Bioactive flavonoids from endophyte-infected blue grass (Poa ampla)

Ethanol extract of leaves of Poa ampla, either infected or uninfected with the symbiotic fungus Neotyphodium typhnium, were tested for bioactivity against the mosquito larvae. Results of these tests indicated that only the extracts obtained from endophyte-infected grass are active against mosquito larvae. Relatively high activity was detected in stromata, seeds, spikelets, and leaves of plants, while only weak or no activity was found in extracts of the isolated fungus. The ethyl acetate fraction had approximately the same activity as that of the crude extract, while the activities from 1-butanol and hexane were intermediate and low, respectively. Bioassay-guided fractionation of the ethyl acetate fraction yielded tricin (1), 7-O-(beta-D-glucopyranosyl)tricin (2), and isoorientin (3) as the bioactive constitutents. A fourth compound, 7-O-[alpha-L-rhamnopyranosyl(1-6)-beta-D-glucopyranosyl]tricin (4), was also isolated from the active fraction but showed little activity in this assay.