Fa-Liang An

Cytotoxic Rocaglate Derivatives from Leaves of Aglaia perviridis.

Rocaglates are a series of structurally complex secondary metabolites with considerable cytotoxicity that have been isolated from plants of the Aglaia genus (Meliaceae). A new rocaglate (aglapervirisin A, 1) and its eight new biosynthetic precursors of rocaglate (aglapervirisins B-J, 2–9) together with five known compounds, were isolated from the leaves of Aglaia perviridis. Their structures were elucidated based on a joint effort of spectroscopic methods [IR, UV, MS, ECD, 1D- and 2D-NMR, HRESIMS], chemical conversion and single-crystal X-ray diffraction. Among these isolates, three (1, 10–11) were silvestrols, a rare subtype rocaglates, exhibiting notable cytotoxicity against four human tumor cell lines, with IC50 values between 8.0 and 15.0 nM. Aglapervirisin A (1) induces cell cycle arrest at the G2/M-phase boundary at concentration 10 nM accompanied by reductions in the expression levels of Cdc2 and Cdc25C in HepG2 cells after 72h co-incubation, and further induces the apoptosis of HepG2 cells at concentrations over 160 nM.

Icariside II, a natural mTOR inhibitor, disrupts aberrant energy homeostasis via suppressing mTORC1-4E-BP1 axis in sarcoma cells

The aberrant energy homeostasis that characterized by high rate of energy production (glycolysis) and energy consumption (mRNA translation) is associated with the development of cancer. As mammalian target of rapamycin (mTOR) is a critical regulator of aberrant energy homeostasis, it is an attractive target for anti-tumor intervention. The flavonoid compound Icariside II (IS) is a natural mTOR inhibitor derived from Epimedium. Koreanum. Herein, we evaluate the effect of IS on aberrant energy homeostasis. The reduction of glycolysis and mRNA translation in U2OS (osteosarcoma), S180 (fibrosarcoma) and SW1535 (chondrosarcoma) cells observed in our study, indicate that, IS inhibits aberrant energy homeostasis. This inhibition is found to be due to suppression of mammalian target of rapamycin complex 1 (mTORC1)-eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1) axis through blocking the assembly of mTORC1. Furthermore, IS inhibits the cap-dependent translation of c-myc through mTORC1-4E-BP1 axis which links the relationship between mRNA translation and glycolysis. Inhibition of aberrant energy homeostasis by IS, contributes to its in vitro and in vivo anti-proliferation activity. These data indicate that IS disrupts aberrant energy homeostasis of sarcoma cells through suppression of mTORC1-4E-BP1 axis, providing a novel mechanism of IS to inhibit cell proliferation in sarcoma cells.

Limonoids with diverse frameworks from the stem bark of Entandrophragma angolense and their bioactivities

Entangolensins A–P (1–16), sixteen new limonoids with diverse frameworks, were isolated from the stem bark of Entandrophragma angolense. Their planar structures were elucidated on the basis of spectroscopic data (HRMS, 1D/2D NMR), and the absolute configurations of most isolates were determined by the electronic circular dichroism (ECD) exciton chirality method and time-dependent density functional theory (TDDFT)/ECD calculations. Entangolensin A (1) was the first example of C-9/10-seco mexicanolide reported as a natural product. These diverse carbon skeletons, associated in a clear plausible biosynthetic pathway, indicated that the biosynthetic reactions in the title plant were varied and active. Bioactivity screening indicated that compounds 6, 12, 15 and 17 showed moderate cytotoxicities against HepG2 and MCF-7 cell lines, with IC50 values from 13.19 to 36.93 μM; meanwhile, 6, 11 and 17 exhibited significant NO inhibitory activities in LPS-activated RAW 264.7 macrophages, with IC50 values of 1.75, 7.94 and 4.63 μM.

New Structurally Diverse Limonoids from the Seeds of Khaya senegalensis

Twelve new limonoids (khasenegasins O-Z; 1-12) with three different kinds of skeletons, including eight mexicanolides, two gedunins, and two andirobins, together with four known limonoids (13-16) were isolated from the seeds of Khaya senegalensis. Their structures were determined by extensive spectroscopic analyses (HR-ESI-MS, 1D/2D NMR), and the absolute configurations of 1 and 2 were established by the electronic circular dichroism exciton chirality method. Moreover, a new andirobin-type limonoid (12) showed significant neuroprotective activity against glutamate-induced injury in primary rat cerebellar granule neuronal cells with increased viability of 83.3 ± 6.0 % at 10 µM and 80.3 ± 3.2 % at 1 µM.

Cipadessains A–K, eleven limonoids from the fruits of Cipadessa cinerascens

Eleven new mexicanolide-type limonoids, cipadessains A–K (1–11), were isolated from the fruits of Cipadessa cinerascens (Pellegr) Hand.-Mazz. Their planar structures were determined based on IR, UV, 1D and 2D NMR spectra and HRESIMS data. The absolute configuration of 1 was elucidated by single-crystal X-ray diffraction using mirror Cu Kα radiation, and that of compounds 2–8 were determined by ECD analysis. Two mexicanolides bearing methoxybutenolide moiety originated from the furan ring 3 and 6, showed significant cytotoxicity against HepG2 cell line with IC50 values of 5.23 ± 0.12, 8.67 ± 1.02 μM, respectively; and NO inhibitory activities in LPS-activated RAW 264.7 macrophages at nontoxic concentration (IC50 5.79 ± 0.18, 6.93 ± 0.89 μM, respectively).

Walrobsins A and B, Two Anti-inflammatory Limonoids from Root Barks of Walsura robusta

Walrobsins A (1) and B (2), two limonoids featuring an unprecedented 5-oxatricyclo[5.4.11,4]hendecane ring system, were isolated from the root barks of Walsura robusta. Their structures, including their absolute configurations, were determined by analyses of HR-ESIMS, 1D/2D NMR, and X-ray crystallography. Compounds 1 and 2 possessed a stable hemiketal structure formed between the OH-11 and 3-carbonyl group in the hexatomic oxoheterocyclic ring. Compound 1 showed significant anti-inflammatory activity with an IC50 value of 7.8 μM and inhibited the expression of iNOS and IL-1β in a dose-dependent manner.