Characterization of Volatile Constituents from Origanum onites and Their Antifungal and Antibacterial Activity

Abstract

Essential oils obtained by hydrodistillation (HD) and microwave-assisted HD (MWHD) of Origanum onites aerial parts were analyzed by GC and GCIMS. Thirty-one constituents representing 98.6% of the water-distilled oil and 52 constituents representing 99.6% of the microwave-distilled oil were identified. Carvacrol (76.8% HD and 79.2% MWHD) and thymol (4.7% HD and 4.4% MWHD) were characterized as major constituents in both essential oils. Separation of carvacrol and thymol was achieved by overpressured layer chromatography. HPTLC and TLC separations were also compared. Essential oils were evaluated for antifungal activity against the strawberry anthracnose-causing fungal plant pathogens Colletotrichum acutatum, C. fragariae, and C. gloeosporioides using a direct overlay bioautography assay. Furthermore, main oil components carvacrol and thymol were then evaluated for antifungal activity; only carvacrol demonstrated nonselective antifungal activity against the three Colletotrichum species. Thymol and carvacrol were subsequently evaluated in a 96-well microdilution broth assay against Phomopsis obscurans, Fusarium oxysporum, three Colletotrichum species, and Botrytis cinerea. No activity was observed against any of the three Colletotrichum species at or below 30 pM. However, thymol demonstrated antifungal activity and produced 31.7% growth inhibition of P. obscurans at 120 h and 0.3 pM, whereas carvacrol appeared inactive. Thymol and carvacrol at 30 pM showed 51.5 and 36.9% growth inhibition of B. cinerea at 72 h. The mechanism of antibacterial activity was studied in a bioautography-based BioArena system. Thymol and carvacrol showed similar inhibition/killing effect against Bacillus subtilis soil bacteria; the action could be enhanced by the formaldehyde generator and transporter copper (II) ions and could be decreased in the presence of L-arginine, a formaldehyde capturer. Results indicated that Origanum essential oils and its major components thymol and carvacrol appear to generate antimicrobial activity through a mechanism of action where formaldehyde and its reaction products are produced.

Antibacterial Effects of Origanum vulgare Essence Against Multidrug-Resistant Acinetobacter baumannii Isolated From Selected Hospitals of Tehran, Iran

“…Results of various studies indicated that the antioxidant effects of oregano might be related to the dominant components including carvacrol and pulegone, presentin its essential oil (8). The essential oil of various Origanum species can contain a number of additional chemical constituents (9) including linalool, gamma-terpinene, p-cymene and terpinene-4-ol (9,10). Origanum has long been valued for its culinary, fragrant and medicinal properties.…”

The Antimicrobial Effect of Spice‐Based Marinades against Campylobacter jejuni on Contaminated Fresh Broiler Wings

“…2) delayed the increase of total aerobic bacterial count as their numbers significantly increased after 120 h of experiment by 4.56 log CFU/g and 4.39 log CFU/g, respectively ( P ≤ 0.05). This effect was expected as one of the main thyme constituents, carvacrol, was earlier determined to have an antibacterial and antifungal activity (Altintas and others ). Also, the effect of carvacrol was enhanced by the addition of cinnamaldehyde, lactic acid and linalool, which is well known for the antimicrobial activity against various pathogens like tested C. jejuni , Bacillus subtilis , Escherichia coli , Pseudomonas aeruginosa , and Staphylococcus aureus (Ravishankar and others ; Mild and others ; Chan and others ).…”

Evaluation of the Antibacterial Activity of a Sizable Set of Essential Oils

“…The major constituents of oregano oil are carvacrol, thymol, and p-cymene. However the ratios of these constituents can vary widely depending upon extraction method and plant growth conditions [15,16]. GC-MS quantification of the particular oil used in this study showed 77% carvacrol, 10% p-Cymene, and 7% thymol (GC-MS integration values not shown).…”