45G-2 |
Antioxidant and antimicrobial properties of Hibiscus sabdariffa L. as affected by the presence of naturally occurring cofactors |
D. DEL POZO-INSFRAN1, C. H. Brenes2, and S. T. Talcott1. (1) Dept. of Food Science & Human Nutrition, Univ. of Florida, 359 FSHN Bldg., Newell Dr., PO Box 110370, Gainesville, FL 32611-0370, (2) Dept. of Food Technology, ITESM-Campus Monterrey, E. Garza Sada 2501 Sur, Monterrey, 64849, Mexico Polyphenolics present in spices are a natural source of bioactive constituents. They possess antimicrobial properties and can act as anthocyanin cofactors, serving to improve color and pigment stability in anthocyanin-containing foods. This study assessed antioxidant activity (AOX) and antimicrobial properties of an anthocyanin extract from hibiscus in the presence of flavonoid-rich extracts from rosemary (RE), sage (SA) and thyme (TY). Polyphenolics were exhaustively extracted and then purified using reverse phase C18 columns. Anthocyanins and polyphenolics were characterized and quantified spectrophotometrically using cyanidin 3-sophoroside (Cya) and gallic acid (GAE) equivalents, respectively. AOX of a hibiscus model-drink (100 g/Lsucrose, 10 mgCya/L) was determined alone and in the presence of spice cofactors at several polyphenolic concentrations (200, 400, 800mgGAE/L) using the oxygen radical absorbance capacity assay. Antimicrobial properties against Escherichia coli, Salmonella thyphimurium, and Staphylococcus aureus were performed using a hole-plate diffusion assay for initial screening. Optimized concentrations (6 and 12 mgCya/L for Hibiscus; 200, 400, 800mgGAE/L for spice) were then tested alone and in combination (copigmentation) to determine growth inhibition using an agar dilution method. AOX of hibiscus soft-drink (50mmolTE/mL) increased linearly following addition of cofactors (AOX=0.021*GAE + 51, R2=0.98) and was proportional to color augmentation (r=0.93) yet independent of extract composition. Hibiscus anthocyanins alone inhibited E. coli growth by 19%, while copigmentation with 800mgGAE/L for all sources resulted in only an additional 11% inhibition. For S. aureus, growth inhibition increased from 31 to 99% following RE and SA copigmentation, but only increased to 45% when TY was added. Hibiscus anthocyanins were highly effective against S. thyphimurium (92%), and was increased to >99% following copigmentation. Results indicate that spice polyphenolics have a high AOX and exhibited specificity against several bacterial strains. Results demonstrated favorable bioactive interactions between polyphenolics isolated from various sources and demonstrate potential roles as multifunctional food additives.
Session 45G, Fruit & Vegetable Products: Vegetables (Fresh)
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