A new lanostane-type terpenoid, lucidenic acid SP1 (1), was isolated from a CHCl(3)-soluble fraction of Ganoderma lucidum spores together with four other known compounds (2 - 5). The structure of lucidenic acid SP1 was determined to be 3 beta,7 beta-dihydroxy-4,4,14 alpha-trimethyl-11,15-dioxo-5 alpha-chol-8-en-24-oic acid by spectroscopic means including 2D-NMR. Twelve triterpenes (1-12) isolated from G. lucidum spores were investigated in vitro for their anticomplementary activity. Compounds 1 - 5 were inactive, whereas ganoderiol F (8), ganodermanondiol (9) and ganodermanontriol (10) showed a strong anticomplement activity against the classical pathway (CP) of the complement system with IC(50) values of 4.8, 41.7, and 17.2 microM, respectively. The potency of these triterpene alcohols (8-10) in inhibiting CP activity was improved when the number of hydroxymethyl groups on the side chain moiety is increased. On the other hand, the ganoderic acids 1-7, which contain a carboxyl group in the side chain, and lucidumols A and B (11, 12) had little activity on this system.