Adiantic acid, a new unsaturated fatty acid with a cyclopropane moiety from Adiantum flabellulatum L.

Phytochemical investigation of Adiantum flabellulatum L. led to the isolation of four natural compounds, including a novel unsaturated fatty acid with a cyclopropane moiety, i.e. (S,E)-7-(2-octylcyclopropylidene)heptanoic acid (1), together with three known compounds, isoadiantol B (2), stigmast-4-en-6β-ol-3-one (3), β-sitosterol (4). Compound 3 was isolated from the A. flabellulatum L. for the first time. The structure of 1 was elucidated following a comprehensive analysis of spectroscopic analyses including MS, 1 D and 2 D NMR, and by a mass spectrometry experiment of the dimethyl disulfide (DMDS) adduct, while the known compounds were identified by comparisons with those reported in the literature. Enzyme evaluation of 1 indicated this compound possesses anti- protein tyrosine phosphatase (PTP1B) activity with an IC50 value of 6.99 ± 0.41 μM in vitro.