Phytochemical Analysis and In Vitro Effects on Isolated Murine Lymphocytes and Macrophages of Polymeric Micelles Loaded with Cycloartane Saponin

Abstract

Triterpenoid saponins from the Astragalus species possess valuable effects (cytotoxic, adjuvant, hepatoprotective, neuroprotective, antiviral, etc.). Some also have immunomodulatory activities. Astragalus glycyphyllos is distributed in Bulgaria and mainly accumulates cycloartane saponins. From the overground parts of the species, a triterpenoid cyloartane-type saponin (AGOS3) was isolated by different chromatographic techniques. A quantitative LC-MS method for the determination of the saponin was developed and validated. Further, the saponin was loaded in copolymeric micelles based on triblock copolymers of polyethylene oxide and polypropylene oxide (Pluronics). The LC-MS method was applied on the developed micelles to determine their loading degrees. Afterwards, the possible pharmacological effects of free and encapsulated in polymeric nanoparticles of triterpenoid saponin (1, 5, 10, 25, 50, and 100 µg/mL) were evaluated in isolated murine macrophages and lymphocytes in vitro. Free AGOS3 stimulated proliferation only at the highest tested concentrations (50–100 µg/mL), and the effect was more evident in isolated macrophages. Interestingly, AGOS3-loaded polymeric micelles caused concentration dependency and statistically significant increases in the proliferation of both isolated lymphocytes and macrophages, even at a lower concentration (10 µg/mL). These results could serve as the basis for further research on the immunomodulatory effect of this saponin.