Antiplasmodial β-triketones from the flowers of the Australian tree Angophora woodsiana

Chemical investigations of the MeOH extract of air dried flowers of the Australian tree Angophora woodsiana (Myrtaceae) yielded two new β-triketones, woodsianones A and B (1, 2) and nine known β-triketones (3–11). Woodsianone A is a β-triketone-sesquiterpene adduct and woodsianone B is a β-triketone epoxide derivative. The structures of the new and known compounds were elucidated from the analysis of 1D/2D NMR and MS data. The relative configurations of the compounds were determined from analysis of ¹H–¹H coupling constants and ROESY correlations. All compounds (1–11) had antiplasmodial activity against the chloroquine sensitive strain 3D7. The known compound rhodomyrtone (5) and new compound woodsianone B (2) showed moderate antiplasmodial activities against the 3D7 strain (1.84 µM and 3.00 µM, respectively) and chloroquine resistant strain Dd2 (4.00 µM and 2.53 µM, respectively).     

A new δ-lactone from the flowers of Grewia asiatica

The structure of 3, 21, 24 trimethyl-5,7-dihydroxyhentriacontanoic acid δ-lactone, a new δ-lactone, isolated from the flowers of Grewia asiatica has been deduced on the basis of physico-chemical studies.     

(−)-N-ethylcytisine,a lupin alkaloid from the flowers of Echinosophora koreensis

A new lupin alkaloid, (?)-N-ethylcytisine, was isolated from the fresh flowers of Echinosophora koreensis. Its structure has been confirmed b     

Where have all the flowers gone? Are our woodland flowers disappearing?

The owner of a wood in Norfolk once told me that he thought that the lily of the valley has declined over the last 20 years. In Wytham Woods near Oxford the dense bramble patches I studied in the 1970s didn't seem so thick ten years later. Were these slips of the memory or did Pete Seeger have a point with his 1961 song - Where have all the flowers gone?     

Covalent anthocyanin–flavonol complexes from the violet-blue flowers of Allium ‘Blue Perfume’

Three covalent anthocyanin–flavonol complexes (pigments 1–3) were extracted from the violet-blue flower of Allium ‘Blue Perfume’ with 5% acetic acid-MeOH solution, in which pigment 1 was the dominant pigment. These three pigments are based on delphinidin 3-glucoside as their deacylanthocyanin and were acylated with malonyl kaempferol 3-sophoroside-7-glucosiduronic acid or malonyl-kaempferol 3-p-coumaroyl-tetraglycoside-7-glucosiduronic acid in addition to acylation with acetic acid.By spectroscopic and chemical methods, the structures of these three pigments 1–3 were determined to be: pigment 1, (6^I-O-(delphinidin 3-O-(3^I-O-(acetyl)-β-glucopyranoside^I)))(2^VI-O-(kaempferol 3-O-(2^II-O-(3^III-O-(β-glucopyranosyl^V)-β-glucopyranosyl^III)-4^II-O-(trans-p-coumaroyl)-6^II-O-(β-glucopyranosyl^IV)-β-glucopyranoside^II)-7-O-(β-glucosiduronic acid^VI))) malonate; pigment 2, (6^I-O-(delphinidin 3-O-(3^I-O-(acetyl)-β-glucopyranoside^I)))(2^VI-O-(kaempferol 3-O-(2^II-O-β-glucopyranosyl^III)-β-glucopyranoside^II)-7-O-(β-glucosiduronic acid^VI))); and pigment 3, (6^I-O-(delphinidin 3-O-(3^I-O-(acetyl)-β-glucopyranoside^I)))(2^VI-O-(kaempferol 3-O-(2^II-O-(3^III-O-(β-glucopyranosyl^V)-β-glucopyranosyl^III)-4^II-O-(cis-p-coumaroyl)-6^II-O-(β-glucopyranosyl^IV)-β-glucopyranoside^II)-7-O-(β-glucosiduronic acid^VI))) malonate.The structure of pigment 2 was analogous to that of a covalent anthocyanin–flavonol complex isolated from Allium schoenoprasum where delphinidin was observed in place of cyanidin. The three covalent anthocyanin–flavonol complexes (pigment 1–3) had a stable violet-blue color with three characteristic absorption maxima at 540, 547 and 618 nm in pH 5–6 buffer solution. From circular dichroism measurement of pigment 1 in the pH 6.0 buffer solution, cotton effects were observed at 533 (+), 604 (−) and 638 (−) nm. Based on these results, these covalent anthocyanin–flavonol complexes were presumed to maintain a stable intramolecular association between delphinidin and kaempferol units closely related to that observed between anthocyanin and hydroxycinnamic acid residues in polyacylated anthocyanins. Additionally, an acylated kaempferol glycoside (pigment 4) was isolated from the same flower extract, and its structure was determined to be kaempferol 3-O-sophoroside-7-O-(3-O-(malonyl)-β-glucopyranosiduronic acid).     

Folivorous larvae on flowers: do autumnal moths benefit from catkins of the mountain birch?

Immature leaves of birches and other deciduous trees and shrubs are the principal food resource for the larvae of the autumnal moth, Epirrita autumnata (Borkhausen) (Lepidoptera: Geometridae). However, the larvae of this geometrid, which displays pronounced population cycles and causes massive forest defoliations in northernmost Europe, are also frequently found on the catkins of mountain birch, Betula pubescens ssp. czerepanovii (Orlova) Hämet-Ahti (Betulaceae). To examine whether autumnal moth larvae visit birch catkins for their high nutritional value, we conducted two growth experiments in which the larval diet was supplemented with male catkins, and a single test where female catkins were used. We found that the presence of male catkins in the larval diet had a positive effect on the larvae, in relation to their pupal mass (reflecting life span fecundity), survival probability, as well as the duration of the larval period. The presence of female catkins in the diet did not affect larval performance. Our findings suggest that young autumnal moth larvae actively move to male catkins, which provide a nutritional benefit and thus lead to a better performance compared with those feeding elsewhere. Another possible benefit for young larvae choosing the catkins instead of leaves may involve predator or parasitoid avoidance.     

Bamboo flowers visited by insects: do insects play a role in the pollination of bamboo flowers?

Relatively little is known about pollination and other aspects of the reproductive biology of bamboos, but wind pollination is assumed to be the rule, at least in woody bamboos. Documenting the reproductive biology of woody bamboos is a complex task due to the long periods of time between flowering cycles, which range from 3 to 120 years. Insects visiting Guadua paniculata and G. inermis flowers were collected in the field. Scanning electron micrographs were taken of the visiting insects. Four species of bees, three from tribe Meliponini (Geotrigona acapulconis, Plebeia frontalis and Trigona fulviventris) and one from tribe Apini (Apis mellifera), along with a syrphid fly (Toxomerus teligera) were found visiting bamboo flowers. Some species of Hemiptera were also found feeding on the flowers, such as Neortholomus jamaicensis (Lygaeidae), or preying on the flower visitors (Apiomerus pictipes (Reduviidae)). Insects visiting bamboo inflorescences may facilitate the release of pollen grains into the air, promoting outcrossing and genetic flow among the individuals of the flowering bamboo populations.     

Acylated anthocyanins and flavonols from purple flowers of Dendrobium cv. ‘Pompadour’

Two rare anthocyanins, cyanidin 3-(6-malonylglucoside)-7,3′-di(6-sinapylglucoside) and the demalonyl derivative, were characterised as the purple floral pigments of Dendrobium cv. ‘Pompadour’. Nine known flavonol glycosides were also identified, including the 3-rutinoside-7-glucosides of kaempferol and quercetin. One new glycoside was detected: the ferulyl ester of quercetin 7-rutinoside-7-glucoside. These flavonoid patterns are typical for plants in the family Orchidaceae.     

β-1,3-glucanase activity in the stigma of healthy petunia flowers

β-1,3-Glucanase activity was detected in extracts of different tissues of healthy mature petunia flowers except the filament. The stigma was studied further as it had the highest enzyme activity and there is a paucity of information on the occurrence of this enzyme in this tissue. Specific activity of the enzyme was found to increase within the stigmatic tissue from early development until just before anthesis. Following non-denaturing polyacrylamide gel electrophoresis at pH 8.8, extracts of dehiscent stigma seem to contain three acidic isoforms of β-1,3-glucanase. Crude extracts of stigma was passed through a pachyman affinity column. A fraction of affinity-purified active β-1,3-glucanase enzyme was found to have no antifungal activity against Trichoderma viride, Phloma clematidina and Cladosporium fulvum.     

Lanceoleins A–G,hydroxychalcones, from the flowers of Coreopsis lanceolata and their chemopreventive effects against human colon cancer cells

Seven new chalcones, lanceolein A–G (compounds 5 and 7–12), as well as five known chalcones (1–4 and 6), were isolated from the methanolic extract of Coreopsis lanceolata flowers. The chemical structures of 5 and 7–12 were determined on the basis of spectroscopic data interpretation. All compounds inhibited the production of nitrite oxide (NO) induced by LPS in RAW264.7 macrophage cells. Also, compounds 1–6 showed moderated cytotoxicity against human colon cancer cell lines, while compounds 7–12 hardly showed the cytotoxicity. Especially, compounds 2, 5, and 6 exhibited a little higher cytotoxicity on HCT15 cells, with IC₅₀ values of 43.7 ± 2.17 μM, 35.6 ± 0.24 μM, and 47.9 ± 1.18 μM, respectively. In the Tali assay, compounds 2 and 5 increased the numeral of apoptotic cells. These compounds also significantly promoted the expression of apoptotic proteins including PARP and caspase-3.     

Message from the Editor-in-Chief

The current issue of Acta Biochimica et Biophysica Sinica (ABBS) has turned a new page of this journal since its publication forty five years ago. It is perhaps an appropriate time to share with our readers about the evolution of this journal, the changes that have taken place, and the future that we are looking forward to. ABBS was first established in 1958 with Professor Ying-Lai WANG as the founding Editor-in-Chief and has been ever since an     

Purification and enzymatic properties of a peroxidase from leaves of Phytolacca dioica L. (Ombú tree)

A peroxidase (PD-cP; 0.47 mg/100 g leaves) was purified from autumn leaves of Phytolacca dioica L. and characterized. PD-cP was obtained by acid precipitation followed by gel-filtration and cation exchange chromatography. Amino acid composition and N-terminal sequence of PD-cP up to residue 15 were similar to that of Spinacia oleracea (N-terminal pairwise comparison showing four amino acid differences). PD-cP showed a molecular mass of approx. 36 kDa by SDS-PAGE, pH and temperature optima at 3.0 and 50.0°C, respectively and seasonal variation. The Michaelis-Menten constant (K(M)) for H(2)O(2) was 5.27 mM, and the velocity maximum (V(max)) 1.31 nmol min(-1), while the enzyme turnover was 0.148 s(-1). Finally, the presence of Ca(2+) and Mg(2+) enhanced the PD-cP activity, with Mg(2+) 1.4-fold more effective than Ca(2+)     

Why do honeybees reject certain flowers?

Summary Honeybees often approach flowers of Lotus corniculatus and then fly away without attempting to extract nectar. These rejected flowers contained 41% less nectar than my random sample. The accepted flowers contained 24% more nectar than my random sample. The differences among these three flower-groups were due to differences in the percent of empty flowers in each group rather than the differences in the absolute amount of nectar. Honeybees increased their foraging efficiency by accepting less empty flowers and rejecting more empty flowers than would be expected if they foraged randomly. There are two possible mechanisms for this discrimination-behavior: either the bees are smelling nectar odor or they are smelling bee scent left by previous visitors to the flower. My results are inconsistent with the hypothesis that bees are basing their decision on nectar smell and suggest that they are using bee scent as a means of identifying empty flowers.     

Apigenin 7-glucoside and its 2″- and 6″-acetates from ligulate flowers of Matricaria chamomilla

Dried ligulate flowers of Matricaria chamomilla contain 7–9% glucosides of apigenin and 0.3–0.5% free apigenin. Glucosides were identified as apigenin 7-glucoside and a 1:3 mixture of the 2″- and 6″-acetates, as determined by ¹³C NMR analysis.     

Bird-nest puzzle: can the study of unisexual flowers such as cucumber solve the problem of plant sex determination?

Unisexual flower development has long been used as a model system to understand the mechanism of plant sex determination. However, based on our investigation of the mechanisms regulating the development of unisexual cucumber flowers, we have realized that understanding how organ development is inhibited may not necessarily reveal how an organ is formed. We refer to this problem as a "bird-nest puzzle," meaning one cannot understand how a bird lays and hatches its eggs by understanding how its nest is ruined. To understand the biological significance of unisexual flowers, we reexamine the original meaning of sex and its application in plants. Additionally, we propose that the fundamental biological advantage for the selection and maintenance of unisexual flowers during evolution is to promote cross pollination.     

Are flowers physiological sinks or faucets? Costs and correlates of water use by flowers of Polemonium viscosum

Water loss through inflorescences may place extreme demands on plant water status in arid environments. Here we examine how corolla size, a trait known to influence pollination success, affects the water cost of flowering in the alpine skypilot, Polemonium viscosum. In a potometry experiment, water uptake rates of inflorescences were monitored during bud expansion and anthesis. Corolla volume of fully expanded flowers predicted water uptake during bud expansion (R ²=0.61, P=0.0375) and corolla surface area predicted water uptake during anthesis (R ²=0.59, P=0.044). To probe mechanisms underlying the relationship between corolla size and water uptake, cell dimensions and densities were measured in several regions of fully expanded corollas. Corolla length was positively correlated with cell length in the middle of the corolla tube and cell diameter in the corolla lobe (Pearson's r from 0.26–0.33, n=86, P ≤ 0.05). Cell density was negatively correlated with cell dimensions in the upper corolla tube and lobe (Pearson's r from –0.39 to –0.42, P ≤ 0.0015). These findings suggest that more water may be required to maintain turgor in large corollas in part because their tissues have lower cell wall densities. The carbon cost of water use by flowers was assessed in krummholz and tundra habitats for P. viscosum flowering, respectively, during dry and wet portions of the growing season. For plants in full flower, average leaf water potentials were significantly more negative (P=0.0079) at mid-day in the krummholz (June) than in the tundra (July), but were similar before dawn (P=0.631). Photosynthetic rate at the time of flowering declined significantly with increasing corolla size in the krummholz (P=0.0376), but was unrelated to corolla size on the tundra (P>0.72). Plants losing water through large corollas may close leaf stomata to maintain turgor. If photosynthesis limits growth in this perennial species, then the water cost of producing large flowers should exacerbate the cost of reproduction under dry conditions. Such factors could select for flowers with smaller corollas in the krummholz, countering pollinator-mediated selection and helping maintain genetic variation in corolla size components of P. viscosum. Received: 5 May 1998 / Accepted: 2 October 1998     

The major volatile organic compound emitted from Arabidopsis thaliana flowers, the sesquiterpene (E)-β-caryophyllene, is a defense against a bacterial pathogen

Flowers have a high risk of pathogen attack because of their rich nutrient and moisture content, and high frequency of insect visitors. We investigated the role of (E)-β-caryophyllene in floral defense against a microbial pathogen. This sesquiterpene is a common volatile compound emitted from flowers, and is a major volatile released from the stigma of Arabidopsis thaliana flowers. Arabidopsis thaliana lines lacking a functional (E)-β-caryophyllene synthase or constitutively overexpressing this gene were challenged with Pseudomonas syringae pv. tomato DC3000, which is a bacterial pathogen of brassicaceous plants. Flowers of plant lines lacking (E)-β-caryophyllene emission showed greater bacterial growth on their stigmas than did wild-type flowers, and their seeds were lighter and misshapen. By contrast, plant lines with ectopic (E)-β-caryophyllene emission from vegetative parts were more resistant than wild-type plants to pathogen infection of leaves, and showed reduced cell damage and higher seed production. Based on in vitro experiments, (E)-β-caryophyllene seems to act by direct inhibition of bacterial growth, rather than by triggering defense signaling pathways. (E)-β-Caryophyllene thus appears to serve as a defense against pathogens that invade floral tissues and, like other floral volatiles, may play multiple roles in defense and pollinator attraction.