ANTIMICROBIAL ACTIVITY IN CHESTNUT TISSUES CORRESPONDING WITH FLAVONOL GLYCOSIDE AND TERPENOID SUBSTANCES

Abstract

Chestnut pellicles, as well as shell and leaf tissues, were studied for antimicrobial activities. Chestnut tissues were extracted in 70% ethanol and adjusted to a final concentration of 1 mg dry tissue/ml. Microorganisms, including bacteria, oomycetes, and fungi were incubated on agar medium amended with various concentrations of the extract and the growth inhibition was measured. Overall, bacteria were more sensitive than fungi and oomycetes. The effective concentrations for 50% growth inhibition (EC50) ranged from 5 to 24 µg/µl for bacteria; EC50 was from 24 to 89 µg/µl for most test fungi and oomycetes, or even higher for a few species. Extracts from the cultivar ‘Colossal’ (Castanea sativa × C. crenata) showed a greater inhibition than the Chinese species (C. mollissima). Chestnut pellicle contained a higher concentration of antimicrobial compounds than leaf and shell. Chestnut extract also showed inhibition of seed germination and emergence of radish. When incorporated into potting mix, chestnut shell and pellicle mixture reduced the population of most soil microorganisms and the growth of potato and radish at the early growth stage. The active compounds were isolated on a thin layer chromatography plate and analyzed using high performance liquid chromatography-mass spectrometry. The active fraction contained several substances with molecular masses consistent with one flavonol glycoside and several terpenoid substances.