Mosses, Liverworts, and Hornworts Screened for Antitumor Agents

Abstract

The National Cancer Institute’s record of bryophytes (mosses, liverworts, and hornworts) screened for biologically active chemicals is reviewed. In 1977, an extract of a moss from Maryland, Polytrichum ohioense, showed cytotoxicity in KB cell culture, but antitumor activity was not discovered in bryophytes until 1980. This led to a greater emphasis in collecting and screening bryophytes during 1980–1981. Samples weighing 0.5–2 kg (dried) were collected for each of 208 species and varieties. These included 184 species in 97 genera of mosses, 23 species in 16 genera of liverworts, and 1 hornwort. The methodologies for field work, extraction, and screening are briefly described. The screening results are summarized in a table listing all species alphabetically by family and by genus. For each species, the origin of the sample (country or state), collector’s number, extract number, type of extract, and 3 bioassays employed (including the dose levels used and toxic dose for the P388 lymphocytic leukemia assay) are indicated. Extracts of 75 species were toxic; extracts of 43 species were active. Activity was especially noted in the moss families Thuidiaceae, Mniaceae, Neckeraceae, Hypnaceae, Brachytheciaceae, Polytrichaceae, Dicranaceae, and Grimmiaceae. The authors suggest that bryophytes are a promising source for discovery of novel biologically active compounds. The possibility that biological activity in bryophytes may be the result of allelopathy, or the reputed ability of bryophytes to accumulate toxic substances, is considered.