Diels–Alder Adducts from Maytenus chiapensis

Natural products from plants have played an important role in cancer and neurodegenerative diseases. In this context, the root bark of Maytenus chiapensis (Celastraceae) was investigated to examine its chemical constituents and potential biological activities. Chromatographic separation of the root bark extract yielded a new Diels–Alder adduct (morenine) formed by a triterpenophenolic moiety derived from tingenone and a bicyclic guaiane-type sesquiterpene linked through a 1,4-dioxane bridge. In addition, eight previously reported Diels–Alder adducts—retusonine and cheiloclines A–D and F–H—were isolated, together with their biosynthetic precursors, the quinone-methide triterpenoids (QMTs) pristimerin and tingenone. Structural elucidation was achieved through detailed 1D and 2D NMR spectroscopic analyses. The adducts were tested for cytotoxicity against six cancer cell lines (A549, SW1573, MIA PaCa-2, T-47D, HeLa, and WiDr cell lines), showing moderate-to-low activity compared with their precursors. Continuous live cell imaging identified apoptosis and vacuole formation as the main modes of action of pristimerin in SW1573 cells. Moreover, acetylcholinesterase inhibition assays revealed that cheiloclines B–D, F, and H exhibited up to 50% inhibition. These findings reinforce the potential of Celastraceae species as a source of unique and complex compounds and enhance our understanding of their therapeutic potential.