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Application of pressurized liquid extraction for the isolation of phenols from sea buckthorn leaves

Sea buckthorn (Hippophae rhamnoides L.) is a valuable and unique plant, rich in various bioactive compounds contained in the different parts of the plant, especially in the fruits and leaves. Due to its great potential, the scientific community is showing a great interest in this plant, and numerous studies have reported beneficial health effects, such as antioxidant, anticancer, antiinflammatory, etc. Compounds of interest can be isolated by various extraction methods, either conventional or advanced, however it is of great importance to optimize the process conditions to obtain maximum yield of target compounds. Therefore, this study examined the influence of temperature (80, 100, and 120 °C), static extraction time (5, 10, and 15 min) and number of extraction cycles (1, 2, and 3) during the pressurized liquid extraction (PLE) of phenols from freeze-dried sea buckthorn leaves using an aqueous ethanol solution (70%) as extraction solvent. The extracts obtained were analyzed spectrophotometrically for the content of total phenols (TPC) using the Folin-Ciacolteau method, while the FRAP method was used to determine antioxidant capacity (AC). All results were statistically analyzed by multifactorial analysis of variance and Tukey's HSD test. The TPC was determined in a range of 69.05-112.96 mg GAE g-1 of dry matter (DM) and the values of AC ranged from 766.72-1182.02 µmol TE g-1 DM. Statistical analysis showed a significant influence of all tested PLE parameters on the TPC as well as on the AC of the extracts. The highest TPC were measured in extracts obtained at the highest temperature and cycle number, while there was no significant difference in the TPC extracted during a static extraction time of 10 or 15 min. On the other hand, the AC values of the extracts were highest at the highest level of all three PLE parameters tested. In conclusion, PLE using 70% ethanol showed to be an effective method for the successful extraction of phenols from sea buckthorn leaves, where PLE conditions of 120 °C/10 min/3 cycles provided the highest TPC, while the highest value of AC was obtained at 120 °C/15 min/3 cycles.

sea buckthorn, pressurized liquid extraction, phenols, antioxidant capacity

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