Shuhei Ohnishi

AROMATASE INHIBITORS IN CIGARETTE SMOKE, TOBACCO LEAVES AND OTHER PLANTS

A chance observation that cigarette smoke interferes with the aromatase assay led us to investigate tobacco leaf and smoke extracts for the presence of aromatase inhibitors. The highest inhibitory activity was found in the basic fraction of cigarette smoke. Further purification of this fraction led to the identification of N-n-octanoylnornicotine. Synthesis and testing of a series of acylated nornicotines and anabasines for their ability to inhibit aromatase showed an interesting correlation of activity with the length of the acyl carbon chain, with maximum activity at C-11. The acylated derivatives showed activity which was significantly greater than that of nicotine and anabasine. In vivo studies in rats indicated that administration of this inhibitor delayed the onset of NMU-induced breast carcinoma and altered the estrus cycle. These in vivo studies suggest that tobacco alkaloid derivatives exert their effects by suppression of the aromatase enzyme system. Toxicity studies indicated relatively low toxicity with LD50 for N-n-octanoylnornicotine = 367 mg/kg body weight. When extracts from thirty five varieties of vegetables, plant leaves, and fruits were analyzed, seventeen showed quantitatively significant aromatase inhibition which was comparable to that of green tobacco leaf, suggesting that naturally occurring substances may affect endocrine function through aromatase inhibition.

Competitive inhibition of human placental aromatase by N-n-octanoylnornicotine and other nornicotine derivatives.

In a study of the effect of N-n-octanoylnornicotine and other acyl derivatives of nornicotine on the aromatization of androstenedione by human placental microsomal aromatase, we found that N-n-octanoylnornicotine, a component of cigarette smoke, exhibited competitive inhibition with an apparent Ki of 0.65 microM. This is comparable to that of aminoglutethimide, the clinically-used non-steroidal aromatase inhibitor. N-n-Decanoylnornicotine and N-(4-hydroxyundecanoyl)nornicotine exhibited apparent Ki values of 0.86 microM and 0.24 microM, respectively. This study suggests that cigarette smoke components may have a direct effect on estrogen biosynthesis and that these compounds may prove to be useful parent structures for development of active site probes for further elucidation of estrogen biosynthesis and might eventually lead to the development of alternative non-steroidal anti-cancer therapy.

Synthesis of 19-hydroxy-[7-2H2]androstenedione for human metabolism studies

19-Hydroxyandrostenedione (19-OHA), highly labeled with deuterium at position 7, was synthesized from unlabeled androstenediol diacetate. The deuterium labels were introduced into the 7-keto compound with dichloroaluminum deuteride to obtain [7-2H2]androstenediol. The labeled androstenediol diacetate was converted to the labeled 19-OHA by a five-step sequence without appreciable loss of deuterium. The labeled 19-OHA is useful as an internal standard for gas chromatography-mass spectroscopy analysis of the endogenous levels and as a tracer for in vivo metabolic studies.

Serum level of 19-hydroxyandrostenedione during pregnancy and at delivery determined by gas chromatography/mass spectrometry

19-Hydroxyandrostenedione (19-OHA) is secreted from the adrenal glands in men and women and also from the placenta during pregnancy. It has been found to cause hypertension in animal models. We have synthesized [7,7-2H2]-19-OHA with high deuterium content and, together with [7,7-2H2]A and [9,11-2H2]estrone (E1), have developed a quantitative assay of serum level 19-OHA, A, and E1 using the gas chromatography/mass spectrometry-mass fragmentography method to monitor individual subjects throughout pregnancy. The labeled 19-OHA, used as internal standard, showed only 6.73% of unlabeled compound. Recovery of standard 19-OHA, A, and E1 (5,000 pg each) added to male plasma was 97.4 +/- 2.3%, 96.3 +/- 2.1%, and 100.1 +/- 4.1% (mean +/- SD), respectively; the intraassay coefficient of variation was 2.1%, 3.5%, and 3.8%, respectively. Ten pregnant subjects without complications and 10 pregnant subjects near term with hypertension were selected (with informed consent). The 19-OHA and E1 serum concentrations of maternal venous blood from uncomplicated pregnancies increased significantly as gestation progressed (19-OHA: first trimester, 225 +/- 72; second trimester, 656 +/- 325; third trimester, 1,518 +/- 544 pg/ml), reaching the highest level at delivery (19-OHA: 1,735 +/- 684 pg/ml). Whereas a positive correlation was found between the level of 19-OHA and E1, no apparent change of the A level was observed during pregnancy. Levels of the three steroid hormones in pregnancy complicated by hypertension in the second and third trimester were not found to be significantly different from those of normal pregnancy (19-OHA of hypertensive subjects: second trimester, 762 +/- 349; third trimester, 1,473 +/- 491 pg/ml).(ABSTRACT TRUNCATED AT 250 WORDS)

Functional characterization of active transport of progesterone to adrenal cells.

The characterization of the transport mechanism of progesterone, which is one of the neutral steroids in the adrenal cells, has been studied by the examination of progesterone uptake into the monolayers of SW‐13 cells (a human adrenal adenocarcinoma cell line). The uptake of [3H]progesterone at a tracer concentration (1 nM) exhibited temperature, pH and sodium dependency. According to kinetic analysis of the concentration dependence, the uptake of progesterone involves saturable and non‐saturable processes. The uptake for the saturable process, which gave Kt values (half‐saturation concentration) of 4.7 ± 8.7 μM, was inhibited by metabolic inhibitors and amino‐acid modifiers but not by endocytosis inhibitors or substrates for known transporters. The uptake of progesterone was also inhibited by several neutral steroids but not by anionic steroids. The inhibition by both β‐estradiol and estriol was competitive. The uptake of progesterone by the adrenal cells might be at least partially accounted for by a specific carrier‐mediated transport mechanism generated by sodium ions and an electrochemical mechanism.

Dimerization of 2-alkyl-6-methyl-4H-1,3-thiazin-4-ones

Two unusual modes of dimerization of 2-alkyl-6-methyl-4H-1,3-thiazin-4-ones were observed; one gave the linearly combined dimers (3) and the other led to the novel spiro-compound (4); the structure of one of the spiro-compounds (4a) was confirmed by X-ray crystallography.

An improved method for the synthesis of 2-acetoxysteroid-4-en-3-ones

An improved method is described for the one-step preparation of 2-acetoxysteroid-4-en-3-ones using commercially available lead tetra-acetate in dry benzene.