Configuration of polyisoprenoids affects the permeability and thermotropic properties of phospholipid/polyisoprenoid model membranes

The influence of α-cis- and α-trans-polyprenols on the structure and properties of model membranes was analyzed. The interaction of Ficaprenol-12 (α-cis-Prenol-12, α-Z-Prenol-12) and Alloprenol-12 (α-trans-Prenol-12, α-E-Prenol-12) with model membranes was compared using high performance liquid chromatography (HPLC), differential scanning calorimetry (DSC) and fluorescent methods. l-α-Phosphatidylcholine from egg yolk (EYPC) and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) as the main lipid components of unilamellar (SUVs) and multilamellar (MLVs) vesicles were used. The two-step extraction procedure (n-pentane and hexane, respectively) allowed to separately analyze the fractions of polyprenol as non-incorporated (Prenol_NonInc) and incorporated (Prenol_Inc) into liposomes. Consequently, distribution coefficients, P′, describing the equilibrium of prenol content between phospholipid (EYPC) membrane and the aqueous phase gave different log P′ for α-cis- and α-trans-Prenol-12, indicating that the configuration of the α-terminal residue significantly alters the hydrophobicity of the polyisoprenoid molecule and consequently the affinity of polyprenols for EYPC membrane. In fluorescence experiments α-trans-Pren-12 increased up to 1.7-fold the permeability of EYPC bilayer for glucose while the effect of α-cis-Pren-12 was almost negligible. Considerable changes of thermotropic behavior of DPPC membranes in the presence of both prenol isomers were observed. α-trans-Pren-12 completely abolished the pretransition while in the case of α-cis-Pren-12 it was noticeably reduced. Furthermore, for both prenol isomers, the temperature of the main phase transition (T_m) was shifted by about 1 °C to lower values and the height of the peak was significantly reduced. The DSC analysis profiles also showed a new peak at 38.7 °C, which may suggest the concomitant presence of more that one phase within the membrane.Results of these experiments and the concomitant occurrence of alloprenols and ficaprenols in plant tissues suggest that cis/trans isomerization of the α-residue of polyisoprenoid molecule might comprise a putative mechanism responsible for modulation of the permeability of cellular membranes.     

Subcellular localization and substrate specificity of dolichol kinase from rat liver

When purified subcellular fractions were prepared from rat liver and assayed for dolichol kinase activity using pig liver dolichol as a substrate, the microsomes were found to contain the highest specific activity and greater than 75% of the total actvity. With regard to substrate specificity, the microsomal enzyme showed a marked preference for saturation of the α-isoprene: dolichol-16 and -19 were 2.5-fold more active than the corresponding polyprenols. For a given class of prenol, the 16 and 19 isoprenologs exhibited similar activity, whereas the 11 isoprenolog appeared less active. The enzyme was twice as active against the naturally occurring polyprenol-16 (α-cis-isoprene) compared to synthetic α-trans-polyprenol-16. Taken together, the data indicate that the α-isoprene specificity follows the order: saturated>cis>trans. In addition, all-trans-2,3-dihydrosolanesol was not a substrate, suggesting that at least one cis isoprene residue is required.     

Transmembrane localization of cis-isomers of zeaxanthin in the host dimyristoylphosphatidylcholine bilayer membrane

The effects of the 9-cis and 13-cis isomers of zeaxanthin on the molecular organization and dynamics of dimyristoylphosphatidylcholine (DMPC) membranes were investigated using conventional and saturation recovery EPR observations of the 1-palmitoyl-2-(14-doxylstearoyl)phosphatidylcholine (14-PC) spin label. The results were compared with the effects caused by the all-trans isomer of zeaxanthin. Effects on membrane fluidity, order, hydrophobicity, and the oxygen transport parameter were monitored at the center of the fluid phase DMPC membrane. The local diffusion-solubility product of oxygen molecules (oxygen transport parameter) in the membrane center, studied by saturation-recovery EPR, decreased by 47% and 27% by including 10 mol% 13-cis and 9-cis zeaxanthin, respectively; whereas, incorporation of all-trans zeaxanthin decreased this parameter by only 11%. At a zeaxanthin-to-DMPC mole ratio of 1:9, all investigated isomers decreased the membrane fluidity and increased the alkyl chain order in the membrane center. They also increased the hydrophobicity of the membrane interior. The effects of these isomers of zeaxanthin on the membrane properties mentioned above increase as: all-trans < 9-cis ≤ 13-cis. Obtained results suggest that the investigated cis-isomers of zeaxanthin, similar to the all-trans isomer, are located in the membrane interior, adopting transmembrane orientation with the polar terminal hydroxyl groups located in the opposite leaflets of the bilayer. However, the existence of the second pool of cis-zeaxanthin molecules located in the one leaflet and anchored by the terminal hydroxyl groups in the same polar headgroup region cannot be completely ruled out.     

Proteins are polyisoprenylated in Arabidopsis thaliana

Isoprenoid lipids were found to be covalently linked to proteins of Arabidopsis thaliana. Their identity (polyprenols: Prenol-9-11 with Pren-10 dominating and dolichols: Dol-15-17 with Dol-16 dominating) was confirmed by means of HPLC/ESI-MS with application of the multiple reaction monitoring technique as well as metabolic labeling of Arabidopsis plants with [³H]mevalonate and other precursors. The occurrence of typical farnesol-, geranylgeraniol-, and phytol-modified proteins was also noted. Radioisotopic labeling allowed detection of several proteins that were covalently bound to mevalonate-derived isoprenoid alcohols. A significant portion of polyisoprenylated proteins was recovered in the cytosolic/light vesicular fraction of Arabidopsis cells upon subfractionation. Taken together our data prove that a subset of plant proteins is polyisoprenylated.     

Metabolism of 13-cis-retinoic acid: Identification of 13-cis-retinoyl-and 13-cis-4-oxoretinoyl-β-glucuronides in the bile of vitamin A-normal rats

The metabolism of 13-cis-[11-³H]retinoic acid has been examined in vitamin A-normal rats. Within 24 h after intravenous administration of the parent retinoid (15 μg/kg) to animals with biliary fistulas, 69 ± 9% of the dose was detected in the bile with 9 ± 6% being found in the urine. Analysis of the bile by reverse-phase high-pressure liquid chromatography demonstrated that the retinoic acid was being metabolized to several more polar compounds. A number of these compounds were sensitive to incubation with β-glucuronidase as evidenced by a change in their chromatographic behavior after treatment with the enzyme. Two of the metabolites have been identified as 13-cis-4-oxoretinoyl-β-glucuronide (8.1 ± 1.0% of the dose during the first 4 h after administration of the parent compound) and 13-cis-retinoyl-β-glucuronide (7.0 ± 4.4% of the dose). A comparison of the chromatographic profiles of bile from 13-cis- versus all-trans-retinoic acid-treated rats indicated a difference in their metabolism, with a greater proportion of the all-trans-retinoic acid being converted to compounds that eluted in the more polar regions of the column effluent.     

The naphthylamine palladium(II) template induced E-Z isomerism of exocyclic vinyl group in five-membered P-N chelates: detailed spectroscopic studies

The exocyclic CC bond E-Z isomerism of chelating Ph₂PC(CHPh)-CHNAr in organopalladium complexes containing orthometallated [(S)-1-(dimethylamino)ethyl]naphthalene is reported. In dilute solutions of non-coordinating CH₂Cl₂ or CHCl₃, all the original E-isomers, in which the CHPh phenyl rings are located trans to PPh₂ moieties were partly converted to their Z-isomers. The isomerism was found to be dependent on temperature, concentration and solvent. At higher temperature, the Z-isomers were transformed completely back to their original E-isomers. Removal of the chiral auxiliaries of the E-Z mixtures by concentrated HCl, gave only the dichloro complexes of the E-isomers. The E-Z isomerization processes were well established by detailed spectroscopic studies, including ³¹P NMR, ¹H NMR and 2D ¹H-¹H ROESY NMR studies. It is noteworthy that the dichloro complexes and free P-N ligands did not show such isomerization processes, indicating that the isomerization processes were triggered by the orthopalladated naphthylamine moiety.     

Metabolism of Fatty Acid Hydroperoxides by Chlorella pyrenoidosa

The green alga Chlorella pyrenoidosa was examined for its ability to metabolize 13-hydroperoxylinoleic and 13-hydroperoxylinolenic acids. The study showed that Chlorella extracts possessed hydroperoxide dehydrase and other enzymes of the jasmonic acid pathway. However, under normal laboratory conditions for culture growth, neither jasmonic acid nor metabolites of the jasmonic acid pathway were present in Chlorella. In vitro enzyme studies also revealed the presence of hydroperoxide lyase activity that cleaved 13-hydroperoxylinoleic or 13-hydroperoxylinolenic acid into two products, 13-oxo-cis-9,trans-11-tridecadienoic acid and pentane (from linoleic acid) or pentene (from linolenic acid). The lyase was heat-labile, insensitive to 50 millimolar KCN, and had an approximate molecular weight of 48,000 as estimated by gel filtration. Two other products, 13-hydroxy-cis-9,trans-11,cis-15-octadecatrienoic acid and 12, 13-trans-epoxy-9-oxo-trans-10,cis-15-octadecadienoic acid, were also observed. Because these compounds are also products of nonenzymic, Fe(II)-catalyzed hydroperoxide decomposition reactions, their presence suggested that the observed lyase activity may occur via a homolytic decomposition mechanism.     

Biotransformation of Unsaturated Long-Chain Fatty Acids by Eubacterium lentum

Eubacterium lentum (33 strains) isomerized the 12-cis double bond of C₁₈ fatty acids with cis double bonds at C-9 and C-12 into an 11-trans double bond before reduction of the 9-cis double bond. The 14-cis double bond of homo-γ-linolenic acid was isomerized by 29 strains into a 13-trans double bond. The same strains isomerized the 14-cis double bond of arachidonic acid into a 13-trans double bond and then isomerized the 8-cis double bond into a 7-trans double bond; the 13-cis double bond of 10-cis, 13-cis-nonadecadienoic acid was isomerized into a 12-trans double bond. None of these isomerization products was further reduced. Studies with resting cells showed optimal isomerization velocity at a linoleic acid concentration of 37.5 μM; higher concentrations were inhibitory. The pH optimum for isomerization was 7.5 to 8.5. The isomerase was inhibited by the sulfhydryl reagents iodoacetamide, bromoacetate, and N-ethylmaleimide and by the chelators EDTA and 1,10-phenanthroline.     

Structure and reactivity of [Ru(2,3-Medpp)2Cl2]

The structure and reactivity of the complex [Ru(2,3-Medpp)₂Cl₂](PF₆)₂ (2,3-Medpp⁺=2-[2-(1-methylpyridiniumyl)]-3-(2-pyridyl)pyrazine) was investigated by X-ray diffraction (XRD), ¹H NMR, redox, and UV-Vis absorption measurements. X-ray analysis shows that crystals obtained from an acetonitrile-toluene solution contain the trans-Cl₂, trans-pyrazine isomeric form, while ¹H NMR and redox measurements on the main product of the synthetic workup indicate the presence of the trans-Cl₂, cis-pyrazine isomer. In the dark at 70 °C, the complex [Ru(2,3-Medpp)₂Cl₂]²⁺ reacts slowly in acetonitrile isomerizing to the cis-[Ru(2,3-Medpp)₂(CH₃CN)Cl]³⁺ species. Under ambient light in the presence of excess AgNO₃ the cis-[Ru(2,3-Medpp)₂(CH₃CN)₂]⁴⁺ species is obtained.     

Synthesis and NMR characterization of the novel mixed-ligand Pt(II) complexes cis- and trans-Pt(Ypy)(pyrimidine)Cl2 and trans,trans-Cl2(Ypy)Pt(μ-pyrimidine)Pt(Ypy)Cl2 (Ypy = pyridine derivative)

Mixed-ligand complexes of the type cis- and trans-Pt(Ypy)(pm)Cl₂ where Ypy = pyridine derivative and pm = pyrimidine were synthesized and characterized by IR spectroscopy and by multinuclear (¹⁹⁵Pt, ¹H and ¹³C) magnetic resonance spectroscopy. The cis compounds were prepared from the reaction of K[Pt(Ypy)Cl₃] with pyrimidine (1:1 proportion) in water, while most of the trans isomers were synthesized from the isomerization of the cis compounds. The cis isomers could not be isolated with the Ypy ligands containing two -CH₃ groups in ortho positions. When the aqueous reaction of K[Pt(Ypy)Cl₃] with pyrimidine was performed in a Pt:pm ratio = 2:1, the pyrimidine-bridged dinuclear species were formed. Only the most stable trans-trans isomers could be isolated pure. In IR spectroscopy, the cis monomers showed two ν(Pt-Cl) bands, while the trans monomers and dimers showed only one ν(Pt-Cl) band. The ¹⁹⁵Pt NMR signals of the cis monomers were found at slightly higher fields than those of the corresponding trans isomers. The δ(¹⁹⁵Pt) of the dimers were found close to those of the trans monomers. The NMR results were interpreted in relation to the solvent effect, which seems important in these complexes. The coupling constants J(¹⁹⁵Pt-¹H) and J(¹⁹⁵Pt-¹³C) are larger in the cis geometry. The crystal structures of the compounds cis-Pt(2,4-lut)(pm)Cl₂, trans-Pt(2,6-lut)(pm)Cl₂ and trans,trans-Cl₂(2,6-lut)Pt(μ-pm)Pt(Ypy)Cl₂ were studied by X-ray diffraction methods and the results have confirmed the configurations suggested by IR and NMR spectroscopies.     

Resonance Raman spectroscopy of chemically modified retinals: Assigning the carbon-methyl vibrations in the resonance Raman spectrum of rhodopsin

To assign the observed vibrationsl modes in the resonance Raman spectrum of the retinylidene chromophore of rhodopsin, we have studied chemically modified retinals. The series of analogs investigated are the n-butyl retinals substituted at C₉ and C₁₃. The results obtained for the 11-cis isomer have clearly assigned the CCH₃ vibrational frequencies observed in the spectrum of the retinylidene chromophore. The data show that the C₍₉₎CH₃ stretching vibration can be assigned to the vibrational mode observed in the 1017 cm^?1 region, and the vibration detected at 997 cm^?1 can be assigned to the C₍₁₃CH₃ vibration. The C₍₅₎CH₃ stretching mode does not contribute to the vibrations observed in this region. The splitting in the C_(n)CH₃ (n = 9, 13) vibration is characteristic of the 11-cis conformation. The results on the modified retinals do not support the hypothesis that the splitting arises from equilibrium mixtures of 11-cis, 12-s-cis and 11-cis, 12-s-trans in solution. Thus, this splitting cannot be used to determine whether the chromophore in rhodopsin is in a 12-s-cis or 12-s-trans conformation. However, our results demonstrate that there are other vibrational modes in the spectra which are sensitive to this conformational equilibrium and we use the presence of a strong ~ 1271 cm^?1 mode in bovine and squid rhodopsin spectra as an indication that the chromophore in these pigments is 11-cis, 12-s-trans.     

H NMR spectroscopy as a tool to determine accurate photoisomerization quantum yields of stilbene-like ligands coordinated to rhenium(I) polypyridyl complexes

In this work, the use of proton nuclear magnetic resonance, ¹H NMR, was fully described as a powerful tool to follow a photoreaction and to determine accurate quantum yields, so called true quantum yields (Φ_true), when a reactant and photoproduct absorption overlap. For this, Φ_true for the trans-cis photoisomerization process were determined for rhenium(I) polypyridyl complexes, fac-[Re(CO)₃(NN)(trans-L)]⁺ (NN = 1,10-phenanthroline, phen, or 4,7-diphenyl-1,10-phenanthroline, ph₂phen, and L = 1,2-bis(4-pyridyl)ethylene, bpe, or 4-styrylpyridine, stpy). The true values determined at 365 nm irradiation (e.g. Φ_NMR = 0.80 for fac-[Re(CO)₃(phen)(trans-bpe)]⁺) were much higher than those determined by absorption spectral changes (Φ_UV-Vis = 0.39 for fac-[Re(CO)₃(phen)(trans-bpe)]⁺). Φ_NMR are more accurate in these cases due to the distinct proton signals of trans and cis-isomers, which allow the actual determination of each component concentration under given irradiation time. Nevertheless when the photoproduct or reactant contribution at the probe wavelength is negligible, one can determine Φ_true by regular absorption spectral changes. For instance, Φ_313 nm for free ligand photoisomerization determined both by absorption and ¹H NMR variation are equal within the experimental error (bpe: Φ_UV-Vis = 0.27, Φ_NMR = 0.26; stpy: Φ_UV-Vis = 0.49, Φ_NMR = 0.49). Moreover, ¹H NMR data combined with electronic spectra allowed molar absorptivity determination of difficult to isolate cis-complexes.     

Specificity and transformations of the trisporic acid series of fungal sex hormones

Chromatographic and spectroscopic characterizations and comparative bioassay data are given for trisporic acid A, the separate 9-cis- and 9-trans-isomers of trisporic acids B and C, and trisporol C, all obtained from 'mated' (plus and minus) cultures of Blakeslea trispora. All five acids show comparable levels of hormone activity on both the mating types of Mucor mucedo, whereas natural trisporol C more specifically affects a plus strain and the laboratory-derived methyl esters are minus-specific. Similarly plus and minus strains of B. trispora convert trisporol C and the esters into trisporic acids at different rates, and they effect different transformations of administered methyl ¹⁴C-trisporate C.     

Solid-State H NMR spectroscopy of retinal proteins in aligned membranes

Solid-state ²H NMR spectroscopy gives a powerful avenue to investigating the structures of ligands and cofactors bound to integral membrane proteins. For bacteriorhodopsin (bR) and rhodopsin, retinal was site-specifically labeled by deuteration of the methyl groups followed by regeneration of the apoprotein. ²H NMR studies of aligned membrane samples were conducted under conditions where rotational and translational diffusion of the protein were absent on the NMR time scale. The theoretical lineshape treatment involved a static axial distribution of rotating C-C²H₃ groups about the local membrane frame, together with the static axial distribution of the local normal relative to the average normal. Simulation of solid-state ²H NMR lineshapes gave both the methyl group orientations and the alignment disorder (mosaic spread) of the membrane stack. The methyl bond orientations provided the angular restraints for structural analysis. In the case of bR the retinal chromophore is nearly planar in the dark- and all-trans light-adapted states, as well upon isomerization to 13-cis in the M state. The C13-methyl group at the “business end” of the chromophore changes its orientation to the membrane upon photon absorption, moving towards W182 and thus driving the proton pump in energy conservation. Moreover, rhodopsin was studied as a prototype for G protein-coupled receptors (GPCRs) implicated in many biological responses in humans. In contrast to bR, the retinal chromophore of rhodopsin has an 11-cis conformation and is highly twisted in the dark state. Three sites of interaction affect the torsional deformation of retinal, viz. the protonated Schiff base with its carboxylate counterion; the C9-methyl group of the polyene; and the β-ionone ring within its hydrophobic pocket. For rhodopsin, the strain energy and dynamics of retinal as established by ²H NMR are implicated in substituent control of activation. Retinal is locked in a conformation that is twisted in the direction of the photoisomerization, which explains the dark stability of rhodopsin and allows for ultra-fast isomerization upon absorption of a photon. Torsional strain is relaxed in the meta I state that precedes subsequent receptor activation. Comparison of the two retinal proteins using solid-state ²H NMR is thus illuminating in terms of their different biological functions.     

Long-chain polyprenols in the family pinaceae

Polyprenols with an average number of isoprene residues of 15 to 18 were isolated from the needles of six plants in the Pinaceae, the content being 0.2–2.0% of the dry wt. ¹H and ¹³CNMR, and FDMS spectroscopy revealed that all of the polyprenols were long-chain homologues of betulaprenols with the following sequence of isoprene residues: ω-trans-trans-7 to 19 cis-cis α.     

Microbiologically Catalyzed Enantio- and Diastereoselective Oxidation of Chrysanthemol Stereoisomers to Chrysanthemic Acids

The diastereo- and enantioselective microbial oxidation of a mixture of racemic cis/trans-chrysanthemols to the corresponding stereoisomeric chrysanthemic acids by Aspergillus species is described. Of the three microorganisms which were found capable of oxidizing racemic cis/trans-chrysanthemols, A. ochraceus ATCC 18500 showed complete enantioselectivity for (+)-stereoisomers [(+)-trans-chrysanthemol and (+)-cis-chrysanthemol), whereas A. flavipes ATCC 1030 and ATCC 11013 showed complete enantioselectivity for the (+)-cis-chrysanthemol but a time-dependent enantioselectivity during oxidation of trans-chrysanthemol [oxidation of (+)-trans-chrysanthemol prior to (−)-trans-chrysanthemol]. The diastereoselectivity of all three microorganisms was time dependent, in that the trans-stereoisomers were oxidized prior to the cis-isomers.     

Proline-glutamate chimera’s side chain conformation directs the type of β-hairpin structure

Our aim was to study the impact of two proline chimeras, containing a glutamic acid side chain in cis- or trans-configuration, on secondary structure formation. We further investigated to what extent the configuration of the side chain contributes to the overall peptide conformation. We used a 10 residue peptide (IYSNPDGTWT) that forms a β-hairpin in water. The turn-forming proline was substituted with either a cis- or trans-proline-glutamic acid chimera, resulting in the peptides IYSNP ^{cis -E} DGTWT (P1_P ^cis-E ) and IYSNP ^{trans -E} DGTWT (P1_P ^trans-E ). We studied the conformation of the modified peptides by circular dichroism (CD) and NMR-spectroscopy, and SEC/static light scattering (SLS) analysis. NMR analysis reveals that the modified peptides maintain the β-hairpin conformation in aqueous solution. At 5 °C and pH 4.3, the peptide (P1_P ^cis-E ) was found to adopt two coexisting β-hairpin conformations (2:2 β-hairpin, and 3:5 β-hairpin). In contrast to that, the peptide (P1_P ^trans-E ) adopts a 2:2 β-hairpin that exists in equilibrium with a 4:4 β-hairpin conformation. The adoption of ordered β-hairpin structures for both modified peptides could be confirmed by CD spectroscopy, while SEC/SLS analysis showed a monomeric oligomerization state for all three investigated peptides. With the combination of several NMR methods, we were able to elucidate that even small alterations in the side chain conformation of the proline-glutamate chimera (cis or trans) can significantly influence the conformation of the adopted β-hairpin.     

Isolation and synthesis of trans- and cis-(−)-clovamides and their deoxy analogues from the bark of Dalbergia melanoxylon

N-(3′,4′-Dihydroxy-trans-cinnamoyl)-3-(3,4-dihydroxyphenyl)-L-alanine [(?)-clovamide], the major phenolic metabolite (0.1%) in the bark of Dalbergia melanoxylon, is associated with minor proportions of its cis-isomer, and similar pairs of geometrical isomers of their deoxy analogues N-(4′-hydroxycinnamoyl)-3-(3,4-dihydroxyphenyl)-L-alanine and N-(4′-hydroxycinnamoyl)-3-(4-hydroxyphenyl)-L-alanine. (?)-Trans-clovamide is synthesized by direct condensation of the acid chloride of caffeic acid with L-DOPA. Diagnostic CD spectra of these compounds and ¹³C spectra of (?)-trans- and (?)-cis-clovamides are recorded.     

Comparative metabolism of the cis and trans isomers of N-nitroso-2-6-dimethylmorpholine in rats,hamsters and guinea pigs

The in vivo metabolism of the cis and trans isomers of N-[3,5-³H] nitroso-2,6-dimethylmorpholine (NDMM) was studied in female Fischer rats, Syrian golden hamsters and guinea pigs by analysis of urinary metabolites using high pressure liquid chromatography (HPLC). Animals were treated by gavage with 12 mg/kg body wt. of NDMM, composed of both isomers and 12 μCi/kg body wt. of either of the separated radioactive isomers (cis or trans). Control animals received 12 mg, 12 μCi/kg body wt. NDMM with both isomers labeled in their natural proportion.There was a substantial increase in the excretion of a particular metabolite, 2-(2-hydroxyl-methyl)ethoxy propanoic acid, in the urine of rats, hamsters and guinea pigs 24 h after received the trans isomer (24, 22 and 13% of the total dose excreted, respectively). A minor metabolite was determined to be 2,6-dimethylmorpholine-3-one, another product of α-oxidation. The metabolite 1-amino-2-hydroxypropanol was identified, indicating that NDMM was metabolized by both α-and β-oxidation.In all three species, animals administered the cis isomer excreted larger amounts of N-nitroso(2-hydroxypropyl)(2-oxopropyl)amine (HPOP) and N-nitroso-bis(2-hydroxypropyl)amine (BHP) products of beta oxidation, than those treated with the trans isomer. Hamsters and guinea pigs treated with the more carcinogenic cis isomer in these species, also excreted twice as much of two other metabolites than was found in the urine of animals given the trans isomer.The trans isomer of NDMM appeared to be preferentially metabolized by α-oxidation and from earlier studies this metabolic pathway seemed to be important in carcinogenesis by NDMM in the rat. The cis isomer might be in a conformation more favorable for β-oxidation and this pathway may be of primary importance in carcinogenesis by NDMM in hamsters and guinea pigs.     

Behavioral comparisons of the stereoisomers of tetrahydrocannabinols

The potencies of (?)-$\text{trans}$-Δ⁹-THC, (+)-$\text{trans}$-Δ⁹-THC, (+)-$\text{cis}$-Δ⁹-THC, (?)-$\text{trans}$-Δ⁸-THC and (+)-$\text{trans}$-Δ⁸-THC were compared in several different species. (?)-$\text{trans}$-Δ⁹-THC was 100 times more potent than (+)-$\text{trans}$-Δ⁹-THC in depressing schedule-controlled responding in monkeys. The (+)-$\text{trans}$ isomers were less effective than their corresponding (?)-$\text{trans}$ isomers in the dog static-ataxia test, but potency ratios could not be determined due to a lack of dose-responsiveness of the (+)-$\text{trans}$ isomers. However, it appeared that their potency differed by at least ten fold. The potency of (+)-$\text{cis}$-Δ⁹-THC in the dog static-ataxia test was comparable to that of (+)-$\text{trans}$-Δ⁹-THC. The hypothermia in mice produced by the (?) isomers of $\text{trans}$-Δ⁹-THC and $\text{trans}$-Δ⁸-THC were 9.1 and 30.4 times greater than that produced by their respective (+)-isomers. Also, the potency ratio of the (+)- and (?)-$\text{trans}$-Δ⁹-THC was 5.6 as measured by depression of spontaneous activity in mice. The magnitude of the potency ratios of the THC stereo-isomers is dependent upon the species and the pharmacological test used.