[Phytoecdysteroids: structure, sources and biosynthetic pathways in plants].
Data on the content of ecdysteroids in plant sources are given and the ecdysteroid biosynthesis and role in plants are discussed.
Ecdysteroids↗
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Results for “Plant Structures”
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Abnormal protein associated with tobacco mosaic virus; structure of polymerized tobacco plant protein and tobacco mosaic virus.
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Plant Proteins↗
CONSTANS mediates between the circadian clock and the control of flowering in Arabidopsis.
Flowering is often triggered by exposing plants to appropriate day lengths. This response requires an endogenous timer called the circadian clock to measure the duration of the day or night. This timer also controls daily rhythms in gene expression and behavioural patterns such as leaf movements. Several Arabidopsis mutations affect both circadian processes and flowering time; but how the effect of these mutations on the circadian clock is related to their influence on flowering remains unknown. Here we show that expression of CONSTANS (CO), a gene that accelerates flowering in response to long days, is modulated by the circadian clock and day length. Expression of a CO target gene, called FLOWERING LOCUS T (FT), is restricted to a similar time of day as expression of CO. Three mutations that affect circadian rhythms and flowering time alter CO and FT expression in ways that are consistent with their effects on flowering. In addition, the late flowering phenotype of such mutants is corrected by overexpressing CO. Thus, CO acts between the circadian clock and the control of flowering, suggesting mechanisms by which day length regulates flowering time.
Arabidopsis↗
Molecular basis of seasonal time measurement in Arabidopsis.
Several organisms have evolved the ability to measure daylength, or photoperiod, allowing them to adjust their development in anticipation of annual seasonal changes. Daylength measurement requires the integration of temporal information, provided by the circadian system, with light/dark discrimination, initiated by specific photoreceptors. Here we demonstrate that in Arabidopsis this integration takes place at the level of CONSTANS (CO) function. CO is a transcriptional activator that accelerates flowering time in long days, at least in part by inducing the expression of FLOWERING LOCUS T (FT). First, we show that precise clock control of the timing of CO expression, such that it is high during daytime only in long days, is critical for daylength discrimination. We then provide evidence that CO activation of FT expression requires the presence of light perceived through cryptochrome 2 (cry2) or phytochrome A (phyA). We conclude that an external coincidence mechanism, based on the endogenous circadian control of CO messenger RNA levels, and the modulation of CO function by light, constitutes the molecular basis for the regulation of flowering time by daylength in Arabidopsis.
Arabidopsis↗
Population structure and host-plant specialization in two Scaptodrosophila flower-breeding species.
In contrast to phytophagous insect species, little attention has been paid to the possibility of host races in the Drosophilidae, although flower-breeding species, where courtship and mating take place on the flowers, are likely candidates. Two species of Scaptodrosophila, S. hibisci and S. aclinata, are restricted to flowers of Hibiscus species (section Furcaria), and the Furcaria specialization likely predated the separation of S. hibisci and S. aclinata. In all, 20 microsatellite loci were analysed in nine populations of S. hibisci and five of S. aclinata. For two pairs of S. hibisci populations in close proximity, but breeding on different Hibiscus species, differentiation between the populations of each of these pairs was similar to that between the populations that were from the same Hibiscus species, but geographically distant, suggesting the early stages of host-race formation. Genetic variability was significantly less in S. aclinata than in S. hibisci, suggesting greater drift effects in the former. However, of 253 alleles detected, 82 were present in both species, 160 in S. hibisci only and 11 in S. aclinata only, indicating that S. aclinata was derived from S. hibisci, following a strong bottleneck at the time of separation--possibly 40,000 years BP. Analyses and interpretation of Hardy-Weinberg equilibrium and F statistics needed to account for null alleles known to be present at eight loci in S. hibisci, and possibly present at other loci. The results emphasize the need for caution in studies where the presence of null alleles is inferred only from population data.
Animals↗
Triterpenoids.
This review covers the isolation and structure determination of triterpenoids including squalene derivatives, lanostanes, cycloartanes, dammaranes, euphanes, tirucallanes, tetranortriterpenoids, quassinoids, lupanes, oleananes, friedelanes, ursanes, hopanes, isomalabicanes and saponins. The literature from January to December 2000 is reviewed and 277 references are cited.
Bacteria↗
Natural and hemisynthetic neoclerodane diterpenoids from scutellaria and their antifeedant activity.
The genus Scutellaria (Labiatae) is a very rich source of neoclerodane diterpenoids, with interesting structural features. These secondary metabolites show several biological properties, the most important being the antifeedant activity against pest insects. The present review reports on natural and hemisynthetic diterpenoids and their antifeedant activity.
Animals↗
Amaryllidaceae and Sceletium alkaloids.
This review covers the isolation, biological activity and chemical synthesis of Amaryllidaceae alkaloids and the structurally related Sceletium alkaloids. The literature from July 2001 to the end of 2002 is reviewed, and 61 references are cited.
Alkaloids↗
Amaryllidaceae and Sceletium alkaloids.
This review covers the morphology, isolation, total synthesis and biological activity of the naturally occurring alkaloids isolated from the Amaryllidaceae family, as well as the structurally related Sceletium alkaloids.
Alkaloids↗
Structure and anti-HIV activity of micrandilactones B and C, new nortriterpenoids possessing a unique skeleton from Schisandra micrantha.
Two new highly oxygenated nortriterpenoids with a unique norcycloartane skeleton, micrandilactones B and C, were isolated from Schisandra micrantha; micrandilactone C exhibited an EC50 value of 7.71 microg/mL (SI > 25.94) against HIV-1 replication with minimal cytotoxicity, and the potent anti-HIV-1 activity and unique structural features of make it a promising lead for therapeutic development of a new generation of anti-HIV drug.
Animals↗
Effects of analogues of MOA-stilbene on the chloroplast cytochrome bf complex.
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Binding Sites↗
In vitro activity of hederacolchisid A1 compared with other saponins from Hedera colchica against proliferation of human carcinoma and melanoma cells.
Hederacolchisid A1, a new oleanolic acid monodesmoside, isolated from Hedera colchica K. Koch, an ivy species endemic in Georgia, was evaluated in vitro for antiproliferative activity on cancer cells versus normal cells in comparison to cisplatin. Investigations were made on six human cell lines (colon adenocarcinoma DLD-1, ovarian teratocarcinoma PA 1, lung carcinoma A 549, breast adenocarcinoma MCF7, prostatic adenocarcinoma PC 3 and malignant melanoma M4 Beu) versus normal human fibroblasts, by assaying both cellular metabolic activity (RTT test) and DNA content in living cells (test with Hoechst 33,342) after 48 h continuous contact. Results demonstrated the strong cytotoxicity of hederacolchisid A 1 on all cancer cells (IC50 from 4.5 to 12 microM). The antiproliferative effects on malignant melanoma M4 Beu (IC50 ca 4.5 microM) versus normal cells (IC50 ca 7.5 microM) suggests that, despite a lack of specificity for cancer cells, hederacolchisid A1 has potential anti-tumor applications. Comparison of the cytotoxicity of hederacolchisid A 1 with that of five other saponins from H. colchica, offers some new information about structure-activity relationships. It was observed that i) for a same sugar sequence, monodesmosides with oleanolic acid as aglycone exhibit higher cytotoxicity than those containing hederagenin, ii) the sugar sequence O-alpha-L-rhamnopyranosyl (1 --> 2)-alpha-L-arabinopyranoside at C3 induces strong cytotoxicity and might be identified as a basic sequence for anti-tumor activity of oleanolic acid monodesmosides. iii) a complementary glucopyranosyl moiety branched at C1 of arabinose increases the cytotoxicity against malignant melanoma M4 Beu, prostatic adenocarcinoma PC 3 and normal fibroblasts in a different manner for each type of monodesmoside. A slight increase whose amplitude was quite similar on cancers and normal cells, was observed with oleanolic acid monodesmoside. This increase was much higher with hederagenin monodesmoside and markedly elevated in normal cells than in cancer cells.
Antineoplastic Agents↗
Structure-activity relationships of flavonoids, isolated from Scutellaria baicalensis, binding to benzodiazepine site of GABA(A) receptor complex.
Twenty-six flavonoids were isolated from Scutellaria baicalensis. Their affinities for the benzodiazepine (BDZ) binding site of GABA A receptor have been studied using [ 3H]flunitrazepam binding to rat cortical membranes in vitro. The structure-activity relationships suggested that 2'-OH flavones exhibited the most potent binding affinity, which could lead to the design and discovery of new BDZ receptor ligands.
Animals↗
New eremophilenolides from Cacalia pilgeriana.
Five new eremophilenolides and a known sesquiterpene were isolated from the methanol extract of the roots of Cacalia pilgeriana. Their structures were identified as 1 beta-hydroxy-2 beta-methyl-senecioyloxyeremophil-7(11)-en-8 beta(12)-olide (1), 1 beta-hydroxy-2 beta-methylsenecioyloxy-8 alpha-methoxyeremophil-7(11)-en- 8 beta(12)-olide, 2 beta-hydroxy-3 beta-methylsenecioyloxyeremophil-7(11)-en-8 alpha(12)-olide ( 3), 2 beta,8 beta-dihydroxy-3 beta-methylsenecioyloxyeremophil-7(11)-en-8 alpha(12)-olide and 1 beta,8 beta-dihydroxy-2 beta,3 alpha-diangeloyloxyeremophil-7(11)-en-8 alpha(12)-olide ( 5) and caryolane-1,9 beta-diol by spectroscopic methods including 2D-NMR techniques ( (1)H- (1)H COSY, HMQC, HMBC) and HR-ESI-MS. The structure and relative stereochemistry of compound 1 were unequivocally established by X-ray diffraction analysis. Bioassays showed compounds 3 and 5 to possess strong cytotoxic activity in vitro against human leukemia cells (HL-60) (IC (50) < 15 microg mL (-1)). The structure-activity relationship is discussed.
Asteraceae↗
Biological activities of pyrrolidinoindoline alkaloids from Calycodendron milnei.
Certain genera of the tribe Psychotrieae, specifically Calycodendron and Psychotria, found on Pacific Islands, synthesize a series of Nb-methyltryptamine-derived alkaloids made by linking together 2 to 8 pyrrolidinoindoline units. Nine alkaloids of this class have been isolated from the aerial parts and stem bark of Calycodendron milnei, a species endemic to the Vaté Islands (New Hebrides), and examined for potential application as anti-cancer and anti-infective agents. All members of the series exhibited readily detected cytotoxic activity against proliferating and non-proliferating Vero African green monkey kidney cells in culture, with the most potent activity being exhibited by vatamine and quadrigemine C. Only hodgkinsine A exhibited substantial antiviral activity against a DNA virus, herpes simplex type 1, and an RNA virus, vesicular stomatitis virus. All members of the series showed readily detected anti-bacterial, anti-fungal, and anti-candidal activities using both tube dilution and disc diffusion assay methods. The most potent anti-microbial alkaloids were hodgkinsine A and quadrigemine C, which exhibited minimum inhibitory concentration (MIC) values as low as 5 micrograms/ml.
Alkaloids↗
Sesquiterpene lactones and other constituents of Centaurea napifolia.
Aerial parts of Centaurea napifolia furnished the sesquiterpene lactones cnicin, 4'-acetoxycnicin, melitensin, dehydromelitensin, two known esters of dehydromelitensin, lappaol and a lappaol isomer, and a 1,2-diacylated glucose.
Lactones↗
Structure-related inhibiting activity of some tobacco cembranoids on the prostaglandin synthesis in vitro.
Structure-related inhibitory effects on the prostaglandin synthesis in vitro have been detected among eight diterpenoids of the cembrane class (1-8). The 4,6-diols 1 and 2 are the most active of the cembranoids studied with IC50 values of 0.36 and 0.39 mM, respectively, as compared with an IC50 value of 1.4 for acetylsalicylic acid. Lower activities are found for cembranoids having undergone oxidation of/at the 11,12 double bond (5-8), while the 4-hydroxy-6-oxocembranoids 3 and 4 exhibit effects lower than those of 1 and 2 but higher than those of 5-8.
Animals↗
Involvement of NMDA receptors in the analgesic properties of psychotridine.
We have previously reported that the alkaloid extract of Psychotria colorata (Willd. ex R. & S.) Muell. Arg., had marked dose-dependent, opioid-like activity. Phytochemical analyses of P. colorata flowers and leaves identified several pyrrolidinoindoline alkaloids, including psychotridine. To further investigate the activity and mechanism of action of Psychotria alkaloids, we studied the effects of psychotridine on thermal and chemical models of analgesia. In the tail-flick model, psychotridine presents a dose-dependent analgesic effect; the effect is not reversed by prior treatment with naloxone. Psychotridine dose-dependently decreased capsaicin-induced pain. Performance in the rotarod test showed that psychotridine does not induce motor deficits at doses effective in analgesia models. Psychotridine inhibited [3H]MK-801 (dizocilpine) binding to cortex membranes in a dose-dependent manner. Binding is completely abolished at 300 nM. The data rule out opioid activity, and the inhibition of capsaicin-induced pain and of radioligand binding strongly suggest the participation of NMDA receptors in psychotridine-induced analgesia.
Alkaloids↗