N. Savitri Kumar

An antifungal constituent from the stem bark of Butea monosperma

The petroleum and ethyl acetate extracts of the stem bark from Butea monosperma displayed antifungal activity against Cladosporium cladosporioides. The active constituent of low polarity was isolated by bioassay-monitored chromatographic fractionation, and identified as (-)-medicarpin by comparison of physical data. The antifungal activity of (-)-medicarpin was found to be greater than that of Benlate, a standard fungicide, while (-)-medicarpin acetate also exhibited significant activity against C. cladosporiodes.

Separation of proanthocyanidins isolated from tea leaves using high-speed counter-current chromatography

The proanthocyanidin extract from tea (Camellia sinensis) leaves was purified for the further study of the biological role of proanthocyanidins in blister blight leaf disease of tea, which is caused by the fungus Exobasidium vexans. An aqueous acetone extract of proanthocyanidins prepared from healthy tea leaves was partially purified using Sephadex LH-20 chromatography. The crude proanthocyanidin extract obtained was fractionated with high-speed counter-current chromatography (HSCCC) using the solvent system n-hexane-EtOAc-MeOH-water (1:5:1:5). The purity of the each isolated fraction after a single HSCCC run was evaluated by high-performance liquid chromatography (HPLC). Seven fractions of high purity were isolated. The identity of the compound present in each fraction isolated was established using electrospray ionization mass spectrometry (ESI-MS) and nuclear magnetic resonance (NMR) spectroscopy. Five proanthocyanidins and two flavanol digallates, (-)-epigallocatechin digallate (EGCDG) and (-)-epicatechin digallate (ECDG) were isolated. Comparison of spectral data of the proanthocyanidins isolated with those previously reported indicated that all five were known B-type proanthocyanidins with 2,3-cis stereochemistry in both the upper (u-unit) and the terminal (t-unit) units, and 4R configuration of the C-ring in the u-unit. The proanthocyanidins were established to be dimers composed of (-)-epigallocatechin gallate (EGCG), (-)-epicatechin gallate (ECG) and (-)-epiafzelechin gallate (EAG) units with the following structures: EGCG-(4beta-->6)-EGCG, ECG-(4beta-->6)-EGCG, EGCG-(4beta-->6)-ECG, EAG-(4beta-->6)-EGCG, ECG-(4beta-->6)-ECG by analysis of spectral data. Therefore HSCCC offers a powerful method for the separation of a group of closely related naturally occurring compounds.

Attack on tea by Xyleborus fornicatus: inhibition of the symbiote, Monacrosporium ambrosium, by caffeine.

Abstract Methylene chloride extracts of tea ( Camellia sinensis ), stems from two clones, TRI 2023 and TRI 2025, inhibited growth of the fungus, Monacrosporium ambrosium , the symbiote of the shot-hole borer beetle, Xyleborus fornicatus . Activity-guided fractionation of the extracts yielded caffeine as the major antifungal compound. The caffeine content of healthy pencil-thick stems of the two clones was estimated and compared with the caffeine content of pencil-thick stems infected by the beetle. Healthy stems of clone TRI 2023 had a very low caffeine content, but accumulation of caffeine was found to have occurred to a greater extent in infected samples of stems from this clone. Infected stems from both clones had a higher caffeine content than samples of healthy stems. The effect of caffeine on mycelial growth, sporulation and spore germination of M. ambrosium in liquid and agar media was also studied. Inhibition of mycelial growth was observed with 5000 ppm of caffeine, while 500 ppm resulted in 21% inhibition in the liquid medium. In the agar medium, colony-size was reduced by 500 ppm of caffeine, while no growth took place with 5000 ppm of caffeine. Inhibition of sporulation was observed with 2000 ppm of caffeine. Germination of conidia was inhibited completely with 3750 ppm of caffeine; inhibition was also observed with 500–2500 ppm of caffeine.

A lupane derivative and the 13C NMR chemical shifts of some lupanols from Pleurostylia opposita

Abstract A new lupane derivative isolated from Pleurostylia opposita has been assigned the structure 6,β-hydroxy-lup-20(29)-en-3-one, using spectral evidence and chemical interconversions. The 13C NMR spectral assignments of 20-hydroxy-lupan-3-one, 6β, 20-dihydroxy-lupan-3-one, 6β,28-dihydroxy-lup-20(29)-en-3-one and 20-hydroxy-lupane-3, 6-dione previously isolated from the same plant are also reported.

Effect of caffeine on shot-hole borer beetle (Xyleborusfornicatus) of tea (Camellia sinensis)

Abstract Caffeine was found to inhibit oviposition in shot-hole borer beetle ( Xyleborusfornicatus ) of tea ( Camellia sinensis ) in laboratory culture media. Caffeine also delayed theappearance of the different developmental stages in the life cycle, but apparently did not have alethal effect on the beetle. The inhibitory effect of caffeine on the beetle was partially reduced inthe presence of the polyphenol tannic acid.

A lupenediol from Euonymus revolutus

Abstract A new lupane derivative isolated from Euonymus revolutus (Celastraceae) has been established to be 2α,3α-dihydroxy-lup-20(29)-en-28-oic acid on the basis of chemical interconversions and spectroscopic data.

Structural studies of an arabinoxylan isolated from Litsea glutinosa (Lauraceae)

A water-soluble arabinoxylan (D-xylose and L-arabinose in the molar ratio 1.0:3.4) was isolated from the mucilaginous bark of Litsea glutinosa (Lauraceae). The results of methylation analysis, partial hydrolysis, and 1H- and 13C-n.m.r. spectroscopy indicated a backbone of (1----4)-linked beta-D-xylopranosyl residues substituted at both positions 2 and 3 with side chains composed of either single or (1----3)-linked arabinofuranosyl residues. Both alpha-L- and beta-L-arabinofuranosyl residues were present. It is possible that side chains composed of two beta-L-arabinofuranosyl residues are attached mainly at O-2 of some xylosyl residues.

Anti-bacterial activity of extracts from the brown seaweed Stoechospermum marginatum

Abstract The methanol extract of the brown seaweed Stoechospermum marginatum was found to inhibit the growth of Staphylococcus aureus . The active constituents were found to be a mixture of diterpenoid monoacetates having the spatane skeleton.

Arylalkanones from Myristica dactyloides

Abstract Four new arylalkanones isolated from the stem bark of Myristica dactyloides were identified as 1-(2-methoxy-6-hydroxyphenyl)tetradecan-1-one, 1-(2-methoxy-6-hydroxyphenyl)-9-(3′,4′-methylenedioxyphenyl)-nonan-1-one, 1-(2,6-dihydroxyphenyl)tetradecan-1-one and 1-(2-methoxy-6-hydroxyphenyl)-9-(4′-hydroxyphenyl)-nonan-1-one.

Structural studies of an arabinoxylan isolated from the leaves of Neolitsea cassia

Abstract A water-soluble arabinoxylan giving highly viscous solutions was isolated from the leaves of Neolitsea cassia (L.). The molar ratio of d -xylose to l -arabinose was 1:2.7, but small proportions of other sugars were also present. Linkage analysis, partial acid hydrolysis, and 1 H- and 13 C-n.m.r. spectroscopy revealed that the polysaccharide was highly branched with a backbone of (1→4)-linked β- d -xylopyranosyl residues each of which was substituted at both O-2 and O-3 with short side-chains composed of terminal α- and β- l -arabinofuranosyl groups and (1→3)-linked α- l -arabinofuranosyl residues.