Terpenoid and phenolic derivatives from the aerial parts of Elsholtzia rugulosa and their anti-inflammatory activity

Seven undescribed terpenoids, including three pairs of enantiomers, named (±)-rugulolides A-C, and one cyclopentenone derivative, named rugulolide D, together with twenty-six known compounds, were isolated from the aerial parts of Elsholtzia rugulosa. The chiral separation of rugulolides A-C was achieved by high-performance liquid chromatography using the chiral column. Their structures were elucidated unambiguously based on comprehensive spectroscopic analysis in conjunction with electronic circular dichroism (ECD) and single-crystal X-ray diffraction experiments. Rugulolides A-D are rare naturally occurring terpenoid derivatives featuring a methylated α,β-unsaturated-γ-lactone or a cyclopent-2-en-1-one nucleus. All the isolates were evaluated for their inhibitory effects on lipopolysaccharide-induced nitric oxide production in RAW264.7 cell, among them, four compounds showed moderate inhibition with IC₅₀ values ranging from 12.46 to 23.10 μM.

Keywords: Anti-inflammatory activity; Chiral separation; Elsholtzia rugulosa Hemsl.; Enantiomers; Lamiaceae.