In the course of a continuing search for tumor inhibitors from plant sources, an extract of Aristolochia indica L. was found to show reproducible tumor inhibitory activity against the adenocarcinoma 755 test system. Aristolochic acid (1) was characterized as the principal tumor-inhibitory principle. We report herein the isolation and structural elucidation of three new companion aristolochic acid derivatives, aristolochic acid-D (4), aristolochic acid-D methyl ether lactam (6), and aristololactam β-D-glucoside (8). In addition, we report the isolation of aristololactam (7), previously isolated from other species of Aristolochia. Aristolochic acid-D (4), separated from methanol as deep wine-red crystals (mp 269-272°), was assigned the molecular formula C₁₇H₁₁NO₈ on the basis of elemental analysis. Its nmr spectrum supported the empirical formula and indicated the presence of methoxyl, methylenedioxy, aromatic, and two D₂O-exchangeable protons; the ir spectrum showed bands for phenolic hydroxyl, carboxyl, and nitro functions; and the uv spectrum suggested a phenanthrene chromophore. Methylation with diazomethane yielded the dimethyl derivative (5, C₁₉H₁₅NO₈, mp 238-240°), whose ir spectrum indicated an ester carbonyl. Hydrogenation of 5 with 10% palladium-charcoal gave the lactam (6, C₁₆H₁₃NO₅, mp 350-355°), identical to the natural product. The structure of 5 was deduced via spectral evidence and confirmed by comparison with a synthetic sample, supporting the 3,4-methylenedioxy-6-hydroxy-8-methoxy-10-nitro-1-phenanthroic acid structure (4) for aristolochic acid-D. Aristololactam β-D-glucoside (8), isolated as light yellow crystals (mp 330-333°), had the formula C₂₃H₂₁NO₉ (elemental analysis). Its uv spectrum resembled aristololactam (7) but with lower intensities (suggesting a sugar moiety); ir lacked N-H stretching, and nmr showed no N-H signal but included sugar protons. Acetylation gave the tetraacetate (9, mp 287-288°). Lithium aluminum hydride reduction followed by mild acid hydrolysis yielded α-D-glucose and aglycone (11), confirmed by comparison with the product from aristololactam reduction.