Martin Weidenbörner

Antifungal activity of flavonoids against storage fungi of the genus Aspergillus.

Abstract The fungicidal activity of two isoflavones, one isoflavanone and seven isoflavans was tested in malt extract broth against five storage fungi of the genus Aspergillus . While the isoflavones and isoflavanone show only low activity, the two isoflavans 7,8-dihydroxy-4′-methoxyisoflavan and 6,7-dihydroxy-3′-methylisoflavan were highly inhibitory to Aspergillus . Structure-activity relationships are discussed.

Antifungal activity of isoflavonoids in different reduced stages on Rhizoctonia solani and Sclerotium rolfsii.

Abstract Two naturally occurring isoflavones, genistein and biochanin A, and their dihydroderivates (isoflavanones) as well as nine perhydrogenated isoflavones (isoflavans) were tested for their effects on mycelial growth of the two soil borne fungi Rhizoctonia solani and Sclerotium rolfsii . All the isoflavonoids of the biochanin A series showed high antifungal activity. Genistein isoflavan and the other isoflavans with two hydroxyl groups and one methoxy group were fungitoxic, while isoflavans with two or three methoxy groups were almost inactive.

Growth control of different Fusarium species by selected flavones and flavonoid mixtures

The antifungal activity of five substituted flavones and their mixtures with unsubstituted flavone or a flavanone was tested on malt extract agar against five Fusarium spp. 4′-Methylflavone and 2′,6′-dichloroflavone showed the highest activity while 4′-benzyloxyflavone caused the lowest inhibition of all test substances. A significant increase in the antifungal effect of the substituted flavones could be observed if mixtures in combination with the unsubstituted flavone or flavanone were used. Some aspects of structure-activity relationships are discussed.

Antifungal spectrum of flavone and flavanone tested against 34 different fungi

The antifungal activity of flavone and flavanone was tested in three different concentrations, 0.5, 2 and 8 × 10 -4 M, against 34 fungi. In general, flavone was the substance with the higher activity, and could at 2 × 10 -4 M completely inhibit several fungi. No linear relationships between the concentration and the antifungal activity could be observed for some fungi. Chaetomium globosum was the only fungus which was totally inhibited by flavanone at 8 × 10 -4 M. Several fungi did, however, show a higher inhibition rate at 2 × 10 -4 M.

Mycelial Deformations of Cladosporium herbarum due to the Application of Eugenol or Carvacrol

ABSTRACT Varying concentrations of eugenol and carvacrol were added to cultures of Cladosporium herbarum to determine their effect on the growth and cell morphology of this common food spoiling mold. Microscopically, significant morphological deformations of the hyphae in relation to their age could be observed. These phenomena were accompanied by macroscopic changes of the colonies in combination with substantial growth inhibitions. Carvacrol possessed a higher antifungal activity than eugenol.

Contamination of different muesli components by fungi

16 different muesli components were studied for mould contamination and their qualitative mycobiota on three media. High counts of moulds were found in hazelnuts, cashew kernels, sunflower seeds, cornflakes, peanuts and almonds. Linseeds, raisins and different kinds of grain products showed lower contamination. The fungal flora consisted of 60 different species belonging to 21 genera. Penicillium (19 species), Aspergillus (11 species) and Eurotium (4 species), together with the Mucoraceae, predominated.

Mold Spectra of Various Foods in Relation to Plating Medium

Freeze-dried strawberries and pears, raisins, sliced roasted almonds, and hazelnuts were investigated for their qualitative and quantitative mycoflora on four different media. The foodstuffs investigated showed relatively low infestation rates. Slightly higher fungus counts were observed in the case of almonds, while strawberries, hazelnuts, raisins, and pears (in decreasing order) were contaminated only to a minor degree. The mycoflora was dominated by molds of the genera Aspergillus and Penicillium and fungi of the Mucoraceae. Most fungus isolates could be enumerated from DRBC, followed by PDA and DG-18, while 7.5% MSA showed only low effectiveness. Minor differences were seen when the number of different species/genera from each medium were compared with each other. DRBC allows the isolation of the broadest spectrum of fungi. Differences between the remaining media were small.

Mycoflora of cereal flakes

Twelve brands of cereal flakes were examined for their qualitative and quantitative mold contamination. Higher fungal counts were observed in the case of two wheat and one oat flake sample (s) while the remaining brands showed minor contamination rates. The fungal flora consisted of 64 different species belonging to 23 fungal genera. Fungi of the genus Eurotium (4 species), Aspergillus (7 spp.) and Penicillium (25 spp.) predominated on most samples.

Increased antifungal activity of 3- and 7-hydroxyflavone against Cladosporium herbarum and Penicillium glabrum through ester formation

3- and 7-hydroxyflavone and their acetic acid esters were tested against Cladosporium herbarum and Penicillium glabrum for antifungal activity. The effect of the hydroxylated flavones was relatively low whereas the ester derivatives were substantially more active.