Dysregulation of the autophagy–lysosome pathway is implicated in neurodegenerative disorders. To extend the chemical diversity of jatrophane diterpenoids from Euphorbia peplus and evaluate lysosome-associated phenotypes, phytochemical isolation and a LysoTracker Green assay in HeLa cells were performed. Five previously undescribed jatrophane diterpenoids, Euphjatrophanes M–Q (1–5), together with three known analogues (6–8), were isolated. The structures of 1–5 were assigned from one- and two-dimensional NMR, IR, and UV and the available HR-ESI-MS data, together with a comparison with reported compounds. At 10 and 40 μM, compounds 1, 2, and 4–8 produced higher LysoTracker-associated fluorescence than the DMSO vehicle control, whereas compound 3 showed a small numerical increase at 10 μM and a decrease at 40 μM. Compound 1 gave the largest numerical response (1.76-fold and 3.01-fold at 10 and 40 μM, respectively). These findings provide preliminary cell-based phenotypic evidence of lysosome-modulating activity and require orthogonal validation.