Shashi B. Mahato

13C NMR spectra of pentacyclic triterpenoids--a compilation and some salient features

Abstract A compilation of the13C NMR data of a selected variety of naturally occurring pentacyclic triterpenoids, arranged skeletonwise, is provided. A bri

Advances in microbial steroid biotransformation

Microbial biotransformations of various steroids are reviewed. Developmental studies on hydroxylation, carbon-carbon bond cleavage, enzymatic catalysis in nonaqueous solvents, use of cyclodextrin medium, cell immobilization, and new microbial reactions are highlighted. Various steroid substrates, their metabolites and the microorganisms used for the transformations are compiled covering the literature for the period 1992-1995.

Advances in triterpenoid research, 1990-1994

Triterpenoids isolated and characterized from various sources are reviewed. The newer spectroscopic techniques used in their structure elucidation, the new skeleta characterized, their total chemical synthesis, and their biosynthesis are discussed. A compilation of the triterpenoids isolated during the period 1990-1994 along with their occurrence, physical data, spectroscopy and X-ray analysis used for their characterization, is included. The biological activities of the triterpenoids are also discussed.

Review article number 38Triterpenoid saponins

Triterpenoid saponins isolated from various sources are reviewed. The recent techniques used in their isolation and structure elucidation are discussed. A compilation of the triterpenoid saponins isolated and characterized during the period 1979–1986 along with their occurrence is included. The biological activities of the triterpenoid saponins are also covered.

Current trends in microbial steroid biotransformation

Microbial transformations of various steroids are reviewed. Developmental studies on immobilization of microbial cells, techniques for selective transformation and better yields of desired metabolites are highlighted. The present position of microbial biotechnology in the steroid drug industry and the future prospects are discussed. Various steroid substrates, their metabolites and the micro-organisms used for the transformations are compiled covering the literature for the period late 1987-mid 1992.

Dammarane-type triterpenoid saponins from Bacopa monniera

Three new dammarane-type triterpenoid saponins, bacopasaponins A, B and C, of biological interest have been isolated from the reputed Indian medicinal plant Bacopa monniera and identified as 3-O-alpha-L-arabinopyranosyl-20-O-alpha-L-arabinopyranosyl-+ ++jujubogenin, 3-O-[alpha-L-arabinofuranosyl (1--> 2)alpha-L-arabinopyranosyl]pseudojujubogenin and 3-O-[beta-D-glucopyranosyl (1 -->3)[alpha-L-arabinofuranosyl (1--> 2)]alpha-L-arabinopyranosyl]pseudojujubogenin by spectroscopic methods and some chemical transformations. The hitherto undetermined configurations at C-20 and C-22 of pseudojujubogenin were elucidated by phase-sensitive ROESY, and 1H and 13C signals of the saponins were assigned by DEPT, 1H-1H COSY, HSQC and HMBC techniques.

A Review of the Hepatotoxic Plant Lantana camara

Lantana (Lantana camara Linn) is a noxious weed that grows in many tropical and subtropical parts of the world. Ingestion of lantana foliage by grazing animals causes cholestasis and hepatotoxicity. Both ruminants and nonruminant animals such as guinea pigs, rabbits, and female rats are susceptible to the hepatotoxic action of lantana toxins. The hepatotoxins are pentacyclic triterpenoids called lantadenes. Molecular structure of lantadenes has been determined. Green unripe fruits of the plant are toxic to humans. Lantana spp. exert allelopathic action on the neighboring vegetation. The allelochemicals have been identified as phenolics, with umbelliferone, methylcoumarin, and salicylic acid being the most phytotoxic. In addition to phenolics, a recent report indicates lantadene A and B as more potent allelochemicals. Management of lantana toxicosis in animals is achieved by drenching with activated charcoal and supportive therapy. Recent reports on the bilirubin clearance effect of Chinese herbal tea Yin Zhi Huang (decoction of the plant Yin Chin, Artemisia capillaries, and three other herbs) or its active ingredient 6,7-dimethylesculetin, in jaundice are very exciting and warrant investigations on its, possible, ameliorative effects in lantana intoxicated animals. Research is being conducted on new drug discovery based on natural products in different parts of the lantana plant.

Flavonol glycosides from Calotropis gigantea

Besides isolation and characterization of isorhamnetin-3-O-rutinoside, isorhamnetin-3-O-glucopyranoside and taraxasteryl acetate, a new flavonol trisaccharide was isolated from the aerial parts of Calotropis gigantea, and its structure was established as isorhamnetin-3-O-[2-O-beta-D-galactopyranosyl-6-O-alpha-L-rhamnopy ranosyl]- beta-D-glucopyranoside by a combination of fast atom bombardment mass spectroscopy, 1H and 13C NMR spectra and some chemical degradations.

Triterpenoid saponins discovered between 1987 and 1989

Triterpenoid saponins isolated and characterized from various sources are reviewed. The recent techniques used in their isolation and structure elucidation are discussed. A compilation of the triterpenoid saponins isolated during the period from 1987 to mid-1989, together with their occurrence, available physical data and spectroscopy used for their characterization is included. The biological activities of the triterpenoid saponins are also covered.

Steroid transformations by microorgamisms

Abstract Microbial transformations of various steroids are reviewed. Newer developments in this field are discussed. A compilation of different steroid substrates used for transformations by various microorganisms during the period 1979–1982, along with the metabolites formed, is included