One new dibenzocycloheptene, validinol ( ), and one butanolide firstly isolated from the natural source, validinolide ( ), together with 17 known compounds were isolated from the stem of . Among the isolates, lincomolide A ( ), secosubamolide ( ), and cinnamtannin B1 ( ) exhibited potent inhibition on both superoxide anion generation (IC values of 2.98 ± 0.3 µM, 4.37 ± 0.38 µM, and 2.20 ± 0.3 µM, respectively) and elastase release (IC values of 3.96 ± 0.31 µM, 3.04 ± 0.23 µM, and 4.64 ± 0.71 µM, respectively) by human neutrophils. In addition, isophilippinolide A ( ), secosubamolide ( ), and cinnamtannin B1 ( ) showed bacteriostatic effects against in in vitro study, with minimal inhibitory concentration (MIC) values at 16 μg/mL, 16 μg/mL, and 500 μg/mL, respectively. Further investigations using the in vivo ear infection model showed that the intraperitoneal administration of the major component cinnamtannin B1 ( ) reduced immune cell infiltration and pro-inflammatory cytokines TNF-α and IL-6 at the infection sites. The results demonstrated the potential of cinnamtannin B1 ( ) for acne therapy. In summary, these results demonstrated the anti-inflammatory potentials of Formosan during bacterial infections.