sábado, 23 de fevereiro de 2013
BY– JULY 28, 2012
Alkaloids are basic nitrogen containing compounds. They are generally obtained from plants, animals and microorganisms and often demonstrate a marked physiological action. Alkaloids show greatly diverse structure and origins as well as pharmacological action. The only thing that unites all these natural compounds under the term ‘alkaloids’ (alkali-like) is the nitrogen atom which is present in all of them. According to pharmacognosy, alkaloids are broadly classified into two classes depending upon whether the nitrogen is a part of a ring or not.
1] Non-Heterocyclic Alkaloids or Atypical Alkaloids:
These are also sometimes called proto-alkaloids or biological amines. These are less commonly found in nature. These molecules have a nitrogen atom which is not a part of any ring system. Examples of these include ephedrine, colchicine, erythromycin and taxol etc. Table below shows the chemical structure and biological significance of these compounds:
|Ephedrine||Adrenergic agent-used for asthma and hay fever|
|Taxol (Paclitaxel)||Used in the treatment of ovarian cancer, breast cancer and non-small cell lung cancer|
2] Heterocyclic Alkaloids or Typical Alkaloids:
Structurally these have the nitrogen as a part of a cyclic ring system. These are more commonly found in nature. Heterocyclic alkaloids are further subdivided into 14 groups based on the ring structure containing the nitrogen.
|1.||Pyrrole and Pyrrolidine||Hygrine, Stachydrine|
|2.||Pyrrolizidine||Senecionine, Symphitine, Echimidine, Seneciphylline|
|3.||Pyridine and Piperidine||Lobeline, Nicotine, Piperine, Conine, Trigonelline|
|4.||Tropane (piperidine/N-methyl-pyrrolidine)||Cocaine, Atropine, Hyoscyamine, Hyoscine|
|5.||Quinoline||Quinine, Quinidine, Cinchonine, Cinchonidine|
|6.||Isoquinoline||Morphine, Emetine, Papaverine, Narcotine, Tubocurarine, Codeine|
|7.||Aporphine (reduced isoquinoline/naphthalene)||Boldine|
|8.||Quinolizidine||Lupanine, Cytisine, Laburnine, Sparteine|
|9.||Indole or Benzopyrole||Ergometrine, Vinblastine, Vincristine, Strychnine, Brucine, Ergotamine, Yohimbine, Reserpine, Serpentine, Physostigmine|
|11.||Imidazole or glyoxaline||Pilocarpine, Pilosine|
|12.||Purine (pyrimidine/imidazole)||Caffeine, Theobromine|
|13.||Steroidal (some combined as glycosides)*||Conessine, Solanidine|
|14.||Terpenoid*||Aconitine, lycaconitine, Aconine|
*Note- Steroidal and terpenoid classes are also treated as separate classes or along with glycosides.
Other methods of classification of alkaloids include:
- Based on their pharmacological action: Alkaloids have very diverse pharmacological actions. They are known to be adrenergics, antibiotics, poisons, stimulants, diuretics, astringents, anti-inflammatory, anti-hypertensives, anti-mydriatics, analgesics, anti-gout, expectorant, emetic, anti-spasmodic and many others. However, structurally diverse molecules may show similar pharmacological actions while in certain cases the activity might be identical for specific structure. Hence it is very difficult to classify them on the sole basis of pharmacological action.
- Based on their taxonomy: Alkaloids can be classified on the basis of the biological source from which they are obtained but this generalizations do not work most often.
- Based on their biosynthetic origin: Biosynthetic origin here means from which fundamental chemical building block these alkaloids are derived. For example indole alkaloids often come from tryptophan, pyrrolidine and tropane containing alkaloids come from proline and ornithine, quinolizidine containing alkaloids are derived from lysine. Biosynthetic origin of classification is beneficial in a more ordered classification, however, it is often unknown how most of the alkaloids are synthesized by the plants.
- Evans, W. C. Trease and Evans Pharmacognosy, 16th ed.; Elsevier: New York, 2009.
- Kokate, C. K.; Gokhale, S. B.; Purohit, A. P. A textbook of Pharmacognosy, 29th ed.; Nirali Prakashan: Pune, 2009.
Feb. 21, 2013 — Experts tout the health benefits of low-dose aspirin and omega-3 fatty acids found in foods like flax seeds and salmon, but the detailed mechanisms involved in their effects are not fully known. Now researchers reporting in the February 21 issue of the Cell Press journal Chemistry & Biologyshow that aspirin helps trigger the production of molecules called resolvins that are naturally made by the body from omega-3 fatty acids. These resolvins shut off, or "resolve," the inflammation that underlies destructive conditions such as inflammatory lung disease, heart disease, and arthritis.
"In this report, we found that one resolvin, termed resolvin D3 from the omega-3 fatty acid DHA, persists longer at sites of inflammation than either resolvin D1 or resolvin D2 in the natural resolution of inflammation in mice," explains senior author Dr. Charles Serhan of Brigham and Women's Hospital and Harvard Medical School. "This finding suggests that this late resolution phase resolvin D3 might display unique properties in fighting uncontrolled inflammation."
The researchers also confirmed that aspirin treatment triggered the production of a longer acting form of resolvin D3 through a different pathway. "Aspirin is able to modify an inflammatory enzyme to stop forming molecules that propagate inflammation and instead produce molecules from omega-3 fatty acids, like resolvin D3, that help inflammation to end," explains coauthor Dr. Nicos Petasis of the University of Southern California.
The team went on to reveal detailed information about resolvin D3. "We were able to produce by chemical synthesis both resolvin D3 and aspirin-triggered resolvin D3 in pure form, which allowed us to establish their complete structures and biological activities," says Dr. Petasis. When administered to human cells, both of these resolvins demonstrated potent anti-inflammatory actions. When given to mice, the compounds also stimulated the resolution of inflammation in the body.
"We also identified the human receptor that is activated by resolvin D3, which is critical in understanding how resolvin D3 works in the body to resolve inflammation," says Dr. Serhan. "With this new information, investigators will now also be able to study the pro-resolving and anti-inflammatory actions of resolvin D3 in other systems." In addition, researchers will be interested in determining which inflammation-associated diseases might be treated with this newly identified resolvin.
This shows key molecules (DHA, aspirin, AT-RvD3) and cells undergoing actions promoted by AT-RvD3 (i.e. macrophages phagocytosing apoptotic cells). (Credit: Chemistry & Biology, Dalli et al.)
Jesmond Dalli, Jeremy W. Winkler, Romain A. Colas, Hildur Arnardottir, Chien-Yee C. Cheng, Nan Chiang, Nicos A. Petasis, Charles N. Serhan. Resolvin D3 and Aspirin-Triggered Resolvin D3 Are Potent Immunoresolvents.Chemistry & Biology, 2013; 20 (2): 188 DOI:10.1016/j.chembiol.2012.11.010
Feb. 21, 2013 — Flowers' methods of communicating are at least as sophisticated as any devised by an advertising agency, according to a new study, published Feb. 21 in Science Express by researchers from the University of Bristol. However, for any advertisement to be successful, it has to reach, and be perceived by, its target audience. The research shows for the first time that pollinators such as bumblebees are able to find and distinguish electric signals given out by flowers.
Flowers often produce bright colours, patterns and enticing fragrances to attract their pollinators. Researchers at Bristol's School of Biological Sciences, led by Professor Daniel Robert, found that flowers also have their equivalent of a neon sign -- patterns of electrical signals that can communicate information to the insect pollinator. These electrical signals can work in concert with the flower's other attractive signals and enhance floral advertising power.
Plants are usually charged negatively and emit weak electric fields. On their side, bees acquire a positive charge as they fly through the air. No spark is produced as a charged bee approaches a charged flower, but a small electric force builds up that can potentially convey information.
By placing electrodes in the stems of petunias, the researchers showed that when a bee lands, the flower's potential changes and remains so for several minutes. Could this be a way by which flowers tell bees another bee has recently been visiting? To their surprise, the researchers discovered that bumblebees can detect and distinguish between different floral electric fields.
Also, the researchers found that when bees were given a learning test, they were faster at learning the difference between two colours when electric signals were also available.
How then do bees detect electric fields? This is not yet known, although the researchers speculate that hairy bumblebees bristle up under the electrostatic force, just like one's hair in front of an old television screen.
The discovery of such electric detection has opened up a whole new understanding of insect perception and flower communication.
Dr Heather Whitney, a co-author of the study said: "This novel communication channel reveals how flowers can potentially inform their pollinators about the honest status of their precious nectar and pollen reserves."
Professor Robert said: "The last thing a flower wants is to attract a bee and then fail to provide nectar: a lesson in honest advertising since bees are good learners and would soon lose interest in such an unrewarding flower.
"The co-evolution between flowers and bees has a long and beneficial history, so perhaps it's not entirely surprising that we are still discovering today how remarkably sophisticated their communication is."
The research was supported by the Leverhulme Trust.
Dominic Clarke, Heather Whitney, Gregory Sutton, and Daniel Robert. Detection and Learning of Floral Electric Fields by Bumblebees. Science, 21 February 2013 DOI:10.1126/science.1230883
Geranium magnificum showing a composite of immediately before and after application of charged powder paint. The pattern of powder deposition reveals the shape of the electric field. (Credit: Image by Dominic Clarke and Daniel Robert)
Feb. 22, 2013 — The fruit fly study adds to the evidence "that using toxins in the environment to medicate offspring may be common across the animal kingdom," says biologist Todd Schlenke.
When fruit flies sense parasitic wasps in their environment, they lay their eggs in an alcohol-soaked environment, essentially forcing their larvae to consume booze as a drug to combat the deadly wasps.
The discovery by biologists at Emory University is being published in the journal Science on February 22.
"The adult flies actually anticipate an infection risk to their children, and then they medicate them by depositing them in alcohol," says Todd Schlenke, the evolutionary geneticist whose lab did the research. "We found that this medicating behavior was shared by diverse fly species, adding to the evidence that using toxins in the environment to medicate offspring may be common across the animal kingdom."
Adult fruit flies detect the wasps by sight, and appear to have much better vision than previously realized, he adds. "Our data indicate that the flies can visually distinguish the relatively small morphological differences between male and female wasps, and between different species of wasps."
The experiments were led by Balint Zacsoh, who recently graduated from Emory with a degree in biology and still works in the Schlenke lab. The team also included Emory graduate student Zachary Lynch and postdoc Nathan Mortimer.
The larvae of the common fruit fly, Drosophila melanogaster, eat the rot, or fungi and bacteria, that grows on overripe, fermenting fruit. They have evolved a certain amount of resistance to the toxic effects of the alcohol levels in their natural habitat, which can range up to 15 percent.
Tiny, endoparasitoid wasps are major killers of fruit flies. The wasps inject their eggs inside the fruit fly larvae, along with venom that aims to suppress their hosts' cellular immune response. If the flies fail to kill the wasp egg, a wasp larva hatches inside the fruit fly larva and begins to eat its host from the inside out.
Last year, the Schlenke lab published a study showing how fruit fly larvae infected with wasps prefer to eat food high in alcohol. This behavior greatly improves the survival rate of the fruit flies because they have evolved high tolerance of the toxic effects of the alcohol, but the wasps have not.
"The fruit fly larvae raise their blood alcohol levels, so that the wasps living in their blood will suffer," Schlenke says. "When you think of an immune system, you usually think of blood cells and immune proteins, but behavior can also be a big part of an organism's immune defense."
For the latest study, the researchers asked whether the fruit fly parents could sense when their children were at risk for infection, and whether they then sought out alcohol to prophylactically medicate them.
Adult female fruit flies were released in one mesh cage with parasitic wasps and another mesh cage with no wasps. Both cages had two petri dishes containing yeast, the nourishment for lab-raised fruit flies and their larvae. The yeast in one of the petri dishes was mixed with 6 percent alcohol, while the yeast in the other dish was alcohol free. After 24 hours, the petri dishes were removed and the researchers counted the eggs that the fruit flies had laid.
The results were dramatic. In the mesh cage with parasitic wasps, 90 percent of the eggs laid were in the dish containing alcohol. In the cage with no wasps, only 40 percent of the eggs were in the alcohol dish.
"The fruit flies clearly change their reproductive behavior when the wasps are present," Schlenke says. "The alcohol is slightly toxic to the fruit flies as well, but the wasps are a bigger danger than the alcohol."
The fly strains used in the experiments have been bred in the lab for decades. "The flies that we work with have not seen wasps in their lives before, and neither have their ancestors going back hundreds of generations," Schlenke says. "And yet, the flies still recognize these wasps as a danger when they are put in a cage with them."
Further experiments showed that the flies are extremely discerning about differences in the wasps. They preferred to lay their eggs in alcohol when female wasps were present, but not if only male wasps were in the cage.
Theorizing that the flies were reacting to pheromones, the researchers conducted experiments using two groups of mutated fruit flies. One group lacked the ability to smell, and another group lacked sight. The flies unable to smell, however, still preferred to lay their eggs in alcohol when female wasps were present. The blind flies did not make the distinction, choosing the non-alcohol food for their offspring, even in the presence of female wasps.
"This result was a surprise to me," Schlenke says. "I thought the flies were probably using olfaction to sense the female wasps. The small, compound eyes of flies are believed to be more geared to detecting motion than high-resolution images."
The only obvious visual differences between the female and male wasps, he adds, is that the males have longer antennae, slightly smaller bodies, and lack an ovipositor.
Further experimentation showed that the fruit flies can distinguish different species of wasps, and will only choose the alcohol food in response to wasp species that infect larvae, not fly pupae. "Fly larvae usually leave the food before they pupate," Schlenke explains, "so there is likely little benefit to laying eggs at alcoholic sites when pupal parasites are present."
The researchers also connected the exposure to female parasitic wasps to changes in a fruit fly neuropeptide.
Stress, and the resulting reduced level of neuropeptide F, or NPF, has previously been associated with alcohol-seeking behavior in fruit flies. Similarly, levels of a homologous neuropeptide in humans, NPY, is associated with alcoholism.
"We found that when a fruit fly is exposed to female parasitic wasps, this exposure reduces the level of NPF in the fly brain, causing the fly to seek out alcoholic sites for oviposition," Schlenke says. "Furthermore, the alcohol-seeking behavior appears to remain for the duration of the fly's life, even when the parasitic wasps are no longer present, an example of long-term memory."
Finally, Drosophila melanogaster is not unique in using this offspring medication behavior. "We tested a number of fly species," Schlenke says, "and found that each fly species that uses rotting fruit for food mounts this immune behavior against parasitic wasps. Medication may be far more common in nature than we previously thought."
B. Z. Kacsoh, Z. R. Lynch, N. T. Mortimer, T. A. Schlenke.Fruit Flies Medicate Offspring After Seeing Parasites.Science, 2013; 339 (6122): 947 DOI:10.1126/science.1229625
Neil F. Milan, Balint Z. Kacsoh, Todd A. Schlenke. Alcohol Consumption as Self-Medication against Blood-Borne Parasites in the Fruit Fly. Current Biology, 2012; 22 (6): 488 DOI: 10.1016/j.cub.2012.01.045
sexta-feira, 22 de fevereiro de 2013
Publicado em fevereiro 19, 2013 por zhannko
O Projeto da Horta Permacultural iniciado em 2010 e com continuidade em 2011, com parceria entre escola, pais e profissionais das Secretarias Municipais.
A horta foi projetada com canteiros em forma de mandalas que a tornam mais bonita, interessante e de fácil acesso para seu manejo, seja pelas crianças ou adultos.
Neste ano damos continuidade ao projeto com a organização de novos canteiros com a participação de pais, mães, professores e alunos, com a colocação de bambus e a adubação.
O plantio de mudas de alface, beterraba, couve-flor e repolho foi realizado com os alunos no período letivo com atividades pedagógicas específicas.
Serão desenvolvidas diversas atividades com o tema central HORTA no decorrer do ano letivo envolvendo alunos, famílias, professores e profissionais da área, buscando aprimorar e desenvolver novos conhecimentos.
ABAIXO SEGUEM REGISTROS DE ATIVIDADES DESENVOLVIDAS NOS MESES DE MAIO E JUNHO:
LIMPEZA GERAL DA HORTA COM MÃES
COLOCAÇÃO DE BAMBUS PARA FORMAÇÃO DE NOVOS CANTEIROS EM FORMA DE MANDALAS COM PARTICIPAÇÃO DE PAIS
ENTREGA DE MUDAS DE ALFACE CULTIVADAS NA HORTA
PARA CADA FAMÍLIA
DIA DE PLANTIO COM ALUNOS