Phytochemical Profiles and In Vitro Immunomodulatory Activities of Extracts Obtained from Limonium gmelinii Using Different Extraction Methods

Limonium (L.) gmelinii is a valuable pharmacopoeial Kazakhstani plant. Several studies have reported on the various biological activities of the plant. The purpose of our research was to study and compare the extraction yields, immunomodulatory activities, and chemical compositions of extracts from the above-ground parts of L. gmelinii obtained via conventional extraction (CE; Extract 1) and ultrasound-assisted extraction (UAE; Extract 2). The extracts were characterized by a considerable number of polyphenols and flavonoids: 378.1 ± 4.5 and 382.2 ± 3.3 GAE mg/g, and 90.22 ± 2.8 and 94.61 ± 1.9 QE mg/g in Extract 1 and Extract 2, respectively. Extract 2 had a slightly higher extraction yield (33.5 ± 2.4%) than Extract 1 (30.2 ± 1.6%). Liquid Chromatography–Diode-Array Detection–Electrospray Ionization–Quadrupole Time-of-Flight Mass Spectrometry (LC-QToF-MS) revealed the presence of 54 biologically active compounds in both extracts. It was shown that the studied extracts stimulate the secretion of TNF-α and IL-6 by intact mouse peritoneal macrophages and splenic lymphocytes, whilst they have an inhibitory effect on the secretion of these cytokines by activated immune cells. Both extracts demonstrated similar patterns of stimulation and inhibition in a splenocyte proliferation assay. Altogether, the L. gmelinii extracts obtained via CE and UAE might be suggested as effective immunomodulatory agents. The application of UAE for this purpose seems to be more efficient with a view of obtaining of a highly potent extract in a much shorter time.