Aflatoxin Inhibition Research Articles

Trametes versicolor bioactive compounds stimulate Aspergillus flavus antioxidant system and inhibit aflatoxin synthesis

Aflatoxins are bioactive compounds, which are toxic and carcinogenic for humans and animals, and are produced mainly by Aspergillus flavus and A. parasiticus. We studied the effect of some bioactive compounds produced into the culture filtrates of the basidiomycete Trametes versicolor on A. flavus growth and aflatoxin synthesis. Some aspects of the mechanism of action of different filtrate fractions were investigated.The results showed that these compounds stimulate the antioxidant system of the Aspergillus mycelia by the induction of a transient and modulated oxidative burst (peroxides and superoxide anions formation) perceived by Afyap1 transcription factor. T. versicolor culture filtrate fractions, significantly inhibited aflatoxin biosynthesis (A: 75% and B: 55%) apparently by stimulating endogenous antioxidant system. In conclusion, bioactive compounds present in the T. versicolor filtrates probably act by modulating the fungal antioxidant system, eventually leading to aflatoxin inhibition. T. versicolor could represent a novel promising tool to control aflatoxins in foods and feeds.

AtoxigenicAspergillus flavus biological control of aflatoxin contamination: what is the mechanism?

The term ‘competitive exclusion’ involving physical blockage of growth or access of the toxigenic strain to the seed target has been used to describe the mechanism of biological control of aflatoxin contamination. However, recent evidence suggests that a form of intraspecific aflatoxin inhibition requiring growth of the competing strains together during the infection process in such a way that hyphae physically interact or touch is the trigger for preventing induction of aflatoxin synthesis. This direct touch-based inhibition of aflatoxin synthesis is posited to be the mechanistic basis of biological control in this system. Evidence for this idea comes from the published observations that co-culture of toxigenic and atoxigenic strains in a suspended disc system, in which the hyphae physically interact, prevents aflatoxin production. However, growth of the same strains in the same medium in the two compartments of a filter insert plate well system, separating the atoxigenic and toxigenic strains with a 0.4 μm or 3.0 μm filter, allows aflatoxin production approaching that of the toxigenic strain alone. When the strains are mixed and placed in both the insert and the well compartments, the intraspecific aflatoxin inhibition occurs as it did in the suspended disc culture system. This further suggests that neither nutrient competition nor soluble signal molecules, which should pass through the filter, are involved in intraspecific aflatoxin inhibition. When the two strains are separated by a 12 μm filter that would allow some passage of conidia or hyphae between the compartments the aflatoxin synthesis is approximately half that of the toxigenic strain alone. This phenomenon could be termed ‘competitive inclusion’ or ‘competitive phenotype conversion’. Work of others that relates to understanding the phenomenon is discussed, as well as anAspergillus flavus population biology study from the Louisiana maize agro-ecosystem which has biological control implications.

Aflatoxin inhibition in Aspergillus flavus for bioremediation purposes

Although Aspergilli are known for their efficiency in bioremediation, some strains produce aflatoxins as secondary metabolites adding another problem to the already existing environmental problem. A number of fungal isolates were tested for their ability to treat laboratory waste water. A single isolate, Aspergillus flavus, was chosen for its ability to treat a mixture of laboratory wastes in 7 days; the long duration resulted in the production of aflatoxins. This production was assumed to be the result of fungal exposure to stress. The oxidative stress-related transcription factor (OSTRF) Yap1 was present on the genomic level, suggesting the regulation of aflatoxin biosynthesis. Although exposure of the fungus to 2.5 kGy gamma radiation was effective in aflatoxin and mycelial inhibition, green tea phenolic extract (ca. 70 mg/ml phenol) was used because it inhibited aflatoxin production while fungal mycelial growth was not affected. Aflatoxins B1, B2 and G1, G2 were evident in control cultures (0.34 μg/g) along with cultures spiked with hydrogen peroxide (2.4 μg/g) which was considered the positive oxidant. On the other hand, aflatoxins were absent completely in cultures supplemented with gallic acid (positive antioxidant) and green tea phenolic-containing extract. Lipid peroxidation results followed the same trend. The addition of phenolic green tea extract inhibited aflatoxin biosynthesis; moreover, it did not affect the potential of the fungus in bioremediation, or its growth.

Effects of temperature and medium composition on inhibitory activities of gossypol-related compounds against aflatoxigenic fungi

To investigate the effects of temperature and medium composition on growth/aflatoxin inhibitory activities of terpenoids gossypol, gossypolone and apogossypolone against Aspergillus flavus and A.parasiticus. The compounds were tested at a concentration of 100μgml(-1) in a Czapek Dox (Czapek) agar medium at 25, 31 and 37°C. Increased incubation temperature marginally increased growth inhibition caused by these compounds, but reduced the aflatoxin inhibition effected by gossypol. Gossypolone and apogossypolone retained good aflatoxin inhibitory activity against A.flavus and A.parasiticus at higher incubation temperatures. However, increased temperature also significantly reduced aflatoxin production in control cultures. The effects of the terpenoids on fungal growth and aflatoxin production against the same fungi were also determined in Czapek, Czapek with a protein/amino acid addendum and yeast extract sucrose (YES) media. Growth of these fungi in the protein-supplemented Czapek medium or in the YES medium greatly reduced the growth inhibition effects of the terpenoids. Apogossypolone displayed strong anti-aflatoxigenic activity in the Czapek medium, but this activity was significantly reduced in the protein-amended Czapek and YES media. Gossypol, which displayed little to no aflatoxin inhibitory activity in the Czapek medium, did yield significant anti-aflatoxigenic activity in the YES medium. Incubation temperature and media composition are important parameters involved in the regulation of aflatoxin production in A.flavus and A.parasiticus. These parameters also affect the potency of growth and aflatoxin inhibitory activities of these gossypol-related compounds against aflatoxigenic fungi. Studies utilizing gossypol-related compounds as inhibitory agents of biological activities should be interpreted with caution due to compound interaction with multiple components of the test system, especially serum proteins.

Diversity of culturable root-associated/endophytic bacteria and their chitinolytic and aflatoxin inhibition activity of peanut plant in China

A total of 72 isolates of root-associated/endophytic (RAE) bacteria were isolated from peanut plants grown in the main producing areas of 6 provinces in China. The 16S rRNA gene sequences of these isolates were determined and phylogenetic analyses revealed that 72 isolates belonged to the classes Bacilli (49 isolates) and Gammaproteobacteria (23 isolates). The majority of RAE bacteria in Bacilli belonged to 2 genera, Bacillus and Lysinibacillus (48 and 1) while those in Gammaproteobacteria belonged to the genera Enterobacter, Serratia, Stenotrophomonas, and Pseudomonas (7, 11, 3 and 2 isolates, respectively). This is the first report of Lysinibacillus xylanilyticus isolate as biocontrol agent against AFs. All of the selected RAE bacteria showed inhibitory activities against Aspergillus parasiticus (A. parasiticus) growth and/or aflatoxins (AFs) production by visual agar plate assay and tip culture method. Most of the RAE bacteria strains (96 % strains) were determined to have decreased mycelia growth or AFs production levels by >50 % (p < 0.05). Bacterial isolates were further characterized for chitinolytic activity and 22 strains (30 % strains) of identified RAE bacteria degraded colloidal chitin on the chitin medium plate. Ten selected chitinolytic RAE bacteria were tested for antifungal activity on peanuts and most of them significantly decreased mycelial growth and AFs production levels by >90 %. These results showed a wide distribution of biological control bacteria against AFs in Chinese peanut main producing areas and the selected RAE bacteria could potentially be utilized for the biocontrol of toxicogenic fungi.

ANTIFUNGAL, AFLATOXIN INHIBITORY AND FREE RADICAL‐SCAVENGING ACTIVITIES OF SOME MEDICINAL PLANTS EXTRACTS

ABSTRACTThe antifungal, aflatoxin inhibitory and antioxidant activity of methanol–aqueous extract (2:1) of 62 medicinal plants was explored. Based on the antifungal results, the extracts of 25 plants showed more than 50% antifungal activity and were further investigated for their aflatoxin inhibition and antioxidant properties. Methanol–aqueous extracts of Phyllanthus emblica and Terminalia chebula fruits caused 100% inhibition of aflatoxin production by the toxigenic strain of Aspergillus flavus in semisynthetic medium at 1 mg/mL. In addition, P. emblica (IC50 = 4.1 µg/mL) and T. chebula (IC50 = 6.9 µg/mL) fruits extracts exhibited strong antioxidant activity during the 2,2‐diphenyl‐1‐picrylhydrazyl radical‐scavenging assay in comparison with butylated hydroxytoluene (IC50 = 8.1 µg/mL) and butylated hydroxyanisole (IC50 = 6 µg/mL).PRACTICAL APPLICATIONSBased on the results of the present study, methanol–aqueous extracts of Phyllanthus emblica and Terminalia chebula, being endowed with strong antifungal, aflatoxin inhibitory and antioxidant activity, may be recommended as plant‐based preservatives for the enhancement of shelf life of food items and their protection from the undesirable harmful effects of molds, aflatoxin and free radical‐mediated damages.

Antifungal, aflatoxin inhibition and antioxidant activity of Callistemon lanceolatus (Sm.) Sweet essential oil and its major component 1,8-cineole against fungal isolates from chickpea seeds

The present investigation reports the extent of molds and aflatoxin contamination to Avarodhi, Kabuli, Pusa 256, Radha and Samrat varieties of chickpea seeds. The study also examines the chemical composition of Callistemon lanceolatus (Sm.) Sweet essential oil and its antifungal, antiaflatoxin and antioxidant activity. During standardization of chemical profile, a total of 8 compounds constituting 0.862 mg/mL of oil composition were analyzed by GC–MS analysis where 1,8-cineole was recorded as a major component (0.56 mg/mL). The antifungal activity of EO and 1,8-cineole was evaluated by contact assay on Czapek’s dox agar. The EO (0.227–0.908 mg/mL) and 1,8-cineole (0.918 mg/mL) showed remarkable antifungal effect against all the fungal isolates of chickpea. Their minimal inhibitory (MIC) and fungicidal (MFC) concentrations for Aspergillus flavus were lower than those of the prevalent systemic fungicide Nystatin. Aflatoxin B1 (AFB1) production by NKD-208 isolates of A. flavus was strongly inhibited even at the lower fungistatic concentration of EO and 1,8-cineole.There was no adverse effect of EO treatment on chickpea seed germination suggesting its non-phytotoxic nature. Based on the findings of present investigation, C. lanceolatus essential oil may be recommended as botanical preservative for the enhancement of shelf life of food items in- view of the adverse effect of synthetic preservatives and its strong antifungal, aflatoxin inhibition and antioxidant activity.

Intraspecific aflatoxin inhibition in Aspergillus flavus is thigmoregulated, independent of vegetative compatibility group and is strain dependent.

Biological control of preharvest aflatoxin contamination by atoxigenic stains of Aspergillus flavus has been demonstrated in several crops. The assumption is that some form of competition suppresses the fungus's ability to infect or produce aflatoxin when challenged. Intraspecific aflatoxin inhibition was demonstrated by others. This work investigates the mechanistic basis of that phenomenon. A toxigenic and atoxigenic isolate of A. flavus which exhibited intraspecific aflatoxin inhibition when grown together in suspended disc culture were not inhibited when grown in a filter insert-plate well system separated by a .4 or 3 µm membrane. Toxigenic and atoxigenic conidial mixtures (50∶50) placed on both sides of these filters restored inhibition. There was ∼50% inhibition when a 12 µm pore size filter was used. Conidial and mycelial diameters were in the 3.5–7.0 µm range and could pass through the 12 µm filter. Larger pore sizes in the initially separated system restored aflatoxin inhibition. This suggests isolates must come into physical contact with one another. This negates a role for nutrient competition or for soluble diffusible signals or antibiotics in aflatoxin inhibition. The toxigenic isolate was maximally sensitive to inhibition during the first 24 hrs of growth while the atoxigenic isolate was always inhibition competent. The atoxigenic isolate when grown with a green fluorescent protein (GFP) toxigenic isolate failed to inhibit aflatoxin indicating that there is specificity in the touch inhibiton. Several atoxigenic isolates were found which inhibited the GFP isolate. These results suggest that an unknown signaling pathway is initiated in the toxigenic isolate by physical interaction with an appropriate atoxigenic isolate in the first 24 hrs which prevents or down-regulates normal expression of aflatoxin after 3–5 days growth. We suspect thigmo-downregulation of aflatoxin synthesis is the mechanistic basis of intraspecific aflatoxin inhibition and the major contributor to biological control of aflatoxin contamination.

Algae as biological detoxificant of aflatoxin produced by Aspergillus flavus isolated from sunflower seed

Aspergillus flavus is the widely reported food-borne fungus and the most important mycotoxin source in the world's food supplies. A new approach using algae- Spirulina platensis (blue-green alga), Ulva faciata (green alga) and Sargassum wightii (brown alga) was experimented to control the growth of A. flavus and its aflatoxin B1 production. Among the three algae, S. wightii was found as most suitable biocontrolling agent. The optimum biomass concentration of the alga to detoxify the aflatoxin B1 and inhibition of the fungal mycelial growth was worked out in a controlled condition. An algal biomass of 1.8% (in final concentration) of S. wightii effectively eliminated (100%) aflatoxin B1 and total inhibition of the fungal growth of A. flavus was also achieved concomitantly. The experimental results were encouraging for possible application of algal biomass as biocontrolling agent to recuperate aflatoxin contaminated food and feed commodities.

Trametes versicolor: A possible tool for aflatoxin control

The genotoxic, mutagenic and cancerogenic aflatoxins produced by Aspergillus parasiticus are not yet efficiently controlled besides the increasing researches on this topic. Aflatoxin production by A. parasiticus is related to oxidative stress and some antioxidants can inhibit their production. Some basidiomycetes as Trametes versicolor used as “healing mushrooms” present β-glucans and glycoproteins which are responsible for the stimulation of the host immune response. In this work T. versicolor culture filtrates, from different isolates, have been tested on A. parasiticus cultures to assay their inhibiting effect on aflatoxin production. Filtrates from T. versicolor were lyophilised and exopolysaccharides and glycoproteins were extracted by subsequent steps and added (2% w / v) to liquid cultures of a toxigenic A. parasiticus strain. Fungal growth and aflatoxins production by A. parasiticus were analysed both in filtrates and in mycelia and no interference on the output of toxins from mycelia was evidenced. Furthermore antioxidant capacity (by crocin test) of the T. versicolor extracts was analysed. All the strains assayed are able to inhibit the toxin production from 40% to above 90% in liquid cultures as well as in maize and wheat seeds inoculated with A. parasiticus. Antioxidant activity and β-glucans amount in T. versicolor extracts showed a close relationship with aflatoxin inhibition ability and demonstrated that β-glucans could be involved in aflatoxin inhibition. Molecular data indicate the almost complete inhibition of norA mRNA expression and a delay of aflR mRNA transcription. Filtrates and fractions from T. versicolor could be promising agents in the challenge against aflatoxins.

Antioxidant enzymes stimulation in Aspergillus parasiticus by Lentinula edodes inhibits aflatoxin production

Biosynthesis of aflatoxins, toxic metabolites produced by Aspergillus parasiticus, is correlated to the fungal oxidative stress and cell ageing. In this paper, the mechanism underlying the aflatoxin-inhibiting effect of the Lentinula edodes culture filtrates was studied by analysing their anti-oxidant activity and beta-glucan content. Mushroom beta-glucans are pharmacologically active compounds stimulating anti-oxidant responses in animal cells. L. edodes lyophilised filtrates stimulate A. parasiticus anti-oxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase) and aflatoxin inhibition was better correlated with beta-glucan content than with anti-oxidant activity of the filtrates. RT-PCR analyses on treated mycelia showed a delay in the activation of aflR, and norA, genes of aflatoxin cluster and a synchronous activation of hsf2-like, a homologue of a yeast transcription factor involved in oxidative stress responses. The first evidence of hsf2-like in A. parasiticus and its activation during aflatoxin biosynthesis is reported. L. edodes filtrates could play a role as external stimulus affecting the anti-oxidant status in the fungal cell that, in turn, leads to aflatoxin inhibition. In the fungal cell, beta-glucans present in the filtrates could stimulate the activation of transcription factors related to anti-oxidant response and anti-oxidant enzyme activity with a contemporaneous delay of aflatoxin genes transcription, which led to a marked reduction of aflatoxin production. This research suggests new perspectives to set suitable strategies against aflatoxins and L. edodes could be considered a promising tool.

Inhibition of aflatoxin biosynthesis in Aspergillus flavus by diferuloylputrescine and p-coumaroylferuloylputrescine.

A mixture of diferuloylputrescine/p-coumaroylferuloylputrescine (85:15, w/w) demonstrated inhibitory activity against aflatoxin B1 biosynthesis in Aspergillus flavus isolate AF13. Inhibition was concentration dependent, with a 50% effective dose of 30 microg of diferuloylputrescine/p-coumaroylferuloylputrescine per milliliter of medium. Aflatoxin inhibition levels of up to 93% were achieved using this conjugated polyamine material. This diconjugated polyamine mixture did not display inhibitory effects on A. flavus growth (mycelial weight) at any of the concentrations tested. A survey of hand-dissected corn (Zea mays) kernel tissues, including endosperm, germ, pericarp, and wax, revealed that the highest concentrations of these conjugated polyamines were localized in the pericarp of the seed. Analysis of a number of corn accessions did not reveal a correlation between diferuloylputrescine/ p-coumaroylferuloylputrescine concentration and resistance/susceptibility to A. flavus infection. The localization of these diconjugated polyamine components in the pericarp, which functions as a physical barrier and surrounds the internal food storage reserves, suggests a defensive role for these materials.

Inhibition of growth and aflatoxin production in Aspergillus flavus by Garcinia indica extract and its antioxidant activity

Garcinia is a large genus of polygamous trees or shrubs, distributed in the tropical Asia, Africa and Polynesia and is a rich source of bioactive molecules including xanthones, flavonoids, benzophenones, lactones and phenolic acids. In the present study, an attempt was made to evaluate the antimicrobial and antioxidant properties of Garcinia sp. Concentrated and vacuum dried chloroform extract of rinds of Garcinia indica was tested for the inhibition of Aspergillus flavus and aflatoxin B 1 production using peanut powder as a model food system. Aflatoxin B 1 was estimated by Spectrofluorophotometric and thin layer chromatographic methods. At lower concentrations of G. indica extract (500–1000 ppm), the relative aflatoxin inhibition was much higher than the growth inhibition. At 3000 ppm the aflatoxin production was completely inhibited, which was taken as the minimum inhibitory concentration. The antioxidant activity (AA) of G. indica extract was evaluated using β-carotene-linoleate and 1,1-diphenyl-2-picryl hydrazyl (DPPH) model systems. G. indica extract showed 53% and 78% AA at 50 ppm concentration in β-carotene-linoleate and DPPH model systems, respectively. The major compound present in the extract was found to be garcinol as confirmed by fractionation using silica gel chromatography and spectroscopic studies. The G. indica extract has both antifungal and antioxidant properties and has a potential for use as a biopreservative in food applications and neutraceuticals.

Antimycotic and Antiaflatoxigenic Effect of Lactic Acid Bacteria: A Review

Lactic acid bacteria are extensively used in the fermentation of a wide variety of food products and are known for their preservative and therapeutic effects. Many lactic acid bacteria species have been reported to inactivate bacterial pathogens, and numerous antibacterial substances have been isolated. However, the antimycotic and antimycotoxigenic potential of lactic acid bacteria has still not been fully investigated. Fermented foods such as cheese can be contaminated by molds and mycotoxins. Mold causes spoilage and renders the product unusable for consumption, and the presence of mycotoxins presents a potential health hazard. A limited number of reports have shown that lactic acid bacteria affect mold growth and aflatoxin production. Although numerous lactic acid bacteria such as Lactobacillus spp. were found to inhibit aflatoxin biosynthesis, other lactic bacteria such as Lactococcus lactis were found to stimulate aflatoxin production. The morphology of lactic acid bacteria cells has also been found to be affected by the presence of fungal mycelia and aflatoxin. Lactococcus lactis cells became larger and formed long chains in the presence of Aspergillus flavus and aflatoxins. Numerous investigations reported that low pH, depletion of nutrients, and microbial competition do not explain the reason for aflatoxin inhibition. Some investigators suggested that the inhibition of aflatoxin is due to lactic acid and/or lactic acid bacteria metabolites. These metabolites have been reported to be heat-stable low-molecular-weight compounds.

Bioactivation of Aflatoxin G1 and Inhibition of Aflatoxin B1 Toxicity in Yeast Cells Expressing Mouse CYP2A Enzymes

Bioactivation of Aflatoxin G1 and Inhibition of Aflatoxin B1 Toxicity in Yeast Cells Expressing Mouse CYP2A Enzymes

Inhibition of Aflatoxin Production by Surfactants

The effect of 12 surfactants on aflatoxin production, growth, and conidial germination by the fungus Aspergillus flavus is reported. Five nonionic surfactants, Triton X-100, Tergitol NP-7, Tergitol NP-10, polyoxyethylene (POE) 10 lauryl ether, and Latron AG-98, reduced aflatoxin production by 96 to 99% at 1% (wt/vol). Colony growth was restricted by the five nonionic surfactants at this concentration. Aflatoxin production was inhibited 31 to 53% by lower concentrations of Triton X-100 (0.001 to 0.0001%) at which colony growth was not affected. Triton X-301, a POE-derived anionic surfactant, had an effect on colony growth and aflatoxin production similar to that of the five POE-derived nonionic surfactants. Sodium dodecyl sulfate (SDS), an anionic surfactant, and dodecyltrimethylammonium bromide, a cationic surfactant, suppressed conidial germination at 1% (wt/vol). SDS had no effect on aflatoxin production or colony growth at 0.001%. The degree of aflatoxin inhibition by a surfactant appears to be a function of the length of the hydrophobic and hydrophilic chains of POE-derived surfactants.

Inhibition of aflatoxin production inAspergillus flavus by cotton ovule extracts

The effect of cotton ovule extracts onAspergillus flavus growth and aflatoxin biosynthesis was investigated. Extracts derived from either noninoculated cotton ovule tissue or cotton ovule tissue challenged withA. flavus inhibited aflatoxin (B1) synthesis by fungal cultures ofA. flavus. When added to fungal cultures in concentrations of 50 µg per mL of medium, extracts derived from fungus‐challenged ovule tissue inhibited aflatoxin synthesis by as much as 93%. The ED50 for this type of extract was 18 µg per mL of medium (P &lt; 0.01; r2=0.46). Similar experiments with a noninoculated ovule extract (50 µg/mL medium) produced aflatoxin inhibition levels of up to 77%. The ED50 for noninoculated extracts was 35 µg per mL of medium (P &lt; 0.01; r2=0.66). These extracts did not inhibit the growth ofA. flavus in culture. Cultures ofA. flavus that contained pure gossypol (10–50 µg/mL medium) also showed significantly reduced levels of aflatoxin production. Gossypol may account for the aflatoxin‐inhibitory activity observed in the extracts derived from noninoculated cotton ovule tissue.

Immunological and HPLC detection of aflatoxin adducts in human tissues after an acute poisoning incident in S.E. Asia

Acid hydrolysed, purified DNA, extracted from formalin fixed human tissues from persons acutely exposed to aflatoxins during a poisoning incident, was found to inhibit antibody binding in a competitive aflatoxin inhibition ELISA both before and after immunoaffinity column purification. HPLC analysis of acid hydrolysates of the DNA revealed a peak with a retention time 3 min earlier than 8,9-dihydro-2-(N7-guanyl)-9-hydroxy AFB1 synthesized either by peracid activation or direct reaction of the 8,9-oxide with DNA. The major peak seen when DNA was extracted from formalin fixed tissues from rats treated with aflatoxin B1 was identical to that seen in the formalin fixed human tissues. Adduct levels ranged from 0 to 170 x 10(6) nucleotides depending on tissue type and individual examined.

Aflatoxin inhibition of rat liver mitochondrial cytochrome oxidase activity.

Aflatoxins B1, B2, G1, G2, and M1 have been evaluated for activity toward cytochrome oxidase in isolated rat liver mitochondria employing ferrocytochrome c and p-phenylene diamine as reductants. The aflatoxins inhibited the cytochrome oxidase activity to a greater extent when monitored by O2 uptake measurements than by substrate oxidation. AFG2 and AFM1 were the most potent (50-70%). Using oligomycin and 2,4-DNP as respiratory inhibitor and uncoupler, respectively, the aflatoxins appear to inhibit e- rather than energy transfer reactions. These toxins did not uncouple cytochrome oxidase activity.

Aflatoxin Inhibition and Fungistasis by Peanut Tannins1

Abstract Three fractions of tannins were isolated from Florunner peanut testa. Both the growth of Aspergillus parasiticus (NRRL 2999) on PDA agar and production of aflatoxins in liquid culture were inhibited by the tannins. The ability to inhibit growth was inversely related to the ability to inhibit aflatoxin production for each fraction. Two types of tannin assays were inadequate as predictors of the biological activity of the tannin fractions.