Uncoupling activities of chalcones and dihydrochalcones on isolated mitochondria from potato tubers and mung bean hypocotyls

The uncoupling properties of 23 chalcones and dihydrochalcones were studied. Twelve compounds completely uncouple oxidative phosphorylation in mung bean hypocotyl and potato tuber mitochondria, four are weak uncouplers and seven are without effect. Usually, mung bean mitochondria are more sensitive to uncoupling agents than potato mitochondria. The uncoupling activity of chalcones and dihydrochalcones appears to be connected with the presence of hydrogen or hydroxyl groups in the 2′-position and hydrogen, hydroxyl or nitrate groups in the 4′-position. The α-β-unsaturated carbonyl system is not essential for activity. For the compounds which are not very lipophilic, substituents on the B-ring are without effect on the uncoupling properties. Phloretin appears to be an active uncoupler; its 6′-glucoside is without effect.     

Biosynthesis of tropane ester alkaloids in Datura

Datura meteloides plants were fed via the roots with [1″,2′-¹⁴C]tigloyl hygroline and as a control, [2′-¹⁴C]hygrine. After a week the alkaloids were isolated and degraded. Despite hydrolysis of the putative precursor it was possible, by label ratio, to show that esterification occurs after, and not before, the tropane ring has been synthesized. Hygroline is proposed as a possible intermediate.     

A Δ16-withanolide in Withania somnifera as a possible precursor for α-side-chains

The structure of a new naturally occurring steroidal lactone of the withanolide group isolated from Withania somnifera chemotype III has been elucidated as (20R,22R)-14α,2Oα_F-dihydroxy-1-oxowitha-2,5,16,24-tetraenolid. This compound is considered to be an intermediate in the biosynthesis of withanolide E, and is at the origin of the unusual α-oriented side-chain in this compound. The comparative composition of withanolides in different sub-chemotypes of III is provided.     

Aromatic alcohol dehydrogenase from potato tubers

The purification of NADP specific aromatic alcohol dehydrogenase is reported. The properties of the enzyme suggest that it should be classified as E.C. 1.1.1.2. Kinetic constants for a number of substrates are reported. The relative rates of reaction of a variety of substituted benzaldehydes have been found to correlate with Hammett's sigma values yielding a biphasic relationship. The physiological significance of the enzyme is briefly discussed.     

Induction d'un cytochrome du type P450 et de péroxydase durant la survie du tubercule de pomme de terre

During the ageing of potato tubers, a labile cytochrome of the P₄₅₀ type appears, always accompanied by the presence of P₄₂₀-type pigment. This induction of P₄₅₀ coincides with an increase in peroxidase activity together with an increase in the amount of cytochrome b₅.     

Changes in the activity of enzymes of phenylpropanoid metabolism in tomatoes stored at low temperatures

A large increase in the activity of an enzyme involved in chlorogenic acid metabolism, hydroxycinnamyltransferase occurs in tomatoes stored at low temperatures. In contrast, the activity of the enzyme remains constant or falls slightly during normal ripening at 20°. The rise in activity occurs at temperatures below 10° and fails to occur at 15° or 20°. This increase in activity during low temperature storage occurs with fruit at all stages of ripening from mature green to fully ripe. The hydroxycinnamyltransferase of chilled tomatoes falls rapidly on transfer to 20° with a lag of about 4–8 hr and within 48 hr returns to that of unchilled fruit. The effects of such warming treatments are reversible since when a chilling period is resumed following warming to 20°, the rise in hydroxycinnamyltransferase activity is also resumed. Of the 5 other enzymes of phenylpropanoid metabolism studied, only PAL shows a similar increase in activity during low temperature storage although the activity of the other enzymes was maintained at higher levels in fruit at 2° than at 20°. The possible relationship between the behaviour of hydroxycinnamyltransferase activity at various temperatures and the known susceptibility of tomatoes to chilling injury is discussed.     

Formation of putrescine and cinnamoyl putrescines in tobacco cell cultures

A p-fluorophenylalanine- (PFP) resistant cell line of Nicotiana tabacum and wild type cells accumulating high and low levels of cinnamoyl putrescines, respectively, were used to study the formation of putrescine in the biosynthesis of cinnamoyl putrescines. Labelled arginine and ornithine were equally well incorporated into the main conjugates caffeoyl and feruloyl putrescine. Trapping experiments indicated that both amino acids were decarboxylated for putrescine biosynthesis. Nearly all alcohol-extractable radioactivity from the labelled amino acids was found as cinnamoyl putrescines in the PFP-resistant cell line, whereas wild type cells retained significant radioactivity in the amino acids. The enzyme activities of arginine and ornithine decarboxylases in the resistant cell line were increased 3- to 6-fold.     

Immunological properties of β-fructofuranosidase from ripening tomato fruit

The amount of tomato fruit β-fructofuranosidase extractable from the cell walls during ripening parallelled the changes in activity of the enzyme. Using the techniques of radioimmunoassay, double immunodiffusion analysis and immunotitration, no differences in immunological properties of β-fructofuranosidase between the various stages of fruit ripening were detected.     

Two New Amides from Physochlainae Radix

In this article, two undescribed amides ( 1 – 2 ) with an unusual (2-formyl-5-hydroxymethyl)pyrroyl-butylamine moiety were obtained from the Physochlainae Radix. Comprehensive spectroscopic studies, including NMR and HR-ESI-MS, coupling with spectroscopic data comparisons were used to determine structures. Anti-inflammatory assay results showed that new amides possessed significant inhibitory activities of the NO production of LPS-induced RAW 264.7 cells, with IC₅₀ values of 17.52±1.68 μM and 20.37±2.42 μM, respectively.     

In vitro callus induction and regeneration studies in Withania somnifera

Callus cultures were initiated from axillary leaves, axillary shoots, hypocotyls, and root segments on Murashige and Skoog (MS) (1962) medium supplemented with 2,4-D (2 mg l⁻¹) and KN (0.2 mg l⁻¹). Shoots differentiated best from axillary shoot base callus on MS medium containing BA (2 mg l⁻¹). Regenerated shoots rooted best on MS medium containing IBA (2 mg l⁻¹) alone, and IBA (2 mg l⁻¹) with IAA (2 mg l⁻¹). Plantlets were transferred to pots containing sand and soil mixture, acclimatized in a culture room and afterwards transferred to the glasshouse. This revised version was published online in June 2006 with corrections to the Cover Date.