Chemical Composition, Antibacterial and Radical Scavenging Activity of Essential Oils from Satureja macrantha C.A.Mey. at Different Growth Stages

Essential oils (EOs) from medicinal and aromatic plants are interesting products to be used as natural food preservatives. The EOs from the genus Satureja are reported to inhibit foodborne pathogens being worthy of use as food preservatives. Satureja macrantha is found in Western and Northwest Iran and commonly used as a food flavoring agent and for the treatment of urinary diseases. The objective of the present study was to identify the chemical composition of S. macrantha EOs at different growth stages (vegetative, flowering and fruiting stages) and to evaluate their biological activities. Chemical compositions were analyzed using GC-FID and GC-MS. The antibacterial activity was evaluated using the broth microdilution method against the foodborne pathogenic bacteria Staphylococcus aureus (ATCC23922), Enterococcus faecalis (ATCC29212) (Gram-positive), Enterobacter aerogenes (ATCC13046) and Escherichia coli. The antioxidant activity was estimated using the DPPH, ABTS and reducing power assays. The yields of S. macrantha EOs were in the range of 1.4-1.8%, thus scalable for the manufacture of food preservatives on an industrial level. The main compounds of EOs were carvacrol (42.7-48.2%), thymol (0.2-16.5%), p-cymene (10.1-14.7%) and γ-terpinene (7.9-9.1%) in all phenological stages examined. The strongest antibacterial activity (MICs = 5-20 µg/mL) of the EOs was recorded in samples obtained during the flowering stage where carvacrol (42.7%) and thymol (16.5) were present both at high percentages. On the other hand, the antioxidant activity was found to be slightly higher in the other stages. As the EO obtained at flowering showed the best inhibitory properties against foodborne pathogenic bacteria, it is suggested that plants at this stage can be selected as main sources of food preservative agents.