ANANDAMIDE, OLEAMIDE AND OTHER SIMPLE FATTY AMIDES

Transcription

1 Anndmide, olemide nd other simple ftty mides: structure, occurrence, biology nd nlysis. ANANDAMIDE, LEAMIDE AND THER SIMPLE FATTY AMIDES STRUCTURE, CCURRENCE, BILGY AND ANALYSIS Ftty mides re produced syntheticlly in industry in lrge mounts (> 300,000 tons per nnum) for use s ingredients of detergents, lubricnts, inks nd mny other products. In nture, ftty cids re linked to the complex sphingolipids vi mide bonds. However, here we re concerned only with those simple ftty mides tht occur nturlly, some of which hve profound biologicl functions. Simple ftty cid-mino cid conjugtes (lipomino cids) re discussed on seprte web pge. 1. Anndmide nd Relted Endocnnbinoids Long-chin N-cylethnolmides re ubiquitous trce constituents of niml nd humn cells, tissues nd body fluids, with importnt phrmcologicl properties. For exmple, in rt plsm, the concentrtions of plmitoyl-, oleoyl- nd rchidonoylethnolmides were found to be 17, 8 nd 5 pmol/ml, respectively. Somewht higher concentrtions re reported in brin nd other tissues. Similr lipids hve lso been found in fish, molluscs, slime moulds, nd certin bcteri. f these, nndmide or N-rchidonoylethnolmide hs ttrcted specil interest, becuse of its mrked biologicl ctivities ( nnd mens inner bliss nd trnquility in Snskrit). Like the phrmcologiclly ctive compounds in mrijun or cnnbis (from Cnnbis stiv), it exerts its effects through binding to nd ctivting specific cnnbinoid receptors (see below). As with 2-rchidonoyl-glycerol, discussed elsewhere on this website, nndmide hs been termed n endogenous cnnbinoid or endocnnbinoid. N H H nndmide Anndmide is synthesised upon demnd from phospholipid precursors in cell membrnes in lmost ll cells nd tissues of the body in response to rise in intr-cellulr clcium levels. Although direct N-cyltion of ethnolmine is possible, the min mechnism for the biosynthesis of nndmide nd relted mides requires s first step the production of N-cylphosphtidylethnolmine (see the seprte webpge), lipid tht is normlly present in niml tissues t very low levels only, other thn during injury. Unusul trnscylse rections, rther thn hydrolysis nd re-synthesis vi CoA esters, re involved, nd the rection is C 2+ -dependent nd energy-independent. It seems tht only 1--cyl groups of cn serve s cyl donors nd tht much of the cyl trnsfer is intrmoleculr, with production of hypotheticl intermedite, 2--cyl-snglycero-3-phospho-(N-cyl)-ethnolmine (or N-cyl-lysoPE). The free sn-1 hydroxy group is then subjected to re-cyltion, presumbly by the sme trnscylse system. A second mechnism involves this trnscylse ctlysing direct trnsfer of the ftty cids of position 1 of W.W. Christie lipidlibrry.ocs.org 1

2 Anndmide, olemide nd other simple ftty mides: structure, occurrence, biology nd nlysis. phosphtidylcholine to N-cylte phosphtidylethnolmine. A surprising feture of this rection is the fct tht the rchidonic cid levels in position 1 of phospholipids re usully very low (typiclly <0.3%), other thn in testis. In neurons, there is evidence tht 1,2-dirchidonoylphosphtidylcholine, produced by specific cyltion of 2-rchidonoyl-lysophosphtidylcholine, is the key intermedite. This rection is the key to the specificity of the process, since subsequent rections re independent of the N-cyl substituent. R''C PE CR' + P NH 3 R''C PC C 2+ trnscylse CR x R''C + P N( 3 ) 3 H P C 2+ trnscylse trnscylse C 2+ NHCR' N-cyl-lysoPE H CR' R''C lysopc + P N( 3 ) 3 CR x R''C N-cyl-PE P NHCR x R''C P NHCR' N-cyl-PE The second step in the biosynthesis of nndmide nd relted mides is hydrolysis of the N-cylphosphtidylethnolmine by phosphodiesterse tht is specific for this lipid (NAPE-PLD). It hs similr function to phospholipse D, but it differs from ll others of this type in its mino cid sequence. In ddition to nndmide, phosphtidic cid is formed, nd this lso hs messenger functions. CR' R''C P NHCR x 2 N-cyl-phosphtidylethnolmine.R' H P NHCR x 2 N-cyl-1-lkenyllysophosphtidylethnolmine phosphodiesterse H NHCR x + H 2 nndmide lyso-phospholipse D W.W. Christie lipidlibrry.ocs.org 2

3 Anndmide, olemide nd other simple ftty mides: structure, occurrence, biology nd nlysis. A second pthwy hs been described tht does not use the specific phosphodiesterse. Rther it involves either single or double -decyltion of N-cyl- or N-lkenyl-phosphtidylethnolmine ctlysed by phospholipses prior to the ction of specific phospholipse Ds on the resulting lysoglycerophospho- or glycerophospho-n-rchidonoylethnolmines. Indeed, it hs been suggested tht this my be the mjor route to nndmide from plsmlogens in brin, where the intermedite glycerophospho-n-cylethnolmines hve been detected in mouse model. In rodent brin, the endogenous precursor of nndmide is minly the plsmlogen form of N-rchidonoyl phosphtidylethnolmine (N-cylplsmenylethnolmines), nd contins lkenyl groups (16:0, 18:0, 18:1) in position sn-1 nd mono- (18:1) nd polyunsturted (20:4, 22:4, 22:6) cyl groups in position sn-2 of the glycerol bckbone.. Yet nother pthwy is known in which N-cyl-phosphtidylethnolmine is gin the min precursor, but is cted upon by phospholipse C to relese phospho-nndmide, which is then de-phosphorylted to nndmide by specific phosphtse. This my be the min route when nndmide is produced in response to bcteril endotoxins. Further biosynthetic pthwys to nndmide re known to exist nd the regultion nd reltive importnce of these re obviously complex. Anndmide nd other endocnnbinoids re highly lipophilic nd hve tendency to remin in the membrne, where they cn diffuse to encounter membrne-bound enzymes nd receptors. However, they re lso ble to diffuse in to the cytoplsm, where they re trnsported by highffinity, sturble nndmide trnsporter, process tht my be fcilitted by the ftty cid mide hydrolse (see below), to ct on presynptic cnnbinoid receptors. It ppers tht cytoplsmic lipid droplets ( diposomes ) my ct s reservoir, lthough they re lso n ctive site for metbolism. In plsm, nndmide binds reversibly to serum lbumin nd is presumbly trnsported to other tissues in this form. Andmide exerts its effects t nnomolr to sub-micromolr concentrtions minly through binding to nd ctivting specific cnnbinoid receptors, especilly those designted CB1 nd CB2, both of which re membrne-bound G-proteins ( lrge nd diverse fmily of receptors with chrcteristic membrne spnning structure whose min function is to convert extrcellulr stimuli into intrcellulr signls). CB1 is found in the centrl nervous system nd in some other orgns, including the hert, uterus, testis nd smll intestine, while the CB2 receptor is found in the spleen nd other cells ssocited with immunochemicl functions, but not in brin. Thus, s with the bioctive constituents of mrijun, the endocnnbinoids produce neurobehviorl effects nd my hve importnt signlling roles in the centrl nervous system, especilly in the perception of pin, nxiety nd fer, in the regultion of body temperture nd in the control of ppetite. N-dihomo-γ-linolenoylethnolmine, N-eicos-5,8,11-trienoylethnolmine, N-eicospentenoylethnolmine nd N-docoshexenoylethnolmine re other N-cylethnolmides tht bind to the CB1 nd CB2 receptors. As in mny other membrne ssocited processes, lipid rfts nd cveole serve s importnt pltforms for regultion of the endocnnbinoid system, nd especilly in the modultion of binding nd signlling of the CB1 receptor. Anndmide hs importnt nti-inflmmtory nd nti-cncer properties both in vivo nd in vitro in niml models. It ffects the crdiovsculr system by inducing profound decreses in blood pressure nd hert rte. In ddition, it is n nbolic regultor of metbolism in tht it increses the intke of food, promotes the storge of lipid, nd decreses the expenditure of energy. It is lso involved in the regultion of body temperture, locomotion, feeding nd nxiety. Some of these effects pper to be independent of the two min receptors, nd nndmide is known to bind to number of other proteins including the peroxisome prolifertor-ctivted receptors (PPARα nd PPARγ). There re suggestions tht modultion of nndmide levels in the gut hs potentil for W.W. Christie lipidlibrry.ocs.org 3

4 Anndmide, olemide nd other simple ftty mides: structure, occurrence, biology nd nlysis. tretment of inflmmtory bowel disese nd colon cncer. Anndmide is present in the reproductive fluids of both mles nd femles nd is believed to be importnt in reproduction. Mcrophges generte nndmide in response to the presence of bcteril endotoxin, nd it is involved in the pthology of septic shock nd cirrhosis of the liver. In ddition, nndmide derived from mcrophges hs nti-inflmmtory effects both in the peripherl nd centrl nervous system. It cn induce poptosis in number of cell types. It hs been demonstrted tht nndmide (nd the other endocnnbinoid 2-rchidonoylglycerol) cn be converted by cellulr systems in vitro to ethnolmides of the prostglndins PGE 2, PGD 2 nd PGF 2α ( prostmides ) by the ction of the enzyme cyclooxygense-2 (CX-2), but interestingly not by CX-1. For cyclo-oxygention to occur, there is n essentil requirement for the hydroxyl-group of nndmide. In ddition, nndmide is substrte for the ction of lipoxygenses nd of enzymes of the cytochrome P450 fmily. NH H CX-2 H H PGE 2 -ethnolmide nndmide NH H cytochrome P450 5,6-EET-ethnolmide NH H 12-LX N H H 12-HETE-ethnolmide The biologicl importnce of these novel lipids is now being ctively explored, nd there is evidence tht CX-2 metbolites induce poptosis of cncer cells. The prostmides do not bind to either the cnnbinoid or prostnoid receptors. However, 12(S)-hydroxy-eicos-5Z,8Z,10E,14Ztetrenoyl-N-(2-hydroxy-ethyl)mine binds to both CB receptors with n ffinity similr to tht of nndmide per se. PGE 2 -ethnolmide is extremely stble in humn plsm, nd mobilizes clcium in cell preprtions in vitro t picomolr concentrtions. -Archidonoylethnolmine, i.e. with n ester insted of n mide linkge to rchidonic cid nd termed virodhmine, hs been isolted from brin tissues. It cts s full gonist for the CB2 receptor nd is prtil gonist for the CB1 receptor. It hs yet to be determined how it is synthesised, stored or degrded, but inter-conversion with nndmide cn occur. virodhmine NH 2 Ctbolism: There is currently gret interest in the potentil use of endocnnbinoids for therpeutic purposes, such s the llevition of inflmmtion, sthm nd some forms of chronic W.W. Christie lipidlibrry.ocs.org 4

5 Anndmide, olemide nd other simple ftty mides: structure, occurrence, biology nd nlysis. pin, nd s nti-tumor drugs. In vivo, the concentrtions of ll of these mides re controlled in mny niml species by single hydrolytic enzyme present in most tissues other thn skeletl muscle nd hert, i.e. ftty cid mide hydrolse ( FAAH ), which is n integrl membrne protein (primrily in the perinucler membrnes). It belongs to lrge fmily of enzymes tht shre highly conserved 130 mino cid motif termed the midse signture sequence nd is well conserved in the primry structure. However, second enzyme of this type ( FAAH-2 ) hs been found in humns nd other primtes tht is bsent in mice nd rts. The two enzymes re found in different tissues, with the second being specific to hert nd ovry, where perhps surprisingly it is locted on the surfce of cytoplsmic lipid droplets. There re believed to be ctive trnsport systems for nndmide from the plsm membrne to other tissues, lthough the detiled mechnisms re poorly understood. nce it enters cell, it is rpidly degrded. The products, rchidonic cid nd ethnolmine, my then hve further signlling functions. Becuse of their role in terminting mide signlling, mide hydrolses re the subject of intensive study nd re trgets for potentil drug therpies. For exmple, there is evidence tht by inhibiting hydrolse ctivity nd incresing the concentrtion of nndmide the growth of certin tumor cells is inhibited. Also, dministrtion of inhibitors hs beneficil effects ginst inflmmtory pin. 2. ther Long-Chin N-Acylethnolmides The biologicl effects of the other ftty cyl ethnolmide derivtives re less cler, lthough they re by fr the most bundnt components of this lipid clss. Most do not pper to interct with cnnbinoid receptors, but they my hve role in minimizing the effects of cellulr dmge. They my potentite the ctivity of endocnnbinoids by minimizing their degrdtion. For exmple, there is evidence for n dditionl endocnnbinoid signlling system tht involves N-plmitoylethnolmide nd depends on receptors other thn CB1 nd CB2. This lipid ws first identified in egg yolk more thn 50 yers go, nd its nti-inflmmtory properties were recognized immeditely. However, there hs been resurgence of interest in recent yers, during which it hs lso been shown to hve nticonvulsnt nd ntiprolifertive effects. It is believed tht the effects on inflmmtion nd inflmmtory pin re medited minly through ctions upon peroxisome prolifertor-ctivted receptor-α (PPARα), lthough other mechnisms hve been postulted. For exmple, both N-plmitoyl- nd N-oleoylethnolmides hve been show to bind to specific G- protein coupled receptors. N-Docoshexenoylethnolmide is present in brin tissue in mounts comprble to nndmide. It my hve neuroprotective effects in this form or fter conversion to oxygented metbolites. The ltter re believed to regulte leukocyte motility. N-leoylethnolmide is n endogenous regultor of food intke, nd my hve some potentil s n nti-obesity drug. It is believed to ct s locl stiety signl rther thn s blood-borne hormone. For exmple, food intke ws inhibited in rts following intrperitonel injection nd even fter orl dministrtion. N-oleoylethnolmide N H H Under norml physiologicl conditions, oleic cid from dietry ft is trnsported into enterocytes in the smll intestinl by ftty cid trnslocse, nd some is converted to oleoylethnolmide nd W.W. Christie lipidlibrry.ocs.org 5

6 Anndmide, olemide nd other simple ftty mides: structure, occurrence, biology nd nlysis. cts s sensor for ingestion of ft. The effect is highly specific, s linoleoylethnolmide hs no such ction, lthough it is produced in tissues in significnt mounts. Here lso the effects re medited by binding with high ffinity to PPARα (nd not to receptors CB1/2 so it is not n endocnnbinoid), especilly in the enterocytes in the intestinl brush border. This stimultes the vgl nerve vi the cpsicin receptor, leding to incresed lipolysis nd β-oxidtion of fts. It lso hs nto-inflmmtory nd nti-oxidnt properties. While oleoyl- nd plmitoylethnolmides do not ctivte cnnbinoid receptors directly, they cn enhnce the ctivity of nndmide by inhibiting its inctivtion by ftty cid mide hydrolse. Bsl levels of cylethnolmides re especilly high in the gut. Anndmide nd N-oleoylethnolmide re selectively decresed nd incresed in rt intestine during food deprivtion nd re-feeding through remodelling of the originl cyl donor phospholipids. However, they hve opposing effects upon lipogenesis. These products of phospholipid metbolism re thus in stte of dynmic equilibrium s prt of the norml system of redistribution of moleculr species in phospholipids. Indeed there is incresing evidence tht the blnce between the vrious N-cylethnolmides is importnt for the correct functioning of innumerble biologicl systems, with n imblnce leding to pthologicl conditions. In dipose tissue, oleoylethnolmide reduces the tricylglycerol content by stimulting lipolysis nd elevting the circulting levels of unesterified ftty cids nd glycerol. In ddition, it hs been demonstrted tht oleoylethnolmide by cting s PPAR-α gonist hs novel effect in enhncing memory consolidtion through nordrenergic ctivtion of specific regions of the brin. It my hve n influence on sleep ptterns nd the effects of stress. N-Steroylethnolmide is n immunomodultor nd it induces poptosis of gliom cells. It down-regultes the expression of liver steroyl-coa desturse-1 mrna, n norexic effect, nd lso hs mrked nti-inflmmtory properties. In some stress situtions, incresed levels of sturted nd mono-unsturted ethnolmides re produced nd in others there is selective stimultion of nndmide synthesis. N-cylethnolmides in humn reproductive fluids my help to regulte mny physiologicl nd pthologicl processes in the reproductive system. Sturted nd monoenoic N-cylethnolmides my lso function s intrcellulr messengers by ctivting specific kinses nd intercting with the signlling pthwys medited by cermide, with which it hs some structurl similrities. Some of these effects my be specific to prticulr tissues. N-oleoyl- nd N-plmitoylethnolmide re produced by the sme generl biosynthetic mechnisms in nimls s for nndmide (see bove). They re ctbolized by the ftty cid mide hydrolse similrly, lthough lysosoml enzyme tht is highly specific for N-plmitoylethnolmide hs been chrcterized (N-cylethnolmine-hydrolysing cid midse). 3. lemide cis-9,10-ctdecenmide or olemide is primry ftty cid mide. It ws first isolted from the cerebrospinl fluid of sleep-deprived cts, nd hs been chrcterized nd identified s the signlling molecule responsible for cusing sleep. For exmple, it induced physiologicl sleep when injected directly into the brin of rts. H 2 N It is n gonist for the CB1 receptor, which my be meditor for its biologicl ctivity olemide W.W. Christie lipidlibrry.ocs.org 6

7 Anndmide, olemide nd other simple ftty mides: structure, occurrence, biology nd nlysis. A rther unusul mechnism is suggested for the biosynthesis of olemide, involving the enzyme cytochrome c nd oleoyl-coa nd mmonium ions s the substrtes, with hydrogen peroxide s n essentil cofctor. In ddition to its sleep-inducing properties, olemide hs other neurologicl ctivities including regultion of memory processes, decresing body temperture nd locomotive ctivity, stimulting C 2+ relese, modultion or ctivtion of number of receptors, nd effects on the perception of pin. As with the N-cylethnolmines, the concentrtion of olemide is controlled by the specific ftty cid mide hydrolse in vivo, but it is not known how these simple molecules void hydrolysis by the innumerble proteses, lipses nd midses present in brin. Although other ftty cid primry mides in ddition to cis-9,10-octdecenomide re present nturlly in the cerebrospinl fluid of nimls, only linolemide is known to be biologiclly ctive, for exmple in incresing C 2+ flux. 4. N-Archidonoyldopmine nd ther Biologiclly Active Amides N-rchidonoyldopmine hs been detected s n endogenous component of mmmlin nervous tissue, especilly the brin, with distinctive biologicl effects. For exmple, it intercts with the sme receptor (vnilloid type 1) s cpsicin, the ctive ingredient of chili peppers, with which it hs some structurl similrity. It hs thus been N-rchidonoyldopmine termed vnilloid or endovnilloid. In ddition, it binds to the CB1 receptor nd shows cnnbimimetic effects. N H H H Biosynthesis is believed to occur minly by conjugtion of dopmine with rchidonic cid, ctlysed by ftty cid mide hydrolse (not vi the CoA ester), lthough there re suggestions tht some might be derived from rchidonoyltyrosine. The N-oleoyl nlogue hs chrcteristic biologicl properties of its own, but intercts with the sme receptors s N-rchidonoyldopmine. While the N-plmitoyl nd N-steroyl derivtives of dopmine do not interct with these receptors to significnt extent, they pper to ct together with N-rchidonoyldopmine nd nndmide to enhnce clcium mobiliztion. N-cetyldopmine is lso present in mny niml tissues. The mechnisms for biosynthesis nd ctbolism of these lipids re not fully elucidted. xidized derivtives of rchidonic cid (including hexnoic cid) nd docoshexenoic cid linked to dopmine my be involved in the pthogenesis of Prkinson s disese. N-Hexnoyl dopmine is highly cytotoxic. A number of N-cylserotonins (16:0, 18:0, 18:1 nd 20:) hve been detected in intestinl tissue from the rt nd pig, especilly in the jejunum nd ileum where they re believed to regulte intestinl function. In fct, these lipids with sturted cyl groups were first detected in the wx lyer of green coffee bens. Serotonin or 5-hydroxytryptmine per se is monomine neurotrnsmitter derived from tryptophn, nd is found minly in the gstrointestinl trct, pltelets nd the centrl nervous system of nimls, where it is populrly known s contributor to feelings of well-being. W.W. Christie lipidlibrry.ocs.org 7

8 Anndmide, olemide nd other simple ftty mides: structure, occurrence, biology nd nlysis. H NH C N-plmitoylserotonin 5. N-Acylmides in Plnts N-Acylethnolmides re lso minor but ubiquitous components of plnt tissues, nd they re especilly bundnt in desiccted seeds. The ftty cids re representtive of those in plnts with up to three double bonds, nd with 12 to 18 crbon toms. For exmple, oleoylethnolmide is present nturlly t low levels in such food products s otmel, nuts nd coco powder (up to 2 µg/g). In this instnce, the precursor N-cyl phosphtidylethnolmine is synthesised by different mechnism from tht in nimls, i.e. by direct cyltion of phosphtidylethnolmine by n N-cyl phosphtidylethnolmine synthse. N-cylethnolmides re relesed from this by the ction of two (but not ll) isoforms of phospholipse D in response to stress situtions. The biochemistry of these compounds in plnts is discussed elsewhere on this site. It ppers tht such compounds hve vriety of biologicl functions in plnts For exmple, N-linoleoylethnolmine is involved in the regultion of seed germintion, N-luroylethnolmine influences the elongtion of min nd lterl roots nd root hir formtion, seedling growth nd flower senescence, nd N-myristoylethnolmine functions in plnt defence ginst pthogen ttck nd lso inhibits stomtl closure. However, reserch is still t n erly stge in comprison to tht with nimls. In ddition, structurlly relted N-cylmides hve been identified in few fmilies of plnts nd some fungi in which the mine moiety contins propyl, isopropyl, butyl or often isobutyl moieties. The ftty cid moieties re lso distinctive, sometimes with only ten crbons. Affinin is N-isobutyl- 2E,6Z,8E-dectrienmide, for exmple. The biosynthetic mechnism is believed to be quite different from tht of the N-cylethnolmines; the mine moiety my be derived from mino cids. Importnt biologicl functions re slowly being reveled. NH ffinin 6. Anlysis The min problems in the nlysis of N-cylethnolmines nd other simple mides relte to the low levels t which they occur nturlly. There is concern tht rtefctully high results cn be obtined becuse of the physiologicl effects of smpling methods. However, sensitive methods tht utilize high-performnce liquid chromtogrphy with fluorescent detection or gs chromtogrphy-mss spectrometry with selected ion monitoring re vilble for the ctul mesurements. Liquid chromtogrphy llied to tndem mss spectrometric methods hs lso proved of vlue. W.W. Christie lipidlibrry.ocs.org 8

9 Anndmide, olemide nd other simple ftty mides: structure, occurrence, biology nd nlysis. Recommended Reding º Brown, I., Cscio, M.G., Rotondo, D., Pertwee, R.G., Heys, S.D. nd Whle, K.W.J. Cnnbinoids nd omeg-3/6 endocnnbinoids s cell deth nd nticncer modultors. Prog. Lipid Res., 52, (2013). º Coulon, C., Fure, L., Slmon, M., Wttelet, V. nd Bessoule, J.-J. N-Acylethnolmines nd relted compounds: Aspects of metbolism nd functions. Plnt Science, 184, (2012). º Driscoll, W.J., Chturvedi, S. nd Mueller, G.P. lemide synthesizing ctivity from rt kidney: identifiction s cytochrome c. J. Biol. Chem., 282, (2007). º Fonsec, B.M., Cost, M.A., Almd, M., Correi-DA-Silv, G. nd Teixeir, N.A. Endogenous cnnbinoids revisited: biochemistry perspective. Prostglndins ther Lipid Meditors, 102/103, (2013). º Kim, S.-C., Chpmn, K.D. nd Blncflor, E.B. Ftty cid mide lipid meditors in plnts. Plnt Sci., 178, (2010). º Kokotos, G. Endocnnbinoids. In: Bioctive Lipids. pp (edited by A. Nicolou nd G. Kokotos, The ily Press, Bridgwter) (2004). º Mccrrone, M., Gsperi, V., Ctni, M.V., Diep, T.A., Dinese, E., Hnsen, H.S. nd Aviglino, L. The endocnnbinoid system nd its relevnce for nutrition. Annu. Rev. Nutr., 30, (2010). º Petrosino, S., Iuvone, T. nd Di Mrzo, V. N-Plmitoyl-ethnolmine: Biochemistry nd new therpeutic opportunities. Biochimie, 92, (2010). º Pillrisetti, S., Alexnder, C.W. nd Khnn, I. Pin nd beyond: ftty cid mides nd ftty cid mide hydrolse inhibitors in crdiovsculr nd metbolic diseses. Drug Discovery Tody, 14, (2009). º Piomelli, D. More surprises lying hed. The endocnnbinoids keep us guessing. Neurophrmcology, 76, (2014). º Rouzer, C.A. nd Mrnett, L.J. Endocnnbinoid oxygention by cyclooxygenses, lipoxygenses, nd cytochromes P450: Cross-tlk between the eicosnoid nd endocnnbinoid signling pthwys. Chem. Rev., 111, (2011). º Thbuis, C., Tissot-Fvre, D., Bezelgues, J.-B., Mrtin, J.-C., Cruz-Hernndez, C., Dionisi, F. nd Destillts, F. Biologicl functions nd metbolism of oleoylethnolmide. Lipids, 43, (2008). º Ued, N., Tsuboi, K. nd Uym, T. Enzymologicl studies on the biosynthesis of N-cylethnolmines. Biochim. Biophys. Act, 1801, (2010). º Wellner, N., Diep, T.A., Jnfelt, C. nd Hnsen, H.S. N-Acyltion of phosphtidylethnolmine nd its biologicl functions in mmmls. Biochim. Biophys. Act, 1831, (2013). º Zoerner, A.A., Gutzki, F.M., Btki, S., My, M., Rkers, C., Engeli, S., Jordn, J. nd Tsiks, D. Quntifiction of endocnnbinoids in biologicl systems by chromtogrphy nd mss spectrometry: A comprehensive review from n nlyticl nd biologicl perspective. Biochim. Biophys. Act, 1811, (2011). Willim W. Christie Jmes Hutton Institute (nd Mylnefield Lipid Anlysis), Invergowrie, Dundee (DD2 5DA), Scotlnd Lst updted: Februry 18 th, 2014 W.W. Christie lipidlibrry.ocs.org 9