LC-ESI-MS/MS profiling of phenolics from Eleutherococcus spp. inflorescences, structure-activity relationship as antioxidants, inhibitors of hyaluronidase and acetylcholinesterase.

Nature is a source of many plant-based molecules used as pro- or drugs. Eleutherococcus species are native to Asia and the North Russia, and are traditionally used to treat various diseases. In turn, neither secondary metabolites of the species cultivated in the West Europe nor the bioactivity is known. No differences in the phenols and flavonoids content in the inflorescences were found. The richest in polyphenols was E. giraldii (5.18 mg/g), while in flavonoids it was E. gracilistylus (1.80 mg/g). Using LC-ESI-MS/MS, protocatechuic and trans-caffeic acids have been identified as the most abundant compounds in E. gracilistylus, E. giraldii, E. senticosus (833.4; 855.6; 614.7 and 280.8; 156.0; 167.6 μg/g DE). It was observed that all species were able to chelate Fe2+ with the EC50 value of 0.2, 0.6, 0.3 mg/mL for E. gracilistylus, E. giraldii, E. senticosus, respectively. E. gracilistylus exhibited the strongest antiperoxidation and anti-DPPH∗ activity (EC50 3.2 and 0.48 mg/mL). The weak inhibitory potential has been observed in case of AChE inhibition at the level of 16.17 and 12.2% for E. gracilistylus, E. giraldii. We report for the first time that the extracts inhibited Hyal activity in the range from 16.4 to 60.7%. To our best knowledge, no information was available on this activity of the inflorescences and this provides a background to study inflorescences in more detail. Considering the SAR, an antioxidant activity may be correlated with a high amount of protocatechuic and trans-caffeic acids and their chemical structure.