Evaluation of Chemical Composition of Vaccaria oxyodontha Boiss Plant Essential Oils and Antioxidant and Antibacterial Effects on Gram-Negative and Gram-Positive Bacteria

Caryophyllaceae is a large family of about 2200 herbaceous or subshrub species. Vaccaria oxyodontha Boiss is of the family Caryophyllaceae. This plant grows as a weed in agricultural land of sugarcane, wheat, barley, forage, and summer crops such as sugar beet, potato, cotton, and onion. All parts of the V. oxyodontha Boiss plant, especially its root, contain a type of saponin, which shows its medicinal value. According to traditional Iranian medicine, this plant is a blood purifier and has anti-infective, utilized for cough, anti-rheumatism, and anti-inflammatory properties. This study first aimed to investigate the chemical composition of V. oxyodontha Boiss essential oil (EO) and the antioxidant and antibacterial properties of the hydroalcoholic extract of this plant on gram-positive and gram-negative bacteria.

In this study, EOs were extracted from the aerial parts of V. oxyodontha Boiss using the combination of hydrodistillation and microwave-assisted hydrodistillation methods. Then, the antioxidant properties and antibacterial activity of the extract were evaluated, and the chemical compositions of the EOs of V. oxyodontha Boiss were determined using gas chromatography-mass spectroscopy (GC-MS). The extract’s antioxidant activity was studied by the 2,2-diphenyl-1-picrylhydrazyl-hydrate (DPPH) method. In addition, the plant antimicrobial effects were investigated by the agar disk diffusion method, and minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined as well. Finally, the antibacterial activity of the mentioned plant was compared with the antibiotic discs of gentamicin (10 mg) and vancomycin (30 mg).

The major compounds in the EOs were 2-Pentadecanone,6,10,14-trimethyl (10.52%) and 1,2-Benzenedicarboxylic acid (19.27%). Half maximal inhibitory concentration (IC50) of V. oxyodontha Boiss was 0.49 μg/mL, which was higher than that of vitamin C (IC50 value of 0.56 μg/mL). Further, MIC and MBC for the V. oxyodontha Boiss extract against Staphylococcus aureus and Escherichia coli were 62.5 and 125 mg/mL, as well as 31.25 and 62.5 mg/mL, respectively.

The results of GC-MS demonstrated that the EO of the V. oxyodontha Boiss plant contains antioxidant and antibacterial compounds. Its antioxidant properties are higher than vitamin C. The highest diameter of the inhibition zone caused by the methanol extract of the V. oxyodontha Boiss plant was against S. aureus and E. coli (23.7 ± 0.29 mm and 15.65 ± 0.33 mm, respectively). Compared with the antibiotics vancomycin, the Vaccaria oxyodontha Boiss represented a stronger inhibitory effect in the inhibition of S. aureus (P < 0.05).