Stigmast-5-en-$3{eta}$,$7{eta}$-diol (1), stigmast-5-en-$3{eta}$,$7{alpha}$-diol (2), (+)-isolariciresinol-9-$O$-${eta}$-D-xylopyranoside (3), procyanidin B2 (4), and epicatechin-($4{eta}{ ightarrow}8$)-epicatechin-($4{eta}{ ightarrow}6$)-epicatechin (5) were isolated for the first time from the bark of $Machilus$ $thunbergii$. The chemical structures of the compounds were determined based on nuclear magnetic resonance, electronic ionization mass spectrometry, fast atom bombardment mass spectrometry, and IR. Compound 4 demonstrated inhibitory activity against cyclin-dependent kinases (CDK2, CDK4, and CDK5) $in$ $vitro$ with $IC_{50}$ values 17.22, 1.08, and $0.26{mu}M$, respectively.