Chemical Composition, Antibacterial and Antioxidant Activities of Tagetes patula L. Essential Oil Raised in Erbil, Iraq

Background: Over the years, management of human pathogenic microorganisms has primarily relied on the use of synthetic antibiotics. In the recent past, Tagetes patula essential oils (EOs) and their phytochemistry and bioactivities have received great attention in research. 
Purpose and Methods: In this study, the component, antimicrobial activity, and antioxidant capacity (ferric-reducing antioxidant power assay) of EOs from five plant parts (shoot at vegetative growth stage [TPSV], shoot at flowering growth stage [TPSF], flower [TPF], fruit [TPS], and root [TPR]) of T. patula were investigated. The antibacterial activity against five gram-negative bacterial isolates (including Serratia fonticola, Klebsiella pneumoniae, Acinetobacter baumannii, Proteus mirabilis, and Escherichia coli) and five gram-positive bacterial isolates (including Staphylococcus aureus, S. epidermidis, S. saprophyticus, Streptococcus agalactiae, and Streptococcus oralis) was studied using broth microdilution method. FRAP assay was also used to evaluate their antioxidant activity. 
Results: One hundred and twenty-five compounds of the total EOs were identified, constituting a mixture of oxygenated monoterpenes (33%), monoterpene hydrocarbons (25%), oxygenated sesquiterpenes (19%), sesquiterpene hydrocarbons (12%), and furanocoumarins (8%). In this paper, for the first time, more than 60 new compounds were isolated from T. patula such as bergapten, sylvestrene, (E)-β-farnesene, (E)-epoxy-ocimene, (Z)-jasmone, γ-gurjunene, and γ-himachalene. The EOs of T. patula showed potent antibacterial activity against the studied bacteria with the highest growth inhibition observed in E. coli after 24 h of incubation (MIC value 0.08 and MBC value 0.32 μL/mL). The TPS-EO had the highest mean value for ferric-reducing ability at the three test times, whereas TPR-EO had no activity. 
Conclusion: It was concluded that the potential biocidal activity of T. patula EOs could be substantially associated with their oxygenated constituents or the synergistic activity of their major and minor chemical components.