The cytotoxic and antitumor activities of cis-1,2-diacyloxy-6-methoxy-3,3,14-trimethyl-1,2,3,14-tetrahydro-7H-benzo[b]pyrano[3,2-h]acridin-7-one derivatives 3, 6-9 were strongly correlated with their ability to give covalent adducts with purified, as well as genomic, DNA. Such adducts involve reaction between the exocyclic N-2 amino group of guanines exposed in the minor groove of double helical DNA and the leaving ester group at the benzylic position 1 of the drug. A transesterification process of the ester group from position 2 to position 1 in aqueous medium accounted for the intense activity of the cis-1-hydroxy-2-acyloxy-6-methoxy-3,3,14-trimethyl-1,2,3,14-tetrahydro-7H-benzo[b]pyrano[3,2-h]acridin-7-one derivatives 10-13. Compounds without acyloxy or hydroxy group at position 1, such as 15, 17, 18, and 22, were inert with respect to DNA and almost devoid of significant cytotoxic activity. Condensation of 5-amino-2,2-dimethyl-2H-chromene (26) with 3-bromo-2-naphthoic acid (27), followed by cyclization, gave access to 6-demethoxy analogues. Diacetate 32 and cyclic carbonate 33, both belonging to the latter series, were less reactive toward DNA and less cytotoxic than their 6-methoxy counterparts 3 and 34. DNA alkylation appears thus to play an important role in the antitumor properties of benzo[b]pyrano[3,2-h]acridin-7-one derivatives.

Three new bidesmosidic saponins (1-3) and a new ursane triterpenoid, 2α,3β,11α,23-tetrahydroxyurs-12-en-28-oic acid (4), along with seven known compounds, were isolated from a methanolic extract of the leaves of Symplocos lancifolia. The bidesmosidic saponins were found to possess the same sugar unit part, composed of two β-d-glucose moieties and one α-l-rhamnose moiety, linked to maslinic acid, arjunolic acid, and asiatic acid, respectively. Their structures were elucidated by interpretation of their 1D and 2D NMR spectra and completed by analysis of the HRESIMS data. The antibacterial activity of the isolated triterpenoids was evaluated against Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, and Pseudomonas aeruginosa, and several showed activity against Gram-positive bacteria.

A rapid screening by (1)H and (1)H-(13)C HSQC NMR spectroscopy of EtOAc extracts of Endiandra and Beilschmiedia species allowed the selection of Beilschmiedia ferruginea leaves and flowers extract for a chemical investigation, leading to the isolation of 11 new tetracyclic endiandric acid analogues, named ferrugineic acids A-K (1-11). Their structures were determined by 1D and 2D NMR spectroscopic analysis in combination with HRMS data. These compounds were assayed for Bcl-xL and Mcl-1 binding affinities. Ferrugineic acids B, C, and J (2, 3, and 10) exhibited significant binding affinity for both antiapoptotic proteins Bcl-xL (Ki = 19.2, 12.6, and 19.4 μM, respectively) and Mcl-1 (Ki = 14.0, 13.0, and 5.2 μM, respectively), and ferrugineic acid D (4) showed only significant inhibiting activity for Mcl-1 (Ki = 5.9 μM).

The benzoacronycine derivative, S23906-1, was characterized recently as a novel potent antitumor agent through alkylation of the N2 position of guanines in DNA. We show here that its reactivity towards DNA can be modulated by glutathione (GSH). The formation of covalent adducts between GSH and S23906-1 was evidenced by EI-MS, and the use of different GSH derivatives, amino acids and dipeptides revealed that the cysteine thiol group is absolutely required for complex formation because glutathione disulfide (GSSG) and other S-blocked derivatives failed to react covalently with S23906-1. Gel shift assays and fluorescence measurements indicated that the binding of S23906-1 to DNA and to GSH are mutually exclusive. Binding of S23906-1 to an excess of GSH prevents DNA alkylation. Additional EI-MS measurements performed with the mixed diester, S28053-1, showed that the acetate leaving group at the C1 position is the main reactive site in the drug: a reaction scheme common to GSH and guanines is presented. At the cellular level, the presence of GSH slightly reduces the cytotoxic potential of S23906-1 towards KB-3-1 epidermoid carcinoma cells. The GSH-induced threefold reduction of the cytotoxicity of S23906-1 is attributed to the reduced formation of lethal drug-DNA covalent complexes in cells. Treatment of the cells with buthionine sulfoximine, an inhibitor of GSH biosynthesis, facilitates the formation of drug-DNA adducts and promotes the cytotoxic activity. This study identifies GSH as a reactant for the antitumor drug, S23906-1, and illustrates a pathway by which GSH may modulate the cellular sensitivity to this DNA alkylating agent. The results presented here, using GSH as a biological nucleophile, fully support our initial hypothesis that DNA alkylation is the major mechanism of action of the promising anticancer drug S23906-1.

Four new steroids, 3-epi-gitingensine (1), N-acetylgitingensine (6), kibalaurifoline (7) and kibalaurifenone (8), along with the known paravallarine (2), 7α-hydroxyparavallarine (3), gitingensine (4), and N-methylgitingensine (5) were isolated from the leaves of Kibatalia laurifolia. Their structures were determined primarily from mass spectrometry and 2D NMR analyses. On the basis of the known absolute configurations of 2 and 4, the absolute configurations of the new compounds were proposed. Due to the structural relationships of compounds 1-8, a biosynthetic pathway was suggested. Compound 2 was cytotoxic to KB cells (IC50 12.8 μM), followed by 1 with IC50 21.2 μM.

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