S. S. Rajan

Antifeedant neo-clerodanes from Teucrium tomentosum Heyne. (Labiatae)

From the acetone extract of Teucrium tomentosum, a new antifeedant neo-clerodane diterpenoid teuctosin (1) was isolated along with teuflin (2), teucrin-H(2) (3), 6beta-hydroxyteuscordin (4), 6beta-acetylteuscordin (5) and montanin-D (6). The structure of the new compound was elucidated comprehensively using 1D and 2D NMR methods and confirmed by X-ray crystallography. All the compounds showed effective antifeedancy against Plutella xylostella and Spodoptera litura at 10 mug/cm(2) of leaf area.

Microwave- and ultrasound-assisted oxidation of bio-active limonoids

Abstract Tetranortriterpenoids from Azadirachta indica A. Juss and Soymida febrifuga (Meliaceae), have been selectively oxidized to single major products which exhibit bioactivity higher than the parent compounds, comparable to that of azadirachtin A. The reaction proceeds to completion in less than 15 min and 1 min on being assisted by ultrasound and microwave irradiation, respectively.

Photooxidation of Cedrelone, a Tetranortriterpenoid from Toona ciliata¶

Abstract Cedrelone, a tetranortriterpenoid on photolysis by UV light yields a true photooxidation product 3 [14 β,15β,22β,23β-diepoxy-6-hydroxy-1,5,20(22)-meliatriene-2,7,21-trione] whose structure is well established by NMR studies and confirmed by X-ray crystallography, along with product 4 [14 β,15β-epoxy-6,23-dihydroxy-1,5,20(22)-meliatriene-2,7,21-trione]. Addition of rose bengal increases the rate of photooxidation whereas DABCO decreases rate of photolysis proving the involvement of singlet oxygen in the photooxygenation. Both the photoproducts exhibited antifeedant activity.

Nimbolide and isonimbolide

Nimbolide 1, a potent molecule of biological significance, was isolated. Attempts were made to cleave the ether linkage in nimbolide using boron trifluoride etherate in the presence of tetrabutyl ammonium bromide so as to generate a ring-opened structure akin to azadirachtins, which are known to possess excellent antifeedant properties. However, a novel rearranged product was envisaged during the course of the reaction, which was determined as isonimbolide 2—a structural isomer of nimbolide through spectroscopic methods.

Structure of mangostin

AbstractThe crystal structure of 1,3,6-trihydroxy-2,8-bis (3-methyl-2-butenyl)-9H-xanthen-9-one, Mangostin (C24H26O6) isolated from the fruit hulls of Garcinia mangostana, Guttiferae is reported. The compound crystallizes in space group

Molecular and Crystal Structure of Azadirachtin-H

P\bar 1

Crystal structure of nimbin

, with cell parametersa = 11.194(5), b = 13.450(5), c = 9.875(5) Å, α = 108.13(5), β = 108.13(5), γ = 99.64(5)°. The mean planes of the two isoprenyl side chains are oriented at an angle 49.6° in this structure while it is 159.8(2)° in mangostin acetate. The packing of the molecules is due to the solvent mediated network of hydrogen bonds. The conformation and packing of molecules are also different from mangostin acetate.

Semi-synthetic modification of nimbolide to 6-homodesacetylnimbin and 6-desacetylnimbin and their cytotoxic studies.

14,15-Epoxynimonol, a new tetranortriterpenoid, was obtained from the fresh green whole leaves of Azadirachta indica and its structure has been assigned on the basis of spectral data. The 14,15-epoxide was assigned β-configuration by comparison with cedrelone.