The durability of western redcedar heartwood is influenced by a number of different extractives operating by different mechanisms. In order to guide a systematic isolation of extractives with high fungal toxicity, a micro-bioassay has been developed for measuring the fungal toxicity of extractive fractions. Two additional assays quantify the anti-radical and metal chelating properties of cedar extracts. Eight known WRC heartwood extractives were used to evaluate these methods. The three thujaplicins and ?-thujaplicinol were the only extractives found to have antifungal activity under the conditions tested. Plicatic acid and ?-thujaplicinol exhibited anti-radical activity, and the thujaplicins, ?-thujaplicinol and plicatic acid formed coloured complexes with ferric chloride, indicative of chelation. These methods help to characterise unknown extracts by providing rapid estimates of anti-fungal activity.

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