Method for preparing high-purity cannabidiol

Abstract

A method for preparing high-purity cannabidiol is characterized in that: the leaves of cannabis and top portions of the plant which account for about one-fifth of the whole plant are used as extraction sites; a technology of combined macroporous adsorption resin chromatography and polyamide chromatography is used for purification; and a mixed solvent system is used for crystallization purification so as to ensure that the yield is improved to the maximum extent under the premise of obtaining a high-purity product. The product obtained from this method contains high-purity CBD; the method has a high yield and is a simple process, and thus easy to industrialize.

Claims

1. A method for preparing high-purity cannabidiol, comprising the following steps: (1) a solvent extraction including extracted sites of cannabis sun-dried and pulverized into a coarse powder, and extracted three times with 95% ethanol as a solvent, wherein each time the amount of the solvent is 10-20 times the amount of the powder; the extracts are combined and filtered, and dealcoholized under reduced pressure at 50 C. to 70 C. until a solution which remains is slightly cloudy, and then the solution is cooled to room temperature; (2) a combined use of macroporous adsorption resin chromatography and polyamide chromatography including: a first step of column chromatography using a macroporous adsorption resin as a chromatographic medium, and a column loading of 3-10 g hemp stems and leaves/mL resin; firstly, the column is eluted with 5-10 column volumes of 45-55% ethanol to wash away most highly-polar impurities and then eluted with 3-5 column volumes of 80-95% ethanol to elute cannabidiol; an eluent rich in the cannabidiol is collected, and dealcoholized under reduced pressure at 50 C. to 70 C. until a solution is slightly cloudy, and then cooled to room temperature; a second step of column chromatography using a polyamide adsorption resin as a chromatographic medium, and a column loading is 30-50 mg CBD/mL resin; firstly, the column is eluted with 3-5 column volumes of 30-50% ethanol to wash away impurities and then eluted with 3-5 column volumes of 50-80% ethanol to elute cannabidiol; an eluent rich in the cannabidiol is collected, and concentrated under reduced pressure at 50 C. to 70 C. to obtain a thick paste; and (3) a crystallization purification of mixed solvent including the thick paste dissolved in a mixed solvent system to prepare a saturated solution of CBD, and the solution is allowed to stand to obtain colorless or pale yellow crystals, which are filtered and dried to obtain high-purity CBD crystals.

2. The method for preparing high-purity cannabidiol of claim 1, wherein the extracted sites are the leaves of cannabis and top portions of the plant which account for about one-fifth of the whole plant.

3. The method for preparing high-purity cannabidiol of claim 1, wherein macroporous adsorption resin chromatography and polyimide chromatography are used in combination, wherein the macroporous adsorption resin as employed comprises, but is not limited to, HPD-417, HPD-450, AB-8, ADS-17, D-101, DM-130, LSA-7, and LSA-10.

4. The method for preparing high-purity cannabidiol of claim 1, wherein a mixed solvent system is used as a crystallization solvent for purification, and the mixed solvent system is composed of A (cyclohexane or n-hexane) and B (ethanol or methanol) in a ratio of (1-5):1 (V/V).

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) FIG. 1 is a liquid chromatogram of CBD prepared according to the method provided by a preferred embodiment of the present invention; and

(2) FIG. 2 is a liquid chromatogram of a CBD standard.

DETAILED DESCRIPTION

(3) The following embodiments are intended to illustrate the present invention, rather than limit the essential scope of the present invention.

Preferred Embodiment 1. Preparation of High-Purity CBD

(4) (1) Solvent extraction:

(5) The top portions of cannabis which account for about one-fifth of the whole plant were taken, sun-dried and pulverized into a coarse powder, and extracted three times with 95% ethanol as a solvent, where each time the amount of the solvent was 10 times the amount of the powder. The extracts were combined and filtered, and dealcoholized under reduced pressure at 50 C. until the solution was slightly cloudy, and then cooled to room temperature.

(6) (2) Two-step column chromatography:

(7) The first step of column chromatography: a macroporous adsorption resin of type HPD-417 was used as the chromatographic medium, and the column loading was 5 g hemp stems and leaves/mL resin. Firstly, the column was eluted with 7 column volumes of 45% ethanol to wash away most of the highly-polar impurities, and then eluted with 5 column volumes of 85% ethanol to elute cannabidiol. An eluent rich in the cannabidiol was collected, and dealcoholized under reduced pressure at 50 C. until the solution was slightly cloudy, and then cooled to room temperature.

(8) The second step of column chromatography: a polyamide adsorption resin was used as the chromatographic medium, and the column loading was 30 mg CBD/mL resin. Firstly, the column was eluted with 3 column volumes of 30% ethanol to wash away impurities, and then eluted with 3 column volumes of 80% ethanol to elute cannabidiol. An eluent rich in the cannabidiol was collected, and concentrated under reduced pressure at 50 C., to obtain a thick paste.

(9) (3) Crystallization of mixed solvent: the thick paste was dissolved in a mixed solvent system (cyclohexane:ethanol=3:1, V/V) to prepare a saturated solution of CBD, and the solution was allowed to stand to obtain colorless or pale yellow crystals, which were filtered and dried to obtain high-purity CBD crystals.

Preferred Embodiment 2. Preparation of High-Purity CBD

(10) (1) Solvent extraction: the top portions of cannabis which account for about one-fifth of the whole plant were taken, sun-dried and pulverized into a coarse powder, and extracted three times with 95% ethanol as a solvent, where each time the amount of the solvent was 15 times the amount of the powder. The extracts were combined and filtered, and dealcoholized under reduced pressure at 60 C. until the solution was slightly cloudy, and then cooled to room temperature.

(11) (2) Two-step column chromatography:

(12) The first step of column chromatography: a macroporous adsorption resin of type HPD-450 was used as the chromatographic medium, and the column loading was 3 g hemp stems and leaves/mL resin. Firstly, the column was eluted with 5 column volumes of 55% ethanol to wash away most of the highly-polar impurities, and then eluted with 3 column volumes of 95% ethanol to elute cannabidiol. An eluent rich in the cannabidiol was collected, and dealcoholized under reduced pressure at 60 C. until the solution was slightly cloudy, and then cooled to room temperature.

(13) The second step of column chromatography: a polyamide adsorption resin was used as the chromatographic medium, and the column loading was 50 mg CBD/mL resin. Firstly, the column was eluted with 3 column volumes of 50% ethanol to wash away impurities and then eluted with 5 column volumes of 75% ethanol to elute cannabidiol. An eluent rich in the cannabidiol was collected, and concentrated under reduced pressure at 60 C., to obtain a thick paste.

(14) (3) Crystallization of mixed solvent: the thick paste was dissolved in a mixed solvent system (n-hexane:methanol=3:1, V/V) to prepare a saturated solution of CBD, and the solution was allowed to stand to obtain colorless or pale yellow crystals, which were filtered and dried to obtain high-purity CBD crystals.

Preferred Embodiment 3. Preparation of High-Purity CBD

(15) (1) Solvent extraction: the top portions of cannabis which account for about one-fifth of the whole plant were taken, sun-dried and pulverized into a coarse powder, and extracted three times with 95% ethanol as a solvent, where each time the amount of the solvent was 20 times the amount of the powder. The extracts were combined and filtered, and dealcoholized under reduced pressure at 70 C. until the solution was slightly cloudy, and then cooled to room temperature.

(16) (2) Two-step column chromatography:

(17) The first step of column chromatography: a macroporous adsorption resin of AB-8 type was used as the chromatographic medium, and the column loading was 8 g hemp stems and leaves/mL resin. Firstly, the column was eluted with 3 column volumes of 55% ethanol to wash away most of the highly-polar impurities and then eluted with 3 column volumes of 95% ethanol to elute cannabidiol. An eluent rich in the cannabidiol was collected, and dealcoholized under reduced pressure at 70 C., until the solution was slightly cloudy, and then cooled to room temperature.

(18) The second step of column chromatography: a polyamide adsorption resin was used as the chromatographic medium, and the column loading was 45 mg CBD/mL resin. Firstly, the column was eluted with 5 column volumes of 45% ethanol to wash away impurities and then eluted with 3 column volumes of 80% ethanol to elute cannabidiol. An eluent rich in the cannabidiol was collected, and concentrated under reduced pressure at 70 C., to obtain a thick paste.

(19) (3) Crystallization of mixed solvent: the thick paste was dissolved in a mixed solvent system (n-hexane:ethanol=2:1, V/V) to prepare a saturated solution of CBD, and the solution was allowed to stand to obtain colorless or pale yellow crystals, which were filtered and dried to obtain high-purity CBD crystals.

Preferred Embodiment 4. HPLC Detection of CBD Sample

(20) The detection was conducted according to high performance liquid chromatography (Chinese Pharmacopoeia, Appendix V D, Part II).

(21) Chromatographic conditions and system applicability: octadecyl silane bonded silica was used as a filler; methanol-acetonitrile-water-acetic acid (25:50:25:0.4 by volume) was used as a mobile phase, the detection wavelength was 220 nm, and the number of theoretical plates was not less than 4,000 as calculated by cannabidiol.

(22) Detection method: the appropriate amount of the sample was taken, accurately weighed, and dissolved with the mobile phase and quantificationally diluted into a solution which contained about 0.2 mg of the sample per 1 mL. Twenty l of the solution was accurately measured and injected into a liquid chromatograph and the chromatogram was recorded; and additionally, a cannabidiol control was taken and detected by the same method. The concentration of cannabidiol was obtained by calculating the peak area according to an external standard method.

(23) Detection result: the content of cannabidiol was 99.25% as calculated on the anhydrous substance.

LISTING OF ACRONYMS AND ABBREVIATIONS

(24) C. degrees Celsius CB cannabinoid CBC cannabichromene CBD cannabidiol CBN cannabinol g gram HPLC High Performance Liquid Chromatography mAU milli-Absorbance mg milligram min minute mL milliliter THC tetrahydrocannabinol V volume l microliter

(25) The aforementioned description sets forth preferred specific embodiments of the present invention, and the claimed scope of the present invention is not limited thereto. Equivalent substitutions or modifications can be made by those of skill in the art according to the technical solution and inventive concept of the present invention, without departing from the technical scope disclosed by the present invention. These substitutions or modifications all fall within the claimed scope of the present invention.