Abstract
The rate-limiting enzyme of the 2-methyl-d-erythritol-4-phosphate (MEP) terpenoid biosynthetic pathway, 1-deoxy-d-xylulose-5-phosphate reductoisomerase (DXR), provides the perfect target for screening new antibacterial substances. In this study, we tested the DXR inhibitory effect of 35 plant essential oils (EOs), which have long been recognized for their antimicrobial properties. The results show that the EOs of Zanbthoxylum bungeanum (ZB), Schizonepetae tenuifoliae (ST), Thymus quinquecostatus (TQ), Origanum vulgare (OV), and Eugenia caryophyllata (EC) displayed weak to medium inhibitory activity against DXR, with IC50 values of 78 μg/mL, 65 μg/mL, 59 μg/mL, 48 μg/mL, and 37 μg/mL, respectively. GC-MS analyses of the above oils and further DXR inhibitory activity tests of their major components revealed that eugenol (EC) and carvacrol (TQ and OV) possess medium inhibition against the protein (68.3% and 55.6%, respectively, at a concentration of 20 μg/mL), whereas thymol (ST, TQ, and OV), carveol (ZB), and linalool (ZB, ST, and OV) only exhibited weak inhibition against DXR, at 20 μg/mL (23%−26%). The results add more details to the antimicrobial mechanisms of plant EOs, which could be very helpful in the direction of the reasonable use of EOs in the food industry and in the control of phytopathogenic microbials.
Highlights
It has long been recognized that plant essential oils (EOs) exhibit many types of bioactivities, such as antimicrobial, antiviral, antimycotic, anti-toxigenic, antiparasitic, and insecticidal properties [1], and their microbicidal effects have been well documented [2]
The d-xylulose-5-phosphate reductoisomerase (DXR) inhibitory activities of 35 plant EOs were evaluated and the results showed that the EOs of Zanbthoxylum bungeanum (ZB), Schizonepetae tenuifoliae (ST), Thymus quinquecostatus (TQ), Origanum vulgare (OV), and Eugenia caryophyllata (EC) displayed weak to medium inhibition against the target
Further analyses of these five EOs showed that the major active compounds were eugenol, carvacrol, thymol, carveol, and linalool
Summary
It has long been recognized that plant essential oils (EOs) exhibit many types of bioactivities, such as antimicrobial, antiviral, antimycotic, anti-toxigenic, antiparasitic, and insecticidal properties [1], and their microbicidal effects have been well documented [2]. The speed-limiting enzyme 1-deoxy-d-xylulose-5-phosphate reductoisomerase (DXR) in the MEP pathway has been acknowledged as a superior target for screening antibiotics.
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