Abstract:
The present invention relates to a process for the preparation of pure lycopene or of lipophilic extracts containing it from whole fruits of Lycopersicum esculentum and similar species or parts thereof obtainable as by-products of food industry processes. The partially dehydrated fresh material is extracted with aliphatic or aromatic hydrocarbons or water-immiscible solvents in the presence of phospholipids as surfactant and stabilizing agents and the extracts are concentrated to an oil or fractionated to the desired lycopene concentration.

Description:
TECHNICAL FIELD 
     The present invention relates to a process for the extraction of lycopene. 
     BACKGROUND OF THE INVENTION 
     Lycopene is a highly lipophilic procarotenoid present in greatest amounts in the species Lycopersicum although it may be found in lower amounts in other vegetable and algae species. Lycopene is present in common tomatoes in concentrations ranging from 30 to 100 ppm, on the average at 50 ppm. It is usually present as a secondary metabolite in mammals, where it plays an important role as an antioxidant and free-radicals scavenger, together with substances such as Vitamin E, Vitamin C and other compounds. At the plasma level, lycopene has been found to be incorporated in low-density lipoproteins in which it decreases the oxidation of cholesterol and of other lipids, thus preventing vascular damage. Moreover, an inverse correlation between lycopene blood levels and prostate tumor has recently been proved. The administration of lycopene to humans is therefore important in reducing the risk of tumors and atherosclerosis; hence the need for stable formulations containing lycopene for a preventive chronic treatment in humans. 
     SUMMARY OF THE INVENTION 
     The invention relates to a process for extracting lycopene from Lycopersicum esculentum by combining a quantity of Lycopersicum esculentum containing lycopene with an extraction medium comprising at least one solvent chosen from aromatic hydrocarbons, aliphatic hydrocarbons and halohydrocarbons and from about 0.01 to about 0.100 w/v of a phospholipid. A sufficient amount of the extraction medium may be added to remove all or a portion, as desired, of the lycopene from the Lycopersicum esculentum. The preferred solvents are n-hexane and methylene chloride, most preferably n-hexane. The preferred phospholipid is soy lecithin. 
     Prior to the extraction step the Lycopersicum esculentum may be formed into a slurry by at least partially homogenizing the material, e.g., with a knife mill. The slurry may then be heated to a temperature of from about 70-100° C. for between about 15-60 minutes and then cooled at a temperature of between about 50-70° C. This cooling step is preferably carried out under sterile conditions. In one embodiment of the invention the starting plant material is at least partially dried and the method further comprises adding to the slurry about one-half part by weight of water to lyse the cells of the Lycopersicum esculentum, thus facilitating release of the lycopene. 
     The Lycopersicum esculentum may be extracted one or a plurality of times in order to obtain the lycopene contained therein. The resultant extract(s) may be individually or collectively concentrated by removing a portion of the extraction medium. In a preferred embodiment the extract is concentrated such that the lycopene is present in an amount of from about 1 to about 10% by weight. 
     The lycopene extract, whether concentrated or not, may, if desired, be further purified. In one embodiment the purification is carried out by chromatographic separation through an acidic alumina column wherein the lycopene is eluted with a mixture of ethyl acetate and hexane. Alternatively, the purification may be obtained by extraction with carbon dioxide (CO 2 ) under supercritical conditions, i.e., at a temperature of between about 35-60° C. and at a pressure of between about 150-200 bars. 
     In a further embodiment, the lycopene extract thus obtained can be added to, e.g., food and cosmetic compositions suitable for use by humans. 
     DETAILED DESCRIPTION OF THE INVENTION 
     According to the invention, fruits of Lycopersicum sp. are homogenized, e.g., with a knife mill and the resulting semi-liquid mass is heated to temperatures varying from 70 to 100° C., preferably at 90° C., for a time from 15 to 60 minutes, preferably for about 30 minutes. During heating, an abundant precipitate forms, which includes substantially all of the lycopene present in the biomass. The suspension is cooled at preferably 60° C., keeping the medium sterile, then centrigued through fast decanters or filtered through pressure-filters. 
     The centrifugation or filtration residue, containing about 20% of residual water, can immediately be extracted with stirring or continuously with, for example, hydrocarbons, or it can be frozen to preserve it until the extraction. The residue when immediately extracted, is suspended in a sufficient amount, preferably about 10 vol., of the selected solvent, preferably n-hexane, containing, e.g., soy lecithin at concentrations varying from 0.01 to 0.1%, preferably 0.02%, according to the procedure reported below in the examples. The solvents used in these conditions extract lycopene which generally goes into solution in the first extraction, in a highly selective way, leaving other carotenoids, such as beta-carotene, in the biomass. The extracts are concentrated until the solvent is completely removed, thereby obtaining oily residues containing up to 10% of lycopene. 
     An economically interesting source for the preparation of lycopene are the by-products of the preserved food industry, such as the skins of mature fruits and those fibrous portions which are not green. These materials can be quickly dried or, more preferably, frozen, optionally after removing seeds which are usually present. When the vegetable material is frozen before extraction, the biomass must be ground at temperatures ranging from -25 to -10° C., preferably below -15° C. so as to homogenize it. Subsequently the residue is extracted according to the procedures described herein for use with the whole fruits. If the vegetable material is dried before the extraction it is finely ground and treated with about one-half its weight of water to cause the cells to lyse, thus promoting the extraction. The humid vegetable material is then extracted with aliphatic hydrocarbons or other solvents as described above for the whole fruits. Suitable amounts of phospholipids are added to assist the extraction and avoid lycopene oxidative degradation. These biomasses yield, after evaporation of the extraction solvent, lipid extracts containing one to ten percent of lycopene. Pure lycopene can be prepared from these extracts by chromatography using acidic alumina columns and eluting the product with ethyl acetate/hexane mixtures with a variable gradient. Alternatively, lycopene can be prepared by extracting the lipophilic extract resulting from the concentration of the extraction solvents by partitioning the concentrate with CO 2  under supercritical conditions with multistep columns in a manner well known in the art. For example, lycopene can be purified using a three-step partitioning column, keeping the pressure constant in a range from 150 to 200 bars, preferably under 180 bars and a segment temperature ranging from 35 to 65° C. In these supercritical conditions a substantial purification of the extract and the recovery of lycopene by crystallization of the residue undistilled during fractionation can be obtained. The products obtained according to the invention can be incorporated in formulations, such as hard- and soft-gelating capsules, and normal and gastro-resistant tablets. In nutritional preparations for humans for the prevention of atherosclerosis or for the prevention of tumors, lycopene can advantageously be combined with procyanidole polyphenols such as those prepared from Vitis vinifera and Camellia sinensis. When lycopene is used in a substantially pure form, for the preparation of bio-available formulations, the addition of phospholipids as stabilizers and emulsifiers is convenient. In the unpurified extracts, phospholipids are already present as they are added during the extraction process. 
    
    
     EXAMPLES 
     The following examples further illustrate the invention. The invention is not limited, however, to the specific embodiments disclosed in the following examples. 
     Example I 
     Preparation of a lycopene-enriched lipophilic extract from Lycopersicum esculentum 
     10 kg of mature tomatoes (Lycopersicum esculentum var. Sanmarzano) are homogenized in a knife mill to a semi-fluid mass; the fluid slurry is heated for about three hours with flowing steam to 95° C. and maintained under these temperature conditions with slow stirring for about 30 minutes. During heating, a red flocculate separates consisting of denatured vegetable cell structures which tend to precipitate immediately. This suspension is cooled at 60° C. and centrifuged; the supernatant which does not contain lycopene is discarded and the residue is washed in a centrifuge with water thereby removing any undesired substances. The biomass still containing about 50% of water is extracted for 3 hours with strong stirring and under mild reflux with 2.5 1 of n-hexane containing 0.01% soy lecithin. After separation of the solvent, the residue is re-extracted with a further 2 1 of n-hexane under the same conditions as used in the first extraction. The extraction solvent after filtration and complete decantation is concentrated under vacuum until the solvent is removed completely. 11 g of a bright red-coloured oily residue containing 0.52 g of lycopene are obtained. This extract can be used as such in the formulations for use in humans. 
     Example II 
     Preparation of a lycopene-enriched lipophilic extract starting from dried skins of Lycopersicum esculentum 
     10 kg of mature tomatoes (Lycopersicum esculentum var. Sanmarzano) are coarsely ground and filtered by squeezing through a grid which allows the separation of the fruit skins and seeds. The resultant residue is quickly dehydrated in an air stream. About 150 g of a brightly coloured material are obtained, which is separated from the seeds and finely ground. The ground residue is treated in a mixer with 150 ml of water and left to stand for about one hour, thereby allowing the vegetable material to swell, resulting in the breaking of the cells due to membrane porosity. This wet mass is extracted with 800 ml of n-hexane containing 0.01% soy lecithin with stirring under mild reflux. After 3 hours the solvent is removed and the vegetable residue is extracted again twice with 400 ml each of n-hexane. The combined extracts are filtered, decanted, then concentrated under vacuum until the solvent is completely removed. 5.2 g of a bright red-coloured oily residue containing 4.6% of lycopene are obtained. This extract can be used as such in the formulation for use in humans. 
     Example III 
     Preparation of a lycopene-enriched lipophilic extract starting from not-dried skins of Lycopersicum esculentum 
     The industrial squeezing residue of fresh tomatoes, obtained under conditions similar to those reported in example II, is separated from the juice, washed with water, pressed to remove the residual water as much as possible and frozen. For the extraction, the frozen mass is ground at a temperature of -20° C. and then extracted according to the procedure of example II. 250 g of a frozen biomass yield 4.2 g of a bright red-coloured oily residue containing 5.6% of lycopene. This extract can be used as such in the formulations for use in humans. 
     Example IV 
     Preparation of pure lycopene by extraction from the enriched lipophilic extract 
     0.5 kg of lycopene oil, prepared according to example I, are extracted in counter-current with carbon dioxide in supercritical conditions, using a three step column working at different temperatures (50, 40, 34° C.) and under a 180 bars pressure. In these conditions, the purification of the extract is achieved and lycopene is recovered by crystallization of the residue which has not been distilled during the fractionation. 24 g of a pure product are obtained, having the same chemical-physical and spectroscopical characteristics as lycopene. 
     Example V 
     Preparation of coated tablets containing the lycopene-enriched lipophilic extract 
     
         ______________________________________Lycopene-enriched lipophilic extract                    10.00       mgLactose                  50.60       mgPre-gelatinized starch   73.60       mgMicrocrystalline cellulose                    49.80       mgCross-linked sodium carboxymethylcellulose                    19.00       mgColloidal silica         19.00       mgHydroxypropyl cellulose  5.00        mgHydrogenated vegetable oils                    2.00        mgSoy lecithin             1.00        mgHydroxypropyl methylcellulose                    6.07        mgTalc                     3.96        mgTriacetin                1.21        mgTitanium dioxide         0.40        mgRed iron oxide           0.24        mgPolyethylene glycol 6000 0.12        mg______________________________________ 
    
     Example VI 
     Preparation of hard-gelatin capsules containing the lycopene-enriched lipophilic extract 
     
         ______________________________________Lycopene-enriched lipophilic extract                    10.00       mgLactose                  50.60       mgPre-gelatinized starch   73.60       mgMicrocrystalline cellulose                    49.80       mgCross-linked sodium carboxymethylcellulose                    19.00       mgColloidal silica         19.00       mgHydroxypropyl cellulose  5.00        mgHydrogenated vegetable oils                    2.00        mgSoy lecithin             1.00        mg______________________________________ 
    
     Example VII 
     Preparation of hard-gelatin capsules containing lycopene 
     
         ______________________________________Lycopene                 5.00        mgLactose                  40.00       mgPre-gelatinzed starch    53.00       mgMicrocrystalline cellulose                    30.00       mgColloidal silica         5.00        mgHydrogenated vegetable oils                    2.00        mgCross-linked sodium carboxymethylcellulose                    19.00       mgHydroxypropyl cellulose  5.00        mg______________________________________ 
    
     Example VIII 
     Preparation of soft-gelating capsules containing the lycopene-enriched lipophilic extract 
     
         ______________________________________Lycopene-enriched lipophilic extract                  10.00        mgPeanut oil             151.00       mgPartially hydrogenated vegetable oils                  80.00        mgSoy lecithin           1.00         mgCoatingGelatin                82.00        mgGlycerol               40.10        mgGlycine                1.87         mgRed iron oxide         1.42         mg______________________________________