E. Venkata Rao

8-Substituted flavonoids and 3′-substituted 7-oxygenated chalcones from Tephrosia purpurea

The isolation and characterisation of ten unusual and closely related flavonoids from the roots of T. purpurea are reported. Three of these compounds are new natural products and they all contain an isopentenyl derived unit attached to C-8 (in the flavones) or the corresponding C-3′(in the chalcones), suggesting that they are derived from a common biosynthetic precursor. The 1H and 13C n.m.r. spectra of use in structure elucidation are reported.

Nine isoflavones from Tephrosia maxima

The isolation and characterisation of nine closely related 3′,4′-disubstituted isoflavones from the aerial parts and roots of Tephrosia maxima

A prenylated flavanone from Tephrosia maxima

Abstract A new flavanone, maxima flavanone A, was isolated from the chloroform extract of the roots of Tephrosia maxima along with maxima isoflavone J and t

Prenylated flavonoids from Tephrosia spinosa

Abstract The isolation and characterization of a new chalcone, spinochalcone C, and two new flavanones, spinoflavanones A and B, from various parts of Tephrosia spinosa are reported in addition to the known flavanone, fulvinervin A.

Carbohydrates of Padina tetrastromatica

Abstract Extraction with hydrochloric acid (pH 2.5) of the brown alga Padina tetrastromatica afforded water-soluble and water-insoluble polysaccharides. The water-soluble polysaccharide was fractionated using cetyltritmethyl ammonium bromide and chromatography on DEAE-cellulose and Sephadex G-100. A neutral laminaran like glucan and two new sulphated heteropolysaccharides comprising d -glucuronic acid, l -fucose, l -rhamnose, d -xylose, d -arabinose, d -galactose, d -glucose and half-ester sulphate were obtained. The alginic acid isolated from this brown seaweed was found to be predominantly of poly 1 → 4β- d -mannuronic acid type. The water-soluble sulphated polymer showed high anticoagulant activity.

Cleistanthoside B, a diphyllin glycoside from Cleistanthus patulus heartwood

Abstract From the heartwood of Cleistanthus patulus , a new diphyllin glycoside, cleistanthoside B, has been isolated and its structure elucidated as diphyllin-4-yl 4- O -methyl-β- D -xylopyranoside from its chemical properties and spectral data.

Two chalcones from Tephrosia spinosa

Abstract Chemical examination of the petroleum and chloroform extracts of the roots of Tephrosia spinosa has yielded two new chalcones, spinochalcones A and B, in addition to the known chalcone flemistrictin A.

Two prenylated flavanones from Mundulea suberosa

Abstract Two new prenylated flavanones, mundulea flavanones A and B, were isolated from the chloroform extract of stembark of Mundulea suberosa along with the previously reported compounds munetone, mundulone and mundulea lactone. Their structures were established by spectral data as 4′-hydroxyisoderricin and 7-methyl-4′-hydroxyglabranin

Structural features of the sulphated polysaccharide from a green seaweed, Cladophora socialis☆

A sulphated heteropolysaccharide, [alpha]27D + 59.9 degrees, has been isolated from a green seaweed, Cladophora socialis, by extraction with dilute acid and purified by fractional precipitation. The polymer is composed of galactose (58.3%), arabinose (31.8%), xylose (10.6%) and sulphate (16.9%). The results of methylation analysis, periodate oxidation and partial acid hydrolysis studies indicate that the polymer is a branched one and is composed of 1,3-linked galactose and 1,4-linked arabinose units. Xylose is present at the non-reducing end position of the branches. Both arabinose and galactose carry branches. Desulphation and subsequent analysis of the polymer show that some of the arabinose units carry sulphate groups at C-3 and some of the galactose units carry the sulphate groups at C-4 and some at C-4 and C-6 as well.

Structural studies of a polysaccharide isolated from the green seaweed Chaetomorpha anteninna

Extraction of the green seaweed Chaetomorpha anteninna with water, followed by fractionation using the copper complex, gave a sulphated heteropolysaccharide, [alpha]D27 +84 degrees, that contained arabinose (57.7%), galactose (38.5%), rhamnose (3.8%), and sulphate (11.9%). Application of methylation analysis, periodate oxidation, and partial acid hydrolysis indicated a branched structure with 4-linked arabinose, 4- and 3-linked galactose, and 4-linked rhamnose residues. Both the arabinose and galactose residues carried branches. Desulphation and analysis of the polymeric product showed that sulphate groups were located at C-2 of some of the interior arabinose residues, C-4 of some of the non-reducing-end arabisoyl groups, and C-3 of the non-reducing-end galactosyl groups.