Hiroyuki Ide

Studies on the metabolism of d-limonene (p-mentha-1,8-diene). IV. Isolation and characterization of new metabolites and species differences in metabolism.

1. The main route of elimination of d-limonene administered orally was via the urine in animals and man, 75-95% of the administered radioactivity being excreted in the urine during 2-3 days. Faecal excretion accounted for less than 10% of the dose in animals during 2-3 days. 2. In addition to six metabolites, namely p-mentha-1,8-dien-10-ol (M-I), p-menth-1-ene-8,9-diol (M-II), perillic acid (M-III), perillic acid-8,9-diol (M-IV), p-mentha-1,8-dien-10-yl-beta-D-glucopyranosiduronic acid (M-V) and 8-hydroxy-p-meth-1-en-9-yl-beta-D-glucopyranosiduronic acid (M-VI) isolated from rabbit urine previously (Kodama et al., 1974), five new metabolites have been isolated from dog and rat urine, and which were characterized as 2-hydroxy-p-menth-8-en-7-oic acid (M-VII), perillylglycine (M-VIII), perillyl-beta-D-glucopyranosiduronic acid (M-IX), p-mentha-1,8-dien-6-ol (M-X) and probably p-menth-1-ene-6,8,9-triol (M-XI). 3. The major metabolite of d-limonene in the urine was M-IV in rat and rabbit, M-IX in hamster, M-II in dog and M-VI in guinea pig and man.

Studies on the Metabolism of d-Limonene (p-Mentha-1,8-diene): I. The Absorption, Distribution and Excretion of d-Limonene in Rats

Abstract1. The absorption, distribution and excretion of d-limonene were investigated in rats using the 14C-labelled compound.2. The highest concentration of radioactivity in blood was obtained 2 h after oral administration of [14C]d-limonene and most occurred in the serum fraction. Radioactivity in the tissues reached maximum 1 or 2 h after administration. Radioactivity in liver, kidney and blood was higher than in other tissues, but was negligible 48 h after administration. An autoradiographic study confirmed these findings of tissue distribution.3. About 60% of administered radioactivity was recovered from urine, 5% from faeces and 2% from expired CO2 within 48 h. In bile duct cannulated rats, about 25% of the dose was excreted in bile within 24 h.

Studies on the Metabolism of d-Limonene (p-Mentha-1,8-diene): II. The Metabolic Fate of d-Limonene in Rabbits

Abstract1. The metabolic fate of d-limonene (p-mentha-1,8-diene) was investigated in the rabbit.2. Following oral administration of [14C]d-limonene to three male rabbits, about 72% and 7% of the dose was excreted in urine and faeces during 72 h, respectively.3. Metabolites isolated from the urine after administration of d-limonene were p-mentha-1,8-dien-10-ol, p-menth-1-ene-8,9-diol, perillic acid, perillic acid 8,9-diol, p-mentha-1,8-dien-10-yl-β-D-glucopyranosiduronic acid and 8-hydroxy-p-menth-1-en-9-yl-β-D-glucopyranosiduronic acid.

Studies on the metabolism of d-Limonene (p-Mentha-1,8-diene). III. Effects of d-Limonene on the lipids and drug-metabolizing enzymes in rat livers.

1. After a single oral dose of d-limonene (200-1200 mg/kg) no effects were observed on liver triglyceride, microsomal protein, cytochrome b5, and the drug-metabolizing enzymes. Glycogen content was slightly decreased at doses higher than 800 mg/kg, and cytochrome P-450 and delta-aminolaevulinic acid synthetase activity was slightly increased at 1200 mg/kg. 2. After repeated treatment (400 mg/kg/day) for 30 days, the relative liver weight and hepatic phospholipid content were only slightly increased, and liver and serum cholesterol were decreased 49 and 8%, respectively. Of the phospholipid fatty acids, palmitic, linoleic and arachidonic acids were increased, and stearic acid was decreased. Aminopyrine demethylase and aniline hydroxylase were increased 26 and 22%, respectively, and cytochrome P-450 and b5 were likewise increased 31 and 30%.

Effect of d-Limonene and related compounds on bile flow and biliary lipid composition in rats and dogs

Abstract d-Limonene enhanced bile flow in rats and dogs with a dose response correlation. The choleretic activity was much higher in the metabolites of d-limonene such as p-mentha-1,8-dien-10-ol, p-menth-1-ene-8,9-diol and p-mentha-1,8-dien-6-ol than d-limonene, and this suggested that the choleretic activity of d-limonene was attributable at least in part to its metabolites. The choleretic activities of esters of p-menth-1-ene-8,9-diol with acetic acid, propionic acid, stearic acid, palmitic acid, linoleic acid, benzoic acid, salicylic acid, α-naphthylacetic acid and nicotinic acid were also investigated in rats. Among these compounds, acetate, propionate and nicotinate possessed considerable, but lesser activities than the original diol. In dogs, however, the choleretic activity of p-menth-l-ene-8,9-diol acetate and propionate was much higher than that of original diol, suggesting that the choleretic activity of these esters is attributable to the esters themselves. d-Limonene decreased the ratio of biliary bile salts and phospholipids to cholesterol, whereas p-menth-l-ene-8,9-diol increased it.

Metabolism of 1-(3-Trifluoromethylphenyl)- 3-(2-hydroxyethyl) quinazoline-2,4(1H,3H)-dione(H-88): I. Species Differences in Metabolism

1. Following oral administration of [14C] H-88 to rat, mouse, quinea-pig and hamster, 40-65% and 5-15% of radioactivity was excreted in urine and faeces respectively during 3 or 4 days. In rabbit, monkey and man, more than 80% of radioactivity was excreted in urine during 2 or 3 days, and faecal excretion was negligible. 2. Rabbit, rat or guinea-pig excreted non-labelled H-88 in urine as unchanged H-88 (M-I), 1-(3-trifluoromethylphenyl) quinazoline-2,4(1H,3H)-dione-3-acetic acid (M-II), H-88 glucuronide (M-III) and 1-(3-trifluoromethylphenyl)-3-(2-hydroxyethyl)-6-hydroxyguinazoline-2,4(1H,3H)-dione (M-IV). 3. The carboxylic acid (M-II) was the major metabolite of H-88 in rat, mouse, guinea-pig and hamster urine and faeces, while the major metabolite in urine of rabbit, monkey and man was H-88 glucuronide (M-III). The 6-hydroxy compound (M-IV) was a major metabolite only in guinea-pig.

Metabolism of 1-(3-Trifluoromethylphenyl)-3-(2-hydroxyethyl)quinazoline-2,4(1H,3H)-dione (H-88). II. Absorption, Distribution and Excretion in Rat, Mouse, Rabbit, Monkey and Man

1. The maximum concentration radioactivity in blood occurred 2-4 h after oral administration of [14C]H-88 in mouse, rabbit and man. With rat, a maximum concentration was obtained 24 h after administration of the drug at a dose level of 60 mg/kg, but only 4 h at a dose of 6 mg/kg. Unchanged H-88 comprised about 50% of serum radioactivity in rat and mouse during the first few hours, but only a small proportion of the serum radioactivity in rabbit and man. 2. The distribution pattern of the radioactivity in rat given the drug at two dose levels was similar, and this differed slightly from mouse and considerably from rabbit. Autoradiograms in rat and rabbit confirmed the findings from the distribution studies, and the autoradiographic distribution pattern in monkey was similar to that in rabbit. 3. Of the administered radioactivity 25-30% was recovered from bile within 48 h in bile-duct-cannulated rats and rabbits. Excretion of radioactivity in respiratory CO2 was negligible in the rat.

DEVELOPMENT OF TOLERANCE TO 1-(m-TRIFLUOROMETHYLPHENYL)-3-(2-HYDROXYETHYL)-QUINAZOLINE-2, 4(1H, 3H)-DIONE [H-88]

Tolerance was provoked to all the pharmacological activities of H-88 examined, such as anti-inflammatory (Carrageenin-induced rat paw edema), analgetic (Tail pressure method in mice), hypothermic (Rectal temperature in mice), hypomotor activity (Wheal cage method in mice), prolongation of the sleeping time induced by pentobarbital Na (rats and mice), depression of gastric emptying and intestinal transport (rats) and stimulation to hypothalmo-hypophyse-adrenal axis (rats). The effect of H-88 on the pentobarbital Na-induced sleeping time in rats was not dissipated by adrenalectomy, and did not depend on the depression of intestinal absorption. The development of tolerance to H-88 was antagonized by ethionine pretreatment. It is suggested that tolerance to H-88 is mainly due to the hepatic enzyme induction.