Anil B. Ray

Structures of cleomiscosins, coumarinolignoids of cleome viscosa seeds

Abstract Structures of cleomiscosins A, B and C, three new coumarino-lignoids isolated from the seeds of Cleome viscosa Linne, have been established as 1a , 2a and 1f irrespectively, on the basis of spectral and chemical evidence. The compounds exhibited liver-protective properties.

Withasteroids, a Growing Group of Naturally Occurring Steroidal Lactones

Withasteroids are a group of naturally occurring C28-steroidal lactones built on an intact or rearranged ergostane framework. Withaferin A (64), the first member of this group of compounds, was isolated (1) from the well-known Indian medicinal plant, Withania somnifera (Sanskrit: Aswagandha) and its structure was fully elucidated by Lavie and coworkers in 1965 (2). The structural novelty and interesting biological activities (3) elicited by this compound led to a thorough chemical investigation of the plant and numerous compounds having similar structural features were isolated. These C28-steroidal lactones characterised by a nine carbon side chain with a six membered ring lactone were designated as ‘withanolides’after the name of the plant genus (4). The withanolide skeleton may therefore, be defined as 22-hydroxyergostan-26-oic acid 26,22-lactone (I) and using this trivial name, withaferin A (64) may be designated as 4β, 27-dihydroxy-5β, 6β-epoxy-l-oxowitha-2,24-dienolide, the nomenclature that has been most widely adopted. However, many structurally related C28-steroidal lactones which do not conform to the above definition have also been referred to as with-anolides (5), a practice giving rise to confusion. Also, there are many novel structural variants of withanolides with modifications either of the carbocyclic skeleton or of the side chain and these have often been described as modified withanolides or ergostane-type steroids related to withanolides.

Structure of cleomiscosin A, a coumarino-lignoid of Cleome viscosa seeds

Abstract Cleomiscosin A, isolated from the seeds of Cleome viscosa , has been shown to be a coumarino-lignoid and its structure has been advanced as I on the basis of chemical and physical evidence.

Cleomiscosin D, a coumarino-lignan from seeds of Cleome viscosa

Abstract Cleomiscosin D, a minor coumarino-lignan of the seeds of Cleome viscosa , has been proved to be regioisomer of cleomiscosin C. A method of degradation of coumarino-lignans for the identification of the coumarin moiety has been developed.

Withaminimin, a withanolide from Physalis minima

Abstract The structure of withaminimin, a new ergostane-type steroid from Physalis minima, was established by spectral analysis (1H and 13C NMR, MS) and chemical transformations, as (20S,22R)-15α-acetoxy-5α,6β,14α-trihydroxy-1-oxowitha-2,16,24-trienolide. An unusual MH2O+ quasi-molecular ion was observed in the chemical ionization mass spectrum of the natural product.

Ethyl brevifolin carboxylate from Flueggea microcarpa

Abstract The leaves of Flueggea microcarpa contain the ethyl ester of brevifolin carboxylic acid. The elucidation of the structure of this isocoumarin involved extensive use of 1H and 13C NMR data, which are fully reported and analysed for the first time; especially useful were long-range CH coupling interactions. NMR parameters for some models, including norbergenin, as well as pyrogallol, gallic acid and their triacetates, are also reported.

Withaperuvin E and nicandrin B, withanolides from physalis peruviana and nicandra physaloides☆

Abstract Novel withanolides, withaperuvin E and nicandrin B, isolated respectively, from Physalis peruviana and Nicandra physaloides , were fully characterized by chemical and spectroscopic means.

Non-conventional Lignans: Coumarinolignans, Flavonolignans, and Stilbenolignans

Lignans, by convention, are a group of natural products that are formed by linking two phenylpropanoid units (C6C3 units) by oxidative coupling. Most importantly, in a lignan, two (C6C3 units) are bound through the central carbon of their side chains, i.e. the 8 and 8′ positions (1, 2). The occurrence of C6C3-dimers, linked at sites other than the 8–8′ positions, is also known and these compounds have been termed neolignans (3, 4).

Quaternary alkaloids of Thalictrum foliolosum

Abstract The isolation and identification of eleven alkaloids from the quaternary alkaloid fraction of a root extract of Thalictrum foliolosum are described

Squamostatin-A: Unprecedented bis-tetrahydrofuran acetogenin from Annona squamosa

Abstract Squamostatin-A (2), a new type of bis-tetrahydrofuran fatty acid γ-lactone, has been isolated from Annona squamosa L. (Annonaceae) and its structure has been elucidated on the basis of spectral evidence.