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Phenolic Content and Antioxidant Capacity of Sea Buckthorn (Hippophae rhamnoides L.) Leaf Extracts Obtained by Accelerated Solvent Extraction

Plant parts such as fruits, leaves, stems, shoots, bark and roots are rich source of structurally different BAM which could be incorporated into value-added products or as source of new drugs (Criste et al. 2020), Sea buckthorn (Hippophae rhamnoides L.) is well known as a valuable plant used in traditional medicine due to content of flavonoids, phenolic acids, carotenoids, sterols and vitamins (Sne et al, 2013). Compared to berries sea buckthorn leaf extracts (SBL) have marked antioxidant and antimicrobial activities due to higher phenolic contents (PC) (Yeong et al, 2010). Extraction of phenolics from plants is the first step in their utilization and advanced extraction processes such as accelerated solvent extraction (ASE) have been developed in recent years due to reduction of extraction time and solvent consumption and increased yield of targeted BAM (Gomes et al, 2017). The temperature, time and solvent are the three most important ASE method parameters influencing extraction efficiency. Therefore, the aim of this study was to evaluate the PC and antioxidant capacity (AC) in SBL extracts obtained under different ASE conditions of temperature (80, 100 and 120 °C) and static time (5, 10 and 15 min) using 70% ethanol as a solvent. Phenolic content of SBL extracts was determined using UPLC-MS2 and AC by ORAC method, respectively. A total of 29 phenolic compounds were determined comprising flavonols (FOL), flavones (FON), flavan-3-ols (F-3-OL) and phenolic acids (PA). The FOL (631.34-776.63 mg/100g dm) showed to be the predominant phenolic group in SBL extracts, followed by PA (127.61-189.15 mg/100g dm). FON (7.50-16.90 mg/100g dm) and F-3-ON (843 12.38 mg/100 dm). The most represented phenolic compounds were rutin and kaempferol-3-rutinoside, followed by kaempferol-rhamnoside, Isorhamnetine- 3.7 dihexoside, gallic acid, vanillic acid and luteolin. The SBL extracts showed high AC (8170.06-9458.99 pmol TE/100 g dm). Applied ASE conditions significantly affected the concentration of FOL and AC Generally, higher PC was observed in extracts obtained under extraction temperature of 120 °C and static time of 10 minutes, while the highest AC was observed under temperature of 100 °C and static time of 15 minutes. The ASE is effective method for the production of valuable SBL extracts with great potential for application in the development of functional food and pharmaceutical products.

Hippophae rhamnoides, phenols, antioxidant capacity, accelerated solvent extraction

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