Rajni Jain

Phytochemistry of the genus Piper

Abstract The secondary metabolites isolated from Piper species for the period 1907 to June 1996 have been reviewed. Nearly six hundred chemical constituents belonging to different classes of bioactive compounds are listed together with their source(s) and references.

Polyphenols and alkaloids from piper species

Abstract Thirty eight compounds of different types have been isolated from twelve Piper species. The ether extract of the leaves of P. aduncum yielded eleven compounds, out of which 2,6-dimethoxy-4-(2-propenyl)phenol was isolated for the first time from the genus Piper and 2-acetoxy-1,3-dimethoxy-5-(2-propenyl)benzene is a new compound. The petrol extract of the stems and leaves of P. attenuatum furnished a novel long chain alcohol, 14-benzo 1 , 3 dioxol-5-yl-tetradecan-2-ol. From P. betle, β-sitosteryl palmitate was isolated for the first time from the genus Piper. A novel amide, 3-(3,4-dimethoxyphenyl)propanoyl pyrrole has been obtained from P. brachystachyum. Nerolidol was isolated for the first time from P. falconeri. From the methanol extract of the stems and leaves of P. khasiana, piperlonguminine, piperine, apigenin dimethyl ether and β-sitosterol were obtained. Retrofractamide A was obtained for the first time from P. longum; the structure of (+)-asarinin, isolated from P. longum, was confirmed by X-ray crystallographic studies. Retrofractamide A, apigenin dimethyl ether, tetratriacontanol and tectochrysin were isolated from P. manii. P. pedicellosum furnished β-sitosterol, pellitorine, piperlonguminine, cepharadione A and furacridone, the last compound being isolated for the first time from the genus Piper.

Review Article Number 138: Constituents of the yew trees

Yew trees, taxonomically classified under the genus Taxus, are sources of a number of physiologically active compounds of different classes. Taxane derivatives with various carbon skeletons, lignans, flavonoids, steroids and sugar derivatives have been isolated from different Taxus species. Compounds isolated from the genus Taxus between 1908 and December 1997 have been comprehensively reviewed.

Anti-invasive activity of alkaloids and polyphenolics in vitro

Invasiveness, the ability of certain tumour cells to migrate beyond their natural tissue boundaries, often leads to metastasis, and usually determines the fatal outcome of cancer. The need for anti-invasive agents has led us to search for possibly active compounds among alkaloids and polyphenolics. One hundred compounds were screened in an assay based on the confrontation of invasive human MCF-7/6 mammary carcinoma cells with fragments of normal embryonic chick heart in vitro. Anti-invasive activity was frequently found among chalcones having a prenyl group. Six compounds were found to inhibit invasion when added to the culture medium at concentrations as low as 1 microM. For at least three of them the anti-invasive effect could be associated with a cytotoxic effect on the MCF-7/6 cells, but not on the heart tissue. This selective cytotoxicity was substantiated by different methods, such as histology and growth assays (volume measurements, cell counts, MTT and sulforhodamine B assays). The anti-invasive effects of the compounds could neither be ascribed to induction of apoptosis nor to the promotion of cell-cell adhesion. Our data indicate that among the alkaloids and polyphenolics a number of molecules can inhibit growth and invasion of human mammary cancer cells via selective cytotoxicity.

Sintering characteristics and properties of sol gel derived Sr0.8Bi2.4Ta2.0O9 ceramics

Abstract Strontium bismuth tantalate (Sr 0.8 Bi 2.4 Ta 2.0 O 9 , SBT) powders have been prepared at a low processing temperature of 650°C using a sol–gel method. Sintering conditions have been optimized for preparing ceramics using sol gel powders and the effect of sintering characteristics on microstructure, dielectric and ferroelectric properties have been studied. Sintering conditions at 1000°C for 8 h are found to be optimum for achieving reproducible ferroelectric and dielectric properties. Longer sintering times (20 h) and a higher sintering temperature (1100°C) are found to degrade the microstructure and dielectric response. Reproducible ferroelectric to paraelectric transition is observed at 380°C, and a remnant polarization of 3 μC cm −2 with a coercive field of 30 KV cm −1 has been estimated from the ferroelectric hysteresis measurements.

Piezoelectric properties of nonstoichiometric Sr1−xBi2+2x∕3Ta2O9 ceramics

The effect of poling on the structural, dielectric, and piezoelectric properties has been investigated for sol-gel-derived strontium bismuth tantalate (SBT) [Sr1−xBi2+2x∕3Ta2O9] ceramics with x=0.0,0.15,0.30,0.45. The dielectric and ferroelectric properties are found to improve with increase in x up to 0.3. Beyond x>0.3 the properties are found to degrade due to the limited solid solubility and the presence of a mixed phase of bismuth tantalate (BiTaO4) is detected with x=0.45. Poling treatment reduces the dielectric dispersion and dielectric loss in the frequency range (0.1–100kHz). The resonance and antiresonance frequencies increase with increase in x (x=0–0.30), and the corresponding minimum impedance decreases. The measured coupling coefficients (kp) are small (0.0967–0.1) for x=0–0.30, and the electromechanical quality factor (Qm=915) is a maximum for the Sr0.7Bi2.2Ta2O9 composition (x=0.30). The estimated piezoelectric charge coefficient (d31) and piezoelectric voltage coefficient (g31) are 5.2pC∕N...

Highly oxygenated bioactive flavones from Tamarix

Abstract Two new flavones, 5,7,2′-trihydroxy-6,4′-dimethoxyflavone (tamaridone) and 5,2′,4′-trihydroxy-6,7,8-trimethoxyflavone (tamadone) have been isolated from the aerial parts of Tamarix dioica, along with hexacosyl-p-coumarate, gardenins A, B, C and E, nevadensin A and apigenin. Gardenin B exhibited antiviral activity and anti-invasive activity against solid tumours.

Phenolics from the seeds of Argemone mexicana

Abstract Two new phenolic compounds, 5, 7, 2′, 6′-tetrahydroxyflavone and 5, 7-dihydroxychromone 7- neohesperidoside have been characterized from the seeds of Argemone mexicana.

Occurrence of pongamol as the enol structure in Tephrosia purpurea

Abstract Pongamol in its pure enol form has been found to occur in the whole plant of Tephrosia purpurea together with β-sitosterol, ursolic acid and spinasterol-α.

Dihydroflavonols from Prunus domestica

Abstract Seven compounds have been isolated from the heartwood of P. domestica . Two of them, 5,7,4′-trihydroxy-3-methoxyflavanone and 3,5,7-trihydroxy-6,4′-dimethoxyflavanone, are new natural products. The remaining five compounds were identified as isosakuranetin, prudomestin, dihydrokaempferide, naringenin and 3,5,7-trihydroxy-8,4′-dimethoxyflavanone. The last compound has been isolated for the first time from the genus Prunus .