Subchronic toxicity evaluation of isoeugenyl methyl ether in F344/DuCrj rats by 13-week oral administration

One-Step Green Synthesis of Isoeugenol Methyl Ether from Eugenol by Dimethyl Carbonate and Phase-Transfer Catalysts

In this paper, the green synthesis of isoeugenol methyl ether (IEME) from eugenol by O-methylation and isomerization is completed using a one-step green process. In the methylation reaction, dimethyl carbonate (DMC) was used as a green chemistry reagent instead of the traditional harmful methylation reagents, in accordance with the current concept of green chemistry. The phase transfer catalyst (PTC) polyethylene glycol 800 (PEG-800) was introduced into the isomerization reaction to break the barrier of difficult contact between solid and liquid phases and drastically reduce the reaction conditions by shortening the reaction time and reducing the alkalinity of the reaction system. The catalytic systems for the one-step green synthesis of IEME were screened, and it was shown that the catalytic system "K2CO3 + PEG-800" was the most effective. The effects of reaction temperature, n(DMC):n(eugenol) ratio, n(PEG-800):n(eugenol) ratio, and n(K2CO3):n(eugenol) ratio on eugenol conversion, IEME yield, and IEME selectivity were investigated. The results showed that the best reaction was achieved at a reaction temperature of 140 °C, a reaction time of 3 h, a DMC drip rate of 0.09 mL/min, and n(eugenol):n(DMC):n(K2CO3):n(PEG-800) = 1:3:0.09:0.08. As a result of the conversion of 93.1% of eugenol to IEME, a yield of 86.1% IEME as well as 91.6% IEME selectivity were obtained.

A 13-week subchronic toxicity study of 2-(l-menthoxy)ethanol in F344 rats

2-(l-Menthoxy)ethanol has been frequently employed as a flavoring agent; however, data regarding 2-(l-menthoxy)ethanol toxicity remain limited. We performed a 13-week subchronic toxicity study of 2-(l-menthoxy)ethanol in male and female F344 rats, with doses of 0, 15, 60, or 250 mg/kg body weight (BW)/day orally administered by gavage using corn oil as the vehicle. No significant toxicological changes in general condition, body weight, or food intake were observed in any groups. The hematological assessment showed decreased hemoglobin, hematocrit, mean corpuscular volume, and mean corpuscular hemoglobin and increased platelet count in the male 250 mg/kg group. Serum biochemistry revealed elevated total cholesterol in the 250 mg/kg group of male and female rats, reduced triglyceride in the female 250 mg/kg group, and increased total protein in the male 250 mg/kg group, indicating effects on lipid metabolism and protein synthesis. For organ weights, absolute and relative weights of the liver and adrenal glands were increased in the 250 mg/kg group of both sexes and the male 250 mg/kg group, respectively. Histopathological analysis showed chronic nephropathy in the male 15 mg/kg or higher groups, with increased absolute and relative kidney weights, as well as elevated serum creatinine, in the male 60 and 250 mg/kg groups. However, eosinophilic granules containing α_2u-globulin were identified in proximal tubules, suggesting α_2u-globulin nephropathy specific to male rats and without toxicological significance. These results indicated that the no-observed-adverse-effect level of 2-(l-menthoxy)ethanol was 60 mg/kg BW/day for both sexes.

A 90-day subchronic toxicity study of 5-methyl-2-phenyl-2-hexenal in F344 rats

5-Methyl-2-phenyl-2-hexenal (MPH) has been used as a flavoring agent. In the present study, we performed a subchronic toxicity study in male and female F344 rats with oral administration of MPH by gavage at 0, 8, 24 and 70 mg/kg body weight (BW)/day for 90 days. No mortality or clinical signs were observed during the experimental period. Body weight and food consumption for all treated groups of both sexes were essentially the same as for the respective control groups. Hematologic examination demonstrated significant decreases in monocyte counts for females given 24 and 70 mg/kg BW/day. However, these changes were not substantial and no related histopathological changes were observed, suggesting that these changes were not toxicologically significant. Among organ weights, the absolute and/or relative weights of testes and liver were significantly increased in the 70 mg/kg BW/day groups of males and females, respectively, but no related histopathological changes were observed, suggesting that these changes did not reflect adverse effects. In addition, no treatment-related histopathological changes were observed for any of the tissues examined. Based on the overall data, the no-observed-adverse-effect level (NOAEL) for MPH was determined to be 70 mg/kg BW/day, the highest dose tested, in both male and female rats.