Patent Abstract:
presystemic metabolism in intestine of bioactives such as phenylephrine is avoided by administering a subject the bioactive in combination with one or more inhibitors of sulfation . this can also be enhanced be co - administering inhibitors of monoamine oxidases aka , maos , and uridine diphosphate glucoronysl transferases , aka ugts . preferably the inhibitors are gras compounds . the one or more inhibitor compounds inhibit the enzymes responsible for rapid presystemic metabolism , thus allowing the bioactives to be more readily absorbed intact into the circulatory system .

Detailed Description:
sult1a3 is a major isoform highly expressed in the intestine , but poorly expressed ( or undetectable ) in the liver . ( riches et al ., 2009 ) furthermore , the activity of human gastrointestinal sults has been characterized , and the dopamine sulfation activity ( which includes sult1a3 and 1a1 ) was much higher in the small intestine than the stomach or colon ; it was also three - fold higher than the liver . ( chen et al ., 2003 ) these data have been considered and integrated into pharmacokinetic models , which assert that intestinal sulfation ( particularly mediated by sult1a3 ) is the major determinant of pre - systemic metabolism of terbutaline and salbutamol ( albuterol ). ( mizuma et al ., 2005 ; mizuma , 2008 ) additionally , sult1a1 is expressed in both the small intestine and the liver , although its expression and activity are higher in the liver , and it exhibits a more general substrate selectivity toward phenols . ( pacifici and coughtrie , 2005 ) furthermore , sult1b1 is the most highly expressed isoform in the human intestine , and is capable of sulfating thyroid hormones as well as other prototypical sult substrates including 1 - naphthol and p - nitrophenol ; beyond this , its substrate selectivity is poorly understood . ( riches et al ., 2009 ) sult2a1 is also expressed in the human intestine and sulfates phenols . ( riches et al ., 2009 ) other sults are expressed at low levels in the intestine and / or do not accept phenols / monoamines as substrates . ( pacifici and coughtrie , 2005 ; riches et al ., 2009 ) from the data discussed above , the inventors of the present invention infer that sults ( including isoforms 1a1 , 1b1 , 2a1 , and especially 1a3 ) play an important role in the intestinal presystemic metabolism of phenylephrine , and may play an important role in the intestinal presystemic metabolism of a number of other bioactives . the approach for increasing the bioavailability of phenylephrine ( or other bioactive ) described herein operates on the premise that intestinal sult activity is the major determinant of presystemic metabolism of phenylephrine , and that inhibiting intestinal sult results in a significant increase in oral bioavailability of phenylephrine ( or other bioactives , e . g ., 2 - methoxyestrodiol , resveratrol , etc .). to increase bioavailability of a bioactive , a sufficient quantity of one or more sult inhibitors should be combined with the bioactive ( e . g ., pe ), so that the when the combination is taken orally , a greater amount of the pe remains intact for absorption into the circulatory system than if the sult inhibitors were not included . an oral dose of pe is substantially glucuronidated to form phenylephrine - 3 - o - glucuronide ( pe 3g ). ( hengstmann and goronzy , 1982 ) as with the other metabolic pathways , it is not known which isoform of uridine diphosphate glucuronosyltransferase ( ugt ) is most responsible for the glucuronidation of pe in either the intestine or the liver . however , since ugt1a1 , 1a6 , and 1a9 glucuronidate phenols , serotonin , and propofol ( respectively ), ( court , 2005 ) their activity toward phenylephrine may be inferred . inhibition of intestinal and / or hepatic ugts may help to improve the oral bioavailability of phenylephrine , and this approach may also be effective with other bioactives . in some applications , combining one or more inhibitors of sults with one or more inhibitors of ugts may be advantageous for increasing the bioavailability of bioactives . to increase bioavailability of a bioactive , a sufficient quantity of one or more sult inhibitors and one or more ugt inhibitors should be combined with the bioactive ( e . g ., pe ), so that the when the combination is taken orally , a greater amount of the pe remains intact for absorption into the circulatory system than if the sult inhibitors and / or ugt inhibitors were not included . in addition , monoamine oxidase isoforms a and b ( mao - a and mao - b ) are implicated in the oxidative deamination of phenylephrine . ( kanfer et al ., 1993 ) as a result , phenylephrine is contraindicated in patients taking monoamine oxidase inhibitors , including selegiline , pargyline , and clorgyline for various psychiatric and neurological conditions . ( lexi - comp online ) it is not known whether mao - a or mao - b plays a more important role in phenylephrine metabolism . however , upon intravenous pe dosing , the metabolism of pe occurs mainly through oxidative deamination to form 3 - hydroxymandelic acid ( 3hma ), ( hengstmann and goronzy , 1982 ) suggesting the liver &# 39 ; s role in this pathway . as a result , inhibition of mao enzymes in the intestine alone may not significantly improve the oral bioavailability of phenylephrine ( or other bioactives ). furthermore , inhibition of mao in the intestine and the liver should be avoided to minimize the possibility of adverse effects of dietary and biogenic amines on the nervous system . therefore , in an embodiment of the inventive strategy set forth herein avoids compounds with mao inhibition . however , in some applications , combining one or more inhibitors of sults with one or more inhibitors of maos may be advantageous for increasing the bioavailability of bioactives . to increase bioavailability of a bioactive , a sufficient quantity of one or more sult inhibitors and one or more mao inhibitors should be combined with the bioactive ( e . g ., pe ), so that the when the combination is taken orally , a greater amount of the pe remains intact for absorption into the circulatory system than if the sult inhibitors and / or mao inhibitors were not included . interpreting the data published by hengstmann , the mass balance of total radioactivity excreted into urine following an oral dose was 92 % of what was recovered following an intravenous dose , so that phenylephrine would therefore be considered a “ high permeability ” compound . ( hengstmann and goronzy , 1982 ; amidon et al ., 1995 ) combining this with its high aqueous solubility , phenylephrine would be classified as a biopharmaceutical classification system ( bcs ) class 1 compound . ( amidon et al ., 1995 ) as a bcs class 1 compound , pe disposition is expected mainly to be due to metabolism , and formulation changes which do not affect dissolution are not expected to change bioavailability . ( amidon et al ., 1995 ; wu and benet , 2005 ) therefore , to improve the oral bioavailability of pe , a metabolism - targeted approach would be most useful . as a result , a premise of the inventive approach to improve pe ( or other bioactive ) bioavailability described herein is to escape the intestinal presystemic metabolism . an aspect of the strategy selectively inhibits the enzymes in the gut metabolizing pe , without affecting their activity in the liver . in such a way , oral bioavailability of pe would be increased , while adverse drug interactions or systemic toxicity would be avoided . preferred inhibitors would have similar solubility compared to pe , and would not exhibit toxicities of their own . furthermore , they would not inhibit the systemic metabolism of neurotransmitters ( dopamine , norepinephrine , serotonin ) so that adverse effects on the central nervous system and the cardiovascular system could be avoided . compounds on the fda “ generally recognized as safe ” ( gras ) list , as well as certain food additives (“ everything added to food in the united states ,” eafus ) and dietary supplements ( ds ), would be likely to be safe , and facilitate regulatory approval . the inhibitors which can be used in the practice of the invention are wide ranging . tables 1 and 2 show results with a number of different compounds which can function as inhibitors of sult , mao , cyp , comt or ugt enzymes , or which otherwise may be used to increase the bioavailability of the exemplary bioactive phenylephrine . table 1 shows the effect of combinations of phenolic compounds for inhibiting pe metabolism as indicated by a decrease in pe disappearance , and table 2 shows the same effect as indicated by the loss of pe sulfate formation . in tables 1 and 2 , human ls180 intestinal cells were used for screening the inhibition of pe metabolism . for the experiment which produced the results in table 1 , the concentration of pe was 50m ; the concentration of vitamin c ( where present ) was 1 mm ; the total concentration of other inhibitors was 100 μm . cells were incubated at 37 ° c . for 14 to 17 . 5 hours , as indicated . the ls180 model provides an inexpensive method to imitate the human intestine , with regards to pe metabolism . unlike animal models or recombinant enzymes , this system has the advantages of being of human origin ( thus avoiding species differences ) and including some consideration of the ability of the inhibitors to cross the cell membranes and reach the enzymes . for the ls180 experiments , ls180 cells are seeded at the concentration of 1 . 9 × 10 5 cells / ml in 12 - well plate . cells are incubated with 0 . 5 ml dmem containing 1 % non - essential amino acid ( ph 7 . 4 ) with phenylephrine ( 50 μm )/ inhibitor ( 100 μm ) ( except ascorbic acid : 1000 μm ) for 14 hr to 17 . 5 hr at 37 ° c . with 5 % co 2 . after incubation , medium is removed and stored at − 80 ° c . until analysis . the metabolic reactions are quenched by placing 12 - well plate on ice and quickly rinsing each well . the cell extraction of metabolites is carried out with 1 ml 2 % acetic acid solution in methanol . cells are scraped and collected in centrifuge tubes . the suspension is mixed for 2 - 3 min and centrifuged at 18 , 000 rcf for 5 min . supernatants ( 800 μl ) are collected . after scraping , each well is washed twice as above . the washing solution is collected with the supernatant and dried under reduced pressure . the residue is re - suspended in 35 μl water and analyzed by hplc . all the samples are analyzed for pe by hplc with a phenyl column ( 150 × 3 . 2 mm , 5 μm , 55 ° c .) at the flow rate of 0 . 75 ml ( 20 % methanol and 80 % ( aqueous 1 % acetic acid )) and detected by fluorescence ( excitation 270 nm , emission 305 nm ). the data are processed with one - way anova followed by dunnett &# 39 ; s post test ; * indicates p & lt ; 0 . 05 . these results in tables 1 and 2 demonstrate the extent to which exemplary combinations of inhibitors inhibit the metabolism of phenylephrine ( pe ) in the ls180 intestinal cell culture model . note that some combination treatments were more effective than single agent treatments . while vanillin and eugenol failed to inhibit pe metabolism alone , in combination together or with other agents they significantly and synergistically inhibited it . curcumin and resveratrol were more effective in combination ( s ). in connection with the data above , fig1 illustrates an exemplary synthesis route for phenylephrine 3 - o - sulfate . phenylephrine 3 - o - sulfate was dissolved in 2 molar equivalents of trifluoroacetic anhydride and incubated at room temperature for 15 minutes to protect the alkyl hydroxyl and the secondary amine . the product was purified by silica gel chromatography . it was then dissolved in pyridine with 3 - 4 molar equivalents of pyridine - sulfur trioxide complex with heat and stirring . pyridine was evaporated , followed by hydrolysis in aqueous potassium bicarbonate at room temperature overnight , and purified by hilic - amide chromatography . lc - ms / ms ( esi −) reveals a 246 & gt ; 166 mass transition indicating the loss of so3 from the phenol . this synthesis enables the detection of the main metabolic product of the sult enzyme activity on phenylephrine , as shown in table 2 . in addition to the compounds and combinations of compounds indicated to have inhibitory capacity , and thus , the capacity to increase the bioavailability of pe ( as well as other bioactives ), other compounds which may be employed to increase the bioavailability of orally provided bioactives may be selected from methyl paraben , ethyl paraben , propyl paraben , butyl paraben , (−)- homoeriodictyol ; 2 , 6 - dimethoxyphenol ; 2 - isopropylphenol ; 2 - methoxy - 4 - methylphenol ; 2 - methoxy - 4 - propylphenol ; 4 -( 1 , 1 - dimethylethyl ) phenol ; 4 - allylphenol ; 4 - ethylguaiacol ; 4 - ethylphenol ; anisyl alcohol ; butylated hydroxyanisole ; butylated hydroxytoluene ; carvacrol ; carveol ; dimethoxybenzene ; divanillin ; essential oils + extracts ( e . g ., clove , cinnamon , nutmeg , rosemary , citrus , vanilla , ginger , guaiac , turmeric , grape seed , black pepper , etc . ); ethyl p - anisate ; eugenyl acetate ; eugenyl formate ; isoeugenol ( acetate , formate , or benzoate ); l - tyrosine ; methyl anisate ; methylphenyl ether ; methylphenyl sulfide ; o -( ethoxymethyl ) phenol ; o - cresol ; o - propylphenol ; resorcinol ; salicylates ( amyl , benzyl , butyl , ethyl , methyl , etc . ); thymol ; trans - anethole ; vanillin propylene glycol acetal ; vanillyl acetate ; vanillyl alcohol ; vanillyl ethyl ether ; vanillylidene acetone ; veratraldelhyde ; and xylenols ( 2 , 6 -; 2 , 5 -; 3 , 4 -). other herbal / natural compounds not on gras / eafus list which may be used to increase the bioavailability of orally provided bioactives include hesperetin ; eriodictyonone ; 5 , 3 ′- dihydroxy - 7 , 4 ′- dimethoxyflavanone ; isorhamnetol ; tamarixetin ; syringetin ; 3 ′, 7 - dimethylquercetin ; and methylated and / or dehydroxylated analogs of quercetin . other flavonoids which may be used include but are not limited to flavanols ( such as catechin , gallocatechin , epicatechin , catechin gallate , gallocatechin gallate , epigallocatechin , epicatechin gallate , epigallocatechin gallate , leucoanthocyanidin , and proanthocyanidins ), flavones ( such as luteolin , apigenin , tangeretin ), flavonols ( such as quercetin , kaempferol , myricetin , fisetin , isorhamnetin , pachypodol , rhamnazin ), flavanones ( such as hesperetin , hesperidin , eriodictyol , homoeriodictyol ), flavanonols ( such as taxifolin , dihydroquercetin , dihydrokaempferol ), anthocyanidins ( such as anthocyanidin , cyanidin , delphidin , malvidin , pelargonidin , peonidin , petunidin ), isoflavones ( such as genistein , daidzein , glycitein ), isoflavanes ( such as equol , lonchocarpane , laxiflorane ), and neoflavonoids ( such as dalbergin , nivetin , coutareagenin , dalbergichromene ). glycosides of the flavanols , flavonol , flavones , flavanones , flavanonols , anthocyanidins , isoflavones , isoflavanes , and neoflavonoids may also be used . flavonolignans ( such as silybin , silybinin a , silybin b , silydianin , silychristin , isosilychristin , isosilybin a , isosilybin b , silibinin , silychristin , silydianin , dehydrosilybin , deoxysilycistin , deoxysilydianin , silandrin , silybinome , silyhermin and neosilyhermin , silyamandin , hydnocarpin , scutellaprostin a , b , c , d , e and f ; hydnowightin , palstatin , salcolin a and salcolin b , rhodiolin ) and their glycosides may also be used in the practice of the invention . lignans ( pinoresinol , steganacin , enterodiol , enterolactone , lariciresinol , secoisolariciresinol , matairesinol , hydroxymatairesinol , syringaresinol and sesamin ) and their glycosides would be included . xanthones ( alpha - mangostin , beta - mangostin , gamma - mangostin , garcinone , garcinone a , garcinone c , garcinone d , mangostanol , gartanin ) and their glycosides may be used in the practice of the invention . miscellaneous natural phenolic compounds may also be included such as hydroxy - methoxy - coumarins , hydroxy - chalcones , biochanin a , prunetin , kavalactones ( 11 - hydroxyyangonin ; 11 - methoxy - 12 - hydroxydehydrokavain ; 5 - hydroxykavain ), ellagic acid , rosmarinic acid , emodin , and amentoflavone . furthermore , suitable inhibitory compounds for use in the practice of the invention can be readily identified using enzymatic activity assays . exemplary assays are set forth below : selected recombinant sult isoforms ( including 1a1 , 1a3 , 1b1 , 2a1 ) are available commercially from a variety of sources including xenotech . appropriate control substrates should be used ; for example , 4 - methylumbelliferone for sult1a1 and 1b1 ; 1 - naphthol for sult1a3 ; estradiol for sult2a1 . ( pacifici and coughtrie , 2005 ) assays should be performed according to the manufacturer &# 39 ; s instructions ( cypex / xenotech llc ). briefly , substrates should be incubated at 37 ° c . in the presence or absence of 3 ′- phosphoadenosine 5 ′- phosphosulfate ( paps ; 20 μm ) in 50 mm potassium phosphate buffer ( ph 7 . 4 ) containing 5 mm magnesium chloride and 10 mm dithiothreitol . initial substrate concentration should be 2 μm , with a protein concentration of 2 . 5 μg / ml , incubating for 5 - 60 minutes . reactions should be stopped with acetonitrile , and analyzed by reversed - phase hplc to determine disappearance of the control substrate ( and / or formation of the metabolites ), and pe ( or other bioactive ) and / or their metabolites should be analyzed . selected recombinant ugt isoforms ( including 1a1 , 1a6 , 1a9 ) are commercially available from a variety of sources including bd biosciences . appropriate control substrates should be used ; for example , estradiol , 1 - naphthol , and propofol should be used as control substrates for ugt1a1 , 1a6 , and 1a9 , respectively . ( court , 2005 ) determinations should be performed in tris - hcl buffer ( 50 mm ; ph 7 . 5 ) containing magnesium chloride 8 mm , alamethicin 25 μg / ml , incubated at 37 ° c . in the presence or absence of 2 mm uridine 5 ′- diphospho - glucuronic acid ( udpga ). initial substrate concentration should be 1 μm , with a protein concentration of 200 μg / ml , incubating for 5 - 60 minutes . recombinant mao isoforms ( a and b ) are commercially available from a variety of sources including bd biosciences . appropriate control substrates should be used ; for example , kynuramine is a substrate of both isoforms forming a fluorescent product by oxidative deamination . ( herraiz and chaparro , 2006 ) determinations should be performed in 100 mm potassium phosphate buffer ( ph 7 . 4 ), incubated at 37 ° c . the initial substrate concentrations should be 1 μm , with a protein concentration of 50 μg / ml , incubating for 5 - 60 minutes . while the data are particularly compelling in terms of showing that certain inhibitory compounds or combinations of compounds can prevent the metabolism of phenylephrine , the invention may be practiced with a variety of other bioactives including the following : albuterol , raloxifene , estradiol , ethinyl estradiol , terbutaline , etilephrine , synephrine , octopamine , resveratrol , pterostilbene , magnolol , mangiferin , puerarin , resveratrol , salvianolic acid a , rasketone ( a . k . a . “ raspberry ketone ”), tyrosol , honokiol , marsupsin , irigenin , caffeic acid phenethyl ester ( phenylethyl caffeate ; “ cape ”), and nimbidiol . clinically , the inhibitors utilized in the practice of the invention are preferably acceptable to regulatory bodies ( such as the fda ) and without adverse effects . for example , the acceptable daily intake of eugenol , ethyl vanillin , and vanillin are 2 . 5 , 3 . 0 , and 10 mg / kg / day , respectively ( fenaroli , 2010 ). as another example , pterostilbene is fda approved as a gras compound in dosages of 30 mg / kg / day . quercetin is a gras substance which is also marketed as a dietary supplement in dosages reaching 500 mg / day , while resveratrol and curcumin as dietary supplements are used in doses of 250 mg or 500 mg / day , respectively . propylparaben is fda - approved as an antioxidant / preservative food additive amounting to 0 . 1 % w / w food fat content , thus individual dosages in excess of 10 mg are expected to be permissible . doses of each inhibitor is expected to be such that when dissolved in gi fluid ( 250 ml ) concentration will be between 10 - 3000 μm : minimum dose = 2 . 5 μmol ( 0 . 25 - 0 . 75 mg ); maximum dose = 750 μmol ( 75 - 225 mg ), assuming approximate molecular weights of inhibitors in the range of 100 - 300 daltons . bioactive ingredients would be dosed ranging from 0 . 5 to 200 mg , depending upon the compound and the therapeutic application . many natural phenolic compounds have very low oral bioavailability , thus they often fail to result in clinical benefits . this technology would enable the biological activities of many natural phenolic compounds to be realized by inhibiting their presystemic metabolism thereby improving their oral bioavailability . examples of clinical utilities would include diabetes ( especially pre - diabetes and type 2 diabetes ), heart disease ( including hyperlipidemia ), liver disease ( including cholestasis and hepatoprotection ), obesity , metabolic syndrome , various cancers , inflammatory diseases ( including arthritis ), and anti - aging ( antioxidant ) activities . in vitro inhibition of phenylephrine ( pe ) sulfation by phenolic dietary compounds this in vitro study aimed to investigate the feasibility of inhibiting the pre - systemic sulfation of pe . phenolic compounds were selected from fda &# 39 ; s “ gras ” list , approved food additives , or dietary supplements . ls180 cells were used as a model to test the effect of these phenolic compounds on the pre - systemic sulfation of pe . the cells were incubated in 0 . 5 ml medium with pe ( 50 μm )± inhibitor ( 100 μm ) overnight . extracellular buffer was collected and cells were extracted with methanol . pe was determined by reversed - phase hplc with fluorescence detection . the formation of pe - sulfate was analyzed by lc - ms / ms . results ( n = 3 per group ) were analyzed by one - way anova with dunnett &# 39 ; s post - test ( p & lt ; 0 . 05 ; prism 5 ). the extent of disappearance of pe ( control = 503 ± 127 pmol / hr ) was significantly ( p & lt ; 0 . 05 ) decreased to the following ( mean ± sd , as % of control ): curcumin 24 ± 24 %, guaiacol 51 ± 14 %, isoeugenol 74 ± 8 %, pterostilbene 71 ± 7 %, resveratrol 14 ± 48 %, zingerone 52 ± 25 %, and the combinations eugenol + propylparaben 43 ± 15 %, vanillin + propylparaben 37 ± 19 %, eugenol + propylparaben + vanillin + ascorbic acid 31 ± 19 %, eugenol + vanillin 58 ± 36 %, and pterostilbene + zingerone 37 ± 12 %. the combinations of curcumin + resveratrol and curcumin + pterostilbene + resveratrol + zingerone almost completely inhibited pe disappearance . correspondingly , pe - sulfate formation was inhibited by guaiacol to 33 ± 7 % ( control = 100 %; 6650 ± 260 μv * s ) and by pterostilbene + zingerone to 28 ± 4 %. the combinations of curcumin + resveratrol and curcumin + pterostilbene + resveratrol + zingerone inhibited ≧ 99 % of pe - sulfate formation . however , when propyl gallate , vanillin , or eugenol was used alone , they had no significant effect on pe disappearance , suggesting synergy when vanillin or eugenol was used with other compounds . several compounds and combinations including resveratrol inhibit the pre - systemic sulfation of pe and can improve its oral bioavailability . resveratrol ( res ; 25 μm ) was incubated with ls180 cells for 4 hours ( as described in example 1 ) in the absence or presence of the inhibitors ( 100 μm ) listed below . the compounds marked with asterisks indicate a significant inhibition of resveratrol metabolism ( disappearance ) compared to controls in the absence of the inhibitors . methylparaben and ethyl vanillin showed the greatest extent of inhibition of resveratrol metabolism , while cinnamic acid , piperine , eugenol , vanillin , propylgallate , and propylparaben also showed significant inhibition . 2 - methoxyestradiol ( 2 - me ; 10 μm ) was incubated with ls180 cells for 4 hours ( as described above ) in the absence or presence of the inhibitors ( 100 μm ) listed below . the compounds marked with asterisks indicate a significant inhibition of 2 - methoxyestradiol metabolism ( disappearance ) compared to controls in the absence of the inhibitors . significant inhibition of 2me metabolism was observed with eugenol , vanillin , propyl gallate , and propylparaben . compounds were incubated with ls180 cells as described above in the absence or presence of inhibitor treatment combinations a or b or resveratrol . combination a comprises quercetin 50 μm , ethyl vanillin 25 μm , isoeugenol 25 μm , and propylparaben 25 μm ; combination b comprises 25 μm each of resveratrol , curcumin , zingerone , and pterostilbene ; the 3rd treatment is resveratrol 100 μm . the compounds , their concentrations , and incubation times were 4 - methylumbelliferone ( 1 μm ; 1 . 5 hrs . ; fig2 a ), 1 - naphthol ( 1 μm , 0 . 5 hrs ; fig2 b ), raspberry ketone ( 2 . 5 μm , 15 hrs . ; fig2 c ), pinoresinol ( 1 μm , 1 . 5 hrs . ; fig2 d ), magnolol ( 1 μm , 1 . 5 hrs . ; fig2 e ), and α - mangostin ( 1 μm , 1 . 5 hrs . ; fig2 f ). to control for any effects of the inhibitors on the stability of the compounds , solutions lacking ls180 cells were incubated under the same conditions and used to correct for the expected concentrations of the compounds in the absence of metabolism . samples were analyzed by reversed phase hplc with ultraviolet and / or fluorescence detection , results were compared by one - way anova with dunnett &# 39 ; s post test . fig2 a - 2f show that ls180 cells were able to metabolize & gt ; 50 % of the compounds in the absence of any inhibitor treatment ( controls ). the data show that combination a was the most effective treatment for inhibiting metabolism of 4 - methylumbelliferone , 1 - naphthol , pinoresinol , magnolol , and α - mangostin , while combination b was the most effective for inhibiting metabolism of raspberry ketone . compounds such as raspberry ketone , pinoresinol , magnolol , and α - mangostin have preclinical biological activities which would be useful in the treatment or prevention of diseases such as hyperlipidemia , diabetes , obesity , cancer , and inflammation . however , these compounds also have very low oral bioavailability due to presystemic metabolism , which masks their clinical utility . our data show that the inhibitor combinations described herein can decrease the intestinal metabolism of selected phenolic compounds . these phenolic natural compounds , when utilized with our inhibitor combinations to improve their oral bioavailability , can be used more effectively to achieve a clinical benefit . silybin ( 20 μm ) and albuterol hemisulfate salt ( 20 μm ) were incubated for 15 hours with ls180 cells as described in example 4 , in the presence or absence of combination a . albuterol metabolism was significantly inhibited by combination a ( p & lt ; 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