•Five new monoterpenoid indole alkaloids (MIAs) together with 20 known ones were isolated from Alstonia rostrata.•A new skeletal MIA, alstrostine G was identified by spectroscopic data and ECD calculations.•Systematic phytochemical analysis partly disclosed the reticulate evolutionary relationships of MIAs.Five new alkaloids together with 20 known ones were isolated from Alstonia rostrata, and identified on the base of NMR, MS, UV and IR spectroscopic data. Additionally, alstrostine G (1) possessed an unprecedented 6/5/6/6/5/6-ring system. The analysis of those alkaloids’ biosynthetic pathway partly indicated their reticulate metabolic relationship. The research result disclosed diverse biogenesis of monoterpenoid indole alkaloids from Alstonia rostrata speciesin combination with previous reported alstrostine A.Download high-res image (85KB)Download full-size image

•Two new monoterpenoid indole alkaloids were isolated from Melodinus henryi.•1 represents the first indole alkaloids with an ester carbonyl group at C-19.•1 and 2 were evaluated for cytotoxicity against several human cancer cell lines.Two new monoterpenoid indole alkaloids, melohenryines A and B (1 and 2), along with six known indole alkaloids, were isolated from the twigs and leaves of Melodinus henryi. Structures of the new alkaloids were established by extensive spectroscopic techniques including NMR spectroscopy and mass spectrometry. Melohenryine A (1) represents the first example of monoterpenoid indole alkaloids characterized an ester carbonyl group at C-19 position. All of the new compounds were evaluated for in vitro cytotoxicity against several human cancer cell lines.Download high-res image (86KB)Download full-size image

Fourteen new limonoids, munronins A–N (1–14), and eight known limonoids (15–22) were isolated from the whole plants of Munronia henryi. The structures of the new compounds were elucidated by 2D NMR spectroscopy and mass spectrometry, and the structure of 8 was confirmed by single-crystal X-ray diffraction analysis. Compound 1 represents the first limonoid found with a novel 7-oxabicyclo[2.2.1]heptane moiety produced by incorporating C-11 and C-14 via an oxygen atom. All compounds were evaluated for their anti-tobacco mosaic virus (TMV) activity and in vitro cytotoxicity against the human cancer HL-60, SMMC-7721, A-549, MCF-7, and SW-480 cell lines. Among them, compounds 2, 8, 9, 10, 11, 12, 18, and 20 showed significant anti-TMV activity, with IC50 values in the range 19.6–44.4 μg/mL. Compounds 1 and 18 exhibited cytotoxic effects for all five cancer cell lines, with IC50 values between 0.4 and 4.8 μM.

One Myrioneuron alkaloid, myrifabine (1), the first example of a dimer with 12 chiral centers embraced in a decacyclic novel skeleton, was isolated from Myrioneuron faberi. Its structure was elucidated by spectroscopic data and single-crystal X-ray diffraction. The antimicrobial and cytotoxic activities of 1 were evaluated in vitro.

Two new bisindole alkaloids, angustifonines A (1) and B (2), comprising the union of a rearranged monoterpenoid quinoline and an aspidospermine alkaloid, as well as 27 known indole alkaloids were isolated from the twigs and leaves of Bousigonia angustifolia. Their structures and absolute configurations were elucidated by a combination of MS, NMR, and computational methods. Angustifonines A and B exhibited cytotoxicity against various human cancer cell lines with IC50 values of 2.71–16.22 μM. A possible biosynthesis pathway toward the new bisindole alkaloids 1 and 2 is presented.

•New acyclic diterpenoids from the fruits of Aphanamixis grandifolia were isolated and characterized.•The structure of nemoralisin B was revised.•All of the diterpenoids were evaluated for inhibitory activities against lipopolysaccharide-induced nitric oxide production in RAW 264.7 cells.Four new acyclic diterpenoids (i.e., nemoralisin B (1) and nemoralisins H–J (2–4)) along with three known acyclic diterpenoids (i.e., nemoralisin, nemoralisin A, and nemoralisin D) were isolated from the fruits of Aphanamixis grandifolia. Their structures were determined by extensive spectroscopic studies using NMR spectroscopy and mass spectrometry. In addition, the structure of nemoralisin B has been revised from the previously reported α,β-unsaturated δ-lactone structure to an α,β-unsaturated γ-lactone one. Nemoralisin J (4) exhibited moderate inhibitory activity against lipopolysaccharide-induced nitric oxide production in RAW 264.7 cells with an IC50 value of 9.96 μM.

Two new daphnicyclidin-type Daphniphyllum alkaloids, daphmacrodins A and B (1 and 2) were isolated from the leaves and stems of Daphniphyllum macropodum. Their structures were elucidated by extensive spectroscopic techniques, including 2D NMR spectroscopy and mass spectrometry. The relative configuration of 1 was further confirmed by a single-crystal X-ray diffraction analysis. Their cytotoxic activities against five human cancer cell lines, pesticidal activities against brine shrimp (Artemia salina), and antibacterial activities against five standard bacterial and fungal strains were evaluated. The structure of 1 was successfully transformed to 2 by a chemical method.

Daphnioldhamine A, the first Daphniphyllum alkaloid with transannular effect, easily tautomerized under acidic or alkaline conditions, was isolated from the fruits of Daphniphyllum oldhami. The structure was elucidated by spectroscopic and computational approaches and chemical transformation. A plausible biosynthetic pathway of daphnioldhamine A was also proposed.

Mekongenine A (1) possessing an unprecedented structure constituted from the union of a rare 2,7-seco eburnamine half and an aspidospermine alkaloid, together with a new bisindole alkaloid, mekongenine B (2), consisting of an eburnamine-aspidospermine type skeleton, was isolated from Bousigonia mekongensis. Their structures were elucidated by means of spectroscopic methods and those of 2 were further confirmed by X-ray diffraction. The absolute configurations of 1 and 2 were determined by comparison of quantum chemical TDDFT calculated and experimental ECD spectra. Mekongenines A (1) and B (2) exhibited cell growth inhibitory activities against various human cancer cell lines.

Four vobasinyl–ibogan type bisindole alkaloids, ervachinines A–D (1–4), along with 12 known terpenoid indole alkaloids, were isolated from the whole plant of Ervatamia chinensis. Their structures were elucidated by analysis of spectroscopic data, including 1D and 2D NMR, and the absolute configurations of 1–4 were determined by CD exciton chirality method. All of the compounds were evaluated for in vitro cytotoxicity against five human cancer cell lines: HL-60, SMMC-7721, A-549, MCF-7 and SW480. Bisindole alkaloids 1–6 exhibited inhibitory effects, with IC50 values comparable to those of cisplatin.Graphical abstractSix bisindole alkaloids including ervachinines A–D (1–4), along with 10 known indole alkaloids (5–16), were isolated from the whole plants of Ervatamia chinensis. The structures and absolute configurations of 1–4 were elucidated by a combination of spectroscopic data and CD exciton chirality method.Highlights► Six bisindole alkaloids (1–6) were isolated from Ervatamia chinensis. ► Absolute stereochemistries of 1–4 were elucidated by CD exciton chirality method. ► First report of chemical investigation of E. chinensis. ► Alkaloids 1–6 exhibited inhibitory activities against five human cancer cell lines.