Biomedical subjects
S D Sarker
Publications and source records attributed to S D Sarker.
Isolation and structure elucidation of viscoazucine, a novel sesquiterpene from Polygonum viscosum.
A new sesquiterpene, 1,4-dimethoxycarbonyl-7-(1-methylethyl)- 3,3a,6,7,8,8a-hexahydroazulene (viscoazucine) (1), and a known flavone, 3',5,7-trihydoxy-3,4',5'-trimethoxyflavone (4), have been isolated from Polygonum viscosum. The structures of these compounds were elucidated by spectroscopic analyses, notably UV, MS and NMR.
Resveratrol-type oligostilbenes from Iris clarkei antagonize 20-hydroxyecdysone action in the Drosophila melanogaster B(II) cell line.
Bioassay-guided high-performance liquid chromatography analysis of a MeOH extract of Iris clarkei seeds yielded the resveratrol-type oligomeric stilbenes, ampelopsin B and alpha-viniferin, which antagonize the action of 20-hydroxyecdysone; with a 20-hydroxyecdysone concentration of 50 nM, the ED50 values were 33 microM and 10 microM, respectively. The structures of these compounds were determined by spectroscopic analysis, notably ultraviolet, liquid secondary ion mass spectrometry and modern one- and two-dimensional nuclear magnetic resonance techniques.
A sesquiterpene acid and flavonoids from Polygonum viscosum.
4-Isobutyl-6-methyl-5-oxo-3a,4,5,7a-tetrahydro-1H-inden-13-oic acid (named viscosumic acid) and quercetin 3-O-(6"-feruloyl)-beta-D-galactopyranoside, and the known 3',5-dihydroxy-3,4',5',7-tetramethoxyflavone have been isolated from Polygonum viscosum. The structures of these isolates were determined primarily on the basis of extensive 1D and 2D NMR spectral analyses, notably, 13C PENDANT, COSY45, TOCSY, GOESY, NOESY, HMQC and HMBC.
Constituents of Cassia laevigata.
Calendin (1), cinnamic acid (2), 3-hydroxy-1-(4-hydroxy-3-methoxyphenyl)-propan-1-one (3), 2,3-dihydroxy-1-(4-hydroxy-3-methoxyphenyl)-propan-1-one (4), 3-hydroxy-1-(4-hydroxy-3,5-dimethoxyphenyl)-propan-1-one (5), syringic acid (6) and vanillic acid (7) have been isolated from a dichloromethane extract of the leaves and branches of Cassia laevigata.
Pyranoisoflavones from Rinorea welwitschii.
Reversed-phase HPLC analysis of a dichloromethane extract of the stem-barks of Rinorea welwitschii has afforded two pyranoisoflavones, alpinumisoflavone (1) and di-O-methylalpinumisoflavone (2).
Alkaloids from Balanites aegyptiaca.
High performance liquid chromatographic (HPLC) analysis of a dichloromethane extract of the stem-barks of Balanites aegyptiaca has yielded two known alkaloids, N-trans-feruloyltyramine (1) and N-cis-feruloyltyramine (2), and three common metabolites, vanillic acid, syringic acid and 3-hydroxy-1-(4-hydroxy-3-methoxyphenyl)-1-propanone.
Phytoecdysteroids from Atriplex nummularia.
A bioassay for ecdysteroid agonists/antagonists and ecdysteroid-specific radioimmunoassays, together with a photo-diode-array detector-monitored high-performance liquid chromatography, have been used to analyse a methanol extract of the seeds of Atriplex nummularia. This yielded two phytoecdysteroids, 20-hydroxyecdysone (1) and polypodine B (2).
Quercetin 3-O-(6"-caffeoyl)-beta-D-galactopyranoside from Polygonum viscosum.
The methanol extract of the whole plant parts of Polygonum viscosum has yielded a flavonol glycoside, 3-O-(6"-caffeoyl)-beta-D-galactopyranoside (1), the structure of which has been determined unambiguously by UV and a series of one- and two-dimensional NMR experiments, notably, (1)H, (13)C, DEPT, COSY45, HMBC and HMQC.
Phytoecdysteroids in seeds and plants of Rhagodia baccata (Labill.) Moq. (Chenopodiaceae).
Seeds of Rhagodia baccata afforded, in addition to 20-hydroxy-ecdysone and polypodine B, a novel phytoecdysteroid, (20R)-22-deoxy-20,21-dihydroxyecdysone, the structure of which was elucidated unequivocally by UV, LSIMS and NMR techniques. This compound possessed agonistic activity in the Drosophila melanogaster BII cell bioassay, with an ED50 value of 2.0 x 10(-7)M (ED50 value for 20-hydroxyecdysone = 7.5 x 10(-9)M). The distribution of ecdysteroids in plants of R. baccata has been determined. Highest levels are associated with the youngest aerial tissues and with the roots. Ecdysteroid profiles are qualitatively very similar throughout the plant, with 20-hydroxyecdysone and polypodine B predominating in all plant parts tested.
1 alpha,20R-dihydroxyecdysone from Axyris amaranthoides.
Bioassay/RIA-directed phytochemical examination of the seeds of Axyris amaranthoides afforded a new ecdysteroid: 1 alpha,20R-dihydroxyecdysone [1-epi-integristerone A], together with 20-hydroxyecdysone and polypodine B. The structure of 1 alpha,20R-dihydroxyecdysone was determined unequivocally by UV, LSIMS, and a combination of 1D and 2D NMR techniques.
Two limonoids from Turraea obtusifolia (Meliaceae), prieurianin and rohitukin, antagonise 20-hydroxyecdysone action in a Drosophila cell line.
Bioassay-assisted HPLC analyses yielded two prieurianin-type limonoids, prieurianin and rohitukin, from the seeds of Turraea obtusifolia, which act as antagonists of 20-hydroxyecdysone action in the Drosophila melanogaster BII cell line. With a 20-hydroxyecdysone concentration of 5 x 10(-8) M, the ED50 values for prieurianin and rohitukin are 10(-5) M and 1.25 x 10(-4) M, respectively.
Cucurbitane-type compounds from Hemsleya carnosiflora antagonize ecdysteroid action in the Drosophila melanogaster BII cell line.
The ecdysteroid agonist and antagonist activities of 3 cucurbitanes, 2 cucurbitane glycosides and 2 cucurbitacins isolated from Hemsleya carnosiflora (Cucurbitaceae) have been determined in the Drosophila melanogaster BII bioassay. Carnosiflogenins A and C and carnosiflosides II and VI possess antagonistic activity. Carnosiflogenin A was also found to induce the formation of spindle-shaped cells with high frequency in both the agonist and antagonist assays. At 10(-3) M, carnosiflogenins B and C were cytotoxic, 23,24-Dihydrocucurbitacin F and 25-acetoxy-23,24-dihydrocucurbitacin F are also antagonistic at high concentrations. The concentration dependencies of the antagonistic activities of these two cucurbitacins, carnosiflosides II and VI and carnosiflogenin C are presented. The biological and ecological significance of these results are discussed in relationship to the concentrations present in the rhizomes of H. carnosiflora.
Application of gradient-enhanced nuclear Overhauser effect spectroscopy GOESY) in the structure elucidation of plant secondary metabolites.
Gradient enhanced nuclear Overhauser effect spectroscopy (GOESY) has been applied in the structural elucidation of five plant secondary metabolites: eucalyptin, arctigenin, 5-geranyloxy-7-methoxycoumarin, 2,6-dihydroxy-4-methoxyisovalerophenone and N-feruloyltyramine. The importance and sensitivity of this technique in structure elucidation of plant secondary metabolites are discussed.