| Abstract [eng] |
The aim of the study: to determine and compare the amounts of phenolic compounds and tannins in some Ericaceae species, growing wild in Lithuania, using different concentrations of ethanol, methanol and acetone for extraction. Objectives: 1. To determine and compare the amounts of phenolic compounds and tannins in the leaves of lingonberry (Vaccinium vitis-idaea), blueberry (Vaccinium myrtillus), and bearberry (Arctostaphylos uva-ursi) as well as in the leaves-flowers mixture of heather (Calluna vulgaris), irrespective of solvent used. 2. Determine and compare the amounts of phenolic compounds in the raw materials of plants of these species when extracted with different concentrations of solvents. 3. Determine and compare the amounts of tannins in the raw materials of plants of the above-mentioned species when extracted with different solvent concentrations. Methods: The leaves of blueberry and lingonberry were collected in south-western Lithuania, the leaves of bearberry as well as the mixture of leaves and flowers of heather were collected in south-eastern Lithuania. All raw materials were dried separately at room temperature. The moisture content in the plant material was determined by the thermal drying method. Extraction was performed using ultrasound, with solvents including 50%, 70%, and 100% concentrations of methanol, acetone, and ethanol. The total amounts of phenolic compounds and tannins in leaves of blueberry, lingonberry, and bearberry as well as in mixture of leaves and flowers of heather were determined spectrophotometrically by the Folin-Ciocalteu method, calculated based on tannic acid and expressed as a percentage of the absolute dry weight of the raw material. The tannin content was calculated from the total amount of phenolic compounds by subtracting the phenolic compounds remaining after tannin binding to polyvinylpyrrolidone. The statistical data analysis was performed using STATISTICA® 7 and Microsoft Excel 2023. Results and conclusions: Regardless of the solvents used for extraction and their concentrations, the highest amount of total phenolic compounds was found in the leaves of bearberry, which was 5 times higher than in the leaves of blueberry and in a leaves-flowers mixture of heather, as well as 3 times higher than in the leaves of lingonberry. The highest amount of total tannins was also found in bearberry leaves, where it accounted for 82% of the total phenolic compounds. Tannins in blueberry leaves were found to be 10 times, in bilberry leaves 3 times, and in a leaves-flowers mixture of heather 5.5 times less than in bearberry leaves. The highest amounts of total phenolic compounds and tannins were extracted from bearberry leaves with 50% ethanol and 70% ethanol. Undiluted acetone was the least effective in extracting both phenolic compounds and tannins from bearberry leaves. The highest amount of phenolic compounds in lingonberry leaves was determined after extraction with 50% ethanol. Meanwhile, the highest amount of tannins in lingonberry leaves was determined after extraction with 50% methanol. The lowest amounts of phenolic compounds and tannins were extracted from bilberry leaves using undiluted acetone. Undiluted methanol, 50% ethanol, and 50% acetone were the most effective in extracting phenolic compounds from heather raw material. However, tannins from a leaves-flowers mixture of heather were predominantly extracted only with 50% acetone. Undiluted acetone was the least effective for extraction of phenolic compounds and tannins from heather raw material. The most effective extraction of phenolic compounds from blueberry leaves was achieved with 50% and 70% acetone as well as with 50% and 70% ethanol. The highest amount of tannins from blueberry leaves was extracted with 50% acetone. Undiluted solvents were the least effective for the extraction of phenolic compounds and tannins from blueberry leaves. |
