Macroline, talpinine, and sarpagine alkaloids from Alstonia penangiana. An NMR-based method for differentiating between A. penangiana and A. macrophylla

Engaging Isatins and Amino Acids in Multicomponent One-Pot 1,3-Dipolar Cycloaddition Reactions-Easy Access to Structural Diversity

Multicomponent reactions (MCRs) have undoubtedly emerged as the most indispensable tool for organic chemists worldwide, finding extensive utility in the synthesis of intricate natural products, heterocyclic molecules with significant bioactivity, and pharmaceutical agents. The multicomponent one-pot 1,3-dipolar cycloaddition reactions, which were initially conceptualized by Rolf Huisgen in 1960, find extensive application in contemporary heterocyclic chemistry. In terms of green synthesis, the multicomponent 1,3-dipolar cycloaddition is highly favored owing to its numerous advantages, including high step- and atom-economies, remarkable product diversity, as well as excellent efficiency and diastereoselectivity. Among the numerous pieces of research, the most fascinating reaction involves the utilization of azomethine ylides generated from isatins and amino acids that can be captured by various dipolarophiles. This approach offers a highly efficient and convenient method for constructing spiro-pyrrolidine oxindole scaffolds, which are crucial building blocks in biologically active molecules. Consequently, this review delves deeper into the dipolarophiles utilized in the 1,3-dipolar cycloaddition of isatins and amino acids over the past six years.

Monoterpene Indole Alkaloids with Cav3.1 T-Type Calcium Channel Inhibitory Activity from Catharanthus roseus

Catharanthus roseus is a well-known traditional herbal medicine for the treatment of cancer, hypertension, scald, and sore in China. Phytochemical investigation on the twigs and leaves of this species led to the isolation of two new monoterpene indole alkaloids, catharanosines A (1) and B (2), and six known analogues (3–8). Structures of 1 and 2 were established by ¹H-, ¹³C- and 2D-NMR, and HREIMS data. The absolute configuration of 1 was confirmed by single-crystal X-ray diffraction analysis. Compound 2 represented an unprecedented aspidosperma-type alkaloid with a 2-piperidinyl moiety at C-10. Compounds 6–8 exhibited remarkable Ca_v3.1 low voltage-gated calcium channel (LVGCC) inhibitory activity with IC₅₀ values of 11.83 ± 1.02, 14.3 ± 1.20, and 14.54 ± 0.99 μM, respectively.

The Bisindole Alkaloids Angustilongines M and A from Alstonia penangiana Induce Mitochondrial Apoptosis and G0/G1 Cell Cycle Arrest in HT-29 Cells through Promotion of Tubulin Polymerization

A new linearly fused macroline-sarpagine bisindole, angustilongine M (1), was isolated from the methanolic extract of Alstonia penangiana. The structure of the alkaloid was elucidated based on analysis of the spectroscopic data, and its biological activity was evaluated together with another previously reported macroline-akuammiline bisindole from the same plant, angustilongine A (2). Compounds 1 and 2 showed pronounced in vitro growth inhibitory activity against a wide panel of human cancer cell lines. In particular, the two compounds showed potent and selective antiproliferative activity against HT-29 cells, as well as strong growth inhibitory effects against HT-29 spheroids. Cell death mechanistic studies revealed that the compounds induced mitochondrial apoptosis and G0/G1 cell cycle arrest in HT-29 cells in a time-dependent manner, while in vitro tubulin polymerization assays and molecular docking analysis showed that the compounds are microtubule-stabilizing agents, which are predicted to bind at the β-tubulin subunit at the Taxol-binding site.