Characterization of related impurities in megestrol acetate

doi:10.1016/j.jpba.2006.02.048

Journal of Pharmaceutical and Biomedical Analysis

Volume 41, Issue 4, 16 June 2006, Pages 1418-1422

https://doi.org/10.1016/j.jpba.2006.02.048 Get rights and content

Abstract

Three new compounds, 17α-acetoxy-2,6-dimethylpregna-1,4,6-triene-3,20-dione (1), 17α-acetoxy-2α,6-dimethylpregna-4,6-diene-3,20-dione (2), 17α-acetoxy-6α-methoxylmethylpregna-4-ene-3,20-dione (3), together with five known ones, 17α-acetoxy-6β-hydroxyl-6α-methylpregna-4-ene-3,20-dione (4), 17α-acetoxy-6α-hydroxyl-6β-methylpregna-4-ene-3,20-dione (5), 17α-acetoxy-pregna-4-ene-3,6,20-trione (6), 17α-acetoxy-pregna-4-ene-3,20-dione (7) and 17α-acetoxy-6-methylene-pregna-4-ene-3,20-dione (8), were isolated and identified from the residual mother liquor of megestrol acetate. Their structures were established by spectroscopic methods. These compounds seem to be minor impurities in production of the drug megestrol acetate.

Introduction

Megestrol acetate (MA), 17α-acetoxy-6-methylpregna-4,6-diene-3,20-dione, is a semi-synthetic progestogenic hormone. It is prescribed primarily for the treatment of breast cancer and sometimes also used to treat endometrial cancer and prostate cancer [1]. Moreover, other application is described as an appetite stimulant for people experiencing loss of appetite and weight loss because of advanced cancer [2].

Five possible impurities in megestrol acetate are listed in the European Pharmacopoeia [3] (Fig. 1): medroxyprogesterone acetate (A), megestrol (B), d-homo megestrol acetate (C), 6-methylene hydroxyprogesterone acetate (D) and 6-methyl-3,20-dioxopregna-1,4,6-trien-17-yl acetate (E). As it is known, the impurity profile of drugs depends on the synthetic route. In our studies on impurities of MA from Shenzhou Pharm. Inc., three new compounds, 17α-acetoxy-2,6-dimethylpregna-1,4,6-triene-3,20-dione (1), 17α-acetoxy-2α,6-dimethylpregna-4,6-diene-3,20-dione (2), 17α-acetoxy-6α-methoxylmethylpregna-4-ene-3,20-dione (3), together with five known ones 4–8 were isolated and identified from the residual mother liquor of MA. Their structures were elucidated by spectroscopic methods. Here we report the isolation, structure elucidation and spectral data of impurities 1–8.

Section snippets

Chemicals and reagents

Megestrol acetate samples and its mother liquor were supplied by Shenzhou Pharm. Inc., Xianju, Zhejiang Province, China. HPLC grade acetonitrile (Merck, Germany) was used for the HPLC tests. Analytical-grade petroleum ether, ethyl acetate, cyclohexane, acetone, chloroform and methanol purchased from Shanghai Reagent Co. were used as solvents for column chromatography. Water was obtained from a Milli-Q purification system.

High-performance liquid chromatography

An Agilent 1100 series HPLC system equipped with G1311A quaternary

Synthetic route of megestrol acetate

The reaction scheme used for the synthesis of megestrol acetate is shown in Fig. 2.

Detection and isolation of impurities 1–8

The details of the isolation of impurities 1–8 was described in Section 2.3. The relative retention times and HPLC chromatogram are shown in Fig. 3. Structures of these impurities are given in Fig. 4, Fig. 2.

Structure elucidation of impurities 1–3

Impurity 1 was obtained as colorless needles from methanol. Its molecular formula C₂₅H₃₂O₄ was determined by EI-MS and ¹³C, DEPT NMR. In the IR spectrum, the absorption bands at 3411 cm⁻¹ (OH), 1731 cm⁻¹ (ester carbonyl) and 1660 cm⁻¹ (C double bond O) were apparent. The UV data of impurity 1 (Table 1)

Conclusions

Three new compounds and five known ones were isolated and identified from the residual mother liquor of megestrol acetate. Their structures were elucidated mainly by means of 1D and 2D NMR spectra supported by MS, UV and IR spectral data.

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