Bousmekines A-E, New Alkaloids from Two Bousigonia Species: B.angustifolia and B. mekongensis

Corydecusines A-H, new phthalideisoquinoline hemicetal alkaloids from the bulbs of Corydalis decumbens inhibit Tau pathology by activating autophagy mediated by AMPK-ULK1 pathway

Twelve phthalideisoquinoline hemiacetal alkaloids including eight new ones (1-8) and one natural alkaloid characterized by an aziridine moiety with unassigned NMR data (9), were isolated and identified from the bulbs of Corydalis decumbens. Their structures were established by comprehensive analyses of HRESIMS, NMR, X-ray crystallography, and ECD analyses. The unambiguously established structures of the phthalideisoquinoline hemiacetal alkaloids indicated that the absolute configurations of C-1, C-9, and C-7' were confusable only relied on coupling constants. A summary of their ECD spectra was concluded and provided an insight for C-1, C-9, and C-7' absolute configuration assignment. These new compounds were evaluated to induce autophagy flux through flow cytometry analysis. Moreover, compounds 2 and 6 could significantly induce autophagy and inhibit Tau pathology by AMPK-ULK1 pathway activation, which provided an avenue for anti-AD lead compounds discovery.

Two new monoterpenoid indole alkaloids from the kernels of Kopsia arborea

Two new monoterpenoid indole alkaloids, (2 R, 7 R, 16 R, 20 R, 21S)-12-hydroxypleiocarpine (1) and (2S, 7 R, 16S, 20 R, 21S)-N-methoxycarbonyl-11,12-methylenedioxy-Δ^14,15-kopsinaline (2), along with six known alkaloids were isolated from the methanol extract of the kernels of Kopsia arborea. Their structures including the absolute configurations were elucidated by HRESIMS, NMR spectroscopy, and quantum computational methods. Their cytotoxicity against two human cancer cell lines were also evaluated.

The current scenario of naturally occurring indole alkaloids with anticancer potential

Naturally occurring indole alkaloids are ubiquitously present in nature and possess extensive biological properties and structural diversity. Mechanistically, naturally occurring indole alkaloids have the potential to inhibit cancer cell proliferation, arrest cell cycle and induce apoptosis. Accordingly, naturally occurring indole alkaloids exhibit promising activity against both drug-sensitive and drug-resistant cancers including multidrug-resistant forms. Therefore, naturally occurring indole alkaloids constitute an important source of anticancer drug leads and candidates. The goal of this review is to highlight the current scenario of naturally occurring indole alkaloids with anticancer potential, covering articles published from 2018 to present. The names, sources, and antiproliferative activity are discussed to continuously open up a map for the remarkable exploration of more effective candidates.

Monoterpenoid indole alkaloid dimers from Kopsia arborea inhibit cyclin-dependent kinase 5 and tau phosphorylation

Three undescribed monoterpenoid indole alkaloid dimers (kopoffines A-C, which are connected via a methylene unit) and with nine known alkaloids were isolated and identified from the fruits of Kopsia arborea Blume. Their structures, including their absolute configurations, were established by HRESIMS, NMR, single-crystal X-ray diffraction, and ECD analyses. Kopoffines A-C showed significant inhibition against cyclin-dependent kinase 5 (IC₅₀: 0.34-2.18 μM). Western blotting analyses showed that kopoffines A-C significantly decreased the protein levels of CDK5 and phospho-CDK5 (Tyr15) (pCDK5) at concentrations of 2.5 and 10 μM. The levels of phospho-Tau (Thr217) (pTau217, a new biomarker of AD), and phospho-Tau (Ser396) (pTau396), which play major roles in the formation of neurofibrillary tangles , were decreased by the kopoffines A-C treatment. Molecular docking studies indicated that kopoffines A-C could form stable interactions with CDK5.

Taberdines L and M, two new alkaloids from Tabernaemontana divaricata

Two new alkaloids, taberdines L (1) and M (2), together with six known alkaloids, were isolated from the twigs and leaves of Tabernaemontana divaricata. Taberdine L (1) represents the first optically active natural member of the allo iboga class of alkaloids with the ethyl side chain in a bridgehead position. Their structures including absolute configuration were elucidated by a combination of MS, NMR, and ECD calculation. The in vitro cytotoxic activities of 1 and 2 against five human cancer cell lines were also evaluated.

New Secodaphnane-Type Alkaloids with Cytotoxic Activities from Daphniphyllum angustifolium Hutch

One new Daphniphyllum alkaloid, daphnioldhanol A (1), together with three known ones, were isolated from the stem part of Daphniphyllum angustifolium Hutch. Their structures were elucidated by spectroscopic methods and comparing with the literature data. Compound 2 is a new natural product, but known by synthesis as a racemate. Compound 1 exhibited week cytotoxic activity against Hela cell line with IC₅₀ of 31.9 μM.