Nitric oxide inhibitory substances from the rhizomes of Dioscorea membranacea

Thai medicinal plants locally known as Hua-Khao-Yen were examined for their inhibitory activities against lipopolysaccharide (LPS) induced nitric oxide (NO) production in RAW 264.7 cell lines. Among the plant species studied, an ethanolic extract of Dioscorea membranacea exhibited the most potent inhibitory activity, with an IC(50) value of 23.6 microg/ml. From this extract, eight compounds [two naphthofuranoxepins (1, 2), one phenanthraquinone (3), three steroids (4-6) and two steroidal saponins (7, 8)] were isolated and further investigated for their inhibitory properties of NO production. It was found that diosgenin-3-O-alpha-L-rhamnosyl (1-->2)-beta-D-glucopyranoside (7) possessed the highest activity (IC(50)=3.5 microM), followed by dioscoreanone (3, IC(50)=9.8 microM) and dioscorealide B (2, IC(50)=24.9 microM). Regarding structural requirements of diosgenin derivatives for NO production inhibitory activity, compound 7 which has a rhamnoglucosyl moiety at C-3 exhibited much higher activity than compounds that have either a diglucosyl substitution (8) or its aglycone (9); whereas, hydroxyl substitution at position 8 of naphthofuranoxepin derivatives conferred higher activity than the methoxyl group. It is concluded that diosgenin-3-O-alpha-L-rhamnosyl (1-->2)-beta-D-glucopyranoside (7), dioscoreanone (3) and dioscorealide B (2) are active principles for NO inhibitory activity of Dioscorea membranacea. Compounds 1-3 were also tested for the inhibitory effect on LPS-induced TNF-alpha release in RAW 264.7 cells. The result revealed that 3 possessed potent activity against TNF-alpha release with an IC(50) value of 17.6 microM, whereas, 1 and 2 exhibited mild activity. The present study may support the use of Dioscorea membranacea by Thai traditional doctors for treatment of the inflammatory diseases.     

HIV-1 integrase inhibitory substances from Coleus parvifolius

For the purpose of discovering anti-HIV-1 agents from natural sources, water and EtOH extracts of 50 Thai plants were screened for their inhibitory activity against HIV-1 integrase (IN), an enzyme essential for viral replication. Of these plants, an EtOH extract of Coleus parvifolius Benth. (aerial parts) showed potent activity against HIV-1 IN with an IC50 value of 9.2 microg/mL. From this extract, 11 compounds were isolated and identified as luteolin 5-O-beta-d-glucopyranoside (1), luteolin (2), luteolin 7-methyl ether (3), luteolin 5-O-beta-d-glucuronide (4), 5-O-beta-d-glucopyranosyl-luteolin 7-methyl ether (5), rosmarinic acid (6), rosmarinic acid methyl ester (7), daucosterol (8), a mixture of alpha- and beta-amyrin (9, 10) and phytol (11). Of these compounds, rosmarinic acid methyl ester (7), rosmarinic acid (6), luteolin (2) and luteolin 7-methyl ether (3) exhibited inhibitory activities against HIV-1 IN with IC50 values of 3.1, 5.0, 11.0 and 11.0 microM, respectively. Among rosmarinic acid derivatives, the HIV-1 IN inhibitory activity increased in turn for a dimer (IC50 = 5.0 microM), a trimer (IC50 = 1.4 microM), and a tetramer (IC50 = 1.0 microM).     

Indole glucoalkaloids from Chimarrhis turbinata and their evaluation as antioxidant agents and acetylcholinesterase inhibitors

As part of our study on bioactive agents from Brazilian rainforest plants, two new glucoalkaloids, 3,4-dehydro-strictosidine (1) and 3,4-dehydro-strictosidinic acid (2), were isolated from Chimarrhis turbinata, along with seven known glucoalkaloids, cordifoline (3), strictosidinic acid (4), strictosidine (5), 5 alpha-carboxystrictosidine (6), turbinatine (7), desoxycordifoline (8), and harman-3-carboxylic acid (9). The structures of the new alkaloids were established on the basis of comprehensive spectral analysis, mainly 1D and 2D NMR experiments, as well as high-resolution HRESIMS. Alkaloid 3 showed strong free-radical scavenging activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) as well as pronounced antioxidant activity evidenced by redox properties measured by ElCD-HPLC. Additionally, alkaloids 1-9 were submitted to TLC screening for acetylcholinesterase inhibitors. Both 7 and 8 were shown to be moderate acetylcholinesterase inhibitors at a concentration of 0.1 and 1.0 microM, respectively. In an in vitro rat brain assay, 7 showed moderate activity (IC(50) 1.86 microM), compared to the standard compound, galanthamine (IC(50) 0.92 microM).     

Cytotoxic alkaloids and antibiotic nordammarane triterpenoids from the marine-derived fungus Aspergillus sydowi

Three new diketopiperazine alkaloids, 6-methoxyspirotryprostatin B (1), 18-oxotryprostatin A (2), and 14-hydroxyterezine D (3), with an oxaspiro[4.4]lactam moiety, 14-norpseurotin A (4), and the 29-nordammarane triterpenoid 6beta,16beta-diacetoxy-25-hydroxy-3,7-dioxy-29-nordammara-1,17(20)-dien-21-oic acid (5), as well as 12 known compounds (6- 17), were isolated from the ethyl acetate extract of a marine-derived fungal strain, Aspergillus sydowi PFW1-13. The structures of compounds 1- 5 were elucidated by comprehensive spectroscopic analysis. Compounds 1- 3 exhibit weak cytotoxicity against A-549 cells, with IC 50 values of 8.29, 1.28, and 7.31 microM, respectively. Compound 1 also shows slight cytotoxicity against HL-60 cells, with an IC 50 value of 9.71 microM. Compounds 4 and 5 display significant antimicrobial activities against Escherichia coli, Bacillus subtilis, and Micrococcus lysoleikticus with MICs of 3.74, 14.97, and 7.49 microM and 10.65, 5.33, and 10.65 microM, respectively.     

Antioxidative phenolics from the fresh leaves of Ternstroemia japonica

Six new phenylethanoid glucosides, ternstrosides A-F (1-6), a new kaempferol derivative (7), and eight known compounds were isolated from the fresh leaves of Ternstroemia japonica. The structures were elucidated by 1D and 2D NMR spectroscopic analyses. Compounds 1-7 showed potent antioxidative activity in three different tests, with IC50 values in the range 3.26-6.50 microM in the hydroxyl radical (*OH) inhibitory activity test, 33.29-82.21 microM in the total ROS (reactive oxygen species) inhibitory activity test, and 1.14-13.53 microM in the peroxynitrite (ONOO-) scavenging activity test.     

Neoflavonoids and related constituents from Nepalese propolis and their nitric oxide production inhibitory activity

A methanolic extract of Nepalese propolis yielded 10 new open-chain neoflavonoids (1-10), a new chalcone (11), and eight previously reported compounds (12-19). Their structures were determined on the basis of spectroscopic data and chemical conversion. The isolated compounds other than 5, 8, and 16 showed dose-dependent inhibitory activities on nitric oxide production in lipopolysaccharide-activated macrophage-like J774.1 cells and were more active than a positive control, N(G)-monomethyl-L-arginine (IC(50), 27.1 microM). The most potent activities, of 6 and 7 (IC(50), 0.5 microM), were greater than another positive control, caffeic acid phenethyl ester (IC(50), 4.8 microM).     

Bioactive 5alpha-pregnane-type steroidal alkaloids from Sarcococca hookeriana

The bioassay-guided phytochemical investigation of Sarcococca hookeriana with respect to cholinesterase inhibitory properties has yielded two new 5alpha-pregnane-type steroidal alkaloids, hookerianamides J (1) and K (2), along with eight known compounds (3-10). The structures of 1 and 2 were elucidated by spectroscopic methods. These compounds displayed good to moderate activities in vitro against the enzymes acetylcholinesterase (IC 50 8.1-48.5 microM) and butyrylcholinesterase (IC 50 0.4-4.0 microM). Compounds 1-10 were also tested in vitro for their leishmanicidal activity against Leishmania major and for their antibacterial activities against Bacillus subtilis, Micrococcus luteus, Streptococcus faecalis, and Pseudomonas pallida.     

Cytotoxic acylated triterpene saponins from the husks of Xanthoceras sorbifolia

Four new oleanane-type triterpene saponins, xanifolia-Y0 (1), xanifolia-Y2 (2), xanifolia-Y3 (3), and xanifolia-Y7 (4), were isolated from the husks of Xanthoceras sorbifolia along with two known analogues, xanifolia-Y8 (5) and xanifolia-Y10 (6). The structures of 1-4 were determined by spectroscopic data interpretation and chemical degradation. Compounds 1-6 were evaluated for their cell-growth inhibition activity toward human ovarian cancer cells (OVCAR3) by a MTT assay, and the IC50 values ranged from 4 to 13 microM. On the basis of the results obtained, it is concluded that a C-3 trisaccharide with a galactose and acylation with an angeloyl group at both C-21 and C-22 are important for cell inhibition activity for this class of compounds.     

Bioactive secolignans from Peperomia dindygulensis

Thirteen secolignans, including eight new ones (1-8), were isolated from the EtOAc extract of Peperomia dindygulensis. The structures were mainly elucidated by 1D and 2D NMR and MS experiments, the relative configurations were determined by NOE correlations, and the absolute configurations were established by the optical rotations and CD spectra. Cytotoxicity and MDR (multidrug resistance) reversal activity of the isolated compounds were examined. Compounds 6 and 7, peperomins B (10) and E (12), showed moderate to strong growth inhibitory activity against a malignant lung tumor cell (VA-13) with IC(50) values of 15.2, 13.5, 13.9, and 1.93 microM, respectively, and also inhibited the growth of a normal lung fibroblast cell (WI-38) at the same levels. Compound 7 and peperomin E (12) exhibited inhibitory activity against a liver tumor cell (HepG2) with IC(50) values of 22.3 and 12.1 microM. Compounds 5 and 7 and peperomins A, B, C, and E (9-12) enhanced calcein accumulation in MDR 2780 cells at 25 microg/mL. Compounds 2, 3, 7, and peperomin E (12) showed inhibitory activity on induction of the intercellular adhesion molecule-1 (ICAM-1).     

Sesquiterpenes and flavonol glycosides from Zingiber aromaticum and their CYP3A4 and CYP2D6 inhibitory activities

Three new sesquiterpenes, (2R,3S,5R)-2,3-epoxy-6,9-humuladien-5-ol-8-one (1), (2R,3R,5R)-2,3-epoxy-6,9-humuladien-5-ol-8-one (2), and (5R)-2,6,9-humulatrien-5-ol-8-one (3), and two new flavonol glycosides, kaempferol-3-O-(2,3-di-O-acetyl-alpha-l-rhamnopyranoside) (4) and kaempferol-3-O-(2,3,4-tri-O-acetyl-alpha-l-rhamnopyranoside) (5), were isolated from the EtOAc-soluble fraction of the water extract of Zingiber aromaticum, along with 13 known compounds (6-18). The structures of the isolated compounds were elucidated on the basis of spectroscopic and chemical analyses. The isolated compounds were tested for their inhibitory activity on the metabolism mediated by CYP3A4 or CYP2D6 using [N-methyl-(14)C]erythromycin or [O-methyl-(14)C]dextromethorphan as a substrate, respectively. Kaempferol-3-O-(2,3,4-tri-O-acetyl-alpha-l-rhamnopyranoside) (5) showed the most potent inhibitory activity (IC(50), 14.4 microM) on the metabolism mediated by CYP3A4, and kaempferol-3-O-methyl ether (14) inhibited CYP2D6 most potently (IC(50), 4.63 microM).     

Benzylphenethylamine alkaloids from Hosta plantaginea with inhibitory activity against tobacco mosaic virus and acetylcholinesterase

Five new benzylphenethylamine alkaloids, hostasine (1), 8-demethoxyhostasine, 8-demethoxy-10-O-methylhostasine, 10-O-methylhostasine, and 9-O-demethyl-7-O-methyllycorenine, along with 12 known compounds, were isolated from Hosta plantaginea by bioassay-guided fractionation. The structures of the new alkaloids were established by means of extensive spectroscopic methods, and the relative configuration of 1 was further confirmed by single-crystal X-ray diffraction. 7-Deoxy-trans-dihydronarciclasine (IC(50) = 1.80 microM), a known alkaloid, showed strong activity against tobacco mosaic virus by the half-leaf method. Some of these alkaloids were also evaluated for their inhibitory activity against acetylcholinesterase. 8-Demethoxy-10-O-methylhostasine was found to possess significant activity, with an IC(50) of 2.32 microM.     

Isoflavonoids and other compounds from Psorothamnus arborescens with antiprotozoal activities

Bioactivity-guided fractionation of the root extract of Psorothamnus arborescens yielded the new isoflavone 5,7,3',4'-tetrahydroxy-2'-(3,3-dimethylallyl)isoflavone (1a) and the new 2-arylbenzofuran 2-(2'-hydroxy-4',5'-methylenedioxyphenyl)-6-methoxybenzofuran-3-carbaldehyde (2), together with seven known compounds, including three isoflavones, fremontin (3a), glycyrrhisoflavone (4a), and calycosin (5), two pterocarpans, maackiain (6) and 4-hydroxymaackiain (7), one triterpene, oleanolic acid (8), and one chalcone, isoliquiritigenin (9). In addition, the structure of the isoflavone fremontin was revised using spectroscopic and chemical methods and was assigned the new structure 3a. The isoflavone 1a and the chalcone 9 displayed leishmanicidal activity with IC50 values of 13.0 and 20.7 microM, respectively, against Leishmania donovani axenic amastigotes. Calycosin (5) exhibited selective toxicity against Trypanosoma brucei brucei (IC50 12.7 microM) compared to L. donovani amastigotes and Vero cells (IC50 100 and 159 microM, respectively). These results prompted us to test a small group of structurally related isoflavones for their antitrypanosomal activities. Genistein and 7,3',4'-trihydroxyisoflavone displayed promising activity (IC50 values 4.2 and 7.1 microM, respectively) and selectivity (IC50 versus Vero cells: 32.9 and 135 microM, respectively). These studies suggest that the isoflavone skeleton deserves further investigation as a template for novel antileishmanial and trypanocidal compounds.     

Vasorelaxing alkaloids and flavonoids from Cassytha filiformis

Two new aporphine alkaloids, isofiliformine ( 1) and cassythic acid ( 3), along with 22 known compounds were isolated from whole herb of Cassytha filiformis. Cassythic acid ( 3), cassythine ( 4), neolitsine ( 7), and dicentrine ( 8) had potent vasorelaxing effects on precontracted rat aortic preparations with mean IC 50 values between 0.08 and 2.48 microM. Compounds 1, 1,2-methylenedioxy-3,10,11-trimethoxyaporphine ( 2), (-)- O-methylflavinatine ( 10), (-)-salutaridine ( 11), isohamnetin-3- O-beta-glucoside, and isohamnetin-3- O-rutinoside exerted moderate vessel-relaxing activities with IC 50 values from 16.50 to 32.81 microM at the test concentrations.     

Isolation of glycosidase-inhibiting hyacinthacines and related alkaloids from Scilla socialis

An examination of the bulbs of Scilla socialis has resulted in the isolation of 11 hyacinthacines, two pyrrolidines, and three piperidines. The structures of the new alkaloids were elucidated by spectroscopic methods as beta-1-C-ethyldeoxymannojirimycin (5), hyacinthacines B7 (10), C2 (11), C3 (12), C4 (13), and C5 (14), and alpha-5-C-(3-hydroxybutyl)hyacinthacine A2 (15). Although, beta-l-homofuconojirimycin (3) and alpha-7-deoxyhomonojirimycin (alpha-7-deoxy-HNJ, 4) are previously known alkaloids, this is the first report of their occurrence in the plant family Hyacinthaceae. Alkaloid 11 was found to be a good inhibitor of bacterial beta-glucosidase and human placenta alpha-l-fucosidase, with IC50 values of 13 and 17 microM, respectively, while alkaloid 12 showed no inhibitory activity toward alpha-l-fucosidase but was a more potent inhibitor of bovine liver beta-galactosidase (IC50 = 52 microM) than 11. Alkaloids 13 and 14 were shown to be inhibitory toward mammalian alpha-glucosidase (IC50 = 45 and 77 microM, respectively), and alkaloid 14 was demonstrated as a moderate inhibitor of bacterial beta-glucosidase (IC50 = 48 microM).     

New pyridinium alkaloids from a marine sponge of the genus Spongia with a human phospholipase A(2) inhibitor profile

Four new bioactive pyridinium alkaloids, named spongidines A-D (5-8), have been isolated from a Vanuatu sponge of the genus Spongia, together with known petrosaspongiolides D (1) and G (2). Compounds 3 and 4 are 21-hydroxy derivatives of petrosaspongiolides K and P. Structure elucidation was accomplished through extensive 2D NMR experiments (COSY, ROESY, HMBC, HMQC) and IR, UV, and FABMS data. All compounds significantly inhibited human synovial phospholipase A(2) (PLA(2)) at 10 microM, with an IC(50) value of 5.8 microM for compound 4, which is the most potent inhibitor, with a higher selectivity toward this enzyme than the reference inhibitor manoalide. Pyridinium alkaloids (5-8) mainly inhibited human synovial PLA(2). Compound 8, which contains a sulfonic acid group, is the most interesting inhibitor.     

New cytotoxic clerodane diterpenoids from the leaves and twigs of Casearia membranacea

Bioassay-guided fractionation of an EtOAc-soluble extract of Casearia membranacea has resulted in the isolation of six new clerodane diterpenes, caseamembrins A-F (1-6), and a known compound, rel-(2S,5R,6R,8S,9S,10R,18S,19R)-diacetoxy-18,19-epoxy-6-hydroxy-2-(2-methylbutanoyloxy)cleroda-3,13(16),14-triene (7). The structures of 1-6 were established on the basis of extensive 1D and 2D NMR spectroscopic analysis. In addition, the new derivatives, 8 and 9, were prepared by acylation of 7 and 3, respectively. The isolated diterpenoids and their derivatives were tested against human prostate (PC-3) and hepatoma (Hep3B) cancer cells. Compounds 1, 3-5, and 7 exhibited cytotoxicity against both tumor cells, with IC(50) values below 3 micromicro, while compounds 2, 6, 8, and 9 were less effective.     

Glycosidase-inhibiting pyrrolidines and pyrrolizidines with a long side chain in Scilla peruviana

2,5-Dideoxy-2,5-imino-d-glycero-d-manno-heptitol (homoDMDP) is widely distributed in Hyacinthaceae plants and can also be regarded as the alpha-1-C-(1,2-dihydroxyethyl) derivative of 1,4-dideoxy-1,4-imino-d-arabinitol (d-AB1). In a search for glycosidase inhibitors in this family of plants, we isolated three new d-AB1 derivatives bearing the 2-hydroxypropyl (1), 1,2-dihydroxypropyl (2), and 1,5,7,12,13-pentahydroxytridecyl (3) side chains at the C-1alpha position, respectively, from the bulbs of Scilla peruviana. Alkaloid 3 was a powerful inhibitor of bacterial beta-glucosidase (IC(50) = 80 nM) and bovine liver beta-galactosidase (IC(50) = 90 nM). This plant coproduced four new pyrrolizidine alkaloids, alpha-5-C-(3-hydroxybutyl)-7-epi-australine (4), alpha-5-C-(3-hydroxybutyl)hyacinthacine A(1) (5), alpha-5-C-(1,3-dihydroxybutyl)hyacinthacine A(1) (6), and alpha-5-C-(1,3,4-trihydroxybutyl)hyacinthacine A(1) (7). Alkaloids 4 and 6 were potent inhibitors of yeast alpha-glucosidase, with IC(50) values of 6.6 and 6.3 microM, respectively, and alkaloid 6 was also a potent inhibitor of bacterial beta-glucosidase with an IC(50) value of 5.1 microM.     

Cytochrome P3A4 inhibitors and other constituents of Fibraurea tinctoria

Four new furanoditerpenoids, fibrauretin A ( 1), fibrauretinoside A ( 2), epi-fibrauretinoside A ( 3), and epi-12-palmatoside G ( 4), and a new ecdysteroid glucoside, fibraurecdyside A ( 5), together with seven known compounds including two furanoditerpenoids ( 6 and 7), an ecdysteroid ( 8), and four quaternary protoberberine alkaloids ( 9- 12) were isolated from the stems of Fibraurea tinctoria. The structures of 1- 5 were established on the basis of spectroscopic evidence. Among these compounds, palmatine ( 9) and jatrorrhizine ( 10) showed inhibitory effects against cytochrome P450 3A4 (CYP3A4) with IC 50 values of 0.9 and 2.1 microM, respectively.