Biological activities isolation

Epothilones A, B and E (4,5 and 6) (Fig. 2) are representative members of a new class of bacterially derived natural products which exhibit potent biological activity. Isolated by Hofle and coworkers [6] from a soil sample collected near the Zambesi river, the compounds have provided a great deal of excitement in the scientific community due to their potent cytotoxicity against a number of multiple drug-resistant tumor cell lines and because of the mechanism by which they exert this effect. Like Taxol [7], the epothilones promote the combination of a- and 3-tubulin subunits and stabilize the resulting microtubule structures. This mode of action inhibits the cell division process and is, therefore, an attractive strategy for cancer chemotherapy [7,8]. 

Since the discovery of amphimedine by Schmitz and co-workers in 1983 [36], the polycyclic alkaloids based on the pyrido[, /]acridine skeleton have emerged as a well-defined class of marine metabolites, with significant biological activities, isolated from sponges and tunicates [37]. The less common group of sulfide pyridoacridines were only obtained from tunicates and they include the shermilamines, the varamines-lissoclins-diplamine group, and tintamine, another polycyclic alkaloid closely related to them. 

Said SI, Mutt V. Polypeptide with broad biological activity isolation from small intestine. Science 1970 169 1217-1278. 

No known biological activity. Isolated from Pseudomonas GH fermentation in yield of 1.0 g from 10 1 of medium. Also produced by B. roseus fluorescens. 

Said SI, Mutt V. Polypeptide with broad biological activity isolation from small intestine. Science 1970 169 1217-1218. Bodanszky M, Klausner YS, Lin CY, Mutt V, Said SI. Synthesis of the vasoactive intestinal peptide (VIP). J. Am. Chem. Soc. 1974 96 4973-4938. 

Srocmre determination of a compound with biological activity isolated from a natural source,... 

The posterior lobe of the pituitary, ie, the neurohypophysis, is under direct nervous control (1), unlike most other endocrine organs. The hormones stored in this gland are formed in hypothalamic nerve cells but pass through nerve stalks into the posterior pituitary. As early as 1895 it was found that pituitrin [50-57-7] an extract of the posterior lobe, raises blood pressure when injected (2), and that Pitocin [50-56-6] (Parke-Davis) causes contractions of smooth muscle, especially in the utems (3). Isolation of the active materials involved in these extracts is the result of work from several laboratories. Several highly active posterior pituitary extracts have been discovered (4), and it has been deterrnined that their biological activities result from peptide hormones, ie, low molecular weight substances not covalendy linked to proteins (qv) (5). 

Additional compounds having similar biological activities and stmctural components were isolated resulting in the recognition of PGs as a family of closely related compounds. Stmctural and stereochemical assignments of PGE and PGF, were confirmed by x-ray crystallographic analysis of their... 

Homofolic acid, 5,11-methenyl-tetrahydro-biological activity, 3, 327 Homofolic acid, tetrahydro-biological activity, 3, 327 Homoisoflavanones occurrence, 3, 722 thermoisomerization, 3, 722 thermolysis, 3, 728 Homolytic reactions heterocyclic compounds reviews, 1, 74 Homophthalic acid isocoumarins synthesis from, 3, 830 synthesis, 3, 830 Homophthalic anhydride isochroman-l-one synthesis from, 3, 860 20a-Homoporphyrin nomenclature, 1, 30 Homopterocarpin isolation, 4, 998 ( )- D- Homotestosterone synthesis, 1, 453 Homer-Emmons reaction chromene synthesis by, 3, 749 Hortiacine isolation, 3, 149 Hortiamine isolation, 3, 149... 

The process of isolation finally adopted by the former authors consists in precipitating as reineckates the water-soluble bases contained in a methyl alcoholic extract of the curare. The mixed reineckates are further purified, by solution in acetone and precipitation with water as often as may be necessary. The product so cleaned represents the bulk of the biological activity of the crude drug the mother liquors may contain curine (p. 374), which indicates a menisperm as one of the components of such curares. The mixed reineckates are then fractionated chromato-graphically over alumina and the components isolated as chlorides by the use of silver sulphate and barium chloride in succession. This process has been modified in detail by Schmid and Karrer, who have also found that with their curare, the more soluble reineckate fraction includes less potent quaternary alkaloids. 

Finally, in 1797, the Frenchman L. N. Vauquelin discovered the oxide of a new element in a Siberian mineral, now known as crocoite (PbCr04), and in the following year isolated the metal itself by charcoal reduction. This was subsequently named chromium (Greek xpco ia, chroma, colour) because of the variety of colours found in its compounds. Since their discoveries the metals and their compounds have become vitally important in many industries and, as one of the biologically active transition elements, molybdenum has been the subject of a great deal of attention in recent years, especially in the field of nitrogen fixation (p. 1035). 

Hundreds of flavonols have been isolated and characterized many of them are biologically active. Hence a great synthetic interest has arisen. Some of the efforts have concentrated on the synthesis of naturally oecurring flavonols while others have focused on the synthesis of flavonol derivatives for structure activity relationships. ... 

The TMM [4-1-3] cycloaddition to pyrone has been employed in a synthetic study of a novel biologically active diterpene pseudolaric acid B (106), in which the formation of the bridged adduct (107) from the 2-pyrone (108) is the key step in the sequence (Scheme 2.29). A mixture of the other isomer (109) and the methylenecyclopentane (110) was also isolated from the reaction. It is important to point out that the presence of a tin co-catalyst is critical in effecting the reaction. This is the first example a "tin-effect observed in a [4-1-3] cycloaddition [40]. 

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