Abstract

Seeds of native and naturalized plants currently found in the Mississippi River Basin of the United States were evaluated as potential new sources of antimicrobial and antioxidant activity. Methanol extracts of seeds were tested for antioxidant levels using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) antioxidant assay and for antimicrobial activity using a disk diffusion assay againstStaphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli andCandida albicans. A wide range of antioxidant and antimicrobial activities were observed in the 158 species tested.  Antioxidant levels ranged from 2,400 µM Trolox/100 gm (TE) to 261,384 TE.  Lythrum salicaria L. (261,384 TE), Lythrum alatum Pursh (206,154 TE), Spiraea tomentosa L. (141,430 TE), Rumex verticillatus L. (123,423 TE) and Oenothera biennis L. (98,563 TE) had the highest levels of antioxidant activity. Extracts of seeds from 35 species had antimicrobial activity.  L. salicaria L., Rumex crispus L., Rumex verticillatus L. and Spirea tomentosa L. had high levels of antioxidant activity and correspondingly high levels of antimicrobial activity against all four microorganisms.  The correlation between seeds with high antioxidant levels and those with antimicrobial activity was quite low.  In this study, we identified native and naturalized plants from the Mississippi River Basin as potential sources of antioxidant and antimicrobial compounds.

Key words:  Antibacterial, antimicrobial, antioxidant, medicinal plants, native plants.