Effect of soybean volatile compounds on Aspergillus flavus growth and aflatoxin production.

Soybean homogenates produced volatile compounds upon exposure to lipase. These induced volatiles were identified by SPME. Seventeen volatile compounds identified by SPME were chosen for determination of their ability to inhibit Aspergillus flavus growth and aflatoxin B(1) (AFB1) production in a solid media assay. These volatiles included aldehydes, alcohols, ketones, and furans. Of the tested compounds, the aldehydes showed the greatest inhibition of fungal growth and AFB1 production. These compounds inhibited up to 100% of the observed growth and AFB1 production as compared to the controls. The greatest activity by the aldehydes to disrupt growth was ranked as follows: 2,4 hexadienal > benzaldehyde > 2-octenal > (E)-2-heptenal > octanal > (E)-2-hexenal > nonanal > hexanal. The greatest activity by the aldehydes to reduce AFB1 was ranked as follows: (E)-2-hexenal > 2,4 hexadienal > (E)-2-heptenal > hexanal > nonanal. (E)-2-hexenal and (E)-2-heptenal were tested further in an A. flavus-inoculated corn kernel assay. Both compounds prevented colonization by A. flavus and eliminated AFB1 production when exposed to compound volumes < 10 muL as also shown in the solid media assay. The results suggest that soybeans react to lipase by production of potent antifungal volatiles.

Effect of biotic elicitors on enrichment of antioxidant properties and induced isoflavones in soybean.

The antioxidant properties of methanolic extracts from soybean obtained with germination, wounding, and application of biotic elicitors were evaluated. Also, the relationship between observed antioxidant properties and compositional changes in isoflavone content was determined. The 2 biotic elicitors used in this study were the food-grade fungus Aspergillus sojae and A. sojae cell wall extract. Isoflavone content was determined by C(18) reverse phase high-performance chromatography coupled with a photodiode array detector. Antioxidant activities of the extracts were measured using 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging and beta-carotene cooxidation in a linoleate system. Higher antioxidant activities were observed in wounded and elicitor-treated extracts when compared with nonwounded control extracts. In addition, the phenolic content was higher in extracts from wounded and elicitor-treated soybean. Germination for 3 d slightly decreased total isoflavone content (-4.3%); however, wounding increased total isoflavone content (25.8%). The soybean extracts from seeds treated with A. sojae biotic elicitors had the highest total isoflavone contents (9.8 to 11.6 mg/g extract) and displayed the highest antioxidant activities in both the DPPH and beta-carotene assays. Also identified in the wounded and elicitor-treated extracts were the induced isoflavones glyceollins that contributed to the higher isoflavone contents observed.

Anticancer properties for 4,4'-dihydroxybenzophenone-2,4-dinitrophenylhydrazone (A-007)/3,7-diaminophenothiazin-5-ium double salts.

4,4'-Dihydroxybenzophenone-2,4-dinitrophenylhydrazone (A-007) formed stable double salts with phenothiazin-5-ium salts (2a-d), which have improved in vitro anticancer activities, as compared to A-007 alone. The stable salt between methylene blue (2a) and A-007 allowed the latter to diffuse into the dermis layers of skin. It is anticipated that these new salts will allow A-007 to penetrate into the deep lymphatic/vascular channels of the dermis, which contain metastatic cancer cells, and improve in vivo anticancer activities.

Phytochemical glyceollins, isolated from soy, mediate antihormonal effects through estrogen receptor alpha and beta.

The flavonoid family of phytochemicals, particularly those derived from soy, has received attention regarding their estrogenic activity as well as their effects on human health and disease. In addition to these flavonoids other phytochemicals, including phytostilbene, enterolactone, and lignans, possess endocrine activity. The types and amounts of these compounds in soy and other plants are controlled by both constitutive expression and stress-induced biosynthesis. The health benefits of soy-based foods may, therefore, be dependent upon the amounts of the various hormonally active phytochemicals within these foods. The aim was to identify unique soy phytochemicals that had not been previously assessed for estrogenic or antiestrogenic activity. Here we describe increased biosynthesis of the isoflavonoid phytoalexin compounds, glyceollins, in soy plants grown under stressed conditions. In contrast to the observed estrogenic effects of coumestrol, daidzein, and genistein, we observed a marked antiestrogenic effect of glyceollins on ER signaling, which correlated with a comparable suppression of 17 beta-estradiol-induced proliferation in MCF-7 cells. Further evaluation revealed greater antagonism toward ER alpha than ER beta in transiently transfected HEK 293 cells. Competition binding assays revealed a greater affinity of glyceollins for ER alpha vs. ER beta, which correlated to greater suppression of ER alpha signaling with higher concentrations of glyceollins. In conclusion, we describe the phytoalexin compounds known as glyceollins, which exhibit unique antagonistic effects on ER in both HEK 293 and MCF-7 cells. The glyceollins as well as other phytoalexin compounds may represent an important component of the health effects of soy-based foods.

adhA in Aspergillus parasiticus is involved in conversion of 5'-hydroxyaverantin to averufin.

Two routes for the conversion of 5'-hydroxyaverantin (HAVN) to averufin (AVF) in the synthesis of aflatoxin have been proposed. One involves the dehydration of HAVN to the lactone averufanin (AVNN), which is then oxidized to AVF. Another requires dehydrogenation of HAVN to 5'-ketoaverantin, the open-chain form of AVF, which then cyclizes spontaneously to AVF. We isolated a gene, adhA, from the aflatoxin gene cluster of Aspergillus parasiticus SU-1. The deduced ADHA amino acid sequence contained two conserved motifs found in short-chain alcohol dehydrogenases-a glycine-rich loop (GXXXGXG) that is necessary for interaction with NAD(+)-NADP(+), and the motif YXXXK, which is found at the active site. A. parasiticus SU-1, which produces aflatoxins, has two copies of adhA (adhA1), whereas A. parasiticus SRRC 2043, a strain that accumulates O-methylsterigmatocystin (OMST), has only one copy. Disruption of adhA in SRRC 2043 resulted in a strain that accumulates predominantly HAVN. This result suggests that ADHA is involved in the dehydrogenation of HAVN to AVF. Those adhA disruptants that still made small amounts of OMST also accumulated other metabolites, including AVNN, after prolonged culture.

Induction of the soybean phytoalexins coumestrol and glyceollin by Aspergillus.

Several isoflavonoid phytoalexins produced by soybeans are known to be estrogenic, with potential beneficial health effects in humans. Increased production of phytoalexins by the soybean plant will facilitate research efforts in this area. In this study, phytoalexin induction and accumulation in soybean cotyledon tissue was observed using four species of Aspergillus: A. sojae, A. oryzae, A. niger, and A. flavus. All four Aspergillus species tested elicited phytoalexin accumulation in living soybean cotyledons. Results from a time course study indicated that maximum concentrations of the phytoalexin glyceollin, 955 microg/g fresh weight (fw), occurred at day 3 in soybean cotyledon tissue inoculated with A. sojae. Other Aspergillus species caused an accumulation of glyceollin at significantly lower levels. A maximum concentration of coumestrol of 27.2 microg/g fw was obtained from soybean cotyledons inoculated with A. niger. Soybean phytoalexins induced by food-grade A. sojae and A. oryzae allowed the collection of higher concentrations of phytoalexins for further examination in several in vitro and in vivo biological studies conducted to determine potential estrogenic activities.