptors of brain synaptic membranes. Alkaloids of all three classes were active in inhibiting 3H-clonidine binding to alpha 2-adrenergic receptors. Stereoselectivity of tetrahydropapaveroline in binding to alpha 2-adrenergic receptors was evidenced by the marked activity of the S-(--) isomer (IC50 = 0.65 microM) in comparison to the R-(+) enantiomer (IC50 = 50 microM). The simple tetrahydroisoquinolines (3,4-dihydroxytetrahydroisoquinoline and salsolinol), the four isomeric mono-O-methyl derivatives of 2,3,10,11-tetrahydroxyberbine and tetrahydropapaveroline were the most potent inhibitors of 3H-apomorphine binding to dopaminergic receptor agonist sites. The tetrahydroprotoberberines, as a class, were the most potent inhibitors of 3H-spiroperidol binding to dopaminergic receptor antagonist sites and of 3H-WB-4101 binding to alpha 1-adrenergic receptors. The 1-benzyl-tetrahydroisoquinolines exhibited varying degrees of interaction with beta 1-adrenergic receptors. Tetrahydropapaveroline (IC50 = 0.3 microM) was the most active of the 24 alkaloids tested in inhibiting binding of 3H-dihydroalprenolol to beta 1-adrenergic receptors. None of the alkaloids significantly affected 3H-QNB binding to muscarinic-cholinergic receptors, and selected alkaloids from each class interacted only moderately with serotonergic receptors.

Isoquinolines. 5. Synthesis and antiarrhythmic activity of benzylisoquinoline derivatives.

The synthesis of a series of benzylisoquinolines 2-9 containing aminoacetamide side chains is described. The method involved reduction of the appropriately substituted nitrobenzylisoquinolines followed by acylation to the chloroacylamide derivatives. Amination with the appropriate amine yielded the desires secondary and tertiary amines. The primary amines were prepared via the phthalimides. Two acetanilides 14 and 15 are also described and compared with the benzylisoquinoline derivatives. All compounds were evaluated for their ability to protect against chloroform-induced ventricular fibrillation in mice. The active compounds 6 and 7 were tested for their effect against ventricular arrhythmias in dogs with myocardial infarction. All compounds with the exception of 5 and 12 exhibited some antiarrhythmic effect. The most potent compound, 1-[2-(2-ethylaminoacetyl)amino-3,4-dimethoxybenzyl]isoquinoline (7), showed greater antiarrhythmic potency, was considerably less toxic than lidocaine, and is a candidate for further evaluation.