engleski

Isolation of Thymus Vulgaris L. Leaf polyphenols by microwave-assisted extraction

Thyme (Thymus vulgaris L.) is a Mediterranean herb belonging to the Lamiaceae family well known in the folk medicine for its various health beneficial properties. These properties can be attributed to the high content of biologically active molecules, such as polyphenols. In recent years, the growing demand on functional products enriched with naturally derived polyphenols has brought the need for more sustainable isolation technologies that would allow for their fast and effective isolation. Microwave-assisted extraction has emerged as a green extraction technology due to its main advantage of reducing the extraction time and solvent consumption while achieving higher extraction efficiency and lower degradation of targeted compounds compared to conventional extraction techniques. In the present study, the influence of different microwave-assisted extraction parameters on the isolation efficiency of Thymus vulgaris L. leaf polyphenols was examined in two phases. In the first phase, different percentages of aqueous ethanol (0, 30, 50, 70 and 96%) and sample:solvent ratios (1:10, 1:20 and 1:30) were varied while other extraction parameters (temperature 60°C ; microwave power 800W ; irradiation time 10 min) were kept constant. The total phenolic content (TPC) of the extracts was determined by Folin-Ciocalteu spectrophotometric method. Both ethanol percentage and sample:solvent ratio have shown significant influence on the TPC of the Thymus vulgaris L. leaf extracts, and the highest TPC (10.59 mg GAE/g leaf) was achieved when 30% ethanol and a ratio of 1:20 were applied. In the second research phase, the ethanol percentage and sample:solvent ratio were kept constant (30% ethanol and 1:20), while the temperature (40, 60 and 80°C) and irradiation time (5, 10 and 15 min) were varied. The results of Folin-Ciocalteu analysis showed that temperature had a significant influence on the TPC of the Thymus vulgaris L. leaf extracts, while the influence of irradiation time was not significant. The highest TPC (11.99 mg GAE/g leaf) was achieved at 60°C after 5 min of irradiation. The results showed how different parameters of microwave-assisted extraction influence the TPC of Thymus vulgaris L. extracts, proving the importance of establishing optimal isolation methodologies that would result in the highest recovery effectiveness and utilization of the plants’ beneficial properties.

Thymus vulgaris L., polyphenols, green extraction, microwave-assisted extraction

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