Chemical Constituents of Black Locust Bark and their Biocidal Activity

Samples of the inner and outer bark of black locust (Robinia pseudoacacia) were analyzed for extractive content (ether, ethanol and hot water) and structural components (suberin, holocellulose and lignin). Fractions obtained were tested for their antibacterial and antifungal activity. None showed antibacterial activity against Streptococcus faecium or Escherichia coli. Only the suberin monomer fraction from the outer bark had significant antifungal activity against Aphanomyces euteiches. Two dicarboxylic and two monocarboxylic fatty acids were identified in the active fraction. No condensed tannin was found in an acetone/water extract of the outer bark but monomeric flavonoids (catechin and epicatechin) were found, along with caffeic acid, ferulic acid and tryptophan. An aqueous buffer extract of the inner bark contained protein with hemagglutinating activity (lectin).