Prabir K. Chaudhuri

Lagerenyl acetate and lagerenol two tetracyclic triterpenoids with the cycloartane skeleton from Lagerstroemia lancasteri

Abstract Lagerenyl acetate and lagerenol two new tetracyclic triterpenoids with the cycloartane skeleton together with four other triterpenoids 2α-hydroxy- 3β-E-p-coumaryloxy-urs-12-en-28-oic acid (jacoumaric acid, isolated as its monoacetylmethylcarboxylate derivative), 2α-hydroxyursolic acid (isolated as its diacetate), germanicyl acetate and friedelin, and sitosterol were isolated from the leaves and twigs of Lagerstroemia lancasteri. The structures of lagerenyl acetate and lagerenol were established as 3β-acetoxycycloart-24-one and 3β-hydroxycycloart-24-one, respectively, on the basis of spectral and chemical evidence.

Echinozolinone, an alkaloid from Echinops echinatus☆

Abstract In addition to echinopsine and echinopsidine, a new alkaloid, echinozolinone, has been identified in Echinops echinatus as 3(2-hydroxyethyl)-4(3H)-quinazolinone from its spectral data. This is the first report of alkaloids from this plant and the first occurrence of a 4-quinazolinone alkaloid in the Compositae.

An acylated flavone apigenin 7-O-β-D-(4″-cis-p-coumaroyl)glucoside from Echinops echinatus

Abstract Besides apigenin 7-O-glucoside, a new acylated flavone has been identified in Echinops echinatus as apigenin 7-O-β- D -(4″-cis-p-coumaroyl)glucoside from spectral and chemical analysis.

(−)-Maglifloenone, a novel spirocyclohexadienone neolignan and other constituents from Magnolia liliflora

Abstract A new neolignan designated (−)-maglifloenone and the known one futoenone, both of which contain the rarely occurring spirocyclohexadienone skeleton, have been isolated together with the tetrahydrofuranolignan (+)-veraguensin, an optically inactive tertiary base taspine and β-sitosterol from the leaves and twigs of Magnolia liliflora. The structure and stereochemistry of (−)-maglifloenone have been deduced from the spectral data and the mass fragmentation of (−)-maglifloenone and futoenone have been rationalized. This is the first report of two neolignans of spirocyclohexadienone skeleton and of taspine from the Magnoliaceae family and the second report of the natural occurrence of futoenone.

A new lipid and other constituents from the rhizomes of Nelumbo nucifera

A new ursane triterpenoid ester, urs-12-en-3β-O-9E,12E-octadecadienoate, was identified from the rhizomes of Nelumbo nucifera by spectral and chemical analyses along with the isolation of seven known compounds: palmitic acid, linoleic acid, 9E,12E,15E-octadecatrienoic acid, α-amyrin, β-sitosterol, betulinic acid, and β-sitosterol-3-O-glucoside.

A labdane diterpenoid sterol from Lagerstroemia lancasteri

Abstract A new labdane diterpenoid, lagerstronolide, having a β-substituted γ-butyrolactone moiety, stigmast-4-ene-3β,6α-diol were isolated together with sitosterol glucoside from Lagerstroemia lancasteri . The structures of the new compounds were determined by means of spectral chemical analysis. This is the first report of labdane diterpenoid in the Lythraceae family.

A new triterpenoid from the rhizomes of Nelumbo nucifera

A new triterpenoid, 2α,24–diacetoxy–3β–hydroxyolean–12–en–28–oic acid (1), was characterised from the rhizomes of Nelumbo nucifera Gaertn by spectroscopic and chemical methods along with four known compounds, hyptatic acid-A (2α,3β,24–trihydroxyolean–12–en–28–oic acid) (2), maslinic acid (2α,3β–dihydroxyoleane–12–ene–28–oic acid), betulin and lupeol.

Reduction of andrographolide and its stereostructure by NMR and X-ray study

Andrographolide (1) on asymmetric reduction with nickel boride in situ led to the identification of a product as 12,13 R-dihydroandrographolide (3) in de (>96%). The structure and stereochemistry of compound 3 were established by NMR study and confirmed by X-ray crystallographic analysis. β-Substituent of γ-butyrolactone in andrographolide exerted diastereomeric selectivity in reduction. Neoandrographolide (2) under similar condition yielded 5.

Narceinone, an alkaloid from Papaver somniferum☆

Abstract Besides narceine, a new secophthalideisoquinoline alkaloid, narceinone, has been identified in the unlanced dried capsules of Papaver somniferum as 14-oxonarceine from spectral analysis and by the biomimetic oxidation of narceine.

Structural characteristics, bioavailability and cardioprotective potential of saponins

Graphical abstract Cardioprotective activity of saponins via different molecular targets.