Es ist nicht klar, wie groß die Rolle von Antibiotika https://antibiotika-wiki.de/ in den Wettbewerbsbeziehungen zwischen Mikroorganismen unter natürlichen Bedingungen ist. Zelman vaxman glaubte, dass diese Rolle minimal ist, Antibiotika werden nicht anders als in reinen Kulturen auf reichen Umgebungen gebildet. Anschließend wurde jedoch festgestellt, dass bei vielen Produzenten die Aktivität der antibiotikasynthese in Gegenwart anderer Arten oder spezifischer Produkte Ihres Stoffwechsels zunimmt.
Mjbs 6(1-2).indd
Mongolian Journal of Biological Sciences 2008 Vol. 6(1-2): 45-49Calculation of Quantitative Structure-Activity Relationship Descriptors of Artemisinin Derivatives Jambalsuren Bayarmaa1 and Vladimir Frecer2 1Department of Biochemistry and Bioorganic Chemistry, Faculty of Biology, National University of Mongolia E-mail: bayarmaa_j@biology.num.edu.mn2Area of Pure and Applied Chemistry, International Center for Sciense and High Technology-UNIDO, Trieste, Italy E-mail: vladimir.frecer@ics.trieste.itAbstract
Quantitative structure-activity relationships are based on the construction of predictive models using
a set of known molecules and associated activity value. This accurate methodology, developed with adequate mathematical and computational tools, leads to a faster, cheaper and more comprehensive design of new products, reducing the experimental synthesis and testing on animals. Preparation of the QSAR models of artemisinin derivatives was carried out by the genetic function algorithm (GFA) method for 91 molecules. The results show some relationships to the observed antimalarial activities of the artemisinin derivatives. The most statistically signifi cant regression equation obtained from the fi nal GFA relates to two molecular descriptors.
Key words: molecular model, descriptor, QSAR technique, artemisinin derivatives Introduction
Artemisinin and its derivatives are only the group of compounds that is still effective against drug-
Malaria is one of the most serious parasitic resistant P. falciparum strains, and has the ability
diseases in the world. There are millions of acute
to quickly reduce parasite level (Krishna, 2004).
cases of malaria each year globally, resulting in
From the other side, it has short plasma half-life,
more than one million deaths. The clinical disease
limited bioavailability, poor solubility in oil and
caused by Plasmodium falciparum is widely water, and the low yield from natural sources distributed and entrenched in areas of the world
where climates are suitable for its transmission.
to develop new chemotherapeutic artemisinin
The present level of annual global malaria incident
derivatives. By the chemical modifi cation of
consisted of about 500 million, 350 million in the
artemisinin at the position of C10 semisynthetic
African region and 125 million in the South East
derivatives as artesunate, artemether, artelinic
Asian region. Deaths due to malaria are occurring
acid and dihydroartemisinin were produced,
in increasing numbers because of frequent failure
which have more antimalarial activities in
of the conventional treatments using drugs such
vitro than artemisinin itself (Pinheiro, 2003).
as chloroquine, mefl oquine and sulfadoxine-
Many derivatives have been synthesized using
pyrimethamine, against P. falciparum, the dihydroartemisinin by adding different radicals populations of which have developed a high on its rings. But, the development of a new drug is degree of resistance.
a very long and expensive process. To overcome
Combination therapies with formulations these diffi culties scientists start to use a variety
containing an artemisinin compound have of computational methods to identify novel emerged as a more reliable treatment option. compounds, design compounds with increased Artemisinin is naturally formed in Artemisia
selectivity, effi cacy and safety and develop
annua L(sweet wormwood). This herb of the
compounds into clinical trial candidates. One
Asteraceae family has been used for treatment of these methods is the Quantitative Structure-of fever and malaria in China over many Activity Relationship (QSAR) technique. The centuries. Additional names found in China for
present work is related to the design of a new
artemisinin are qinghaosu and huanghuahaosu. antimalarial active artemisinin analog.
Canadian Multidisciplinary Road Safety Conference ‐ Montreal 2013 ATTENTION DEFICIT HYPERACTIVITY DISORDER, ALCOHOL, DRUGS AND DRIVING: POPULATION-BASED EXAMINATION IN A CANADIAN SAMPLE Evelyn Vingilis, Western University Robert E. Mann, Centre for Addiction and Mental Health Patricia Erickson, University of Toronto Maggie Toplak, York University Umesh J
History of Technology — 4. The Industrial RevolutionHistory of Technology — 4. The Industrial Revolution Síntese da Encyclopaedia Britannica (1750-1900) Nota: para consultar as restantes partes da sínteseconsult no final desta parte e clicanos hyperlinks azuis para abrir os respectivosficheiros pdfHistory of Technology — 4. The Industrial RevolutionIV. The Industrial Revolutio