T. R. Seshadri

Neurotoxic compounds of the seeds of lathyrus sativus

Abstract The seeds of Lathyrus sativus responsible for human lathyrism in India have been examined for toxic components. Four ninhydrin-positive substances were detected in the 30% aqueous ethanol extract by paper chromatography, of which two are present in appreciable amounts. The most prominent one has been isolated in crystalline form and studied for chemical and physiological (neurotoxic) properties and identified as (-)-β-oxalylaminoalanine. The second seems to be homoarginine. The other minor components have still to be identified.

Polyphenols of Pterocarpus and Dalbergia woods

Abstract The flavanoid and neoflavanoid constituents of the Pterocarpus and Dalbergia species are reviewed together with related compounds. Several synthetic procedures analogous to biosynthetic pathways are described.

The glucosides of Butea monosperma

Abstract A reinvestigation of the flowers of Butea monosperma revealed the presence of seven flavonoid glucosides. Two of them are butrin and isobutrin, which have been isolated earlier from the plant. Three glucosides have been identified as coreopsin, isocoreopsin and sulphurein. The remaining two are new and have been assigned the structures IX (monospermoside) and X (isomonospermoside). The glucosides III, IV, IX, and X have been synthesized. The shift in the u.v. spectrum of 3-hydroxy-2′,4,4′-trimethoxy chalcone, on addition of alkali, is similar to what has been earlier noted with 2′-hydroxychalcones.

Chemical components of the fruits of Psidium guava

Abstract The fruits of Psidium guava were examined at three different stages of growth to follow the chemical changes. From the unripe fruits an ester of hexahydroxydiphenic acid with l -arabinose has been obtained and its constitution established. It disappears in the ripe fruits, which contain mainly free ellagic acid. Leucocyanidin and oxalates are present at their maximum in the unripe fruits and diminish with ripening.

New reagents for the synthesis of depsides : Methyl evernate, methyl lecanorate, evernic acid and atranorin

Lichen depsides have now been synthesized by making use of two reagents, dicyclohexyl-carbodiimide (DCC) and trifluoroacetic anhydride. Methyl evernate, methyl lecanorate and evernic acid have been prepared in satisfactory yields. Altranorin has been synthesized for the first time.

Constitution of mangiferin

Abstract Mangiferin, C 19 H 18 O 11 , has been isolated from the leaves, heartwood and stem-bark of Mangifera indica . Its properties indicate that it is a stable C-glycoside of the xanthone group. Reductive hydrolysis with hydriodic acid and oxidation with ferric chloride yield 1,3,6,7-tetrahydroxyxanthone and glucose respectively indicating that it is a glucoside of the former and oxidation with periodic acid reveals that the sugar is in the pyranose form. The position of linkage has been shown to be 2 by oxidizing mangiferin tri and tetra methyl ethers with periodate to the corresponding α-hydroxyacetaldehydes of trimethoxy and tetramethoxyxanthones and comparing them with synthetic samples obtained from the appropriate 2-allylxanthones. This has been further supported by oxidation of mangiferin tetra methyl ether and 2-allyl-1,3,6,7-tetramethoxyxanthone with permanganate yielding 1,3,6,7-tetramethoxyxanthone-2-carboxylic acid.

Constitution and synthesis of maxima isoflavones-A and -A

Abstract By means of the synthesis of 3′, 4′, 7,8-tetramethoxy isoflavone and of the corresponding dimethylenedioxy compound and comparison with the natural products, the constitution of maxima isoflavone-A is revised and its synthesis accomplished. The synthesis of maxima isoflavone-B has been carried out in two ways.

Terpenoids of Pterocarpus santalinus heartwood

From the heartwood of Pterocarpus santalinus a group of six closely related sesquiterpenes has been isolated which includes three new sesquiterpenes namely isopterocarpolone, pterocarptriol and pterocarpdiolone besides the known β-eudesmol, pterocarpol and cryptomeridiol. Their structures have been determined by spectral and chemical studies. Three triterpenes, acetyl oleanolic aldehyde, acetyl oleanolic acid, and an unidentified compound along with pterostilbene have also been obtained.

Structural studies on santalin permethyl ether

Abstract The chloroform extract of the heartwood of Pterocarpus santalinus yielded a mixture of red pigments which could be separated by polyamide column chromatography into two major compounds, santalin- A and santalin- B . Both gave the same permethyl ether, C 38 H 36 O 10 which had 8 methoxyls and formed a number of derivatives typical of anhydrobenzopyranols. IR and UV spectra confirmed the same. NMR and MS suggested the presence of homoveratrayl group supported by the formation of veratraldehyde in alkali degradation. Permanganate oxidation gave 2,4-dimethoxy benzoic acid, veratric acid and 3,4,6-trimethoxy phthalic acid. On a basic fluorone skeleton, the substituents in the A ring are indicated by 2,4-dihydroxy-5-methoxy benzaldehyde, an alkali fission product and, further, 2,4-dimethoxy phenyl and homoveratryl units are located in ring C based on NMR, MS and biogenetic considerations. The residues constitute another benzene ring fused to ring C leading to the complete structures of the permethyl ether as (VII) which explains all its degradations and which constitutes a highly condensed biflavonoid of a new type.

Isolation and synthesis of some coumarin components of Mesua ferrea seed oil

Abstract Two different samples of Mesua ferrea seed oil yielded mammeigin and mesuol as the main phenolic components. The synthesis of mammeisin and mammeigin has been carried out and also the conversion of mesuol into mesuagin.