Antioxidative and antibacterial properties of organically grown thyme (Thymus sp.) and basil (Ocimum basilicum L.)

The biomass per plant and total phenolics (TPH) of ethanol extracts of 3 species of thyme, Thymus vulgaris, T serpyllum, and T citriodorus, and 3 varieties of basil (Ocimum basilicum), Genovese, Thai, and Cinnamon, were investigated. All were grown organically. The 2 herbs that showed the greatest biomass were T citriodorus (26.5 g/plant) and 0. basilicum var. Cinnamon (105 g/plant). For these, total flavonoids (TFL), total flavones and flavonols (TFF), and total flavanones and dihydroflavonols (TFDH) were also determined for their ethanol extracts. Furthermore, the antioxidant potential (AOP) and antibacterial activity were determined against foodborne bacteria: Staphylococcus aureus, Listeria monocytogenes, Campylobacter jejuni, and verotoxin-producing Escherichia coli (VTEC). The highest TPH (36 mg chlorogenic acid equivalents per gram of fresh weight) was seen for T citriodorus collected in 2010. The thyme ethanol extracts contained more TPH and TFL, and their subgroups of TFF and TFDH, than the ethanol extracts from basil, and had AOP comparable to the ethanol extracts from basil, although all of them were lower than the synthetic antioxidant, t-butylated hydroxytoluene. Drying of these herbs decreased TFF and TFDH, while TPH and TFL remained unchanged (for T citriodorus) or even increased (for Cinnamon basil), and AOP was higher than that of the ethanol extracts from the frozen herbs. The antimicrobial activities of these ethanol extracts depended mainly on the bacterial target. They were weak against gram-negative VTEC, while their effects against C. jejuni, S. aureus, and L monocytogenes correlated with their TPH and chemical compositions.