Phytosterol profiles and iridoids of the edible Eucommia ulmoides Oliver seeds and their anti-inflammatory potential

Abstract Eucommia ulmoides (EU) Oliver seeds are rich in oil and serve as a potential edible oil, but little is known about its phytochemical substances. In this study, the sterol profiles of the supercritical CO2 fluid extracted EU seed oil and its contents were first evaluated by GC-MS analysis, and fifteen sterols and three triterpene alcohols were determined. β-sitosterol was detected as the most abundant phytosterol in the seed oil. Additionally, seven iridoid glycosides (1–7), namely aucubin (1), bartsioside (2), linaride (3), geniposidic acid (4), one dimer scyphiphin D (5), two trimers ulmoidoside A (6) and ulmoidoside B (7) were identified from the defatted seed flour, and the compound 3 was reported in E. ulmoides for the first time. Natural and two acetylated compounds (1–9) were evaluated for their inhibitory effects on NO production in the lipopolysaccharide (LPS)-stimulated microglial cells, and 1–3 exerted significant inhibition of NO generation with IC50 values of 3.60, 7.09, and 10.52 μM, respectively. The structure-activity relationships (SARs) of these iridoids indicated that OH groups on C-10 and C-6 were more effective and the COOH group at C-4 position was highly detrimental to the activity. The results suggest that the edible EU seeds could be a potential dietary source of aucubin and β-sitosterol for reducing the risk of neurodegenerative diseases.