Erythromycin Crystallization via Dichloromethane Gradient Cooling
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Solution Overview
Problem
Existing methods for recrystallizing erythromycin result in products with low erythromycin A content and high impurity levels, such as water and solvent residues, which affect their microbiological titre and quality.
Innovation Solution
A method involving the dissolution of erythromycin or its salts in dichloromethane under alkaline conditions, followed by gradual cooling to form crystals, and subsequent washing and drying, using a solvent mixture that includes dichloromethane with a volume content of 60-100%, to achieve high erythromycin A content and low impurity levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If erythromycin is recrystallized using conventional methods (acetone-water or dichloromethane), then the recrystallization process can be completed, but the erythromycin A content is low and impurity levels are high
Solution Approach 1:
The patent changes the solvent system from conventional acetone-water or pure dichloromethane to a specific dichloromethane-containing solvent mixture with controlled composition ratios. This parameter change in solvent composition enables higher erythromycin A content (≥94.5%) and lower impurity levels in the recrystallized product
Solution Approach 2:
The patent utilizes controlled phase transition through gradient cooling of the dichloromethane-containing solvent system from high temperature to low temperature. This controlled phase transition process enables selective crystallization of high-purity erythromycin A while leaving impurities in the mother liquor
2Ease of manufacture
If conventional recrystallization methods are used, then the process is simple, but water content and solvent residues are high in the crystals
Solution Approach 1:
The patent modifies the solvent system parameters by using a dichloromethane-containing mixture with specific composition ratios instead of conventional solvents. This change reduces water content to ≤2.5% and dichloromethane residues to ≤600 ppm in the final crystals while maintaining process feasibility
Solution Approach 2:
The patent employs a solvent system where dichloromethane serves as a volatile carrier that can be easily removed. The specific solvent mixture allows for efficient evaporation of volatile components, leaving minimal residues in the final product
3Ease of operation
If conventional recrystallization is performed, then the procedure is straightforward, but the microbiological titre is low
Solution Approach 1:
The patent changes the solvent composition parameters to a dichloromethane-containing mixture with optimized ratios. This parameter change directly improves the microbiological titre to ≥940 μ/mg by enabling more effective separation of active erythromycin A from inactive impurities and degradation products
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method achieves erythromycin A content greater than 94.5%, dichloromethane content less than 600 ppm, and water content less than 2.5%, along with a microbiological titre exceeding 940 µ/mg, significantly improving the quality of the recrystallized erythromycin.
Implementation Method 1
dissolving erythromycin or an erythromycin salt in dichloromethane or a solvent mixture comprising dichloromethane under alkaline condition to form an erythromycin solution
Implementation Method 2
cooling the erythromycin solution gradiently from 37 °C to -5 °C to form a suspension of erythromycin crystals
Implementation Method 3
The temperature is gradiently cooled from 37 °C to -5 °C at a cooling rate of 1 to 10 °C per hour for a recrystallization time period from 2 to 36 hours
Implementation Method 4
The separating step can be done by commonly used equipment in the field, such as centrifuges, filtration equipment and so on
Implementation Method 5
The separating step can be done by commonly used equipment in the field, such as centrifuges, filtration equipment and so on
Implementation Method 6
The erythromycin crystals separated by centrifugation can be washed by an organic solvent or pure water and the residue of the solvent in the erythromycin crystals can be removed by a drying method
Implementation Method 7
the residue of the solvent in the erythromycin crystals can be removed by a drying method
Data Source
AI summary
The present invention provides an erythromycin crystallizing method, which comprises using dichloromethane containing solvent as a preparation solvent, and the dichloromethane solution of erythromycin received was gradiently cooled from high temperature down to low temperature, and thus making erythromycin crystallize. According to the method of the present invention, the content of erythromycin A is high, the content of erythromycin A in the erythromycin crystalline is more than 94.5% (HPLC detection method), the content of dichloromethane in the erythromycin crystalline is less than 600 ppm, the content of water in the erythromycin crystalline is less than 2.5%, the microbiological titre of the erythromycin crystalline is more than 940µ/mg.