Comprehensive Summary A novel schinortriterpenoid (SNT), schinensilactone A (1), characterized by a unique 7,8‐seco‐1,8‐cyclo‐schisanartane scaffold, was isolated from the leaves of Schisandra chinensis (Turcz.) Baill, together with a new SNT (schinensilactone B, 2) and two known (3, 4). Their structures were elucidated using spectroscopy and X‐ray diffraction. Furthermore, a hypothetical biosynthetic pathway for 1 was postulated due to its novel carbon skeleton. In addition, 1 exhibited significant anti‐proliferative activity against Caco‐2 cells originating from five different tumor cell lines, and its preliminary mechanism of action was investigated with respect to the expression of apoptosis‐related proteins, including P53, Caspase 3, Bax, PUMA, and Bcl2. These biological activities would further our understanding of the food function of Schisandra chinensis leaves. A novel schinortriterpenoid (SNT), schinensilactone A (1), characterized by a unique 7,8‐seco‐1,8‐cyclo‐schisanartane scaffold, was isolated from the leaves of Schisandra chinensis (Turcz.) Baill. In addition, 1 exhibited significant anti‐proliferative activity against Caco‐2 cells originating from five different tumor cell lines, and its preliminary mechanism of action was investigated with respect to the expression of apoptosis‐related proteins, including P53, Caspase 3, Bax, PUMA, and Bcl2.