Abstract: AimTo rapidly separate and determine the nucleosides from natural and cultured Cordyceps kyushuensis Kob., and to compare the content of cordycepin and adenosine in different parts of Cordyceps kyushuensis Kob., which are the main nucleoside active components in medicinal fungus belonging to Cordyceps (Fr.) Link. Methods The nucleosides were separated and determined by the high performance capillary zone electrophoresis (CZE). Beckman P/ACE system MDQ apparatus equipped with a PDA detector and a uncoated fused-silica capillary (41 cm×45 μm ID, 30 cm effective length) were used. The experimental conditions were as follows: the running buffer was borax solution (adjust to pH 9.4 with sodium hydroxide), applied voltage was 20 kV, operated temperature was 20 ℃ and the detector wavelength was 258 nm. The content of cordycepin and adenosine in the fruiting body, stroma and host worm of natural and cultured C. kyushuensis were respectively investigated and quantitatively analyzed. ResultsThere are at least 8 kinds of nucleoside or nitrogen base in Cordyceps kyushuensis Kob. The content of cordycepin which is a bio-active substance with anti-tumor activity in C. kyushuensis is significantly higher than that in C.sinensis and C.militaris and furthermore the cordycepin in the cultured C. kyushuensis is notably higher than the natural one. Adenosine was mainly found from the stroma of C. kyushuensis While the cordycepin content is high in the stroma of both natural and cultured C. kyushuensis as well as in the host worm of the cultured one. ConclusionThere are some differences about the nucleoside components between the natural and cultured C. kyushuensis and between the different parts of them. With a high cordycepin content, C. kyushuensis should have a considerable medicinal potential.