WO2016024283A1

WO2016024283A1 - Process for the preparation of triglycerides of epa and dha

Info

Publication number: WO2016024283A1
Application number: PCT/IN2015/000260
Authority: WO
Inventors: Mangesh Ganesh KULKARNI; Pankaj Ashok CHAUDHARI
Original assignee: Praj Industries Limited
Priority date: 2014-08-12
Filing date: 2015-06-24
Publication date: 2016-02-18

Abstract

The invention relates to a process for the preparation of triglycerides of EPA and DHA by the method of glycerolysis using ethyl esters of EPA and DHA using a carbonate as catalyst. It particularly relates to the use of a metal carbonate as a catalyst for high efficacy conversion of the ester of EPA and DHA to triglycerides.

Description

PROCESS FOR THE PREPARATION OF TRIGLYCERIDES OF EPA AND DHA

FIELD OF INVENTION

BACKGROUND

Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are members of omega-3 fatty acids. It is established that the omega-3 fatty acids reduce inflammation, helping to prevent inflammatory diseases like heart disease and arthritis. They are also essential for the development of brain, affecting behaviour and cognitive function, and are especially necessary during foetal development. EPA is used for high blood pressure in high-risk pregnancies, schizophrenia, personality disorder, cystic fibrosis, Alzheimer's disease, depression, and diabetes. DHA is used for treating type 2 diabetes, coronary artery disease, dementia, and attention deficit-hyperactivity disorder. DHA is also used for improving vision, preventing an eye disease called age- related macular degeneration, preventing and treating depression, and reducing aggressive behaviour in people in stressful situations. EPA and DHA present in several oil preparations are used for a variety of. conditions like asthma, cancer, menstrual problems, hot flashes, hay fever, lung diseases, lupus erythematosus, and kidney disease. EPA and DHA are also used in combination for migraine headache prevention in adolescents, skin infections, Behget's syndrome, high cholesterol, high blood pressure, psoriasis, Raynaud's syndrome, rheumatoid arthritis, Crohn's disease, and ulcerative colitis.

Generally, EPA and DHA are used in its ethyl ester form for nutraceutical uses. In general products containing with 60 % EPA/ DHA [38 % EPA to 22 % DHA], 50 % total EPA/ DHA [30 % EPA to 20 % DHA] and 30% EPA/ DHA [18 % EPA to 12 % DHA] are in demand in the market. Common sources of EPA and DHA fatty acids include fish oils, algal oil, egg oil, squid oils, krill oil, etc. In addition, blue fish oils obtained from sardines, anchovy, etc are rich in EPA and DHA glycerides.

Physiologically triglycerides of EPA and DHA are better absorbed when taken orally compared with ethyl esters of EPA and DHA leading to effective metabolic utilization of it. One of the most promising ways to get omega-3 fatty acid enriched triglycerides is to convert omega-3 enriched ethyl esters to their triglycerides. Ethyl esters can be converted to their triglycerides using mainly enzymatic processes, in enzyme catalyzed glycerolysis lipase are used for reaction because some lipases are selective for EPA and DHA so the recovery of omega-3 fatty acids in triglycerides is good. However, enzymatic reactions are slow and the major disadvantage is the cost of enzymes. The other disadvantages are: 1 ) degradation of enzyme during reaction, and 2) reusability of enzyme. Hence, there is need to develop a cost effective and efficient chemical catalyzed process, which gives more than 80 % triglyceride of EPA and DHA for nutraceutical applications.

Traditionally, these triglycerides are synthesized from free ethyl esters and glycerol by the process of glycerolysis using lipases as enzyme catalysts. The drawback of this method is that the enzymes are expensive and reaction times required are in several hours. Hence, there is a need to develop more economic and simple method to convert these ethyl esters in to triglycerides using chemical catalysts. Herein a process for the preparation of triglycerides EPA and DHA using inorganic catalysts is disclosed having several advantages over known methods and is industrially scalable, economic and safe, yielding high quality triglycerides of EPA and DHA. DETAILED DESCRIPTION OF THE INVENTION

In one embodiment of the invention, the process comprises providing a stream consisting EPA and DHA in ethyl ester forms obtained from fish oils or any other source rich in EPA or DHA omega-3 fatty acids; mixing the said ethyl ester to glycerol with a metal carbonate catalyst and a co-solvent to form a mixture; subjecting the said mixture to glycerolysis at desired temperature and for desired time under inert condition forming a first stream; washing said first stream with a salt solution in hot water and drying it under vacuum for recovering triglycerides of EPA and DHA of about 70 % purity. Subjecting said triglycerides either to molecular distillation or to solvent extraction at desired conditions for recovering triglycerides of EPA and DHA of more than 80 % purity.

Present invention facilitates efficient preparation of triglycerides [TGs] of EPA and DHA by a process comprising three steps namely: 1 ] glycerolysis, 2] residue washing and followed by either 3] molecular distillation or solvent extraction. Each step has one or more elements for performing specific or optional functions as required for achieving selective preparation of TGs of EPA and DHA. A person skilled in the art may appreciate different variations and/ or combinations of these elements that may be used to perform the objects of the invention disclosed herein.

STEP 1 : GLYCEROLYSIS FOR PREPARATION OF TGs OF EPA AND DHA

The stream containing ethyl esters of EPA and DHA is taken as the feedstock. To prepare triglycerides of EPA and DHA, said ethyl esters of omega-3 fatty acids are reacted with glycerol in the presence of a metal carbonate catalyst under desired temperature, vacuum and time parameters. This reaction is called glycerolysis. The metal carbonate catalysts used are from the group of potassium carbonate, caesium carbonate, etc. This reaction further contained co-solvents, to assist the efficiency of the conversion, like toluene, dimethylsulphoxide [DMSO] or dimethylformamide [DMF]. At the end of the reaction, the co-solvent is distilled out under vacuum and recycled. The residue contained a glyceride mixture of triglycerides, diglycerides and monoglycerides.

STEP 2: WASHING OF GLYCERIDE MIXTURE

The glyceride mixture obtained in STEP 1 is washed with salt water for about three times to remove any traces of the catalyst and soap metal. About 10 % by weight of sodium chloride in hot water is used as the washing solution. Next, the cleaned glyceride mixture is then dried under vacuum at desired temperature to obtain the dried mass, which containing about 70 % by weight of triglycerides and said triglycerides enriched with EPA and DHA. STEP 3: MOLECULAR DISTILLATION OR SOLVENT EXTRACTION

To further, purify the triglycerides [TGs] of EPA and DHA the dried mass obtained in STEP 2 is subjected to the molecular distillation at desired temperature, vacuum and agitation conditions. This step leads to two fractions; the residue stream contained about 80 % by weight of triglyceride, while the distillate stream contained all the unreacted ethyl esters of EPA and DHA. Next, said residue stream is further purified using either activated carbon or activated bleaching earth to remove colour and odour forming impurities.

Alternately, said dried mass obtained in STEP 2 is subjected to solvent extraction steps to obtained TGs of higher purity. Herein the dried mass is refluxed with ethanol or methanol at desired conditions. This refluxing is repeated at least three times to achieve the desired purity of TGs. After three reflux steps, a residue with about 95 % by weight of triglyceride is recovered. Next, said residue stream is further purified using either activated carbon or activated bleaching earth to remove colour and odour forming impurities-. ADVANTAGES OF THE DISCLOSED PROCESS

• The disclosed process is substantially more economical compared with a process that uses enzyme catalysts.

• The duration of process is substantially reduced due to the use .. of chemical catalysts and elevated temperatures.

• Disclosed process provides efficient conversion to TGs of EPA and DHA in final products.

• Downstream steps are. simple and efficient due to simplicity of the process.

· The disclosed process can be used to prepare various grades of

TGs containing 70 %, 80 % or 95 % by weight of EPA and DHA.

• The EPA and DHA recovery in the final product is up to 80 % of total amount. EXAMPLES

Examples provided below give wider utility of the invention without any limitations as to the variations that may be appreciated by a person skilled in the art. A non-limiting summary of various experimental results is given in the examples and tables, which demonstrate the advantageous and novel aspects of the process for the preparation of triglycerides of EPA and DHA by the method of glycerolysis using ethyl esters of EPA and DHA using carbonates as catalysts. .

EXAMPLE 1

About 100 kg of fish-oil ethyl esters containing about 60 % by weight of EPA and DHA were reacted with about 8.6 kg of pure glycerol in the presence of about 3.2 kg of potassium carbonate as a catalyst; and using about 240 kg of toluene [or DMSO or DMF] as a co-solvent forming a homogeneous reaction mixture. This mixture was treated at the temperature of about 120 °C under continuous nitrogen purging at a flow rate of about 1 .4 l/h for about 12 h and an agitation of about 400 rpm. Next, on the completion of reaction, toluene was distilled out using a rotary evaporator at about 90 °C under vacuum pressure of about 10 mbar, forming a mixture of triglyceride, diglyceride, monoglyceride and remaining ethyl esters, if any. This mixture was then washed three times with a salt solution. First with about 1 1 kg of sodium chloride [10 % by weight] in hot water solution to remove catalyst and metal soaps followed by two more similar washes to remove soaps and catalyst left, if any. Then the glyceride mixture was dried under vacuum at about 10 mbar and at temperature of about 90 °C. This process afforded about 86 kg of glycerides containing with about 70 % by weight triglyceride content. Said dried mixture was then subjected to a molecular distillation (short path distillation) at temperature of about 160 °C under vacuum at about 0.1 mTorr, at a flow rate about 25 kg/h and at agitation of about 280 rpm. This step recovered about 90 % of residue stream containing about 80 % by weight of triglycerides containing about 50 % by weight of EPA and DHA. Next, said triglycerides were further purified by using either activated carbon or activated bleaching earth to remove unwanted colour and odour of the preparation.

EXAMPLE 2

Herein said triglycerides containing about 50 % by weight of EPA and DHA obtained as per EXAMPLE 1 were further treated. About 86 kg of said triglycerides were subjected to a first solvent extraction step using about 258 kg of methanol at the temperature of about 50 °C under reflux condition at agitation of about 50 rpm for about 1 h. On the completion of first extraction, the layers were separated by gravity and the bottom layer collected and subjected to two more steps of extraction with about 3 times of methanol on weight basis of the bottom layer. The extracted triglyceride mixture was then dried under vacuum at about 10 mbar and at temperature of about 70 °C. These steps afforded about 95 % pure triglycerides containing about 50 % by weight of EPA and DHA. Next, said triglycerides were further purified by using either activated carbon or activated bleaching earth to remove unwanted colour and odour of the preparation. EXAMPLE 3

Table 1 shows different catalysts used in the preparation of triglycerides of EPA and DHA as per the method disclosed herein. Of the metal carbonate catalysts, used only caesium carbonate and potassium carbonate provided effective catalytic properties in the given conditions.

TABLE 1 :

EXAMPLE 4

Table 2 shows different concentrations of potassium carbonate used in the preparation of triglycehdes of EPA and DHA as per the method disclosed herein. At about 3 % by weight potassium carbonate provided best conditions to carry out glycerolysis of ethyl esters of EPA and DHA to get maximum selectivity for TGs of EPA and DHA. TABLE 2:

EXAMPLE 5

Table 3 shows different grades of EPA and DHA ethyl ester used in the preparation of triglycerides of EPA and DHA as per the method disclosed herein. This data show consistent yields on the different grades of ethyl esters of EPA and DHA.

TABLE 3:

EXAMPLE 6

About 100 kg of fish-oil ethyl esters containing about 50 % by weight of EPA and DHA were reacted with about 8.5 kg of pure glycerol in the_. presence of about 3 kg of potassium carbonate as a catalyst; and using about 240 kg of toluene as a co-solvent forming a reaction mixture. This mixture was treated at the temperature of about 120 °C under continuous nitrogen purging at a flow rate of about 1 :4 l/h for about 24 h and an agitation of about 400 rpm. Next, on the completion of reaction, toluene was distilled out using a rotary evaporator at about 90 °C under vacuum pressure of about 1Q mbar, forming a mixture of triglyceride, diglyceride, monoglyceride and remaining ethyl esters, if any. This mixture was then washed twice with about 10% citric acid , solution to remove catalyst and metal soaps followed by one hot water wash to remove soaps and catalyst left, if any. Then the glyceride mixture was dried under vacuum at about 10 mbar and at temperature of about 90 °C. This process afforded about 88 kg of glycerides containing with about 77 % by weight triglyceride content.

While the invention has been particularly shown and described with reference to embodiments listed in examples, it will be appreciated that several of the above disclosed and other features and functions, or alternatives thereof, may be desirably combined into many different systems or applications. Also that various presently unforeseen and unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims. Although the invention has been described with reference to specific preferred embodiments, it is not intended to be limited thereto, rather those having ordinary skill in the art will recognize that variations and modifications may be made therein which are within the spirit of the invention and within the scope of the claims.

Claims

1. A process for preparation of triglycerides of EPA and DHA comprising:

(a) providing a mix of ethyl esters of EPA and DHA;

(b) adding said mix to glycerol with a carbonate catalyst and a co-solvent forming a reaction mixture;

(c) subjecting said reaction mixture to glycerolysis at desired temperature and for desired time under inert condition forming a first stream;

(d) washing said first stream with water and drying under vacuum recovering triglycerides of EPA and DHA of about 70 % purity;

(e) subjecting said triglycerides of (d) to molecular distillation at desired conditions recovering triglycerides of EPA and DHA of more than 80 % purity; and

(f) subjecting said triglycerides of (d) to solvent extraction at desired conditions recovering triglycerides of EPA and DHA of more than 95 % purity.

2. The process of claim , wherein said mix of ethyl esters of EPA and DHA comprises from about 18 % to about 30 % EPA and from about 12 % to about 25 % DHA by weight.

3. The process of claim , wherein said catalyst is one of potassium carbonate or cesium carbonate.

4. The process of claim 1 , wherein said co-solvent is one of toluene, DMSO or DMF.

5. The process of claim 1 , wherein said glycerolysis is performed at temperature between about 100 °C to about 130 °C under nitrogen for about 12 hours to about 24 hours.

6. The process of claim 1 , wherein said molecular distillation is performed at temperature between about 130 °C to about 170 °C in vacuum between about 0.1 mTorr to about 0.5 mTorr and agitation rate of about 280 RPM.

7. The process of claim 1 , wherein said solvent extraction is performed using methanol or ethanol,

8. The process of claim 1 , wherein said mix of ethyl esters of EPA and DHA is obtained from oil consisting of omega-3 fatty acids.

9. A composition of triglycerides of EPA and DHA according to the process of claim 1.

10. A product comprising a composition of triglycerides of EPA and DHA according to the process of claim 1.