(n.) One of a series of organic compounds, regarded as anhydrides of certain hydroxy acids. In general, they are colorless liquids, having a weak aromatic odor. They are so called because the typical lactone is derived from lactic acid.
Example Sentences:
(1) These compounds were tentatively identified as two epimers at C-23 of 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholestano-26,23-lactone, which were probably artifacts formed from the corresponding tetrahydroxycholestanoic acids during the procedures for extraction after hydrolysis.
(2) Second, both lovastatin and simvastatin are administered as prodrugs in their lactone forms.
(3) The method involves the selective joining of two synthetic fragments, namely residues 1-65 of the apopeptide with Met65 replaced by homoserine lactone and residues 66-104 of the protein in the presence of fragment 1-25 of the native heme-containing peptide.
(4) Two new isomeric delta-lactones 2 and 3 have been isolated from the marine fungus Helicascus kanaloanus (ATCC 18591).
(5) Our data do not support the possibility of hydrogen bonding between the 16 beta-hydroxyl of gitoxigenin and the lactone ring, previously suggested to account for the decreased activity of gitoxigenin vis à vis digitoxigenin, but, rather, suggest that the decreased activity may be due to an intramolecular hydrogen bond between the hydroxyls on C-14 and C-16 and an unusual D-ring conformation which combine to alter the carbonyl oxygen of the lactone ring away from the putative active position.
(6) Status epilepticus was provoked in 10 rats by embedding coriaria lactone particle into the left cerebral motor cortex.
(7) Preliminary results indicate that chloride is eliminated during subsequent lactonization of the 2,3-dichloro-cis,cis-muconate, followed by hydrolysis to form 5-chloromaleylacetic acid.
(8) This ester, on standing, gradually formed the corresponding lactone.
(9) Studies were made on the ultraviolet difference-spectra of glucoamylase from Rhizopus niveus [EC 3.2.1.3] specifically produced by the substrate maltose and the inhibitors, glucose, glucono-1: 5-lactone (gluconolactone), methyl beta-D-glucoside, cellubiose, and cyclohexa-, and cyclohepta-amyloses.
(10) Pharmacokinetics of digitoxin (DGT) and its derivative hydrogenated at the unsaturated lactone ring have been studied using the 3H-labelled compounds in cats.
(11) The enzyme hydrolyzes aldonate lactones, such as D-galactono-gamma-lactone and L-mannono-gamma-lactone, stereospecifically.
(12) Since furanoses in the envelope form are analogous (in some ways) to half-chair or sofa conformations and since lactones with six-membered rings probably have half-chair or sofa conformations, the results indicate that beta-galactosidase probably destabilizes its substrate into a planar conformation of some type and that the galactose in the transition state may, therefore, also be quite planar.
(13) An unusual change in absorbance from 300 to 310-320 nm, obtained only with the valienamine-derived inhibitors or when D-glucono-1,5-lactone and maltose are combined, is concluded to arise when subsite 2 is occupied in a transition-state-type of complex.
(14) These studies showed that neither the strained trans-fused alpha-methylene lactone 12 nor the hydroxy-alpha-methylene lactones 5 and 6 reacted with cysteine with rates comparable to elephantopin.
(15) Relative to that of glucagon, biological activity and affinity of [des-Asn-28,Thr-29](homoserine lactone-27)-glucagon, prepared by CNBr treatment of glucagon, were reduced equally by 40- to 50-fold.
(16) These data indicate that PGF2alpha, 1-15 lactone decreases menstrual cycle lengths in non-pregnant rhesus monkeys.
(17) The metabolic pathway from 1 alpha,25-dihydroxyvitamin D3 [1 alpha,25-(OH)2D3] to 1 alpha,25-dihydroxyvitamin D3-26,23-lactone includes the formation of 1 alpha,23,25-26-tetrahydroxyvitamin D3 [1 alpha,23,25,26-(OH)4D3].
(18) The macrocyclic lactone ring is necessary for antibiotic activity.
(19) The lactones were treated with benzyl mercaptide anion to form 4-(benzylthio)butyric acid, which, on treatment with trifluoroacetic acid, cyclized to yield thiololactones.
(20) Thapsigargin is a potent skin irritating sesquiterpene lactone isolated from the roots of Thapsia garganica L. (Apiaceae).
Quassin
Definition:
(n.) The bitter principle of quassia, extracted as a white crystalline substance; -- formerly called quassite.
Example Sentences:
(1) Since tyrosinase is directly involved in sclerotisation of the cuticle, it is suggested that quassin, as a larvicide, inhibits development of the cuticle.
(2) Quassin lost its antilarval activity on treatment with strong alkalies.
(3) Quassin was present to the extent of 0.1 to 0.14 per cent (average 0.12%) on a dry weight basis in wood of Q. amara.
(4) Quassin was over five times as active as carbaryl, a synthetic antilarval agent.
(5) In presence of quassin phenylalanine, tyrosine and L-dopa levels were increased in larvae.
(6) Quassin has been identified to be the antilarval principle present in this plant and was effective against mosquito larvae at a concentration of 6 ppm.
(7) Monoamine oxidase (MAO), an enzyme directly involved in the metabolism of catecholamines, remained unaffected by quassin, in fact the level of adrenaline also remained unchanged in larvae during quassin poisoning.
(8) Quassin, a mosquito larvicide isolated from Quassia amara, inhibits tyrosinase activity in the larvae of Culex quinquefasciatus.