Mixture Of 1a Research Articles

Oligomeric phloroglucinols with hAChE inhibitory and antibacterial activities from tropic Rhodomyrtus tomentosa

Alzheimer’s diseases (AD) and other infectious diseases caused by drug-resistance bacteria have posed a serious threat to human lives and global health. With the aim to search for human acetylcholinesterase (hAChE) inhibitors and antibacterial agents from medicinal plants, 16 phloroglucinol oligomers, including two new phloroglucinol monomers (1a and 1b), four new phloroglucinol dimers (3a, 3b, 4b, and 5a), six new phloroglucinol trimers (6a, 6b, 7a, 7b, 8a, and 8b), and two naturally occurring phloroglucinol monomers (2a and 2b), along with two known congeners (4a and 5b), were purified from the leaves of tropic Rhodomyrtus tomentosa. The structures and absolute configurations of these new isolates were unequivocally established by comprehensive analyses of their spectroscopic data (NMR and HRESIMS), ECD calculation, and single crystal X-ray diffraction. Structurally, 3a/3b shared a rare C-5′ formyl group, whereas 6a/6b possessed a unique C-7′ aromatic ring. In addition, 7a/7b and 8a/8b were rare phloroglucinol trimers with a bis-furan and a C-6′ hemiketal group. Pharmacologically, the mixture of 3a and 3b showed the most potent human acetylcholinesterase (hAChE) inhibitory activity with an IC50 value of 1.21 ± 0.16 μM. The molecular docking studies of 3a and 3b in the hAChE binding sites were performed, displaying good agreement with the in vitro inhibitory effects. In addition, the mixture of 3a and 3b displayed the most significant anti-MRSA (methicillin-resistant Staphylococcus aureus) with MIC and MBC values of both 0.50 μg/mL, and scanning electron microscope (SEM) studies revealed that they could destroy the biofilm structures of MRSA. The findings provide potential candidates for the further development of anti-AD and anti-bacterial agents.

Phosphine substitution and linkage isomerization in cyclopentadienylruthenium bis(triphenylphosphine)thiocyanide and selenocyanide, CpRu(PPh3)2NCS and CpRu(PPh3)2SeCN.

The reaction between CpRu(PPh3)2NCS (1a) and PMePh2 yields CpRu(PPh3)(PMePh2)NCS (2a) while CpRu(PPh3)(PMePh2)Cl reacts with SCN- to form the S-bonded isomer, CpRu(PPh3)(PMePh2)SCN (2b). Compound 1a and the linkage isomers of 2 were characterized by X-ray crystallography. The kinetics of the reaction between 1a and PMePh2 under pseudo-first order conditions in THF and in fluorobenzene to form 2a are consistent with a dissociative interchange mechanism. Activation parameters for the reaction are: ΔH† = 15.7 ± 0.6 kcal mol-1 and ΔS† = -35 ± 2 cal mol-1 K-1 in THF vs. ΔH† = 24.8 ± 1.2 kcal mol-1 and ΔS† = -6 ± 4 cal mol-1 K-1 in C6H5F. In the presence of added SCN-, the rate of phosphine substitution is unchanged but a mixture of 2a and 2b is observed. The selenocyanate derivative, CpRu(PPh3)2SeCN (3b), crystallizes as the Se-bonded linkage isomer. Compound 3b reacts with PMePh2 under pseudo-first order conditions in fluorobenzene to form CpRu(PPh3)(PMePh2)SeCN (4b) at a much faster rate than 1a with activation parameters: ΔH† = 30.9 ± 4.8 kcal mol-1 and ΔS† = 22.4 ± 15.9 cal mol-1 K-1 with no evidence for linkage isomerization to the N-bonded products.

Chiral Lewis Acid-Catalyzed Norrish Type II Cyclization to Synthesize α-Oxazolidinones via Enantioselective Protonation

Chiral Lewis Acid-Catalyzed Norrish Type II Cyclization to Synthesize α-Oxazolidinones via Enantioselective Protonation

Small-Scale Preparation of Fluorescently Labeled Chemical Probes from Marine Cyclic Peptides, Kapakahines A and F.

A number of bioactive marine natural products have been isolated so far, but it is still difficult to disclose their modes of action. In this study, we prepared fluorescently labeled chemical probes from the cytotoxic marine cyclic peptides kapakahines A (1) and F (2) to visualize their localization as the first step of the study of their modes of action. We used fluorescent dyes 3a or 3a/b (a 1:1 mixture of 3a and 3b) whose terminal N-hydroxysuccinimide (NHS) group can react with the free amino groups of kapakahines. The fluorescently labeled kapakahine A (Kap A-5-FL, 5a) stained P388 murine leukemia cells and HeLa human cervical cancer cells, while cells treated with fluorescently labeled kapakahine F (Kap F-5-FL, 6a) only weakly stained them. Further analysis of the confocal images of the stained cells with higher magnification (×100) indicated the localization of Kap A-5-FL (5a) in the cells. In this paper, we report the small-scale preparation and a new delivery method of fluorescent probes, as well as the application of these procedures to cell staining.

Electrochemical Ring Expansion to Synthesize Medium-Sized Lactams Through C–C Bond Cleavage

Medium-sized nitrogen heterocycles are prevalent motifs in many kinds of bioactive molecules and natural products. Owing to the unfavorable enthalpic and entropic barriers during the transition sta...

Novel Very Long-Chain α-Methoxylated Δ5,9 Fatty Acids from the Sponge Asteropus niger Are Effective Inhibitors of Topoisomerases IB.

The novel fatty acids (2R,5Z,9Z)-2-methoxy-25-methyl-5,9-hexacosadienoic acid (1a) and (2R,5Z,9Z)-2-methoxy-24-methyl-5,9-hexacosadienoic acid (1b) were isolated in 80 % purity from the Caribbean sponge Asteropus niger by chloroform/methanol extraction followed by solvent partitioning and silica gel column chromatography. The compounds were characterized by utilizing a combination of gas chromatography-mass spectrometry, nuclear magnetic resonance, and circular dichroism. Acids 1a and 1b were not detected in the phospholipids (PtdCho and PtdIns) of the sponge, but rather as free FA and possibly in glycosylceramides. The mixtures of 1a and 1b displayed cytotoxicity towards THP-1 and HepG2 cells with EC50's between 41 and 35 μg/mL. Apoptosis was not the preferred mode of cell death induced by 1a-1b in the THP-1 cells. This implies other types of cytotoxicity mechanisms, such as membrane disruption and/or the inhibition (EC50 = 1.8 μg/mL) of the human topoisomerase IB enzyme (hTopIB), with a mechanism of inhibition different from the one displayed by camptothecin (CPT). In a separate experiment, the mixture of 1a and 1b also displayed cytotoxicity towards ex vivo mouse splenocytes infected with Leishmania infantum amastigotes (IC(50) = 0.17 mg/mL) and free living promastigotes (IC(50) = 0.34 mg/mL). It was also found that the FA were inhibitory of the Leishmania topoisomerase IB (LTopIB) with an EC(50) = 5.1 μg/mL. Taken together, 1a and 1b represent a new class of FA with potential as TopIB inhibitors that preferentially inhibit hTopIB over LTopIB.

Chemical Constituents of Hoya buotii Kloppenb

Chemical investigation of the dichloromethane extracts of Hoya buotii Kloppenb. afforded taraxerone (1), taraxerol (2), a mixture of β-sitosterol (3a) and stigmasterol (3b) in about 2:1 ratio, and a mixture of α-amyrin cinnamate (4a) and β-amyrin cinnamate (4b) in about 1:2 ratio from the stems; 1, 2, and 3a from the roots; a mixture of 4a and 4b in about 3:2 ratio from the flowers; and 3a, squalene (5) and saturated hydrocarbons from the leaves. The structures of 1-5 were identified by comparison of their NMR data with those reported in the literature.

Cytotoxic Triterpenes and Sterols from Pipturus arborescens (Link) C.B. Rob.

The triterpenes, squalene (1), friedelin (2) and a mixture of ursolic acid (3a) and oleanolic acid (3b) in a 2:3 ratio, and a mixture of β-sitosterol (4a) and stigmasterol (4b) in a 2:1 ratio, obtained from the dichloromethane extract of Pipturus arborescens (Link) C.B. Rob., were evaluated for their anti-proliferative activities against three human cancer cell lines, breast (MCF-7) and colon (HT-29 and HCT-116), and a normal cell line, human dermal fibroblast- neonatal (HDFn) using the in vitro PrestoBlue� cell viability assay. The HCT-116 cell line was most susceptible to the compounds and mixtures tested. Triterpene 1 was most cytotoxic against HCT-116 and MCF-7 with IC50 values of 4.21 and 5.92 μg/mL, respectively. Triterpene 2 and the mixture of 3a and 3b were highly anti-proliferative against HCT-116 cells (IC50 of 1.22 and 1.66 μg/mL, respectively) and moderately inhibitory against MCF-7 cells (IC50 of 16.51 and 23.97 μg/mL, respectively). The mixture of 4a and 4b exhibited high cytotoxicity against HCT-116 cells (IC50 of 1.14 μg/mL). Compounds 1-4b showed the least activity against HT-29 cells (IC50 of 11.97 to 52.52 μg/mL). Cytotoxic effect was not observed against HDFn cells (>100 μg/mL). Comparing the effects of 1-4b on the two colon cancer cell lines, the IC50 values of 1-4b against HCT-116 were lower than those of HT-29.

ChemInform Abstract: Stereochemical Assignment of C‐24 and C‐25 of Amarasterone A, a Putative Biosynthetic Intermediate of Cyasterone.

A C29 phytoecdysteroid named amarasterone A (1) has been isolated from Cyathula capitata (Amaranthaceae), Leuzea carthamoides (Asteraceae), and Microsorum scolopendria (Polypodiaceae). We recently isolated amarasterone A from C. officinalis. Amarasterone A has been postulated as a biosynthetic intermediate of cyasterone in Cyathula sp. The stereochemistry at the C-24 and C-25 positions of these amarasterone A samples was investigated by comparing the NMR spectroscopic data with those of stereodefined model compounds, (24R,25S)-, (24R,25R)-, (24S,25S)-, and (24S,25R)-isomers of (20R,22R)-3β-methoxystigmast-5-ene-20,22,26-triol (2a-d), which were synthesized in the present study. Amarasterone A isolated from Cyathula officinalis was determined to be the (24R,25S)-isomer (1a), while amarasterone A from L. carthamoides was found to be the (24R,25R)-isomer (1b). Amarasterone A from M. scolopendria was found to be a mixture of 1a and 1b. The biosynthesis of cyasterone in Cyathula sp. is discussed on the basis of the identical C-24 configuration of sitosterol and amarasterone A.

Stereochemical assignment of C-24 and C-25 of amarasterone A, a putative biosynthetic intermediate of cyasterone.

A C29 phytoecdysteroid named amarasterone A (1) has been isolated from Cyathula capitata (Amaranthaceae), Leuzea carthamoides (Asteraceae), and Microsorum scolopendria (Polypodiaceae). We recently isolated amarasterone A from C. officinalis. Amarasterone A has been postulated as a biosynthetic intermediate of cyasterone in Cyathula sp. The stereochemistry at the C-24 and C-25 positions of these amarasterone A samples was investigated by comparing the NMR spectroscopic data with those of stereodefined model compounds, (24R,25S)-, (24R,25R)-, (24S,25S)-, and (24S,25R)-isomers of (20R,22R)-3β-methoxystigmast-5-ene-20,22,26-triol (2a-d), which were synthesized in the present study. Amarasterone A isolated from Cyathula officinalis was determined to be the (24R,25S)-isomer (1a), while amarasterone A from L. carthamoides was found to be the (24R,25R)-isomer (1b). Amarasterone A from M. scolopendria was found to be a mixture of 1a and 1b. The biosynthesis of cyasterone in Cyathula sp. is discussed on the basis of the identical C-24 configuration of sitosterol and amarasterone A.

Alkaloids from Xylariaceae sp., a Marine-derived Fungus

A new pyridine derivative, 5-(2'-hydroxypropyl)pyridin-3-ol (1), with seven known alkaloids, 3-hydroxy-5-methyl-5,6-dihydro-7H-cyclopenta[b]pyridin-7-one (2), penicillenol A1 (3), penicillenol A2 (4), a mixture of quinolactacin AI (5a) and quinolactacin A2 (5b), and a mixture of quinolactacin C1 (6a) and quinolactacin C2 (6b), were isolated from the culture broth of a marine-derived fungus Xylariaceae sp. SCSGAF0086. Their structures were elucidated by spectroscopic methods. Compound 2 showed weak antimicrobial activity against Bacillus subtilis, and a mixture of 6a and 6b exhibited strong antifouling activity toward Bugula neritina larval settlement.

Terpenoids from Ardisia squamulosa

The genus Ardisia Swartz belongs to the family Myrsinaceae. Ardisia has 68 recorded species in the Philippines [1], 60 of which are endemic. The hexane extract from A. squamulosa was reported to have a significant effect on sperm count but has a negligible effect on sperm morphology and viability [2]. No chemical study of A. squamulosa has been reported. However, we earlier studied a congener of this plant, Ardisia pyramidalis, which afforded spinasterol, spinasteryl acetate, a mixture of -amyrin, -amyrin and bauerenol, squalene, lutein, and triglycerides from the dichloromethane (DCM) extract of the leaves. Spinasterol was found to exhibit anti-angiogenic potential [3]. This study was conducted as part of our research on the chemical constituents of Ardisia species found in the Philippines. We report herein the chemical constituents of the DCM extract of the leaves of A. squamulosa. Fresh leaves of Ardisia squamulosa were collected from Kanawan, Morong Bataan, Philippines in 2010 by Ramon Bandong. The sample was authenticated by the Jose Vera Herbarium Collection at the Institute of Biology of the University of the Philippines-Diliman and the Philippine National Museum, Manila. The DCM extracts of the air-dried leaves of A. squamulosa afforded terpenoids by silica gel chromatography. These compounds were identified by comparison of their 13C NMR data with those of -caryophyllene (1) [4], squalene (2) [5], bauerenone (3a) [6], ursenone (3b) [7], oleanone (3c) [7], bauerenol (4a) [6], -amyrin (4b) [8], -amyrin (4c) [8], and lutein (5) [9] reported in the literature. Air-dried leaves of Ardisia squamulosa (1 kg) were ground in an Osterizer and then soaked in DCM for three days and filtered. The filtrate was concentrated in vacuo to afford a crude extract (55 g), which was chromatographed in increasing proportions of acetone in dichloromethane at 10% increment. The DCM fraction was rechromatographed (6 ) in petroleum ether to afford 1 (5 mg) and 2 (20 mg). The 10% acetone in DCM and 20% acetone in DCM fractions were combined and rechromatographed (4 ) with 2.5% ethyl acetate in petroleum ether as eluent to afford a mixture of 3a–3c (12 mg). The 30% acetone in DCM fraction was rechromatographed (5 ) using 5% ethyl acetate in petroleum ether to afford a mixture of 4a–4c (15 mg). The 40% acetone in DCM and 50% acetone in DCM fractions were combined and rechromatographed (3 ) with DCM–diethyl ether–acetonitrile (9:0.5:0.5) as eluent to afford 5 (18 mg) after washing with diethyl ether.

Reactions of Tungsten Acetylide–Silylene Complexes with Pyridines: Direct Observation of Silylene/Silyl Migration in Tungsten Acetylide and Carbyne/Vinylidene Frameworks

Reaction of acetylide–silylene complex Cp*(CO)2W(SiPh2)(CCtBu) (1a) with 4-(dimethylamino)pyridine (DMAP) gave an equilibrium mixture of DMAP-stabilized silylene acetylide complexes trans- and cis-Cp*(CO)2W(SiPh2·DMAP)(CCtBu) (trans-4 and cis-4). The corresponding reaction using Cp*(CO)2W(SiPh2)(CCSiMe3) (2) produced the novel DMAP-coordinated silenylcarbyne/silylvinylidene complex Cp*(CO)2W[CC(SiPh2·DMAP)(SiMe3)] (6a) as a major product, which was equilibrated with trans- and cis-Cp*(CO)2W(SiPh2·DMAP)(CCSiMe3) (trans-5a and cis-5a) via silylene/silyl migration. The novel structures of cis-4 and 6a were revealed by X-ray crystallography. A mixture of 2 and pyridine exhibited interesting temperature-dependent NMR spectral changes, indicating the formation of trans- and cis-Cp*(CO)2W(SiPh2·py)(CCSiMe3) (trans-5b and cis-5b) and Cp*(CO)2W[CC(SiPh2·py)(SiMe3)] (6b) at low temperature, while a mixture of 1a and pyridine showed no such spectral changes.

Potent and selective butyrylcholinesterase inhibitors from Ficus foveolata

Four stilbenes (1–4), one inseparable mixture of two alkyl diferulates (5a, 5b), one alkyl ferulate (6) and four flavonoids (7–10) were isolated from Ficus foveolata Wall. Except for quercetin (10), the other ten constituents were isolated from F. foveolata for the first time. In addition, one of the two components in mixture 5 is a new compound identified as (1E,22E)-1,22-docosanediol diferulate (5a). All nine isolated compounds, plus the mixture of 5a and 5b known as 5, exhibited a low or no activity against acetylcholinesterase. However, and interestingly, the stilbenes 1–4 showed a high inhibition towards butyrylcholinesterase. Gnetol (4) had the lowest IC50 value of 1.3μM towards butyrylcholinesterase and showed a reversible and competitive inhibition in the kinetic study.

Essential role of the donor acyl carrier protein in stereoselective chain translocation to a fully reducing module of the nanchangmycin polyketide synthase.

Incubation of recombinant module 2 of the polyether nanchangmycin synthase (NANS), carrying an appended thioesterase domain, with the ACP-bound substrate (2RS)-2-methyl-3-ketobutyryl-NANS_ACP1 (2-ACP1) and methylmalonyl-CoA in the presence of NADPH gave diastereomerically pure (2S,4R)-2,4-dimethyl-5-ketohexanoic acid (4a). These results contrast with the previously reported weak discrimination by NANS module 2+TE between the enantiomers of the corresponding N-acetylcysteamine-conjugated substrate analogue (±)-2-methyl-3-ketobutyryl-SNAC (2-SNAC), which resulted in formation of a 5:3 mixture of 4a and its (2S,4S)-diastereomer 4b. Incubation of NANS module 2+TE with 2-ACP1 in the absence of NADPH gave unreduced 3,5,6-trimethyl-4-hydroxypyrone (3) with a k(cat) of 4.4 ± 0.9 min⁻¹ and a k(cat)/K(m) of 67 min⁻¹ mM⁻¹, corresponding to a ∼2300-fold increase compared to the k(cat)/K(m) for the diffusive substrate 2-SNAC. Covalent tethering of the 2-methyl-3-ketobutyryl thioester substrate to the NANS ACP1 domain derived from the natural upstream PKS module of the nanchangmycin synthase significantly enhanced both the stereospecificity and the kinetic efficiency of the sequential polyketide chain translocation and condensation reactions catalyzed by the ketosynthase domain of NANS module 2.

Structural Rules for the Chiral Supramolecular Organization of OPE-based Discotics: Induction of Helicity and Amplification of Chirality

A systematic study on the structural rules that regulate the chiral supramolecular organization of oligo(phenylene ethynylene) (OPE)-based discotics is presented. This study is based on the chirooptical properties of two different series of triangular shape OPEs. The first of them is composed by OPE-based trisamides with a variable number of chiral side chains (compounds 1) that self-assemble following a cooperative mechanism. The CD experiments carried out with these desymmetrized trisamides demonstrate that only one stereogenic center is sufficient to achieve a helical organization with a preferred handedness. However, the ability to amplify the chirality decreases upon decreasing the number of stereocenters at the peripheral side chains. The second series is constituted by triangular shape OPEs with a variable number of ether and amide functional groups and constant absolute configuration of the stereogenic centers at all of the peripheral chains (compounds 2). These compounds do not self-assemble into helical aggregates as demonstrated by the corresponding CD studies. The amplification of chirality observed in the mixtures of some of the components of both series has been investigated. The combination of chiral trisamide 1d with chiral but nonhelical 2b or 2c does not produce an amplification of chirality most probably due to the mismatch between the stereogenic centers of both components. However, the combination of achiral trisamide 1a with chiral but nonhelical bisamide 2c generates, in a cooperative manner, helical structures with a preferred handedness in a process involving the transfer of helicity from 1a to 2c and the transfer of chirality from 2c to 1a. The structural features of the OPE discotics also exert a strong influence on the columnar aggregates. Thus, while achiral 1a bundles into thick filaments to form an organogel, the gelation ability of these triangular OPEs decreases upon increasing the number of stereogenic centers, being totally canceled for compounds 2 in which the amide functionalities are replaced by ether linkages. Finally, we have also registered AFM images of the helical aggregates obtained from the mixture of 1a+2c, which implies an efficient transfer of the chiral objects from solution to surfaces. The study presented herein increases the understanding of the structural rules that regulate the chiral supramolecular organization of discrete molecules in general and, more specifically, those based on π-conjugated oligomers.

A new triterpene from Barringtonia asiatica

The freeze-dried bark of Barringtonia asiatica afforded a new triterpene: (3β,11α)-11-hydroxyolean-12-en-3-yl palmitate (1). The bark also yielded mixtures of (3β)-olean-12-en-3-yl palmitate (2a), (3β)-urs-12-en-3-yl palmitate (2b) and (3β)-olean-18-en-3-yl palmitate (2c) in a 2 : 1 : 4 ratio; β-amyrin (3a), α-amyrin (3b) and germanicol (3c) in a 3 : 1 : 4 ratio; 22-O-tigloylcamelliagenin A (4a) and betulinic acid (4b) in a 2 : 1 ratio; olean-12-en-3β,16β,22α-triol (5), β-sitosterol, spinasterol, squalene and trilinolein. The roots yielded 2a–c and 3a–c as well as trilinolein, spinasterol and squalene, while the flowers afforded verimol k (6), linoleic acid, spinasterol, squalene, phytyl fatty acid ester and trilinolein. Compounds 1–4 and 6 were tested for antimicrobial property against seven microorganisms. All compounds tested exhibited slight activity against Candida albicans and were found inactive against Escherichia coli, Bacillus subtilis, Trichophyton mentagrophytes and Aspergillus niger. Except for the mixture of 4a and 4b that proved to be inactive, all the compounds were slightly active against the bacterium Staphylococcus aureus, while 3a–c were slightly active against Pseudomonas aeruginosa.

Thermal characteristics of oleochemical carbonate binary mixtures for potential latent heat storage

AbstractThe thermal properties for binary mixtures at various weight fraction ratios between dodecyl carbonate (1a), tetradecyl carbonate (1b), hexadecyl carbonate (1c), and octadecyl carbonate (1d) were examined by DSC at 0.5, 1.0, and 5.0°C/min. At 5°C/min sharp well defined phase transitions were observed at 80:20, 88:12, and 90:10, for 1a:(1b, 1c, and 1d), respectively, at 74:26 and 80:20 for 1b:(1c, and 1d), respectively, and at 82.5:17 for 1c:1d. The melting and solidification temperatures for these mixtures ranged between 12–37°C (melting) and 8–34°C (solidification). The latent heat of melting and solidification determined for the binary carbonate mixtures ranged between 135 and 175 J/g. At 0.5 or 1.0°C/min, mixtures of 1a:(1b, 1c, and 1d) and 1b:1d melted and solidified similarly when run at 5°C/min while the melting curves for 1b:1c and 1c:1d were not as well defined. These carbonate mixtures extend the thermal properties of the pure oleochemical carbonates and compliment other biobased phase change materials (PCMs) substances such as fatty acids, esters, and alcohols and may provide useful biobased alternatives to paraffin wax and salt hydrate PCM currently dominating the market.

Click reactions of 2 H-azaphosphirene chromium and molybdenum complexes and a surprisingly facile access to a 2 H-1,4,2-diazaphosphole derivative

Ring expansion reactions of 2 H-azaphosphirene chromium and molybdenum complexes 1a, b with dimethyl cyanamide, triflic acid, and, subsequently at ambient temperature, with triethylamine gave a mixture of the respective 2 H-1,4,2-diazaphosphole complex 2a, b and the non-ligated heterocycle 3. If the deprotonation with NEt 3 was carried out at low temperature, the selective formation of complexes 2a, b was observed, which were isolated in excellent yields and fully characterized (including single-crystal X-ray crystallography). Experimental and computational results revealed that the P, Cr and P, Mo bonds of 2 H-1,4,2-diazaphosphole complexes are significantly weakened upon N-protonation of the heterocyclic ligand. When mixtures of 1a, b, TfOH, and Me 2NCN were warmed to ambient temperature, the primarily formed N-protonated of 2 H-1,4,2-diazaphosphole complexes 4a, b could be observed by 31P NMR spectroscopy. The latter underwent decomplexation to give the N-protonated free ligand 5, which could be isolated and characterized by multinuclear NMR experiments. The neutral non-ligated heterocycle 3 was isolated from a one-pot reaction of 1b with TfOH and Me 2NCN by adding NEt 3 to a solution of intermediately formed 5.

Hypoglycemic Effects of Tea Extracts and Sterols from Momordica charantia

Mice administered with different doses of infusion obtained from commercial tea preparations of Momordica charantia fruit and leaf displayed variable hypoglycemic activity. M. charantia fruit tea extract at 100 mg/kg BW had demonstrated significant (P=0.001) blood glucose lowering during 0.5h to 1.0h observation period, while M. charantia leaf tea extract was most effective at 100 mg/kg BW with sustained blood glucose reduction pattern starting at 1.5h to 2.5h. The dichloromethane extract of the freeze-dried fruit of M. charantia afforded a mixture of clerosterol (1a) and 5α-stigmasta-7-en-3β-ol (1b) in a 2:1 ratio by silica gel chromatography. A single intraperitonial injection of 10 mg/kg BW of a mixture of 1a and 1b in normoglycemic mice significantly (P<0.05) reduced the blood glucose level with distinct percent blood glucose reduction from 1.5h to 2.0h compared with the negative control.