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B-Lapachone, an o-naphthoquinone, induces a novel caspase-and p53-independent apoptotic pathway dependent on NAD(P)H:quinone oxidoreductase1 (NQO1). NQO1reduces B-lapachone to an unstable hydroquinone that rapidly undergoes a two-step oxidation back to the parent compound, perpetuating a futile redox cycle. A deficiency or inhibition of NQO1rendered cells resistant to B-lapachone. Thus, B-lapachone has great potential for the treatment of specific cancers with elevated NQO1levels (e.g., breast, non^small cell lung, pancreatic, colon, and prostate cancers). We report the development of mono(arylimino) derivatives of B-lapachone as potential prodrugs. These derivatives are relatively nontoxic and not substrates for NQO1when initially diluted in water. In solution, however, they undergo hydrolytic conversion to B-lapachone at rates dependent on the electron-withdrawing strength of their substituent groups and pH of the diluent. NQO1enzyme assays, UV-visible spectrophotometry, high-performance liquid chromatographyelectrospray ionization-mass spectrometry, and nuclear magnetic resonance analyses confirmed and monitored conversionof each derivative to B-lapachone. Once converted, B-lapachone derivatives caused NQO1-dependent, A-calpain-mediated cell death in human cancer cells identical to that caused by B-lapachone. Interestingly, coadministration of N-acetyl-L-cysteine prevented derivative-induced cytotoxicity but did not affect B-lapachone lethality. Nuclear magnetic resonance analyses indicated that prevention of B-lapachone derivative cytotoxicity was the result of direct modification of these derivatives by N-acetyl-L-cysteine, preventing their conversion to B-lapachone. The use of B-lapachone mono(arylimino) prodrug derivatives, or more specifically a derivative converted in a tumor-specific manner (i.e., in the acidic local environment of the tumor tissue), should reduce normal tissue toxicity while eliciting tumor-selective cell killing by NQO1 bioactivation.

Thirty-seven naturally occurring withanolides (1-37), previously isolated in our laboratories, were evaluated for their potential to induce quinone reductase with cultured murine hepatoma cells (Hepa 1c1c7). Spiranoid (29, 32) and 18-functionalized withanolides (2-5, 7-9, 24) were found to be potent inducers of the enzyme, while 5alpha-substituted derivatives exhibited weak activity. Preliminary studies were performed with compound 29 to evaluate enzyme-inducing capacity in multiple organ sites of BALB/c mice. Significant induction was observed in liver and colon, but not in lung, stomach, or mammary gland.

Eight new withanolides were isolated from the aerial parts of Vassobia lorentzii and characterized by spectroscopic methods and with the aid of molecular modeling. The compounds were identified as (17S,20R,22R)-5beta,6beta:18,20-diepoxy-18-hydro xy-1-oxowitha-2,5, 24-trienolide (1); (17S,20R,22R)-18,20-epoxy-4beta, 18-dihydroxy-1-oxowitha-2,5,24-trienolide (2); (17S,18R,20R, 22R)-4beta-hydroxy-18,20-epoxy-18-methoxy-1-oxowitha-2,5, 24-trienolide (3); (17S,18S,20R,22R)-4beta-hydroxy-18, 20-epoxy-18-methoxy-1-oxowitha-2,5,24-trienolide (4); (17S,20R, 22R)-4beta-hydroxy-18,20-epoxy-1,18-dioxowitha-2,5,24-tri enolide (5); (17S,18R,20R,22R)-18,20-epoxy-18-methoxy-1,4-dioxowitha++ +-2,5, 24-trienolide (6); (17S,18S,20R,22R)-18,20-epoxy-18-methoxy-1, 4-dioxowitha-2,5,24-trienolide (7); and (17S,20R,22R)-5beta, 6beta-epoxy-4beta,18,20-trihydroxy-1-oxowitha-2,24-die nolide (8). Compounds 1 and 2 were obtained as epimeric mixtures at C-18.

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Three new withanolides, jaborosalactones V (3), W (4), and X (5), which contain a hydroxyl group a t position C-19, have been isolated from the aerial parts of Jaborosa leucotricha and characterized by spectroscopic methods.Withanolides, a group of oxygenated steroidal lactones of the ergostane C-28 type, have been isolated from several genera of the Solanaceae. They are known for the diversity encountered in their substitution patterns, and many of them exhibit interesting biological activities including insecticide and antifeedant pr0perties.l Previous studies on extracts of the aerial parts of Jaborosa leucotricha (Speg.) A. T. Hunziker collected in late spring in Argentina have shown the presence of three withanolides, jaborosalactone L,2 its 2,3-dihydro-19-hydroxy derivative, jaborosalactone 0 ( u3; and jaborosalactone Q (2), which contains an aromatic ring A.4 The presence in the same plant of the latter two compounds suggested the possibility of a degradation pathway for the loss of C-19, although the different substitution pattern of their side chains excluded a direct biosynthetic relationship between them. When we investigated J . leucotricha collected in autumn, we found that jaborosalactones L and 0 were absent and that jaborosalactone Q was the main withanolide. Furthermore, three new 19-hydroxywithanolides, named jaborosalactones V (3), W (41, and X (5), were also present. The structure of 3 is consistent with a straightforward biosynthetic pathway from 19-hydroxylated to A-ring aromatic 19-norwithanolides.The FABMS (m-nitrobenzyl alcohol) of jaborosalactone V (3), C2~H3806, showed a {M + 1>+ ion at mlz 471 (15%). Its lH-NMR spectrum had two olefinic protons at 6 6.91 and 6.06 related to a 2-en-1-one system with a methylene at C-4; a 5/?,6/?-epoxide was inferred from the presence of a doublet at 6 3.09 corresponding to H-6. Regarding the side chain, this was closely related to that of jaborosalactone Q,4 with the presence of a singlet at 6 2.03 (Me-28) and an AB quartet centered at 6 4.37 (CH2-27) being consistent with a 27-hydroxylated a,/?-unsaturated lactone ring; the signal of H-22 was clearly observed at 4.40 ppm. At the highfield end of the spectrum appeared two signals assigned to Me-18 (6 0.73) and Me-21 (6 l . O l ) , the absence of a singlet for H-19 and the appearance of an AI3 quartet at 3.93-4.24 ppm confirmed the presence of a hydroxyl group at C-19, with jaborosalactone 0 (1) being the only 19hydroxywithanolide previously r e p ~r t e d . ~ Final confirmation of structure 3 was provided by the 13C-NMR and DEPT spectral data. Only three methyl groups were

In addition to the known compounds withanolide A (4), withanone (5), and NIC-3 (6), three 16-hydroxylated withanolides were isolated from Exodeconus maritimus. The new withanolides were identified as 6α,7α-epoxy-5α,16β-dihydroxy-1-oxowitha-2,17(20),24-trienolide (exodeconolide A, 1), 6α,7α-epoxy-5α,16α-dihydroxy-1-oxowitha-2,17(20),24-trienolide (exodeconolide B, 2), and 6α,7α-epoxy-5α,16α,17α-trihydroxy-1-oxowitha-2, 24-dienolide (exodeconolide C, 3), by a combination of spectroscopic (1D and 2D NMR, MS) and chemical methods with the aid of molecular modeling.