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Seventeen phenolic compounds that are allowed to be used in the European food industry as aromatizants or antioxidants or that are naturally present in plants were tested for their ability to inhibit 19 strains of Staphylococcus aureus by using a standardized paper disc assay. Most of the strains assayed were foodborne (dairy and meat products). Human isolates and/or strains recommended for testing antimicrobial agents were also included in the study, and some of the test strains were enterotoxin producers. When the content was 200 microg/disc, various phenolic compounds had shown antimicrobial activity against all (hydroquinone, thymol, carvacrol, butylated hydroxyanisole, octyl gallate, and tannic acid) or most (gallic acid, propyl gallate, and ellagic acid) of the S. aureus strains tested. Significant differences in the inhibition zones (p < 0.05) among strains of the same, or similar, origin and among the different origins were observed for most of the phenolic compounds that showed antimicrobial activity for all or most of the strains tested.

D-erythroascorbate (D-EAA), a five-carbon analogue of L-ascorbate (L-AA), and D-erythroascorbate monoglucoside (D-EAAG) are accumulated in Phycomyces blakesleeanus grown on glucose (99.5 and 1084 μg/g mycelial dry weight, respectively) and also excreted into the culture medium. Both compounds showed UV spectral properties and ionization constants similar to those of L-AA. D-EAAG was much more stable to aerobic oxidation than D-EAA and L-AA at acidic pH. D-EAAG is synthesized from D-erythroascorbate by a mycelial glucosyltransferase activity that uses UDP-glucose as glucose substrate donor with K(m) = 2.5 mM and 41.3 μM for D-EAA. This glucosyltransferase activity was maximal in the stationary growth phase in parallel with maximal production of D-EAAG. The presence of D-arabinose or D-arabinono-1,4-lactone in the culture medium produces the maximal accumulation of D-EAA and D-EAAG (about 30- and 4-fold with respect to that obtained in glucose culture). Both compounds showed greater antioxidant activity than L-AA and other standard antioxidants, with a capacity similar to that of L-AA to inhibit the growth of Escherichia coli.