Carcinogenicity of tannin and tannin-free extracts of bracken fern (Pteridium aquilinum) in rats.
F344 inbred and Sprague-Dawley noninbred rats were fed a basic diet (groups 1 and 7) or a basic diet supplemented with 0.1% (later, 0.2 and 0.4%) tannin (group 2) isolated from bracken fern (Pteridium aquilinum) (BF), 33% BF (groups 3 and 6), 2% chloroform fraction of BF (group 4), or 4% tannin-free fraction of BF (group 5). The following incidences of intestinal or bladder tumors were observed: group 1, intestinal and bladder, 0/16; group 2, 0/21; group 7, 0/16; groups 4 and 5, intestinal, 7/15, bladder, 0/15; group 3, intestinal, 19/20, bladder, 12/20; and group 6, intestinal, 22/30, bladder, 15/30. The chloroform-methanol fraction prepared from urine of rats fed BF, chloroform fraction of BF, or tannin-free fraction of BF demonstrated mutagenicity for Salmonella typhimurium TA 100 but not for TA 98. No mutagenicity was detected in other prepared fractions. F344 rats in group 8 received weekly sc injections  of tannin solution (0.1 g/kg body wt) for 38 weeks, and 16/20 developed palpable tumors that were malignant fibrous histiocytomas at the injection site. No tumor was present in any rat of control group 9.
D000818:Animals; D002273:Carcinogens; D005260:Female; D007279:Injections, Subcutaneous; D007414:Intestinal Neoplasms / Q000139:chemically induced*; D008297:Male; D009153:Mutagens; D010945:Plants, Edible; D010947:Plants, Toxic; D011794:Quercetin / Q000633:toxicity; D051381:Rats; D012486:Salmonella typhimurium / Q000187:drug effects; D013634:Tannins / Q000008:administration & dosage / Q000633:toxicity* / Q000652:urine; D001749:Urinary Bladder Neoplasms / Q000139:chemically induced*
D002273:Carcinogens; D009153:Mutagens; D013634:Tannins; D011794:Quercetin