Biological activity and tentative identification of flavonoid components in velvetleaf (Abutilon theophrasti Medik.) seed coats.

The biological activity of aqueous extracts of velvetleaf (Abutilon theophrasti Medik.) seed coats and their flavonoid components against three plant species and five soil fungi was investigated. Aqueous extracts slightly inhibited germination and significantly inhibited radicle growth of all plant species tested. Fungal growth was inhibited or not affected, depending on species, by aqueous extracts. The aqueous extracts were extracted into methanol and separated using paper chromatography for identification of compounds responsible for inhibition of seedling and fungal growth. Six flavonoid compounds were isolated and tentatively identified as delphinidin, cyanidin, quercetin, myricetin, (+)-catechin, and (-)-epicatechin. Bioassays revealed that the flavonoid compounds significantly inhibited germination and radicle growth of all test species at a concentration of 1.0 mM. Individual flavonoids had variable effects on fungi but appeared to inhibit growth and sporulation of potential seed-decomposing fungi rather than "beneficial" fungi. These results indicate that the flavonoid complement of velvetleaf seed coats may function in a dual defensive role against competing seedlings and seed-attacking fungi.