Investigating the phytochemical changes of Thymus vulgaris L. essential oil under the influence of ultrasound waves
Asma Amoozegaran
1
(Department of Applied Chemistry, Faculty of Science, Islamic Azad University, South Tehran Branch, Tehran, Iran)
حسین دهقان
2
(هیئت علمی)
Seyed Saeid Homami
3
(Department of Applied Chemistry, Faculty of Science, Islamic Azad University, South Tehran Branch, Tehran, Iran)
Seyed Abdollah Hashemi
4
(Department of Plant Protection, Faculty of Agriculture, Shahed University, Tehran, Iran)
Keywords: p-Cymene, Essential oil, &gamma, -Terpinene, Thymol, Thyme, Ultrasound,
Abstract :
Many researches have been conducted to introduce ultrasound as an auxiliary factor to increase the efficiency of extraction of essential oils from medicinal plants. But few researchers have studied the role of ultrasound waves in stimulating chemical reactions on the essential compounds of plants. This research was conducted with the aim of investigating the effect of ultrasound on the components of essential oil of Thymus vulgaris L., after extracting the essential oil and without the presence of plant tissue. For this purpose, the aerial parts of the plant were harvested in June 2021 from the south of Tehran at the flowering stage. The essential oil of the plant was extracted using a distillation apparatus (Clevenger) and its compounds were determined by GC and GC/MS. Subsequently, ultrasonic waves were applied to the extracted essential oil by a titanium probe (400 w) and with three variable factors: temperature, time and ratio of essential oil/ water at three levels. Finally, 27 treated essential oils were prepared and their chemical compounds were quantified by GC. The primary essential oil contained 44.37% thymol, 29.80% p-cymene and 21.24% γ-terpinene. The results showed that the application of ultrasound to the essential oil increased the amount of thymol and decreased the amount of γ-terpinene and p-cymene. By optimizing the conditions (1:0 ratio of thyme essential oil and water, 20˚C and 10 min), we succeeded in reducing the active ingredient thymol from 44.37% to 70.18%. Ultrasonic waves in the presence of water and oxygen cause the production of hydroproxyl radical (HOO˙) and then carry out oxidation reactions to produce thymol from γ-terpinene and p-cymene. The results show that, in addition to helping to increase the efficiency of extraction, ultrasound can cause a change in the chemistry and ratio of phytochemical compounds in the essential oil by stimulating radical reactions.
