Three new anti-oxidative ergostanes, methyl antcinate L (1), antcin M (2), and methyl antcinate K (3), together with nine additional known compounds, 3-ketodehydrosulphurenic acid, sulphurenic acid, dehydrosulphurenic acid, 3beta,15alpha-dihydroxylanosta-7,9(11),24-trien-21-oic acid, zhankuic acid A, zhankuic acid B, zhankuic acid C, antcin C, and antcin K were isolated from the basidiomata of Antrodia salmonea, a newly identified species of Antrodia (Polyporaceae) in Taiwan. These three new compounds were identified as methyl 3alpha,7alpha,12alpha-trihydroxy-4alpha-methylergosta-8,24(29)-dien-11-on-26-oate (1), 3alpha,12alpha-dihydroxy-4alpha-methylergosta-8,24(29)-dien-11-on-26-oic acid (2), and methyl 3alpha,4beta,7beta-trihydroxy-4alpha-methylergosta-8,24(29)-dien-11-on-26-oate (3) by spectroscopic analysis. We studied their antioxidative potential on the production of reactive oxygen species and nitric oxide (NO) in neutrophils and microglial cells, respectively. Compounds 1-3 displayed potent antioxidative activity with IC50 values of around 2.0-8.8 microM that was partially due to inhibition (6-67%) of NADPH oxidase activity but not through direct radical-scavenging properties. Compounds 1-3 also inhibited NO production with IC50 values of around 1.7-16.5 microM and were more potent than a non-specific NOS inhibitor. We conclude that these three new compounds 1, 2, and 3 exhibit anti-inflammatory activities in activated inflammatory cells.