Tetracyclic flavan enantiomers from Dianella ensifolia as inhibitors of CuSO4-induced neutrophil recruitment in zebrafish.

Dianella ensifolia (L.) DC. is a medicinal plant traditionally used externally for the treatment of skin infections, abscesses, lymphadenitis, traumatic swelling, and wounds. To characterize its chemical constituents and identify potential anti-inflammatory compounds, a systematic phytochemical investigation of the roots of D. ensifolia was conducted. Seventeen flavans were isolated and characterized, including two undescribed tetracyclic flavans, diaensifols A and B (1 and 2), which were resolved into two pairs of enantiomers, (+)-1/(-)-1 and (+)-2/(-)-2, five undescribed flavans (3-7), and ten known analogues (8-17). Their structures were elucidated by extensive spectroscopic analyses, experimental and calculated ECD analyses, and single-crystal X-ray diffraction. Acute toxicity screening in zebrafish larvae showed that the four enantiomers, (+)-1, (-)-1, (+)-2, and (-)-2, maintained near-complete larval survival at concentrations below 40 μM. In a CuSO4-induced acute inflammation model using Tg (mpo: EGFP) zebrafish larvae, the enantiomers of 1 and 2 reduced neutrophil recruitment to the lateral line region. The enantiomers of 1 showed inhibitory effects at 20-40 μM, whereas those of 2 showed moderate inhibition mainly at 40 μM. These findings expand the structural diversity of flavans from D. ensifolia and identify tetracyclic flavan enantiomers as candidate anti-inflammatory constituents that may contribute to the traditional external use of this plant for inflammation-associated conditions.