Potential anthelmintics: polyphenols from the tea plant Camellia sinensis L. are lethally toxic to Caenorhabditis elegans

A novel gallate of tannin, (−)-epigallocatechin-(2β→O→7′,4β→8′)-epicatechin-3′-O-gallate (8), together with (−)-epicatechin-3-O-gallate (4), (−)-epigallocatechin (5), (−)-epigallocatechin-3-O-gallate (6), and (+)-gallocatechin-(4α→8′)-epigallocatechin (7), were isolated from the tea plant Camellia sinensis (L.) O. Kuntze var. sinensis (cv., Yabukita). The structure of 8, including stereochemistry, was elucidated by spectroscopic methods and hydrolysis. The compounds, along with commercially available pyrogallol (1), (+)-catechin (2), and (−)-epicatechin (3), were examined for toxicity towards egg-bearing adults of Caenorhabditis elegans. The anthelmintic mebendazole (9) was used as a positive control. Neither 2 nor 3 were toxic but the other compounds were toxic in the descending order 8, 7 ≈ 6, 9, 4, 5, 1. The LC₅₀ (96 h) values of 8 and 9 were evaluated as 49 and 334 μmol L⁻¹, respectively. These data show that many green tea polyphenols may be potential anthelmintics.