Phytochemical investigations on the flower of Erythrina arborescens resulted in the isolation of eight new Erythrina alkaloid, erytharborines A–H (1–8), together with 17 known alkaloids. Erytharborines A/B (1–2) and C (3) possessed an 2H-imidazole ring and a unique oxime moiety, respectively. The structures were elucidated on the basis of UV, IR, mass spectrometry and NMR spectroscopic data.

•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

Five monoterpenoid indole alkaloids, namely meloyines A-B (1–2), meloyines II-III (3–4), and 10-O-glucosyl-scandine (5) together with thirty-four known alkaloids were isolated from leaves and twigs of Melodinus yunnanensis. Alkaloid 1 was characterized as an unprecedented skeleton with a 6/5/5/6/6/4 ring system, and alkaloids 3–4 were dimeric monoterpenoid quinolone alkaloids. Their structures were elucidated based on 1D and 2D- NMR, FTIR, UV, and MS spectroscopic data. The cytotoxic activity of new alkaloids were evaluated against three human cancer cell lines.Download high-res image (134KB)Download full-size image

•Two new alkaloids were isolated from Cephalotaxus oliveri and C. lanceolata.•Cephalolancine A features a new skeleton-type.•The discovery of both alkaloids provides direct biogenetic evidences of Cephalotaxus alkaloids.Two new Cephalotaxus alkaloids, (±)-cephaloliverine A (1) and cephalolancine A (2) were isolated from Cephalotaxus oliveri and Cephalotaxus lanceolata respectively. Their structures were determined on the basis of spectroscopic techniques including NMR, IR, UV, mass spectrometry, and X-ray diffraction. Cephalolancine A (2) features a new skeleton-type. The discovery of these alkaloids provides biogenetic evidences of the formation of Cephalotaxus alkaloids.

Five new alkaloids (1–5) were isolated from the leaves and twigs of Cephalotaxus lanceolata and C. fortunei var. alpina along with 24 known alkaloids. The new structures were elucidated based on spectroscopic data including 1D and 2D NMR, FTIR, UV and MS. These new alkaloids showed no cytotoxicity to HeLa, SGC-7901 gastric cancer, and A-549 lung cancer cell lines.

•O-Acetyl-7-methoxycamptothecin was reported as a new compound.•A new natural compound, 10-hydroxy-9-methoxycamptothecin, was reported.•The chemotaxonomic significance of Nothapodytes foetida and N. pittosporoides was discussed.•Mappicine and its derivatives as well as isocoumarins are key chemotaxonomic markers of the species.A new alkaloid, O-acetyl-7-methoxycamptothecin (1), was isolated from the roots of Nothapodytes pittosporoides (Icacinaceae), together with seventeen known compounds (2–18). The structures of these compounds were identified by extensive spectroscopic interpretation. Isocoumarins were reported from the investigated genus for the first time. The alkaloids and isocoumarins in N. pittosporoides could serve as its chemotaxonomic markers.

By emitting strong scents resembling rotting organic materials suitable for oviposition and/or foraging of flies, sapromyiophilous flowers mimic the substrates that attract flies as pollinators. It has been suggested that the wide range of volatile organic compounds emitted by this deceptive pollination system reflects the trophic preferences of flies to different types of substrate, including herbivore and carnivore feces, carrion, and fruiting bodies of fungi. Previous studies suggest that floral scents play a particularly important role in sapromyiophily. However, few studies on the relative importance of floral color or synergy between visual and olfactory cues in sapromyiophily have been substantiated. In this study, we analyzed fetid floral odor, floral pigment composition, and reflectance of an Amorphophallus konjac C. Koch inflorescence, and we conducted bioassays with different visual and/or olfactory cues to explore an unsubstantiated color profile in sapromyiophily: mimicking livor mortis. Our analysis showed A. konjac can emit oligosulphide-dominated volatile blends similar to those emitted by carrion. Necrophagous flies cannot discriminate between the color of an inflorescence, livor mortis, and floral pigments. We concluded that mimicking livor mortis may represent a common tactic of pollinator attraction in “carrion flower” systems within angiosperms.

•Monoterpenoid indole alkaloids (MIAs) have been a focus of natural products research.•Six bisindole and two monomeric MIAs were isolated from T. officinalis.•Voaphylline–vobasinyl type alkaloids were previously unknown structural types, and four vobasinyl–ibogan type bisindole alkaloids showed activity against human cancer cell lines.Continued interest in cytotoxic alkaloids resulted in the isolation of 37 alkaloids including 29 known monoterpenoid indole alkaloids from the aerial parts of Tabernaemontana officinalis. Of the remaining 8 alkaloids, six were bisindole alkaloids named taberdivarines A–F (1–6) and the two were monomers named taberdivarines G and H (7–8). Alkaloids 1 and 2 are voaphylline–vobasinyl type bisindole alkaloids, a structural type previously unknown, while 3–6 exhibited cytotoxicity against three human cancer cell lines HeLa, MCF-7, and SW480 with IC50 values ranging from 1.42 to 11.35 μM.Tabernaemontana officinalis alkaloids were elucidated as six dimeric indole alkaloids taberdivarines A–F (1–6) and two monomers taberdivarines G–H (7–8). Alkaloids 1–2 were the first reported voaphylline–vobasinyl type dimers, while 3–6 exhibited the cytotoxicity.

Unprecedented dimeric Erythrina alkaloids, spirocyclic (6/5/6/6) erythrivarine A (1) and spiro-fused (6/5/7/6) rings erythrivarine B (2), were isolated from the cultivated plant, E. variegata. The structures were determined on the basis of 1D and 2D NMR, FTIR, UV, and mass spectroscopic data and X-ray crystal diffraction. The biogenetic relationship of 1 and 2 is proposed.

Five new vobasinyl–ibogan-type bisindole alkaloids, tabernaricatines A–E (1–5), two new monomers, tabernaricatines F and G (6 and 7), and 24 known indole alkaloids were isolated from the aerial parts of Tabernaemontana divaricata. Alkaloids 1 and 2 are the first vobasinyl–ibogan-type alkaloids possessing a six-membered ring via an ether linkage between C-17 and C-21. All compounds except for 3 were evaluated for their cytotoxicity against five human cancer cell lines; conophylline showed significant bioactivity against HL-60, SMMC-7721, A-549, MCF-7, and SW480 cells with IC50 values of 0.17, 0.35, 0.21, 1.02, and 1.49 μM, respectively.

Eight new bisindole alkaloids, melosuavines A–C (1–3), having an aspidosperma-scandine linkage, melosuavines D–F (4–6), possessing an aspidosperma-aspidosperma skeleton, and melosuavines G and H (7 and 8) of the aspidosperma-venalatonine type, tenuicausine (9), and melodinine J (10) were isolated from the twigs and leaves of Melodinus suaveolens. The structures of 1–8 were elucidated by extensive spectroscopic methods, and compounds 9 and 10 were identified by comparison with data in the literature. The relative configuration 9 was determined from the ROESY spectrum, and some NMR signals were reassigned. Compounds 1, 2, 4–6, 8, and 10 exhibited low micromolar cytotoxicity against one or more of five human cancer cell lines.

Ten monoterpenoid indole alkaloids, namely meloyine, 19S-methoxytubotaiwine N4-oxide, 16,19-epoxy-Δ14-vincanol, 14β-hydroxymeloyunine, meloyunine, Δ14-vincamenine N4-oxide, 16β,21β-epoxy-vincadine, 14β,15β-20S-quebrachamine, 3-oxo-voaphylline, 2α,7α-dihydroxy-dihydrovoaphylline, and 32 known alkaloids were isolated from leaves and twigs of Melodinus yunnanensis. Their structures were elucidated based on 1- and 2-D NMR, FTIR, UV, and MS spectroscopic data. Meloyine I showed weak cytotoxic activity against four human cancer cell lines: MCF-7 breast cancer, SMMC-7721 hepatocellular carcinoma, HL-60 myeloid leukemia, and A-549 lung cancer.Graphical abstractTen new monoterpenoid indole alkaloids, together with thirty two known compounds were firstly isolated from Melodinus yunnanensis. All structures were elucidated based on NMR, FTIR, UV, and MS spectroscopic data. Meloyine I showed activity against four human cancer cell lines.Highlights► Melodinus species have been shown to be good sources of MIAs. ► Ten monoterpenoid indole alkaloids, MIAs, together with 32 known alkaloids were isolated from M. yunnanensis endemic to Yunnan. ► A bisindole alkaloid showed activity against four human cancer cell lines, HL-60, SMMC-7721, A-549, and MCF-7.