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Abstract Bioassay-guided fractionation of dichloromethane extract from Athenaea velutina leaves led to the isolation of three withanolides, all being reported for the first time in this species. They were identified as withacnistin (1), withacnistin acetate (2) and a new withanolide, designated as withalutin (3). The structures were established by spectral data analysis, including MS, 1D and 2D NMR. In addition, in silico ADMET studies were employed to understand the pharmacokinetic properties of these withanolides. The withanolides isolated from A. velutina reduced cancer cell viability with IC50 values ranging from 1.52 to 5.39 µM. In silico prediction revealed that withanolides have good gastrointestinal absorption or oral bioavailability properties; and are not likely to be mutagenic or hepatotoxic. These findings revealed that A. velutina is an important source of cytotoxic withanolides. Graphical ABSTRACT