Structure of chlorflavonin

Abstract

Chlorflavonin, a new antifungal antibiotic isolated from cultures of Aspergillus candidus, is shown to be 3'-chloro-2',5-dihydroxy-3,7,8-trimethoxyflavone.CHLORFLAVONIN, a new antifungal antibiotic, has recently been isolated from cultures of Aspergillus candidas. This paper presents evidence showing that chlorilavonin is 3'-chloro-2',5-dihydroxy-3,7,8-trirnethoxyflavone (I). There appear to be no previous reports of the natural occurrence of a chlorinated flavone and only one report of the occurrence of a flavone as a fungal metabolite. However, that report did not include a description of the isolation and full characterisation of the metabolite.ChlorAavonin, C18H16C10,, is a yellow powder, m.p. 212", with three methoxy-groups, two hydroxy-groups, and a carbonyl group. Reaction with diazomethane gives a monomethyl ether and prolonged refluxing with methyl iodide gives a dimethyl ether. A positive Perkin test 3 on chlorflavonin and its diacetate suggests the presence of a y-pyrone ring. Reduction with magnesium and hydrochloric acid gives a deep red colour, indicative4 of a 3-oxygenated flavone, and a positive Dimroth test suggests the presence of a hydroxy-group adjacent to the carbonyl group. Development of a deep yellow colour with zirconyl chloride in the absence, but not in the presence, of citric acid indicates a 5-hydroxyrather than a 3-hydro~y-flavone.~ Both chlorflavonin and its monomethyl ether show a

Isolation Techniques for Flavonoids

“…The few examples of the use of this technique for the isolation or purification of naturally occurring flavonoids include: the isolation of 3'-chloro-2' ,5-dihydroxy-3, 7 ,8-trimethoxyflavone from a fungal culture extract (at 200 0 , 0.1 mm) (Bird and Marshall, 1969), the purification of 7-hydroxy-6,4'-dimethoxyisoflavone from Cabreuva wood (Harborne et al , 1963) and calycosin (7,3'-dihydroxy-4'-methoxyisoflavone) from Baptisia lecontei (180 0 , 0.05 mm) . Sim (1967), in a general investigation of the sublimation of flavonoids, found that fractional sublimation could be used to separate certain mixtures, e.g.…”

Novel Method for Determination of Partition Coefficients of Penicillins and Cephalosporins by High-pressure Liquid Chromatography

“…Table I lists the log kfm, values extrapolated to 0% methanol. The relationship between log k(,] and the other reported lipophilic indexes (log P or R,) (9,10) is expressed by Eqs. 2-4 for penicillins and cephalosporins: where n, r, and s are number of experiments, correlation coefficient, and standard deviation, respectively.…”

“…While the most useful and widely accepted lipophilic index is the logarithm of the partition coefficient, log P , determined in a l-octanolwater system (8), such a measurement for penicillin molecules often presents practical difficulties because of their high instability in the acidic pH region near the pKa (-2.7). The logP values determined with a rapid pH-stat technique (9) seem to be the most accurate and reliable. Unfortunately, in spite of this technique, it is difficult to determine or compare the true log P values for P-lactam antibiotics because of two or more ionizable substituents in their side chains (e.g., carbenicillin and sulbenicillin) and because of the zwitterion itself (e.g., cyclacillin, ampicillin, amoxicillin, cephaloridine, cephaloglycin, cephalexin, and cephradine).…”

“…Recently, R, values of penicillins were determined in another TLC system (9), but a difference between the actual pH on the plate and that of the mobile phase was observed (9). This pH difference is undesirable for acids such as P-lactam antibiotics, because the R, values, in order to be an expression of the true partition coefficients, have to be corrected according to their degree of ionization at the mobile phase pH.…”

A Quantitative Structure‒Activity Relationship Approach to the Minimization of Albumin Binding

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17 The binding of 2,6-disubstituted xanthones to human serum albumin (HSA) has been investigated using an ultrafiltration technique. A set of 26 compounds was chosen for study using a selection procedure aimed at minimizing the interparameter correlations, while ensuring that the physicochemical properties covered the maximum possible range of values.

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