Activity-guided fractionation of an ethyl acetate extract of the twigs of Hernandia ovigera, using a soft agar assay with JB6 murine epidermal cells, led to the isolation of two new naturally occurring aryltetralin lignans, (7R,8S,7'R,8'R)-(+)-7'-acetyl-5'-methoxypicropodophyllin (1) and (7R,8S,7'R,8'R)-(+)-7'-acetylpicropodophyllin (2), of which 2 was previously identified as a synthetic product, along with eight known compounds, epiyangambin (3), caruilignan C, diasesartemin, (+)-epimagnolin A, N-methylcorydaldine, (-)-5'-methoxyyatein, (+)-syringaresinol dimethyl ether, and (-)-yatein. The structures and stereochemistry of 1 and 2 were determined using spectroscopic methods. Compounds 2 and 3 exhibited significant inhibition of the transformation of murine epidermal JB6 cells, with IC50 values of 0.15 and 0.4 microg/mL, respectively, while the other isolates were regarded as inactive (IC50 >4 microg/mL).