The Investigation of Phenolic Compounds and Antioxidant Activity in Herbal Samples of Knotgrass (Polygonum aviculare L.)

The object of the research: The raw material of P. aviculare L. collected in different regions of Lithuania. The methods of the research: Flavonoids determined by the methods of spectrophotometry and high-performance liquid chromatography. The total amount of phenolic compounds determined by spectrophotometry. The antioxidant activity assessed by spectrophotometry using ABTS, DPPH and FRAP methods. Aim: To determine how the level of flavonoids, phenolic compounds and antioxidant activity in herbal samples of knotgrass (Polygonum aviculare L.) depends on different regions of Lithuania. Objectives: To determine the quantity of flavonoids and phenolic compounds; to evaluate antioxidant activity using ABTS, DPPH and FRAP methods; to compare the variation of the obtained result between different regions of Lithuania; to evaluate the amount of flavonoids by high-performance liquid chromatography; to compare the chemical composition and antioxidant activity of knotgrass herb teas made by different manufacturers. Results: The total content of flavonoids in the raw P. aviculare L. material from different growing site types in Lithuania ranged from 0,25 to 0,81 per cent. The total amount of phenolic compounds ranged from 23,27 to 45,61 mg/g. The antioxidant activity by the DPPH method ranged from 26,05 to 59,61 per cent., by the ABTS method – 192,86 to 381,31 μmol/g, by the FRAP method – 117,72 to 290,64 μmol/g. The total content of flavonoids in the the raw material of different tea manufacturers varies from 0,58 to 0,98 per cent. The antioxidant activity by the DPPH method ranged from 35,76 to 54,35 per cent., by the ABTS method - from 253,68 to 535,8 μmol/g , by the FRAP method - from 150,26 to 201,69μmol/g. Conclusions: The research shows that the highest amount of flavonoids, phenolic compounds and antioxidant activity was observed in P. aviculare L. herbal samples from Leliai village in Klaipeda. The highest total amount of flavonoids in the raw material of different tea manufacturers was in „A2” (1,5 g N 24) tea, phenolic compounds – „A3” (100 g) tea, the strongest antioxidant activity - „A1“ (2 g N 25) tea