Method for the enhanced recovery of catmint oil
View Patent ↗A high yielding method is described for recovery of catmint oil from catmint plants of the genus Nepeta by improved separation of a catmint oil containing phase from the condensed steam distillate of catmint plants. Catmint oil may be obtained in quantitative yields for use in insect repellent compositions.
1. A method for recovering catmint oil from plants of the genus Nepeta , comprising
(a) contacting Nepeta plant material with steam to form a volatilized mixture comprising catmint oil and water;
(b) condensing the volatilized mixture to form a first liquid mixture comprising catmint oil and water;
(c) contacting the first liquid mixture with at least one first non-water miscible organic extracting solvent to form a second liquid mixture that contains a first solvent phase and a first aqueous phase;
(d) in the second liquid mixture, separating the first solvent phase from the first aqueous phase, and recovering the first solvent phase;
(e) removing the first extracting solvent from the first solvent phase to isolate catmint oil and provide a first isolated portion of catmint oil;
(f) contacting the first aqueous phase with at least one second non-water miscible organic extracting solvent to form a third liquid mixture that contains a second solvent phase and a second aqueous phase;
(g) in the third liquid mixture, separating the second solvent phase from the second aqueous phase, and recovering the second solvent phase;
(h) removing the second extracting solvent from the second solvent phase to isolate catmint oil and provide a second isolated portion of catmint oil;
wherein the first and second extracting solvents are the same or different; and
wherein the first and second portions of isolated catmint oil are, optionally, combined.
2. A method for recovering catmint oil from plants of the genus Nepeta , comprising
(a) contacting Nepeta plant material with steam to form a volatilized mixture comprising catmint oil and water;
(b) condensing the volatilized mixture to form a first liquid mixture comprising catmint oil and water;
(c) in the first liquid mixture, separating catmint oil from water, and recovering the catmint oil;
(d) contacting the catmint oil recovered in (c) with at least one first non-water miscible extracting solvent to form a second liquid mixture that contains a first solvent phase and a first aqueous phase;
(e) in the second liquid mixture, separating the first solvent phase from the first aqueous phase, and recovering the first solvent phase;
(f) removing the first extracting solvent from the first solvent phase to isolate catmint oil and provide a first portion of isolated catmint oil;
(g) contacting the first aqueous phase with at least one second non-water miscible organic extracting solvent to form a third liquid mixture that contains a second solvent phase and a second aqueous phase;
(g) in the third liquid mixture, separating the second solvent phase from the second aqueous phase, and recovering the second solvent phase;
(h) removing the second extracting solvent from the second solvent phase to isolate catmint oil and provide a second isolated portion of catmint oil;
wherein the first and second extracting solvents are the same or different; and
wherein the first and second portions of isolated catmint oil are, optionally, combined.
3. A method according to claim 1 or 2 wherein the yield of catmint oil is at least about 50% greater than the yield of catmint oil obtained from the separation of catmint oil from water in the absence of an organic extracting solvent.
4. A method according to claim 1 or 2 wherein the first and/or second water immiscible organic extracting solvent has a density that is different from the density of water by at least about 0.1 g/cc.
5. A method according to claim 4 wherein the first and/or second water immiscible organic extracting solvent is selected from the group consisting of a hexane, petroleum ether, toluene, a xylene, ethyl acetate, dichloromethane (DCM), chloroform and mixtures thereof.
6. A method according to claim 1 or 2 further comprising a step of hydrogenating isolated catmint oil.
7. A method according to claim 6 further comprising a step of formulating the hydrogenated catmint oil in an insect repellent composition.
8. A method according to claim 1 or 2 wherein Nepeta plant material is contacted with steam at an absolute pressure of about 13 kPa to about 70 kPa.
9. A method according to claim 8 wherein Nepeta plant material is contacted with steam at an absolute pressure of about 20 kPa to about 45 kPa.
10. A method according to claim 1 or 2 wherein the first liquid mixture is maintained at a temperature of below about 75° C.
11. A method according to claim 10 wherein the first liquid mixture is maintained at a temperature in the range of about 45° C. to about 55° C.
12. A method according to claim 1 or 2 wherein the first and/or second water immiscible organic extracting solvent has a density that is less than the density of water by at least about 0.1 g/cc.
13. A method according to claim 12 wherein the first and/or second water immiscible organic extracting solvent is selected from the group consisting of a hexane, petroleum ether, toluene, a xylene, ethyl acetate, and mixtures thereof.
14. A method according to claim 1 wherein, in the second liquid mixture and/or in the third liquid mixture, the solvent phase floats on top of the aqueous phase.
15. A method according to claim 2 wherein, in the second liquid mixture and/or in the third liquid mixture, the solvent phase floats on top of the aqueous phase.