Chemical Constituents, Antimicrobial Activity, Antioxidant and Total Phenolic Content in the Leaves of Thecocarpus Meifolious Boiss. Umbelliferae Herbs Growing Wild in Iran

Water-distilled essential oil from the leaves of Thecocarpus meifolious Boiss – a plant that is endemic to Iran, collected from province of Chaharmahal-Bakhtiyari (west of Iran), was analyzed by the GC and GC/MS techniques. The leaf oil of T. meifolious was investigated for its antimicrobial activity, antioxidant and total phenolic content. The antioxidative properties of this oil were determined by three methods: ferric-reducing antioxidant power (FRAP), radical-scavenging capacity of the oil or bleaching of 2,20-diphenylpicrylhydrazyl (DPPH), and β-carotene – linoleic acid assay. In the leaf oil of T. meifolious, 30 components representing 97.53% of the total composition have been identified. Spathulenol (20.51%), camphor (10.20%) and caryophyllene oxide (10.35%) are the major components in this oil. This oil exhibited significant activity against all Gram-positive bacteria (especially, Candida albicans) and moderate inhibitory activity against the Gram-negative bacteria (Escherichia coli was insensitive to the oil). Bactericidal kinetics of the leaf oil of T. meifolious indicates that C. albicans is the most vulnerable strain. Total phenolic contents of the leaf oil of T. meifolious was determined to be 126.80 ± 8.50 μg Gallic acid equivalent/mg sample. The ferric reducing power of this oil was determined to be 8.55 ± 0.5 gallic acid equivalent (mg/g). The leaf essential oil of T. meifolious reduced the concentration of DPPH free radical (55.6 ± 1.5%, 10 mg/mL of essential oil), with an efficacy lower than that of reference Thymus x-porlock oil (69.3% inhibition). IC50 for DPPH radical-scavenging activity was 3.75 μg/mL. In β-carotene-linoleic acid test system, oxidation of linoleic acid was effectively inhibited by T. meifolious oil (40.65 ± 2.5%, 0.625 mg/mL of essential oil). The results suggest application of T. meifolious oil as a natural antioxidant agent.