Antioxidant Activity and Bioactive Compounds of Lamium album Flower Extracts Obtained by Supercritical Fluid Extraction

In this research, supercritical CO2 extraction is applied to extract bioactive compounds from Lamium album (white dead nettle, Lamiaceae). Extraction was performed at various temperatures (40, 50, and 60 °C) using methanol as co-solvent at a constant flow rate of CO2, methanol, and pressure. The collected extracts were characterized in terms of antioxidant capacity by using DPPH, ABTS and FRAP in vitro antioxidant activity assays, whereas the Folin–Ciocalteu procedure was employed to estimate the total phenols content (TPC). On the other hand, phenolic compounds in the extracts were quantitated by liquid chromatography coupled with a photodiode array detector (UPLC-PDA) and confirmed with a mass detector (TQD). The extracts have shown high TPC ranged between 234.17 to 650.17 mg GAE/g extract. DPPH scavenging of the extracts was estimated and obtained EC50 values ranged from 0.12 to 0.37 mg/mL of solution. The ABTS radical scavenging activity ranged from 43.20 to 44.53 µg TE/g. The FRAP value was found within the range of 19.48 to 44.74 µmol TE/g of extract. Differences between extraction conditions were observed. In this research, 50 °C/250 bar was efficient for the TPC, DPPH, ABTS, and FRAP assays; moreover, statistically, TPCs and FRAP assay showed significant differences between the conditions at α = 0.05. The identification of phenolic compounds in the obtained extract of Lamium album flowers, using UPLC/PDA, revealed that chrysin, pinostrobin, myricetin, and trans-3-hydroxycinnamic acid were the significant molecules present, which may be responsible for the high content of polyphenols and antioxidant activity. The results obtained indicated that SC-CO2 could be considered an alternative method for extracting bioactive compounds of Lamium album. High antioxidant activity and the presence of various bioactive compounds indicate the potential of this plant from the Lamiaceae family and the possibility of its application in various industries, including agriculture, food technology, or pharmacy.