Toxicity of coniferous bark extractives

We have, in this work, used several microbial tests to evaluate biological impacts of bark extractives from six industrially important coniferous species in Japan. Hexane, ethyl acetate and ethanol extracts were obtained from successive extractions of bark meals. The minimum concentration of growth-inhibition by each extract was evaluated for several bacteria on an agar-medium. Hexane extracts from all studied coniferous species showed significant inhibitory effect on bacterial growth, while the effect was limited in ethyl acetate and ethanol extracts. Using paper-disk test on an agar-medium, the effects of these bark extracts for their inhibition of fungal growth were also examined In this test, the ethyl acetate and ethanol extracts from all studied coniferous species showed inhibitory effects on fungal growth, while no such activity was observed with any of the n-hexane extracts. The biological impact of these extracts. was also examined with the MICROTOX(TM) test using bioluminescence of Photobacterium phosphoreum. In this test, remarkably high toxic activities were detected in the n-hexane extracts from the barks of Abies sachalinensis and Pinus densiflora.