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Biomedical subjects

D Gunasekar

Publications and source records attributed to D Gunasekar.

16 recordsLinked to original sources
PubMed2005

Synthesis and bioactivity of some new N-aryl/alkyl/cyclohexyl-N'-(2,3-dihydro-2-oxo-4H-benz[e][1,3,2]oxazaphosphorin-2-yl) ureas.

Several new substituted oxazaphosphorinyl urea derivatives of the type RR'P(O)NHC(O)NHR'' were synthesized from alpha-(3-chloro-4-fluoroanilino)-o-cresol by reaction with chlorides of aryl/alkyl/cyclohexyl carbamidophosphoric acids in the presence of triethylamine at 0-50 degrees C. Their significant insecticidal and antimicrobial activity and promotion of Rhizobium bacteria growth in the soil without effect on the host tissue suggests their possible commercial application as ecofriendly pesticides and antimicrobial agents.

Alternaria↗
PubMed2003

Flavonoids from Andrographis lineata.

Three flavonoids, 5,7,2',3',4'-pentamethoxyflavone (1), 2'-hydroxy-2,4',6'-tri methoxychalcone (2) and dihydroskullcapflavone I (3), together with 17,19,20-trihydroxy-5beta, 8alpha H, 9beta H,10alpha-labd-13-en-16,15-olactone (4), a known diterpenoid and six known flavonoids, 5-hydroxy-7,8-dimethoxyflavanone (5), 5-hydroxy-7,8,2',3',4'-pentamethoxyflavone (6), 5,2'-dihydroxy-7-methoxyflavanone (7), 5,2'-dihydroxy-7,8-dimethoxyflavone (8), 5,2'-dihydroxy-7-methoxyflavone (9) and 5,2'-dihydroxy-7-methoxyflavone 2'-O-beta-D-glucopyranoside (10) were isolated from the whole plant of Andrographis lineata. The structures of these compounds were elucidated on the basis of spectral and chemical studies.

Andrographis↗
PubMed2003

New 2'-oxygenated flavonoids from Andrographis affinis.

Three new 2'-oxygenated flavonoids, (2S)-5,7,2',3',4'-pentamethoxyflavanone (1), 5-hydroxy-7,8,2',5'-tetramethoxyflavone (2), and echioidinin 2'-O-beta-d-(6' '-O-acetyl) glucopyranoside (3), together with four known flavonoids, 7-O-methyldihydrowogonin, 7-O-methylwogonin, skullcapflavone I 2'-methyl ether, and skullcapflavone I, and two diterpenoids, andrograpanin and 14-deoxy-11,12-didehydroandrographolide, were isolated from the whole plant of Andrographis affinis. The structures were elucidated by spectral and chemical studies.

Andrographis↗
PubMed2003

A new biflavonoid from Ochna beddomei.

A new biflavonoid, 2,3-dihydroochnaflavone 7,4',7"-tri-O-methyl ether (1) together with two known biflavonoids namely, 2,3-dihydroochnaflavone (2) and ochnaflavone (3) were isolated from the stem bark of Ochna beddomei. The structures were determined by means of spectral and chemical studies.

Circular Dichroism↗
PubMed2003

A new naphthoquinone from Ceiba pentandra.

A new naphthoquinone, 2,7-dihydroxy-8-formyl-5-isopropyl-3-methyl-1,4-naphthoquinone (1) together with a known naphthoquinone, 8-formyl-7-hydroxy-5-isopropyl-2-methoxy-3-methyl-1,4-naphthoquinone (2), has been isolated from the heartwood of Ceiba pentandra. The structures of 1 and 2 have been elucidated by extensive 1D and 2D NMR experiments.

Ceiba↗
PubMed2002

Flavones from Andrographis viscosula.

Two new 2'-oxygenated flavones, 5,7,2'-trimethoxyflavone (1). and 5,7,2',4',6'-pentamethoxyflavone (2). were isolated from the whole plant of Andrographis viscosula along with three known flavones, echioidinin (3). 5,2',6'-trihydroxy-7-methoxyflavone (4). and echioidin (5). The structures of these compounds were elucidated on the basis of 1D and 2D NMR spectral studies.

Andrographis↗
PubMed2001

A new naphthoquinone from Bombax malabaricum.

A new naphthoquinone 1 together with 7-hydroxycadalene (2) and 8-formyl-7-hydroxy-5-isopropyl-2-methoxy-3-methyl-1,4-naphthoquinone (3) were isolated from the heartwood of Bombax malabaricum. The new naphthoquinone was characterized as 7-hydroxy-5-isopropyl-2-methoxy-3-methyl-1,4-naphthoquinone (1) based on spectral and chemical studies.

Chromatography, Gel↗
PubMed2001

Androechin, a new chalcone glucoside from Andrographis echioides.

A new chalcone glucoside, androechin, and a known flavone glucoside, echioidinin 5-O-glucoside, were isolated from the whole plant of Andrographis echioides. Androechin was characterized as 2,2',6'-trihydroxy-4'-methoxychalcone 2'-O-beta-D-glucopyranoside by spectral and chemical studies.

Glucosides↗
PubMed2001

Two new 2'-oxygenated flavones from Andrographis elongata.

Two new 2'-oxygenated flavones, 5,2',6'-trihydroxy-7-methoxyflavone (3) and skullcapflavone I 2'-O-beta-D-(4"-E-cinnamyl) glucopyranoside (5), together with three known flavones, 7-O-methylwogonin (1), skullcapflavone I (2) and skullcapflavone I 2'-O-beta-D-glucopyranoside (4) were isolated from the whole plant of Andrographis elongata, and the structures were elucidated by FAB-MS and one- and two-dimensional (1D- and 2D)-NMR spectral studies including 1H-1H correlation spectroscopy (COSY), heteronuclear single quantum coherence (HSQC), heteronuclear multiple bond connectivity (HMBC) and rotating frame Overhauser enhancement spectroscopy (ROESY) experiments, and chemical studies.

Acanthaceae↗
PubMed2000

A biflavanone from Cycas beddomei.

A new biflavanone, 7,7"-di-O-methyltetrahydrohinokiflavone together with tetrahydrohinokiflavone were isolated from the stems of Cycas beddomei. The structures were established on the basis of spectral and chemical studies.

Biflavonoids↗
PubMed2000

7-O-Methyltetrahydroochnaflavone, a new biflavanone from Ochna beddomei.

7-O-Methyltetrahydroochnaflavone (1), a new biflavanone, together with nine known flavonoids, afrormosin (2), 2,3-dihydroochnaflavone 7-O-methyl ether (3), kaempferol (4), 2,3-dihydroochnaflavone (5), ochnaflavone (6), (-)-epicatechin (7), kaempferol 3-O-rhamnoside (8), taxifolin 3-O-rhamnoside (9), and kaempferol 3-O-glucoside (10), were isolated from the leaves of Ochna beddomei, and the structures were elucidated by spectral and chemical studies.

Biflavonoids↗
PubMed1999

Flavonol glycosides from cassia hirsuta

A new flavonol glycoside, kaempferol 3-O-alpha-L-rhamnopyranosyl (1-->2)-alpha-L-rhamnopyranoside (1), was isolated from the flowers of Cassia hirsuta along with two known flavonol glycosides, kaempferol 3-O-rutinoside and rutin. The structure of compound 1 has been established on the basis of spectral data and by acid hydrolysis.

Journal Article↗
PubMed1998

A flavone glycoside from Andrographis alata.

A new flavone glycoside, echioidinin 5-glucoside along with its known aglycone, echioidinin have been isolated from the whole plant of Andrographis alata. The structure of the new compound was established as 5,2'-dihydroxy-7-methoxyflavone 5-O-beta-D-glucopyranoside on the basis of spectral and chemical studies.

Journal Article↗
PubMed1998

A new flavone 2'-glucoside from Andrographis alata.

A new flavone glucoside, 5,2',6'-trihydroxy-7-methoxyflavone 2'-O-beta-D-glucopyranoside has been isolated from the whole plant of Andrographis alata. The structure was elucidated on the basis of spectral and chemical evidence.

Flavonoids↗
PubMed1993

Two new sesquiterpene lactones from Ceiba pentandra.

Two new sesquiterpene lactones showing moderate antimicrobial activity have been isolated from the root bark of Ceiba pentandra (Bombacaceae) in addition to the known compounds 8-formyl-7-hydroxy-5-isopropyl-2-methoxy-3-methyl-1,4-naphthaquinone+ ++ [1], and 7-hydroxycadalene [2]. The new compounds were characterized as 2,7-dimethoxy-5-isopropyl-3-methyl-8,1-naphthalene carbolactone [3] and 2-hydroxy-5-isopropyl-7-methoxy-3-methyl-8,1-naphthalene carbolactone [4] by chemical and spectroscopic studies.

Anti-Infective Agents↗