the present invention comprises a simplified extraction protocol for preparing biologically active heat stable potato proteinase inhibitors ( ppi ) from whole potato tubers . in a first step , plant proteins are extracted from plant material , such as potato tubers . in addition to potato tubers , representative plant materials can include tubers of sweet potatoes or cassava , leaves and fruits of potatoes , tomatoes and legumes , seeds of all plant species , as well as genetically engineered organisms expressing proteinase inhibitor genes , using an aqueous solvent . in one embodiment , selected tubers are added to a blender and an extractant buffer is supplied simultaneously . for example , the tubers can be added at a 40 % weight basis of the extractant buffer . an example extractant buffer is sodium chloride : acetic acid : water , 1 : 1 : 9 , w : v : v . the mixture is blended until liquefied , and the liquid material is recovered by centrifugation , filtering , or pressing or the like . under these conditions most of the proteins from the ppi fraction will be extracted from the plant tissue and accumulated in the solution . in a second step , the extract liquid is heated to denature the heat sensitive plant proteins . in a third step , the extract liquid is cooled to precipitate the plant proteins . this step allows the removal of heat sensitive proteins due to coagulation . for example , the extract liquid is heated to approximately 70 ° c . and cooled to approximately 30 ° c . in a subsequent step , the liquid portion of the extract liquid is separated by centrifugation , filtering , or pressing to remove the denatured plant proteins . the volume of the liquid is recorded . thereafter , the heat stable fraction of potato proteins is then salted out from this liquid in a subsequent step . for example , sodium chloride can be used in an amount of about 260 g / l of sodium chloride . the sample is mixed until the salt is completely dissolved . under these conditions , the biologically active ppi fraction containing one or more protease inhibitor proteins at a variety of degrees of purity including , but not limited to , potato proteinase inhibitor ii , potato proteinase inhibitor i , potato cysteine protease inhibitor , and potato carboxypeptidase inhibitor is precipitated and can be recovered by centrifugation , filtering , or pressing and is designated as “ ppi fraction ”. a subsequent step of the extraction protocol desalts the ppi fraction . for example , a sephadex gel filtration column can be used . ppi fraction is loaded on the sephadex column and eluted with about 50 mm ammonium bicarbonate in water . finally , the ppi fraction is lyophilized to obtain a dry ppi powder , which retains its biological activity and is highly active against in controlling the appetite and food intake in mammalian subjects . various modes of administration , including all modes known in the art , are contemplated for use in delivering the extract enriched with one or more protease inhibitors to a mammal such as a human patient . preferred modes of administration include parental ( e . g ., intravenous , intramuscular and subcutaneous ), oral administration , and topical administration . the extract enriched with one or more protease inhibitors can be added to a pharmaceutical composition , nutraceutical , functional food and / or cosmetic composition in any suitable amount . in an embodiment , the pharmaceutical composition , nutraceutical , functional food and / or cosmetic composition includes the extract enriched with one or more protease inhibitors of the present invention in an amount of at least 0 . 5 % by weight , preferably from about 1 % to about 80 % by weight , more preferably about 1 % to about 20 % by weight . in an embodiment , the pharmaceutical compositions containing the extract of the present invention may be in any form suitable for oral use , such as e . g ., tablets , troches , lozenges , aqueous or oily suspensions , dispersible powders or granules , emulsions , hard or soft capsules , or syrups or elixirs . compositions intended for oral use can be prepared according to any method known in the art for the manufacture of pharmaceutical compositions and such compositions can contain one or more agents selected from the group consisting of sweetening agents , flavoring agents , coloring agents and preserving agents in order to provide pharmaceutically elegant and palatable preparations . tablets contain the active ingredient ( s ) in admixture with non - toxic pharmaceutically acceptable excipients , such as inert diluents , granulating , disintegrating and lubricating agents , which are suitable for the manufacture of tablets . the tablets may be uncoated or they may be coated by known techniques to delay disintegration and absorption in the gastrointestinal tract and thereby provide a sustained action over a longer period . formulations for oral use may also be presented as hard gelatin capsules wherein the active ingredient is mixed with an inert solid diluent , or as soft gelatin capsules wherein the active ingredients is mixed with water or an oil medium . aqueous suspensions contain the active material in admixture with excipients suitable for the manufacture of aqueous suspensions , such as e . g ., suspending agents , dispersing or wetting agents , preservatives , coloring agents , flavoring agents , and sweetening agents . dispersible powders and granules suitable for preparation of an aqueous suspension by the addition of water provide the active ingredient ( s ) in admixture with a dispersing or wetting agent , suspending agent and one or more preservatives . additional excipients , for example sweetening , flavoring and coloring agents , may also be present . pharmaceutically acceptable carrier preparations for parenteral administration include sterile , aqueous or non - aqueous solutions , suspensions , and emulsions . examples of non - aqueous solvents are propylene glycol , polyethylene glycol , vegetable oils such as olive oil , and injectable organic esters such as ethyl oleate . aqueous carriers include water , alcoholic / aqueous solutions , emulsions or suspensions , including saline and buffered media . parenteral vehicles include sodium chloride solution , ringer &# 39 ; s dextrose , dextrose and sodium chloride , lactated ringer &# 39 ; s , or fixed oils . the active therapeutic ingredient may be mixed with excipients that are pharmaceutically acceptable and are compatible with the active ingredient . suitable excipients include water , saline , dextrose , glycerol and ethanol , or combinations thereof . intravenous vehicles include fluid and nutrient replenishers , electrolyte replenishers , such as those based on ringer &# 39 ; s dextrose , and the like . preservatives and other additives may also be present such as , for example , antimicrobials , anti - oxidants , chelating agents , inert gases , and the like . administration of the extract enriched with one or more protease inhibitors of the present invention can also be used for treating or regulating appetite , food intake , and body weight in a mammalian subject . although the present invention is further described in the examples below , the scope of the present invention is not limited to that described in these examples . one kg of potato tubers was extracted with 400 ml of the extractant buffer ( sodium chloride : acetic acid : water , 1 : 1 : 9 , w : v : v ) using a handheld commercial blender for 5 minutes . the resulting mixture was centrifuged at 13 , 000 g for 10 minutes and filtered through whatman filter paper . the resulting liquid ( 450 ml ) was transferred to an erlenmeyer flask and heated to 70 ° c . on a hot plate . the solution was then cooled to approximately 30 ° c . and centrifuged at 13 , 000 g for 10 minutes to pellet the visible precipitate of unwanted denatured proteins . the clarified potato extract ( 400 ml ) was transferred to an erlenmeyer flask and 104 g of sodium chloride was slowly added to the solution while stirring . the solution was kept stirring for another hour before it was centrifuged at 13 , 000 g for 10 minutes to pellet the visible precipitate , designated as the wet ppi fraction . at the next step , the wet ppi fraction was dissolved in 50 ml of water and loaded onto a gel filtration column ( a total bed volume of 150 ml ) packed with bio - gel p - 6 dg matrix ( bio - rad , hercules , calif .). then the ppi fraction was eluted with 50 mm ammonium bicarbonate . the first 3 fractions ( 20 ml each ) were discarded . the next 6 fractions ( 20 ml each ) were pooled and lyophilized . a 50 ul sample from each selected fraction was analyzed on a 15 % polyacrylamide gel and proteinase inhibitory activity was visualized using a slightly modified method of chavan and hejgaard ( 1981 ). the ppi fraction proteins were solubilized in water and subjected to nondenaturing gel electrophoresis to identify areas of proteinase inhibition in the gel . the gel after electrophoresis was treated with trypsin or chymotrypsin and subsequently developed in the presence of n - acetyl - phenylalanine - naphthylester plus the dye o - dianisidine tetrazotized for 10 minutes at 37 ° c . the gel ( 10 cm by 8 cm ) shows two major regions of inhibitory activity and several minor regions corresponding to approximately 5 - 40 kda molecular weight proteins . the most prominent areas of trypsin inhibitory activity were located at the region of 20 to 25 kda ( 0 . 64 cm 2 ) and 40 kda ( 0 . 41 cm 2 ), while a weaker area of inhibitory activity associated with a 5 - 15 kda region on the gel ( table 1 ). a similar result was obtained when proteins from the ppi fraction were separated on a denatured sds - page gel electrophoresis and stained with coomassie blue dye to reveal all proteins present in the final fraction . the proteins were solubilized in water and subjected to denaturing sds - gel electrophoresis to identify areas of proteinase inhibition in the gel . the gel after electrophoresis was treated with trypsin and subsequently developed in the presence of n - acetyl - phenylalanine - naphthylester plus the dye o - dianisidine tetrazotized for 10 minutes at 37 ° c . the same gel was subsequently stained with coomassie blue dye to reveal all proteins in the sample . six major bands observed under these conditions were excised from the gel and subject to n - terminal sequencing for identification of the proteins present in the potato protein extract ( table 2 ). the complete identification of group 4 protein could not be provided due to signal interference , most probably resulting from the fact that this particular band has not been purified to homogeneity . two proteins co - located with the areas of major serine protease inhibitory activity were successfully confirmed by maldi - tof analysis as potato proteinase inhibitor i and potato proteinase inhibitor ii . in order to confirm the reduction of food intake upon the consumption of the proteins from the ppi fraction of potato , conducted a set of animal feeding studies were conducted . all studies performed so far utilized a thoroughly purified proteinase inhibitor ii as a test article , largely because of the previous claims that other proteins in the test article will have no beneficial affect on the activity of that article , or will have a detrimental effect ( ausich et al ., 2003 ). for example , u . s . pat . no . 6 , 686 , 456 deals specifically with elimination of kunitz family , bowman - birk proteinase and carboxypeptidase inhibitors from other potato proteinase inhibitors ( ausich et al ., 2004 ). by using salting out as the last step of extraction procedure , the method of the present invention recovers all heat stable potato proteins , therefore enriching the ppi fraction with various proteins in addition to proteinase inhibitor ii . in study 1 , male wistar rats ( n = 24 , age = 8 weeks , mean body weight = 250 g ) were obtained from charles river laboratories ( st . constant , canada ). the rats were housed individually in the wire cages and were maintained in an air - conditioned environment at 23 ± 2 ° c . with a 12 h light - dark cycle ( lights on at 2 am ). the rats were fed ain - 93 standard diet and tap water ad libidum , and were adapted to 6 h of food deprivation that began at 8 am . all animals were weighed daily , and food consumed by each animal was determined by differential weighing . on days 3 - 6 after arrival all animals were adapted to gavage with water . experiments began on day 7 when it was determined that the process of gavaging did not significantly affect the daily food uptake . animals were randomly allocated in 2 groups . each group received either a control treatment ( 2 ml of water ) or 100 mg / kg dose of ppi fraction dissolved in 2 ml of water . all treatments were given prior to access to food at 2 pm , which is also the beginning of the night cycle . food consumption was measured to the nearest 0 . 1 g , at 1 h , 2 h , and 24 h ( daily intake ) after the treatment ( table 3 ). higher levels of circulating cck , induced by the proteins from ppi fraction , are a likely cause for the reduced food consumption . it is well established that cck levels gradually increase 20 - 30 minutes after meal initiation and then gradually fall for the next 2 to 3 hours . the animals in the treatment group showed reduced food intake , by almost 40 %, during the first 2 hours after they were presented with a meal . this observation is strongly suggestive of a satiety effect mediated by cck . in study 2 , animals were randomly allocated in 2 groups . each group received either a control treatment ( 2 ml of water ) or 100 mg / kg dose of ppi fraction dissolved in 2 ml of water for 10 consecutive days . all treatments were given prior to access to food at 2 pm , which is also the beginning of the night cycle . food consumption and body weight were recorded daily prior to the 2 pm treatment ( table 4 ). previously ( peikin , 1986 ) it was found that the administration of 100 mg / kg of purified trypsin inhibitor for 7 days decreased daily food intake in rats on average by 2 . 4 % ( obese animals ) and by 2 % ( lean animals ). the above data demonstrates that when applied orally , proteins from the ppi fraction reduce the animal body weight gain by up to 11 % during the 10 - day study . the reduction can be partially explained by a 6 % decrease in energy ( food ) intake , indicating that ppi , a complex mixture of thermostable inhibitors from potato , is more effective in regulating food intake and body weight than the purified trypsin inhibitor alone . although our finding build on the previous studies in different animal models that show that orally administered proteinase inhibitors interfere with a typical satiation response , they also suggest that there exists yet unknown interaction and / or activity within the proteins of ppi fraction that is responsible for additional reduction in weight gain . it is to be understood that the above - described embodiments are illustrative of only a few of the many possible specific embodiments , which can represent applications of the principles of the invention . numerous and varied other arrangements can be readily devised in accordance with these principles by those skilled in the art without departing from the spirit and scope of the invention .
the present invention relates to a method for manufacturing a potato protein extract enriched with one or more protease inhibitors , such as potato proteinase inhibitor ii , potato proteinase inhibitor i , potato cysteine protease inhibitor , and potato carboxypeptidase inhibitor , that offer a significant therapeutic benefit in controlling appetite , food intake , and body weight in mammals . in particular , the present invention relates to a method of obtaining at least one proteinase protein inhibitor from a plant material comprising the steps of extracting plant proteins from the plant material using an aqueous solvent ; heating the extract to denature the plant proteins ; cooling the extract to precipitate the denatured plant proteins ; performing a separation process on the cooled extract to remove the denatured plant proteins ; and salting - out the remaining fraction of the plant proteinase inhibitors designated as ppi fraction , and desalting the ppi fraction .