Extract and the quassinoid ailanthone from Ailanthus altissima inhibit nematode reproduction by damaging germ cells and rachis in the model organism Caenorhabditis elegans

Abstract

Bark and leaves of Ailanthus altissima (Mill.) Swingle are widely used in European folk medicine to treat intestinal worm infections. The study aimed to rationalize a potential anthelmintic effect of A. altissima extract against the model organism Caenorhabditis elegans. A methanol-water (7:3, v/v) extract of the primary stem bark was tested on L4 larvae of C. elegans for induction of mortality and influence on reproduction. Bioactivity-guided fractionation was performed by chromatography on MCI-gel, preparative HPLC on RP18 stationary phase and fast-centrifugal-partition-chromatography. Structural elucidation of isolated quassinoids was performed by NMR and HR-ESI-MS. The sterilizing effect on C. elegans was investigated by light microscopy and atomic force microscopy of ultra-sections. Different GFP-tagged reporter strains were used to identify involved signaling pathways. A. altissima extract (1 mg/mL) irreversibly inhibited the reproduction of C. elegans L4 larvae. This effect was dependent on the larval stage since L3 larvae and adults were less affected. Bioactivity-guided fractionation revealed the quassinoid ailanthone 1 as the major active compound (IC₅₀ 2.47 μM). The extract caused severe damages to germ cells and rachis, which led to none or only poorly developed oocytes. These damages led to activation of the transcription factor DAF-16, which plays a major role in the nematode's response to stress. A regulation via the respective DAF-2/insulin-like signaling pathway was not observed. The current findings support the traditional use of A. altissma in phytotherapy to treat helminth infections and provide a base for standardization of the herbal material.

Keywords: Ailanthone; Ailanthus altissima; Caenorhabditis elegans; DAF-16; Quassinoid; Reproduction.