Raghunath S. Thakur

Carbon-13 NMR spectroscopy of steroidal sapogenins and steroidal saponins

Abstract The 13 C NMR chemical shifts of 130 naturally occurring steroidal sapogenins and saponin derivatives published up to 1983 are listed and a number of methods for signal assignment are explained. The utility of 13 C NMR spectral analysis for the structure elucidation of these compounds is discussed.

Antihepatotoxic principles of Phyllanthus niruri herbs

Among phyllanthin, hypophyllanthin, triacontanal and tricontanol isolated from a hexane extract of Phyllanthus niruri, phyllanthin and hypophyllanthin protected against carbon tetrachloride- and galactosamine-induced cytotoxicity in primary cultured rat hepatocytes, while triacontanal was protective only against galactosamine-induced toxicity.

Biosynthesis of artemisinin in Artemisia annua

Abstract The isotope ratios ( 3 H: 14 C) in arteannuin B and artemisinin biosynthesized in Artemisia annua from [4 R - 3 H 1 ,2- 14 C]-, [5- 3 H 2 ,2- 14 C]- and [2- 3 H 2 ,2- 14 C](3 RS )- mevalonate have revealed that two specific 1,2-hydride shifts take place during the oxidation and lactonization of the germacrane skeleton to yield dihydrocostunolide. The gem -methyls of DMAPP retain their identity until the final steps of artemisinin biosynthesis. Arteannuin B is considered to be a late precursor of artemisinin and the following biosynthetic sequence is suggested: farnesylpyrophosphate → germacrane skeleton → dihydrocostunolide → cadinanolide → arteannuin B → artemisinin.

Biotransformation of arteannuic acid into arteannuin-B and artemisinin in Artemisia annua

Abstract In Artemisia annua , [ 14 C]arteannuic acid was incorporated into arteannuin-B as well as artemisinin, both in vivo and in a cell free system. Fe 2 , 2-oxoglutarate, and peroxidase-H 2 O 2 enhanced the incorporations under in vitro conditions. The results suggest that arteannuic acid might be a common precursor for arteannuin-B and artemisinin synthesis.

Occurrence of some antiviral sterols in Artemisia annua

Abstract Out of the twenty one medicinal plants evaluated for their virus inhibitoryactivity against tobamoviruses on their test hosts reacting hypersensitively, extracts of Lawsonia alba, Artemisia annua and Cornus capitata showed high virus inhibitory activity. The virus inhibitory agent (s) occurring in A. annus plant was isolated by conventional methods and identified as sterols. The sterols were characterized by spectral methods as sitosterol and stigmaterol.

Torvonin-A, a spirostane saponin from Solanum torvum leaves

Abstract A new steroidal saponin, torvonin-A, has been isolated from S. torvum leaves and its structure has been established as neochlorogenin-3- O -β- L -rhamnopyranosyl (1→2)β- L -rhamnopyranoside.

Biosynthesis of artemisinic acid in Artemisia annua

Abstract The isotopic and atomic 14 C/ 3 H ratios in artemisinic acid biosynthesized in Artemisia annua from [2- 14 C, 2- 3 H 2 ]-, [2- 14 C,4 R - 3 H 1 ]-, [2- 14 C,5- 3 H 1 ]MVA have revealed that two specific 1,2-hydrogen shifts take place during the formation of the cadinane skeleton of artemisinic acid and that the gem -methyls derived from DMAPP retain their identity during the formation of this compound.

Spirostanol saponins from Paris polyphylla, structures of polyphyllin C, D, E and F

Abstract The structures of four new saponins, polyphyllin C, D, E and F, isolated from the tubers of Paris polyphylla have been elucidated as diosgenin-3- O -α- l -rhamnopyranosyl(1→3)-β- d -glucopyranoside, diosgenin-3- O -α- l -rhamnopyranosyl(1→3)- [α- l -arabinofuranosyl(1→4)]-β- d -glucopyranoside, diosgenin-3- O -α- l -rhamnopyranosyl(1→2)-α- l -rhamnopyranosyl (1→4)[α- l -rhamnopyranosyl(1→3)]-β- d -glucopyranoside and diosgenin-3- O -α- l -rhamnopyranosyl(1→4)[α- l - rhamnopyranosyl(1→3)][β- d -glucopyranosyl(1→2)]-α- l -rhamnopyranoside, respectively, on the basis of chemical and spectral data.

Furostanol glycosides from Trigonella foenum-graecum seeds

Abstract Two new furostanol glycosides, trigofoenosides F and G, have been isolated as their methyl ethers from the methanolic extract of Trigonella foenum-graecum seeds (Leguminosae). The structures of the original glycosides have been determined as (25 R )-furost-5-en-3β,22,26-triol, 3- O -α- l -rhamnopyranosyl (1 → 2)β- d -glucopyranosyl (1 → 6)β- d -glucopyranoside; 26- O -β- d -glucopyranoside and (25 R )-furost-5en-3β,22,26-triol, 3- O -α- L -rhamnopyranosyl (1 → 2) [β- d -xylopyranosyl (1 → 4)]β- d -glucopyranosyl (1 → 6)β- d -glucopyranoside; 26- O -β- d -glucopyranoside, respectively.

Analysis of some tropane alkaloids in plants by mixed-column high-performance liquid chromatography a☆

Abstract A simple and rapid high-performance liquid chromatographic method for the determination of atropine and scopolamine in plants using the combination of two different polarity columns in series and direct injection of plant extract is described. Application of the method to the analysis of two species of solanaceous plants is reported.