Bioactivity and characterization of exudates from Cryptomeria japonica bark

Tree exudates play an important role in the defense system of trees. In this study, the composition of exudates secreted from the wound site of Cryptomeria japonica was examined. Seven diterpenoids, including ferruginol (1), cryptojaponol (2), isopimaric acid (3), 7β-hydroxydeoxocryptojaponol (4), isopimarol (5), sandaracopimarinol (6) and phyllocladan-16α-ol (7), were identified through chromatographic separation and spectroscopic analyses. Among them, ferruginol was the most abundant compound, accounting for 76.6 % of the total content in exudates. Exudates, ferruginol and isopimaric acid possessed the strongest antibacterial activity and had MIC values of 25–250, 12.5–100 and 6.25–100 μg/mL, respectively, against one strain of Gram-negative bacteria (Escherichia coli) and four strains of Gram-positive bacteria (Staphylococcus aureus, methicillin-resistant S. aureus, S. epidermidis and Enterococcus faecalis). In addition, exudates and ferruginol presented 79 and 53 % at 100 μg/mL, respectively, of antioxidant activities against 1,1-dipheny1-2-picrylhydrazyl radical. C. japonica bark exudates and their diterpenes exhibit the strongest antioxidant activity and can inhibit bacterial growth and thus have the potential to be developed into natural antioxidants and bactericides.