Patent Application: US-626401-A

Abstract:
a method for the isolation of delta - 9 - tetrahydrocannibinol from , cannabis plant material , wherein delta - 9 - thc acid and thc are separately obtained comprising the steps of extracting the cannabis plant material , chelating delta - 9 - thc acid on alumina solid support from cannabis extracts rich in the acid washing of non - acid components of the extract with organic solvents and eluting of the delta - 9 - thc acid with strong polar solvents . the method also includes a process by which to increase the thc content and decrease the weight of cannabis extracts or residue from distillation of cannabis extracts containing a low concentration of thc , comprising treatment of such materials with water - missible organic solvents followed by filtration and evaporation of the solvent to obtain the concentrated residue .

Description:
the present invention provides an improvement to a procedure for providing an efficient and economic method for isolating thc from cannabis plant material . the plant material is extracted with a non - polar organic solvent . useful solvents include lower alkanes , such as , for example , hexane , heptane or iso - octane . the extract containing thc , after solvent removal , is subjected to fractional distillation at reduced pressure and a second distillate is collected . in one embodiment of the present invention , the first distillate is again subjected to fractional distillation at reduced pressure and a second distillate is collected . the second distillate has a thc content of greater than 90 % by wt . in another embodiment of the invention , which is improved by applicants , the crude extract from the plant material is first subjected to column chromatography . one possible method by which the material can be placed on the column is by mixing the extract residue in an organic solvent with a portion of the column packing material and transferring the dried slurry onto the top of a packed column . direct application of the extract residue in the initial elution solvent ( minimum volume ) directly to the top of the packed column is also possible . the column is eluted with an organic solvent in a manner such that the column is eluted with a solvent or a solvent mixture with progressively increasing polarity . the fraction or fractions containing the major portion of thc from the column elution is subjected to fractional distillation at reduced pressure . distillate is collected in the substantially constant boiling temperature range and this distillate was found to contain greater than 90 % by weight thc . thc with purity of greater than 95 %, preferably greater than 98 % can be obtained by further purification of the distillate from fractional distillation by column chromatography or by normal or reversed phase hplc . the column chromatography can be carried out using any known packing material including , for example , silica or alumina for normal phase operation or c 18 or c 8 bonded phase silica for reversed phase operation . elution of the normal phase chromatography column is carried out with solvents having an increasing polarity . non - polar solvents include the lower straight chain and branched chain alkanes , including , for example , pentane , hexane , isooctane and petroleum ether . more polar solvents include various organic ethers , alcohols , esters or ketones , including , for example dialkyl ethers , lower alkyl acetates , lower dialkyl ketones and lower alkanols . illustrative polar solvents include , for example , acetone , ethylacetate , diethylether and isopropyl alcohol . the ratio of non - polar solvent to polar solvent can vary between 100 : 0 to 80 : 20 . elution chromatography under the reversed phase conditions is carried out with solvents having decreasing polarities . these solvents include water or acidic buffer as the polar portion and lower alkanol ( such as methanol , ethanol and isopropanol ) or acetonitirle as the less polar portion , in mixtures ranging from 50 : 50 to 0 : 100 aqueous to organic . the chromatographic process can also be carried out under hplc conditions in much the same way as described above under either normal or reversed phase operation using a preparative scale column . flash distillation is carried out under reduced pressure , i . e . under vacuum at pressures below 1 mm hg , preferably close to 0 . 1 mm hg . improving the delta - 9 - thc content of the cannabis extracts prior to chromatography and / or fractional distillation the concentration of delta - 9 - thc in the initial cannabis extract is a function of the potency (% thc ) of the starting plant material . for example , cannabis plant material with thc content of approximately 3 % will produce a hexane extract of approximately 35 % thc in the first extract and less than 20 % in the second extract which might necessitate keeping the first and second extracts separate for further processing . cannabis biomass of 4 % will produce a first hexane extract of approximately 40 % thc and a second extract of slightly over 20 % thc , while extracts of 5 - 7 % thc plant material will produce a first hexane extract of 45 - 55 % thc with a second extract of approximately 25 % thc . processing of cannabis extracts of less than 40 % thc ( whether it be a first extract of a low potency plant material or the second extract of almost any plant material ) would be made much more economic if one could pre - treat such extract in a simple step that would result in increasing the thc content to approximately 40 % or more . it has been discovered that treatment of “ low thc ” extracts with one of a selection of polar , water missible solvents ( such as , for example , lower alkyl alcohols , dialkyl ketones , such as , for example acetone or methylethyl ) or acetonitrile in combination with water in various ratios would result in precipitation of significant amount of residue containing small percentage of thc , leaving behind ( in solution ) the main bulk of thc . a simple filtration step results in removal of the unwanted residue , and evaporation of the solvent of the filtrate results in a concentrated extract with much lower weight than the starting extract and much higher thc content . the resulting extract could then be processed as usual . furthermore , the residue left from fractional distillation of cannabis extracts is usually of low thc content . this material could be reprocessed in the same manner as discussed above , making the overall process more economical . delta - 9 - thc ( 1 ) exists in the fresh cannabis plant material as its precursor δ 9 - thc - acid a ( 2 ) almost exclusively . during the drying and extraction processes variable amounts of the precursor acid 2 is decarboxylated to 1 with the resulting extracts containing a mixture of 1 and 2 , in a ratio that depends on the drying and extraction conditions . under mild conditions of drying of the plant material ( 40 °- 50 °) and mild temperature of evaporation of the extraction solvent , the main component of extract is the acid precursor 2 . the improvement of this invention is , therefore , directed especially to extracts prepared under conditions which preserve the δ 9 - thc - acid a and minimize decarboxylation to δ 9 - thc . treatment of a solution of an extract with alumina allows the strong binding ( chelation ) of the acid to the exclusion of other components ( neutral cannabinoids and the non - cannabinoid components such as terpenes , hydrocarbons , sterols . etc .). the alumina could then be washed ( eluted ) with non - polar to moderately polar solvents to remove unwanted components followed by elution of δ 9 - thc - acid a using strong solvents such as , for example , methanol with varying amounts of acetic acid . the eluted acid could then be subjected to fractional distillation to give δ 9 - thc in a relatively pure form (& gt ; 80 % chromatographical purity ) with a final chromatographic step to remove minor impurities . alternatively , the eluted acid could be further purified from other similar cannabinoid acids , with the fractional distillation step used at the end to generate δ 9 - thc in a pure form . the alumina chelation , therefore , offers an alternative clean - up step which has the advantage of providing the thc - acid a in relatively pure form in a simple adsorption ( filtration ) step . this could be especially useful if one desires the separation of the pure acid a for biological evaluation without losing the ability to generate δ 9 - thc from the acid by a simple fractional distillation step . it is to be noted that all three types of alumina solid supports could be used for this process ( basic , neutral , and acidic ), although basic alumina is preferred . it will be understood by those skilled in the art that various modifications and substitutions may be made to the invention as described above without departing from the spirit and scope of the invention . accordingly , it is understood that the present invention has been described by way of illustration and not limitation . 200 g of the air - dried and powdered buds ( 7 . 82 % thc ) and 270 g of the air - dried and powdered buds ( 6 . 61 % thc ) were mixed and extracted by maceration at room temperature with hexane for 24 hours ( 2 . 2 l hexane × 4 ). the hexane extracts were combined and evaporated under vacuo to give 76 . 5 g ( 16 . 3 % extractives ). 56 g of the hexane extract ( 40 % thc ) was mixed with 100 g silica gel ( silica gel 60 , e . merck ) and 50 ml hexane . the dried slurry was transferred onto the top of a silica gel column ( 850 g silica gel 60 , dimensions : 10 × 60 cm ). elution was carried out with petroleum ether and ether in manner of increasing polarities . twelve fractions were collected and tlc screened . identical fractions were pooled together . the fraction eluted with pet . ether - ether ( 9 : 1 ) was evaporated to give 37 . 3g of residue which showed thc content of 55 . 87 % using gas chromatography ( gc ) analysis . this fraction contained the majority of thc ( 93 %) in the material applied onto the column . a portion ( 7 . 1 g ) of the collected fraction was subjected to fractional distillation under vacuum ( between 0 . 08 - 0 . 1 mmhg ) to get two major fractions , one collected between 170 - 175 ° c . ( 2 . 34 g @ 90 % thc ) and one between 175 - 180 ° c . ( 1 . 32 g @ 88 . 2 % thc ). the air - dried and powdered buds ( 380 g , 2 . 20 % thc ) were extracted with hexane by maceration at room temperature for 24 hours ( 1 . 8 l hexane × 3 ). the total weight of the hexane extracts was 29 . 1 g ( 7 . 7 % extractives ). the % of thc in the hexane extract was 28 . 76 %. the hexane extract ( 29 . 1 g ) was mixed with 100 g of silica gel ( silica gel 60 , e . merck ) and 50 ml hexane . the dried slurry was transferred on to the top of silica gel column ( 850 g silica gel 60 , dimensions : 10 × 60 cm ). elution was carried out with petroleum ether - ether mixtures in a manner of increasing polarities . nine fractions were collected and tlc screened . identical fractions were pooled together to give 4 fractions . the fraction collected with petroleum either - ether ( 9 : 1 ) was evaporated to yield 13 . 3 g of residue . gc analysis of this fraction showed a concentration of thc of 58 . 98 %, again representing & gt ; 93 % recovery of all thc in the material applied to the column . a portion ( 7 . 3 g ) of the fraction collected above was subjected to fractional distillation at vacuum ( 0 . 08 - 0 . 1 . mmhg ). the major fraction ( 3 . 738 g ) was collected between 172 - 180 ° c . and was found to contain 89 % thc by weight . one kg of the fine powdered marijuana plant material [ average % of thc was about 5 . 21 %] was macerated with 6 l hexanes ( hexanes gr from em sciences ) in a percolator ( 9 ″ in diameter from the top and 20 ″ long , cone shaped ) for 24 hours at room temperature and filtered . the macerate was reextracted with 5 l hexanes for another 24 hours . the hexane extracts were combined and evaporated under reduced pressure at low temperature to give 110 . 7 g residue ( 11 . 07 % extractives ). the % of thc in the hexane extract was 41 . 21 %. the hexane extract ( 110 . 7 g ) was mixed with 150 g silica gel ( silica gel 60 , art .# 9385 - 3 ) and 50 ml hexane . the air dried slurry was transferred to the top of a silica gel column ( 800 g silica gel 60 , particle size 0 . 04 - 0 . 063 mm , from em science , art . # 9385 - 3 ). the column was eluted with hexane : ether mixtures in a manner of increasing polarities . fractions were collected and tlc screened ( analytical silica gel plates , developing system : hexane : ether ( 80 : 20 ), visualizing agent : fast blue ). the fractions collected with hexane ( 3 l .) and hexane - ether ( 95 : 5 , 2 l .) were discarded . the following fractions collected with hexane - ether ( 95 : 5 , 3 l .) and hexane - ether ( 9 : 1 , 5 l .) were combined and evaporated to yield 77 . 2 g of residue . gc analysis of the residue showed thc concentration to be 54 . 74 %. a portion ( 30 . 5 g ) of the residue collected above was subjected to fractional distillation under reduced pressure ( 0 . 1 - 0 . 15 mm / hg ). the temperature was slowly raised to 125 ° c . and the materials collected were kept separate . the temperature was then raised between 140 - 160 ° c . where the major fraction was collected ( 14 g ). gc analysis showed & gt ; 96 % thc . one kg of the fine powdered marijuana plant material [ average % of thc is 4 . 42 ] was macerated with 6 l hexanes and extracted by the same procedure followed in example 3 to yield 105 . 8 g residue ( 10 . 58 % extractives ). the % of thc in the hexane extract was 40 . 35 % by gc analysis . a portion ( 23 . 0 g ) of the hexane extract was subjected to fractional distillation under reduced pressure ( vacuum , 0 . 1 - 0 . 2 mm / hg ). the temperature was raised slowly to 160 ° c . where a small amount of material (& lt ; 1 g ) was collected and left separate . the major fraction ( 10 . 1 g ) was collected between 170 and 180 ° c . gc analysis of this fraction showed 72 . 66 % thc concentration . a second portion ( 25 . 0 g ) of the hexane extract was subjected to fractional distillation under similar conditions as the first portion . the major fraction collected between 170 - 180 ° c . weighed 11 . 6 g and had a thc concentration of 73 . 62 %. a third portion ( 25 . 0 g ) of the hexane extract was subjected to fractional distillation under similar conditions to the previous portions . the major fraction containing thc weighed 10 . 2 g and had a thc concentration of 73 . 72 %. the three major fractions obtained from the above three distillations were combined and analyzed . the analysis showed the concentration of thc to be 70 . 31 %. the mixture ( 28 . 9 g ) was subjected to fractional distillation , again under similar conditions . the temperature was raised slowly to 135 ° c . under vacuum ( 0 . 1 - 0 . 15 mmhg ) and the fractions collected were kept aside . the major thc containing fraction was collected at 140 - 160 ° c . and 0 . 05 - 0 . 06 mm / hg . the fraction weight was 18 . 4 g and the thc content was 92 . 15 %. a portion ( 0 . 8 g ) of the pure thc obtained in example no . 3 (% of thc was about 96 %) was mixed with one gram silica gel ( silica gel 60 ) and one ml hexane . the dried slurry was transferred on to the top of a silica gel column ( 12 g silica gel 60 , dimensions : 1 × 50 cm ). elution was carried out with hexane : ether mixtures in a manner of increasing polarities . six fractions were collected and screened using tlc . fraction nos . 3 - 5 ( hexane : ether 98 : 2 ) were combined and yielded 0 . 63 g of residue (% of thc was 98 %). one gram of the thc prepared in example no . 4 purity was about 92 %) was mixed with one gram of silica gel ( silica gel 60 ) and one ml hexane . the dried slurry was transferred on to the top of a silica gel column ( 13 g silica gel 60 , dimensions : 1 × 50 cm ). elution was carried out under similar conditions as under example 5 . fraction nos . 3 - 5 yielded 0 . 78 g of residue (% of thc was 98 %). 1000 g of the air - dried and powdered cannabis ( buds % of thc by glc analysis was 6 . 49 %) were extracted by maceration at room temperature for 24 hours ( 5 l × 3 , l lot . no . 970424 ). the hexane extracts were combined and evaporated under vacuo to give 97 g residue . 67 g of the hexane extract was dissolved in 200 ml isooctane ( lot . no . 904038 ) and the solution was transferred onto the top of a silica gel column ( 280 g silica gel , 40 mm particle size , dimensions of column : 10 × 60 cm ). the column was eluted with iso - octane : methyl - t - butyl ether mixture 8 : 2 ( 3 l , fraction 1 ) and then washed with methanol ( 1 l , fraction 2 ). glc analysis of fraction 1 ( 53 g ) showed a concentration of thc of 55 . 56 %. fraction 1 ( 53 g ) was subjected to fractional distillation at vacuum 0 . 1 - 0 . 6 mm / hg . the major fraction ( 20 . 0 g ) was collected between 160 - 170 ° c . and was found to contain 94 % thc by weight . 10 g of the major fraction ( purity about 94 %) was purified on hplc ( water delta prep 4000 ) connected to a waters 486 tunable absorbance detector and using column prep pak500 / silica . the eluent was iso - octane : methyl - t - butyl ether mixture ( 98 : 2 ). the flow rate was programmed to be 10 ml / minute for 10 minutes , 25 ml / minute for 60 minutes and finally 50 ml / minute for 200 minutes . time volume analysis fractions ( minutes ) ( ml ) weight ( g ) for thc 1 22 - 48 600 trace 2 67 - 72 300 0 . 3 g 3 72 - 74 100 0 . 9 g 4 74 - 81 450 2 . 7 g 96 . 6 % 5 81 - 97 800 4 . 0 g 99 . 0 % 6 97 - 100 1200 1 . 9 g 97 . 5 % purification of thc prepared by fractional distillation using flash column chromatography 2 . 1 g of thc ( 91 % purity ) were dissolved in 10 ml isooctane and the solution was transferred onto the top of a silica gel column ( 30 g silica gel , 40 mm particle size ; dimensions of the column : 2 . 5 cm × 40 cm ). the column was eluted with isooctane then a mixture of isooctane - acetone ( 99 : 1 ). seven fractions were collected and analyzed by glc . isooctane - acetone ( 99 : 1 ) fractions containing the bulk of the thc were obtained and yielded 1 . 84 g of residue (% of thc was 97 %). 1 g of thc ( 91 % purity ) was dissolved in 5 ml isooctane and the solution was transferred onto the top of a silica gel column ( 15 g silica gel , 40 mm particle size , dimensions : 2 . 5 cm × 40 cm ). the column was eluted with isooctane - ethyl acetate mixture in a manner of increasing polarities and the fractions were collected . fraction no . 5 ( eluted with isooctane - ethylacetate 98 : 2 ) yielded 0 . 56 g of residue (% of thc was 97 %). fraction no . 4 ( eluted with iso - octane - ethylacetate 98 . 5 : 1 . 5 ) yields 0 . 32 g of residue (% of thc was 94 . 9 %). 1 . 1 g of thc ( 91 % purity ) was dissolved in 5 ml isooctane and the solution was transferred onto the top of a silica gel column ( 15 g silica gel , 40 mm particle size , dimensions : 2 . 5 cm × 40 cm ). the column was eluted with a mixture of isooctane : isopropyl alcohol in a manner of increasing polarities . five fractions were collected . fraction nos . 4 and 5 ( eluted with iso - octane - isopropyl alcohol ( 98 : 2 and 95 : 5 , respectively ) were combined and yielded 1 g of of thc was 94 %). 9 . 6 g of thc ( purity 92 . 8 %) was purified on hplc ( water delta prep 4000 ) connected to waters 486 tunable absorbance detector ( wave length used : 254 mm ) and using column prep pak c18 ( from waters , dimensions 46 mm × 30 cm , 55 - 105 mm , lot no . t 72852 ). the eluent was a mixture of methanol : water ( 75 : 25 ). the flow rate was programmed to be 10 ml / minute for 10 minutes , 25 ml / minute for 50 minutes and finally 50 ml / minute for 140 minutes . the results are summarized in the following table : time analysis for fraction ( minutes ) volume ( ml ) weight ( g ) thc 1 69 - 96 1400 0 . 10 2 96 - 105 500 0 . 34 3 105 - 123 1000 6 . 00 99 % 4 123 - 135 600 1 . 98 98 % 5 135 - 155 1000 1 . 00 95 % 6 174 - 180 300 0 . 10 thc can be prepared directly from a hexane extract of cannabis sativa l . by double fractional distillation . the purity of thc by glc analysis is about 90 - 92 %. further purification on a silica gel column gives thc with approximately 98 % purity . thc can be prepared directly from a hexane extract of cannabis sativa l . by column chromatography ( silica gel ) followed by fractional distillation . the purity of thc is about 95 - 96 %. further purification on a silica gel column gives thc with at least 98 % purity . 5 g of the cannabis hexane extract ( thc content 26 . 28 %; ratio of thc to thca is 48 : 52 ) were heated at 110 ° c . for 1 hour to convert all the thc acid to free thc , then mixed with 10 g of alumina and 3 ml of hexanes , and the dried slurry was transferred onto the top of alumina column ( 70 g , basic alumina , 80 - 225 mesh ; dimensions : 3 × 40 cm ). the column was eluted with hexanes then hexanes : mtbe mixtures in a manner of increasing polarities . results are summarized as follows : fractions eluent volume weight comments 1 hexanes 500 ml 1 . 60 g thc content 20 . 8 % 2 , 3 , 4 hexanes : mtbe 1000 ml 1 . 05 g thc content 47 . 4 % ( 98 : 2 ) 5 hexanes : mtbe 1500 ml 0 . 90 g thc content 54 . 8 % ( 90 : 10 ) 6 methanol 300 ml 1 . 00 g thc content 7 . 5 % the column was loaded with 5 g of the extract ( thc content 1 . 35 g ). the total weight of the eluted material is 4 . 55 g ( thc content 1 . 324 g ). this example shows that free δ 9 - thc does not bind strongly to alumina and could easily be eluted with moderately polar solvents . 20 g of the cannabis hexane extract ( thc content 26 . 28 %, ratio of thc to thca is 48 : 52 ) were heated at 110 ° c . for 1 hour , then mixed with 40 g of alumina and 10 ml of hexanes and the dried slurry was transferred onto the top of an alumina column ( 210 g basic alumina , 80 - 225 mesh ; dimensions : 2 . 9 × 60 cm ). the column was eluted with hexanes , then hexanes : mtbe mixtures in a manner of increasing polarities . results are summarized as follows : fractions eluent volume weight comments 1 hexanes 450 ml 1 . 90 g thc content 7 . 1 % 2 , 3 hexanes 900 ml 1 . 54 g thc content 26 . 7 % 4 hexanes 1000 ml 1 . 30 g thc content 67 . 6 % 5 hexanes : mtbe 1000 ml 4 . 10 g thc content 77 . 8 % ( 95 : 5 ) 6 hexanes : mtbe 450 ml 0 . 53 g thc content 63 . 0 % ( 95 : 5 ) 7 methanol 500 ml 4 . 90 g thc content 12 . 0 % 8 methanol 300 ml 4 . 80 g no thc the column was loaded with 20 g of the extract ( thc content : 5 . 26 g ). the ratio of the extract to the alumina is 1 : 12 . 5 . the total weight of the eluted material is 19 . 07 g ( thc content 5 . 54 g ). this example shows that thca requires strong polar solvents to elute from alumina . this example , again , shows the case with which free thc elutes off alumina . 5 g of the cannabis hexane extract ( thc content 26 . 28 %; the ratio between thc and thca is 48 : 52 ) were mixed with 10 g of activated alumina and 3 ml of hexanes and the dried slurry was chromatographed over an alumina column ( 70 g , basic alumina , 80 - 225 mesh , chrom . grade ; dimensions ; 3 × 40 cm ). the column was eluted with hexanes , then hexanes : mtbe mixtures in a manner of increasing polarities and the results are summarized as follows : fractions eluent volume weight comments 1 , 2 hexanes 900 ml 1 . 10 g no thc 3 , 4 hexanes : mtbe 400 ml 0 . 38 g thc content 31 . 6 % ( 98 : 2 ) 5 , 6 hexanes : mtbe 600 ml 0 . 72 g thc content 81 . 6 % ( 98 : 2 ) 7 , 8 hexanes : mtbe 900 ml 0 . 25 g thc content 30 . 1 % ( 90 : 10 ) 9 hexanes : mtbe 500 ml 0 . 60 g thc content 8 . 6 % ( 50 : 50 ) 10 methanol 200 ml 0 . 50 g thc content 7 . 6 % the column was loaded with 5 . 0 g of the extract ( thc content 1 . 314 g ). the total weight of the eluted material is 3 . 55 g ( thc content 0 . 872 g ). this means that 29 . 0 % of the loaded extract is still on the column ( 0 . 442 g thc ). further elution of the column with methanol containing 2 % acetic acid afforded 0 . 405 g of thca . this example shows that thca requires strong polar solvents to elute from alumina . the fine powdered plant material ( 2 . 09 kg , thc content : 4 . 34 %; ratio of thc to thc acids ( 1 : 9 ) was macerated with hexanes ( 3 gallons ) in a 2 . 5 gallon percolator for 24 hours at room temperature . the hexane extract was collected and the marc was re - extracted with 2 gallons of hexanes for 24 hours . the combined extracts were concentrated at temperature not exceeding 40 ° c . until the total volume is 3000 ml . ratio of thc to thc acids : 1 : 8 . 6 the hexane extract ( 3000 ml ) was transferred onto the top of an alumina column ( 1 . 8 kg basic alumina , lot # 70k3701 , activity grade 1 , type wb 2 ; dimensions : 6 × 60 cm ). the column was eluted with hexanes , then hexanes - acetone mixtures in a manner of increasing polarities . all collected fractions were concentrated at temperature not exceeding 40 ° c . and analyzed for thc and thc acid content . results are summarized in the following table : thc weight ratio of amount of volume weight content of thc to thc thca fr . eluent ( liters ) ( g ) ( gc ) thc thc acids ( g ) ( g ) 1 , 2 , 3 hexanes 9 32 . 0 6 . 3 % 2 . 00 g 100 : 0 2 . 00 — 4 hexanes : acetone ( 98 : 2 ) 3 6 . 0 21 . 1 % 1 . 27 g 100 : 0 1 . 27 — 5 , 6 hexanes : acetone ( 98 : 2 ) 4 25 . 0 22 . 7 % 5 . 68 100 : 0 5 . 68 — 7 hexanes : acetone ( 95 : 5 ) 4 13 . 0 23 . 5 % 3 . 01 100 : 0 3 . 01 — 8 hexanes : acetone ( 90 : 10 ) 4 8 . 5 20 . 0 % 1 . 78 87 : 13 1 . 55 0 . 23 9 methanol * 4 51 . 4 46 . 3 % 23 . 83 10 : 90 2 . 38 21 . 45 10 methanol 4 20 . 0 24 . 1 % 4 . 82 0 : 100 — 4 . 82 11 3 % acetic acid in meoh ** 4 12 3 % acetic acid in meoh ** 4 90 . 0 56 . 6 % 50 . 35 0 : 100 — 50 . 35 the fine powdered plant material ( 2 . 54 kg , thc content : 4 . 1 %, ratio of thc to thc acids : 1 : 13 ) was macerated with hexanes ( 2 . 5 gallons ) for 24 hours at room temperature . the hexane extract was collected and the marc was re - extracted with hexanes ( 1 . 5 gallons ) for 24 hours . the combined hexane extracts were concentrated under reduced pressure at temperature not exceeding 40 ° c . to 3000 ml . the extract was divided into 8 equal volumes ( each volume is 375 ml ). each 375 ml extract equivalent to 317 . 5 g plant material and contains 13 . 0 g thc ( about 1 g thc and 12 g thc acid ). column 1 : dim . 2 . 9 × 60 cm ; column 2 : dim . 4 . 9 × 40 cm . each column was packed with 250 g alumina . the height of alumina in column 1 was 37 cm and column 2 was 13 cm . 375 ml of the concentrated hexanes extract were transferred onto the top of an alumina column ( 250 g basic alumina , dim : 2 . 9 × 60 cm ). the column was eluted with hexanes , hexanes : acetone ( 90 : 10 ), methanol , and 3 % acetic acid in methanol . results are summarized as follows : thc weight ratio of volume weight content of thc to amount of fr . eluent ( ml ) ( g ) ( gc ) thc thc acids thc thca 1 hexanes 750 3 . 9 3 . 2 % 0 . 12 g 100 : 0 0 . 12 g — 2 hex : acetone ( 90 : 10 ) 750 4 . 5 12 . 2 % 0 . 55 g 100 : 0 0 . 55 g — 3 methanol 250 5 . 0 42 . 0 % 2 . 10 g 22 : 78 0 . 47 g 1 . 63 g 4 ** 3 % ch 3 cooh / 1000 14 . 0 62 . 0 % 8 . 68 g 0 : 100 — 8 . 68 g meoh 375 ml of the concentrated extract were transferred onto the top of alumina column ( 250 g neutral alumina , dim : 2 . 9 × 60 cm ). the column was eluted with hexane , hexane : acetone 95 : 5 , hexane : acetone 90 : 10 , methanol . results are summarized in the following table : thc weight ratio of volume weight content of thc to amount of fr . eluent ( ml ) ( g ) ( gc ) thc thc acids thc thca 1 hexanes 750 6 . 70 g 9 . 9 % 0 . 66 g 100 : 0 0 . 66 — 2 hex : acetone ( 95 : 5 ) 750 5 . 00 g 22 . 0 % 1 . 10 g 50 : 50 0 . 55 0 . 55 3 hex : acetone ( 90 : 10 ) 750 2 . 80 g 29 . 7 % 0 . 83 g 50 : 50 0 . 41 0 . 42 4 methanol 1000 8 . 00 g 43 . 3 % 3 . 46 g 10 : 100 0 . 31 3 . 15 5 ** 3 % ch 3 cooh / meoh 750 8 . 50 g 66 . 5 % 5 . 66 g 0 : 100 — 5 . 66 350 ml of the concentrated extract was reconstituted to 750 ml with hexane and transferred onto the top of alumina column ( 250 g neutral alumina , dim : 2 . 9 × 60 cm ). the column was eluted with hexane , followed with hexane : acetone 90 : 10 , then 3 % acetic acid in methanol . results are summarized in the following table . thc weight ratio of volume weight content of thc to amount of fr . eluent ( ml ) ( g ) ( gc ) thc thc acids thc thca 1 hexanes 800 2 . 0 9 . 8 % 0 . 20 g 100 : 0 0 . 20 — 2 hex : acetone ( 90 : 10 ) 800 5 . 3 20 . 0 % 1 . 06 g 80 : 20 0 . 82 0 . 24 3 3 % ch 3 cooh / meoh 800 18 . 0 56 . 2 % 10 . 12 g 5 : 95 0 . 50 9 . 62 325 ml of the concentrated hexanes extract were transferred onto the top of an alumina column ( 250 g neutral alumina , dim . : 2 . 9 × 60 cm ). the column was eluted with hexanes , hexanes : methyl - t - butyl ether ( 90 : 10 ), hexanes : mtbe ( 80 : 20 ); then 3 % acetic acid in methanol . results are summarized in the following table : thc weight ratio to volume weight content of thc to amount of fr . eluent ( liters ) ( g ) ( gc ) thc thc acids thc thca 1 hexanes 1 4 . 1 g — — — — — 2 hexanes : mtbe ( 90 : 10 ) 1 1 . 8 g 17 . 8 % 0 . 32 g 100 : 0 0 . 32 — 3 hexanes : mtbe ( 80 : 20 ) 1 2 . 0 g 21 . 8 % 0 . 44 g 100 : 0 0 . 44 — 4 hexanes : mtbe ( 50 : 50 ) 1 0 . 8 g 20 . 5 % 0 . 16 g 100 : 0 0 . 16 — 5 methanol 1 5 . 9 g 30 . 9 % 0 . 82 g 40 : 60 0 . 73 1 . 09 6 3 % acetic acid / methanol 2 10 . 7 g 60 . 0 % 6 . 42 g 0 : 100 — 6 . 42 650 ml of the concentrated hexanes extract were transferred onto the top of an alumina column ( 500 g basic alumina , dim . ; 4 . 9 × 60 cm ). the column was eluted with hexanes , hexanes : mtbe ( 90 : 10 ), hexanes : mtbe ( 80 : 20 ), then 3 % acetic acid / methanol . results are summarized in the following table : thc weight ratio to volume weight content of thc to amount of fr . eluent ( liters ) ( g ) ( gc ) thc thc acids thc thca 1 hexanes 2 7 . 1 g — — — — — 2 hexanes : mtbe ( 90 : 10 ) 2 2 . 2 g 15 . 2 % 0 . 33 100 : 0 0 . 33 — 3 hexanes : mtbe ( 50 : 50 ) 2 4 . 1 g 23 . 3 % 0 . 96 100 : 0 0 . 96 — 4 methanol 2 18 . 3 g 37 . 6 % 6 . 88 30 : 70 1 . 16 5 . 72 5 3 % acetic acid / methanol 2 18 . 0 g 59 . 0 % 10 . 62 0 : 100 — 10 . 62 200 g of cannabis plant material ( approximately 6 % total thc ; thc : thca = 1 : 2 . 5 ) was extracted with hexane and the hexane extract was brought to a total volume of 1800 ml . 567 ml of the hexane solution ( equivalent to 63 g of plant material ) was stirred for two hours with 44 g of basic alumina and filtered . the collected alumina was added to an alumina column containing 19 g fresh basic alumina ( dim . 2 × 22 . 5 cm , ratio of the extract to alumina is 1 : 10 ) and the column was eluted as follows : thc / thc acid fr # eluent volume weight ratio 1 hexane 200 ml — — 2 hexane : mtbe 90 : 10 200 ml 0 . 02 g — 3 hexane : mtbe 50 : 50 200 ml 0 . 3 g thc ( 0 . 1 g ) 4 methanol 400 ml 1 . 45 g thc : thc acid ( 1 : 1 ) ( 0 . 23 g each ) 5 3 % acetic acid / meoh 500 ml 1 . 54 g thc acid ( 1 . 0 g ) 6 3 % acetic acid / meoh 500 ml 0 . 38 g thc acid ( 0 . 49 g ) analysis of the filtrate from the alumina prior to packing showed the presence of thc but no thc acid ; that is , by adding alumina to the hexane extract all the thc acid and most of the thc was chelated to alumina . therefore , simple filtration and washing of the alumina could be used in lieu of a column . fractional distillation of fractions eluted from alumina column with 3 % acetic acid in methanol . the content of thc acid in these fractions ranges between 58 to 70 %. bulb to bulb distillation unit was used for the distillation . thc was distilled at temperature between 180 - 190 ° c ., vacuum : 0 . 6 mm hg . 13 . 5 g of thc acid fraction ( thc acid content 70 %) was dissolved in 300 ml of methanol and the precipitate was removed by filtration ( 0 . 8 g ppt ). the filtrate was distilled off and the residue was divided into two parts : part a : 6 . 0 g ; part b : 6 . 7 g . 1 . distillate : 3 . 7 g , thc content by gc ( using internal standard ): 82 . 4 %. 5 . 0 g of thc acid fraction [ thc acid content 58 %] was distilled to give : 1 g of thc acid fraction [ the content of thc acid is 68 . 4 %] was dissolved in 20 ml of methanol . the precipitate that formed was separated by centrifuge ( wt 100 mg ). the sample was allowed to sit overnight in a refrigerator . the following day further precipitation was observed ( 40 mg ). the sample was filtered using a 0 . 45 mm filter . the filtrate was loaded on the hplc . solvent system : methanol : water ( 80 : 20 ). equipment : waters delta prep hplc 4000 with 1000 prepak module . column : prepak c18 cartridge , waters , 55 - 105 μm , 125 a ; dimensions : 46 mm × 30 cm . thc acid was isolated in & gt ; 94 % purity by hplc analysis . 5 . 8 g of thc acid [ thc acid content is 68 . 4 ] was dissolved in 20 ml of methanol . the sample was allowed to sit overnight in a refrigerator . the following day the precipitate was filtered . weight of the precipitate was 0 . 485 g . the clear filtrate was loaded on the hlpc . elution was carried out using isocratic solution : methanol : water : acetic acid ( 80 : 20 : 0 . 01 ). again , purified thc acid was isolated from the eluted fractions in solid form . 4 . 35 g of thca fraction ( thca content is 94 . 1 %) was subjected to bulb to bulb distillation . 3 . 45 g of thc were collected at temperatures between 190 - 195 ° c ., vacuum 0 . 50 - 0 . 55 mm / hg . ( 3 . 45 g thc corresponds to 3 . 93 g thca , therefore , the yield is 90 . 4 %). the purity of the thc collected was & gt ; 96 %. a solution of 1 g of marijuana extract that contained 36 % of thc and 11 % of thc acid in 20 ml of hexane was passed through a column ( i . d . 0 . 5 cm ) packed with 5 g of activated acidic aluminum oxide ( aldrich chemical company , standard grade , 150 mesh , 58 å ). the column was subsequently eluted with solvent systems including 2 . 5 % acetone in hexane ( 20 ml ), 5 % acetone in hexane ( 20 ml ), 10 % acetone in hexane ( 20 ml ), methanol ( 20 ml ), and 5 % acetic acid in methanol ( 3 × 20 ml ). each fraction was collected and analyzed for thc and thc acid content . the amount of thc and thc acid in each fraction were : ( 1 ) hexane fraction , 0 . 003 g of thc ; ( 2 ) 2 . 5 % acetone in hexane fraction , 0 . 282 g of thc and 0 . 005 g of thc acid ; ( 3 ) 5 % acetone in hexane fraction , 0 . 044 g of thc ; ( 4 ) 10 % acetone in hexane fraction , 0 . 012 g of thc ; ( 5 ) methanol fraction , 0 . 016 g of thc and 0 . 037 g of thc acid ; ( 6 - 8 ) combined 5 % acetic acid in methanol fractions , 0 . 005 g of thc and 0 . 064 g of thc acid . repeating the work outlined under example 27 using weakly acidic aluminum oxide gave similar results to those in example 27 . an aliquot from a hexane extract of cannabis plant material ( thc content 26 %) was taken and divided into three samples ( a , b , and c ). 44 ml of methanol was added to 4 . 4 g of the extract . this was sonicated for at least one hour then refrigerated overnight . the following day the mixture was filtered and the residue was washed with methanol : water ( 95 : 5 ). the residue was dissolved in hexane then dried using a rotovapor . the filtrate was also dried . 41 ml of 90 % ethanol / water was added to 4 . 1 g of the extract . it was sonicated for at least one hour then refrigerated overnight . the following day the mixture was filtered . the residue was dissolved in hexane and dried . the filtrate was also dried . 100 ml of ethanol ( 95 %) was added to 10 . 2 g of the extract . the mixture was sonicated then filtered . the residue was dissolved in hexane then dried . the filtrate was also dried . all filtrates and residues were then weighed and analyzed . the results are summarized below : sample a sample b sample c ( methanol ) ( 90 % ethanol ) ( 95 % ethanol ) weight starting material 4 . 4 g 4 . 1 g 10 . 2 g wt . filtrate 1 . 6 g 2 . 0 g 7 . 4 g wt . residue 3 . 0 g 2 . 0 g 2 . 8 g % of thc starting material 26 % 26 % 26 % filtrate 47 . 7 % 45 . 9 % 38 . 1 % residue 16 . 9 % 13 . 9 % 5 . 7 % amount of starting thc material 1 . 28 g 1 . 19 g 2 . 96 g filtrate 0 . 76 g 0 . 92 g 2 . 82 g residue 0 . 50 g 0 . 28 g 0 . 16 g % 59 . 8 % 77 . 2 % 95 % recovery of thc in filtrate additional samples from the hexane extract ( 26 % thc ) used in example 1 were used and treated as follows : add 75 . 6 ml of ethanol ( 90 %) to the extract ( 7 . 56 g ). heat and sonicate until the extract goes into solution . refrigerate overnight . filter , then dry residue and filtrate . add 68 . 5 ml of ethanol ( 95 %) to the extract ( 6 . 85 g ). sonicate until the extract goes into solution then add 1 . 9 ml of water drop - wise . ( final concentration 92 . 5 %). refrigerate overnight then filter . add 75 . 6 ml of ethanol ( 200 proof ) to the extract ( 7 . 56 g ). sonicate until the extract goes into solution . then add drop - wise 6 . 1 ml of water . final ethanol concentration ( 92 . 5 %). refrigerate overnight and then filter . add 73 . 9 ml of ethanol ( 92 . 5 %) to the extract ( 7 . 31 g ) sonicate until the extract goes into solution then refrigerate overnight . filter . the filtrates and residues were then dried , weighed , and analyzed for thc content as follows : sam - sam - sam - ple e ple f sam - ple d ethanol ethanol ple g ethanol ( 95 %- ( 100 %- ethanol ( 90 %) 92 . 5 %) 92 . 5 %) ( 92 . 5 %) weight starting 7 . 56 g 6 . 85 g 7 . 56 g 7 . 31 g material wt . filtrate 4 . 3 g 4 . 34 g 5 . 07 g 4 . 53 g wt . residue 3 . 38 g 2 . 37 g 2 . 70 g 2 . 73 g % of thc starting 29 % 29 % 29 % 29 % material filtrate 42 . 2 % 38 . 3 % 39 . 5 % 42 . 8 % residue 11 . 6 % 7 . 8 % 10 . 1 % 16 . 9 % amount of starting 2 . 19 g 1 . 99 g 2 . 19 g 2 . 12 g thc material filtrate 1 . 8 g 1 . 66 g 1 . 92 g 1 . 9 g residue 0 . 39 g 0 . 184 g 0 . 27 g 0 . 4 g % starting 82 . 2 % 83 . 4 % 87 . 6 % 89 % recovery material of thc filtrate residue this example shows that the same result is obtained whether the extract is treated directly with the aqueous ethanolic mixture or if it is first dissolved in absolute ethanol followed by the addition of the water to reach a specific alcohol concentration . 8 g of a hexane extract of cannabis plant material ( thc 20 . 0 %) was dissolved in 80 ml of ethanol ( 200 proof ). this solution was divided evenly among four flasks . to each flask water was added to different concentration while stirring . they were filtered and dried and analyzed . flask f flask g flask h flask i ethanol ethanol ethanol ethanol 85 % 82 . 5 % 80 % 77 . 5 % weight starting material wt . filtrate 2 . 16 g 2 . 16 g 2 . 16 g 2 . 16 g wt . residue 1 . 02 g 0 . 9 g 0 . 8 g 1 . 1 g % of thc starting 20 . 0 % 20 . 0 % 20 . 0 % 20 . 0 % material filtrate 30 % 37 . 5 % 33 % 24 . 2 % amount of starting 0 . 4 g 0 . 4 g 0 . 04 g 0 . 4 g thc material filtrate 0 . 31 g 0 . 38 g 0 . 26 g 0 . 26 g % 75 % 84 . 4 % 66 % 66 . 5 % recovery of thc this example shows that 82 . 5 % ethanol gives the highest thc content and the highest overall recovery . 8 g of a hexane extract of cannabis plant material ( thc 20 . 0 %) was dissolved in 80 ml of iso - propanol by sonication . this solution was equally divided into four flasks . to each flask water was added to different concentrations . flask 1 flask 2 flask 3 flask 4 ipa 90 % ipa 80 % ipa 70 % ipa 60 % weight starting 2 . 0 g 2 . 0 g 2 . 0 g 2 . 0 g material wt . filtrate 1 . 60 g 1 . 0 g 0 . 8 g 0 . 8 g % of thc starting 20 . 0 % 20 . 0 % 20 . 0 % 20 . 0 % material filtrate 22 . 5 % 30 . 4 % 35 % 27 % residue amount of starting 0 . 4 g 0 . 4 g 0 . 4 g 0 . 4 g thc material filtrate 0 . 36 g 0 . 30 g 0 . 28 g 0 . 22 g residue % 88 . 7 % 76 % 70 % 54 % recovery of thc this shows that the highest increase in thc concentration is obtained with 70 % iso - propanol . 17 . 5 g of cannabis hexane extract ( thc content 37 %) was dissolved in 100 ml of iso - propanol . this solution was evenly split into seven flasks . to each flask water was added to while stirring to a desired concentration . ipa : ipa : ipa : ipa : ipa : ipa : ipa : water water water water water water water 7 ( 62 . 5 % ( 77 . 5 %) ( 75 %) ( 72 . 5 %) ( 70 %) ( 67 . 5 %) ( 65 %) ipa ) weight starting 2 . 50 g 2 . 50 g 2 . 50 g 2 . 50 g 2 . 50 g 2 . 50 g 2 . 5 g material wt . filtrate 1 . 38 g 1 . 39 g 1 . 37 g 1 . 18 g 1 . 05 g 1 . 02 g 0 . 51 g wt . residue 1 . 60 g 0 . 90 g 1 . 30 g 1 . 39 g 1 . 69 g 1 . 56 g 1 . 6 g % of thc starting 37 % 37 % 37 % 37 % 37 % 37 % 37 % material filtrate 50 % 47 . 5 % 57 . 9 % 48 % 50 . 9 % 44 . 7 % 50 . 7 % amount of starting 0 . 925 g 0 . 925 g 0 . 925 g 0 . 925 g 0 . 925 g 0 . 925 g 0 . 925 g thc material filtrate 0 . 69 g 0 . 66 g 0 . 79 g 0 . 566 g 0 . 534 g 0 . 455 g 0 . 25 g recovery filtrate 74 . 5 % 71 . 3 % 85 . 4 % 61 . 2 % 57 . 3 % 59 . 2 % 27 % of thc this example shows that best results are obtained with 72 . 5 % iso - propanol . 1 g of cannabis hexane extract ( thc content 48 . 8 %) was added to each of 7 flasks . to flasks 1 - 5 , 5 ml of acetone was added and sonicated . to each of flasks 6 and 7 add 5 acetonitrile . to flasks 1 - 5 water was added while stirring . flask 6 was filtered as is . to flask 7 , 1 ml of hexane was added , then 2 ml of acetonitrile . this was filtered then the filtrate was concentrated to remove the hexane . it was filtered again . amt . amt . flask 5 ml of volume % weight of weight of thc in thc in % # solvent of h20 solvent filtrate residue filtrate residue recovery 1 acetone 0 . 1 ml 98 % 735 mg 248 mg 49 . 8 % 41 % 75 % 2 acetone 0 . 2 ml 96 % 704 mg 302 mg 52 . 4 % 38 . 5 % 75 . 6 % 3 acetone 0 . 5 ml 90 % 866 mg 153 mg 42 . 7 % 33 % 75 . 8 % 4 acetone 1 . 0 ml 83 % 583 mg 346 mg 48 . 8 % 42 . 1 % 58 . 3 % 5 acetone 0 ml 100 % 924 mg 95 mg 49 . 4 % 23 . 3 % 93 % 6 acetonitrile 0 ml 100 % 585 mg 417 mg 59 . 6 % 32 % 71 % 7 acetonitrile 0 ml 100 % 676 mg 324 mg 54 . 5 % 25 . 9 % 75 . 5 % ( with hexane at a ratio of 7 : 1 ) 10 g samples of a hexane extract of cannabis plant material ( 26 % thc ) were dissolved in the following solvents . acetonitrile ( 95 ml , 80 ml , and 70 ml ), iso - propanol ( 70 ml ), and methanol ( 100 ml ). different volumes of water were then added to each solution to yield five final solutions of the extract in 95 % acetonitrile , 80 % acetonitrile , 70 % acetonitrile , 70 % iso - propanol , and 100 % methanol . these final solutions were then filtered and both were dried , weighed , and analyzed for thc content . the results are shown below : weight weight of of amt , thc in amt thc in % solvent filtrate residue filtrate residue recovery aceton - 5 . 19 g 4 . 73 g 40 . 1 % ( 2 . 08 g ) 15 . 8 % ( 0 . 75 g ) 73 . 8 % itrile ( 80 %) aceton - 3 . 44 g 7 . 23 g 31 . 6 % ( 1 . 09 g ) 19 . 5 % ( 1 . 4 g ) 38 . 5 % itrile ( 70 %) aceton - 6 . 37 g 3 . 04 g 35 . 8 % ( 2 . 28 g ) 11 . 0 % ( 0 . 33 g ) 80 . 8 % itrile 95 %) iso - 5 . 72 g 3 . 91 g 34 . 3 % ( 1 . 96 g ) 18 . 5 % ( 0 . 72 g ) 68 . 5 % pro - panol ( 70 %) meth - 8 . 21 g 1 . 64 g 29 . 7 % ( 2 . 47 g ) 10 . 6 % ( 0 . 17 g ) 87 . 5 % anol ( 100 %) the results show that 80 % or 95 % acetonitrile produces comparable results to the 70 % iso - propanol . 10 ml aliquots of a hexane solution of cannabis extract ( thc content 37 %) containing approximately 1 . 8 g extract were partitioned with 10 ml of either acetonitrile , acetonitrile : water ( 9 : 1 ) or acetonitrile : water ( 8 : 2 ). the acetonitrile layer was separated and the partitioning in each case was repeated two more times with 10 ml each of the same solvent . the combined acetonitrile fractions as well as the hexane fraction were analyzed for thc content . fractions weight % of thc 100 % acetonitrile acetonitrile fraction 1 . 15 g 64 . 5 % hexane fraction 0 . 60 g 7 . 3 % 90 % acetonitrile : acetonitrile fraction 1 . 02 g 69 . 3 % hexane fraction 0 . 84 g 10 . 7 % 80 % acetonitrile acetonitrile fraction 0 . 84 g 57 . 6 % hexane fraction 1 . 13 g 20 . 7 % this example shows that in all cases the thc concentrates in the acetonitrile layer with 90 % acetonitrile giving the highest increase in thc concentration 10 . 9 g of the crude heptane extract ( thc content 32 . 05 %) was dissolved in 100 ml of hexane and shaken twice with 40 ml of 1 n koh in meoh - h 2 o ( 90 : 10 ). the hexane layer was collected , dried ( 2 . 2 g ), and analyzed for thc content ( 2 . 2 %). the methanolic koh layer was acidified by adding 65 ml of 2 n hcl , then extracted by shaking twice with hexane ( 200 ml ). the hexane layer was collected , dried ( 7 . 2 g ) and analyzed for thc ( 49 . 1 %) with & gt ; 95 % recovery . 10 . 1 g of the crude heptane extract ( thc content 32 . 05 %) was dissolved in 100 ml of hexane and shaken twice with 40 ml of 1 n koh in meoh - h 2 o ( 80 : 20 ). the hexane layer was collected , dried ( 3 . 4 g ), and analyzed for thc content ( 4 . 4 %). the methanolic koh layer was acidified by adding 65 ml of 2 n hcl , then extracted by shaking twice with hexane ( 200 ml ). the hexane layer was collected , dried ( 5 . 7 g ), and analyzed for thc content ( 54 . 05 %) with a 95 % recovery . 33 . 0 g of the crude heptane extract ( thc content : 41 . 4 %) was dissolved in 300 ml of hexane and shaken twice with 120 ml of 1 n koh in meoh - h 2 o ( 70 : 30 ). the hexane layer was collected , dried ( 8 . 5 g ) and analyzed for thc content ( 7 . 9 %). the methanolic koh layer was acidified by adding 200 ml of 2 n hcl , then extracted by shaking twice with hexane ( 600 ml ). the hexane layer was collected , dried ( 21 . 1 g ) and analyzed for thc content ( 62 . 5 %), with & gt ; 95 % recovery . 5 . 28 g of the heptane extract ( thc content 41 . 4 %) was sonicated very well with 50 ml of 0 . 25 n koh in methanol and filtered . the precipitate weighed 1 g ( most probably hydrocarbons ). the filtrate was acidified with 15 ml of 1 n hcl and extracted twice with hexane ( 100 ml × 2 ) to give 3 . 18 g residue ( thc content 70 . 02 %), with almost quatitative recovery . 34 g of marijuana extract containing 55 % of thc was distilled under vacuum ( 0 . 3 mmhg ) and the distillate at 174 - 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