•Two new pentacyclic triterpenoids were isolated from the stems of Manihot esculenta.•Two triterpenoids showed moderate cytotoxicity activity.•Two triterpenoids were cis- and trans-isomers.In recent years, we have been engaged in a program to discover secondary metabolites with fascinating structural features and significant biological activities from Euphorbiaceae family. Two new pentacyclic triterpenoids, maesculentins A (1) and B (2), were isolated from the stems of Manihot esculenta Crantz, together with eleven known ones. The structures of two new triterpenoids (1–2) were elucidated by extensive spectroscopic techniques including NMR spectroscopy and mass spectrometry. Compounds 1 and 2 were cis–trans isomers, which showed moderate cytotoxicity activity against HGC-27 tumour cell line.

Two new compounds, maniesculentins A (1) and B (6), together with four known ones were isolated from the stems of Manihot esculenta Crantz. The structures of the new compounds were elucidated by extensive spectroscopic methods including NMR spectroscopy and mass spectrometry. The two new compounds (1, 6) were assayed for antibacterial activity against four tested bacteria lines.

•Eight indole alkaloids from Melodinus cochinchinensis were identified.•One is a dimeric bisindole alkaloid with an unusual 6–3′ interunit linkage.•Two of the isolated alkaloids display cytotoxic activity against five human cancer cell lines.Eight indole alkaloids, melosines A–H, together with 13 known alkaloids, were isolated from the fruits of Melodinus cochinchinensis. The structure elucidation of isolated secondary metabolites was based on comprehensive spectroscopic data analysis. Melosine B showed moderate cytotoxic activity against five human cancer cell lines, HL-60, SMMC-7721, A-549, MCF-7, and SW480 with IC50 values ranging from 1.6 to 8.1 μM.Structures and cytotoxic activity of eight indole alkaloids, including three bisindole alkaloids and five monomers, were reported from the fruits of Melodinus cochinchinensis. Compound 1 has a hitherto unknown form of dimeric linkage in aspidosperma–aspidosperma-type bisindole alkaloids, and compounds 2 and 8 showed moderate cytotoxicity against five human cancer cell lines.

Eight new aphanamixoid-type aphanamixoids (C–J, 1–8) and six new prieurianin-type limonoids, aphanamixoids K–P (9–14), along with 10 known terpenoids were isolated from Aphanamixis polystachya, and their structures were established by spectroscopic data analysis. Among the new limonoids, 13 compounds exhibited antifeedant activity against the generalist Helicoverpa armigera, a plant-feeding insect, at various concentration levels. In particular, compounds 1, 4, and 5 showed potent activities with EC50 values of 0.017, 0.008, and 0.012 μmol/cm2, respectively. On the basis of a preliminary structure–activity relationship analysis, some potential active sites in the aphanamixoid-type limonoid molecules are proposed.

•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.

Myriberine A (1) possessing an unprecedented carbon skeleton was isolated from Myrioneuron faberi. The structure and absolute configuration of 1 were elucidated by a combination of spectroscopic data, X-ray crystallographic, and computational methods. Myriberine A (1) demonstrated inhibition against the hepatitis C virus (HCV) life cycle in vitro.

Eleven new limonoids, turrapubins A–K (1–11), and three new triterpenoids (12–14), along with 14 known compounds, were isolated from the twigs of Turraea pubescens. The structures of 1–14 were elucidated on the basis of NMR and MS analysis. Compounds 12, 16, 18, and 19 exhibited inhibitory activities against lipopolysaccharide-induced nitric oxide production in RAW264.7 cells. In addition, compounds 2, 11, 18, and 26 exhibited inhibitory activities against brine shrimp larvae (Artemia salina) at 100 ppm with the corrected mortality ranging from 81.7% to 100%.

•New flavonols (1–2) were isolated from Indigofera stachyodes.•Compound 2 was the flavonol characteristic of a 3-nitropropanoyl moiety.•2 and 3 exhibited good protective effect on CCl4-induced hepatotoxicity to HL-7702.A new flavan dimer, 2α,3α-epoxyflavan-5,7,3′,4′-tetraol-(4β→8)-flavan-5′′,7′′,4′′′-triol (1), and a new flavonol, 3-O-(3-nitropropanoyl)-2,3-cis-5,7,3′,4′-tetrahydroxyflavan (2), together with a known compound, 2α,3α-epoxy-5,7,3′,4′-tetrahydroxyflavan-(4β→8)-epicatechin (3), were isolated from the roots of Indigofera stachyodes. Their structures were elucidated by spectroscopic techniques including MS, 1D NMR, and 2D NMR. Compounds 2 and 3 were evaluated to determine their protective effects against carbon tetrachloride (CCl4)-induced hepatotoxicity in the human liver cell line HL-7702. The results showed that 2 and 3 could protect HL-7702 cells from injury induced by CCl4, with cell survival rates of 122.0% and 72.5%, respectively.

Phytochemical investigation of aerial parts of Glochidion assamicum Hook. f. led to the isolation of one new triterpenoid saponin, 3-O-[β-glucopyranosyl-(1→3)-α-arabinopyranosyl]-gymnestrogenin (assamicoside A, 7), and ten known compounds (1–6, 8–11). Their structures were identified by spectroscopic analysis and by comparison of their spectral data with those reported in the literature. The chemotaxonomic analysis is in agreement with previous work on the constituents of other Glochidion species. A spirostane-type C27 steroid (4) isolated from G. assamicum for the first time can be used to differentiate this species from other Glochidion.Highlights► Eleven compounds were isolated from Glochidion assamicum for the first time. ► One new triterpenoid saponin was isolated from G. assamicum. ► A spirostane-type C27 steroid was first obtained from the genus Glochidion. ► Lupane-type triterpenes may be useful chemotaxonomic markers for the genus Glochidion. ► The presence of the C27 steroid will be chemotaxonomically significant for G. assamicum.

Highlights•Thirteen daphnane-type diterpenoids were isolated from the stems of Trigonostemon lii.•The absolute stereochemistries of trigolins A–G were elucidated by CD spectra.•Eleven of the dapahnane compounds possess a rare 4, 6-oxetane moiety in the family of daphnane diterpenoids.•Four of the compounds displayed modest anti-HIV-1 activity in vitro.Thirteen highly oxygenated daphnane diterpenoids, including six known compounds, were isolated from the stems of Trigonostemon lii. The structures were elucidated by extensive spectroscopic analyses including 2D NMR spectroscopy (HSQC, 1H–1H COSY, HMBC, and ROESY) and mass spectrometry. The absolute stereochemistries of compounds were established on the basis of CD spectra. Four of the compounds showed modest anti-HIV-1 activity (EC50 = 2.04, 9.17, 11.42, and 9.05 μg/ml, TI = 26.49, >21.81, 9.32, and 9.56, respectively) in vitro.Seven daphnane diterpenoids named trigolins A–G (1–7), along with six known diterpenoids (8–13), were isolated from an acetone extract of the stems of Trigonostemon lii. The absolute stereochemistries of compounds 1–7 were elucidated by CD spectra.

Aphanamixoid A (1), a limonoid with a new carbon skeleton, along with its biogenetically related limonoid aphanamixoid B (2), was isolated from the leaves and twigs of Aphanamixis polystachya. Their structures with the absolute stereochemistry were determined by spectroscopic analysis, X-ray crystallography and computational methods. The significant antifeedant activity of 1 against the generalist plant-feeding insect Helicoverpa armigera (EC50 = 0.015 μmol/cm2) suggested it may be a potent defensive component of A. polystachya.

The investigation of the seeds of Strychnos nux-vomica led to the isolation of two novel indole alkaloids, strynuxlines A (1) and B (2), with an unprecedented 6/5/9/6/7/6 hexacyclic ring system. Their structures and absolute configurations were elucidated on the basis of their MS, NMR, and ECD data. A plausible biosynthesis pathway of 1 and 2 is also proposed.

Trigoflavidols A (1) and B (2), tetranorditerpenoid dimers possessing a rearrangement skeleton with a spiroketal core moiety, and trigoflavidol C (3), a hexanorditerpenoid, have been isolated from Trigonostemon flavidus along with two known compounds. Compounds 1 and 2 showed moderate antimicrobial activities (MIC values: 3.12–6.25 μg/mL) against Staphylococcus aureus, 8#MRSA, and 82#MRSA, and 1, 2, and 5 showed weak activities (IC50 values: 3.75–28.99 μM) against various human tumor cell lines.

Two new degraded diterpenoids, trigohowilols A (1) and B (2), four new heterodimers, trigohowilols C–F (3–6), one new homodimer, trigohowilol G (7), and three known degraded diterpenoids (8–10) were isolated from the methanol extract of the stems of Trigonostemon howii. Compounds 1–7 were evaluated for their cytotoxic activity against five human tumor cell lines by an MTT assay, and trigohowilols E (5) and F (6) exhibited inhibitory activity with IC50 values ranging from 2.33 to 12.57 μM. Moreover, compounds 1–6 showed weak antimicrobial activities (MIC values: 6.25–25 μg/mL) against Staphylococcus aureus, Pseudomonas aeruginosa, MRSA 92#, and MRSA 98# using a 2-fold dilution method.

A phytochemical work on the alkaloid constituents from Trigonostemon lii Y.T. Chang was conducted to give six new β-carboline alkaloids, trigonostemines A–F (1–6) and eight known β-carboline alkaloids (7–14). Their structures were elucidated by extensive spectroscopic techniques including 2D NMR experiments and mass spectrometry. All of the compounds were evaluated for their cytotoxic activities against the HL-60, SMMC-7721, A-549, MCF-7, and SW480 human cancer cell lines. Trigonostemines A and B (1 and 2) exhibited stronger inhibitory activities than the positive control (cisplatin) in some cell lines.Fourteen β-carboline alkaloids, including six new ones, were isolated from the leaves of Trigonostemon lii. Trigonostemines A and B (1 and 2) showed stronger inhibitory activities than cisplatin in some human cancer cell lines.

Two new tirucallane triterpenoids, 2 α-ethoxy-2,3-secotirucalla-2,29-epoxy-7-ene-23-oxo-3-oic acid (1) and (23E)-2 α-hydroxytirucalla-7,23,25-triene-3-one (2), along with the known 2,3-secotirucalla-2,3;2,29-diepoxy-7-ene-3,23-dione (3), were isolated from the leaves and twigs of Aphanamixis grandifolia. Their structures were elucidated by extensive NMR and MS data, and compound 3 was further confirmed by X-ray crystal diffraction analysis. Antimicrobial activities and insecticidal activities of these three compounds were also evaluated. Compound 1 showed good antimicrobial activity against Staphylococcus aureus with the MIC value of 1.56 µg/mL, while compounds 1 and 2 showed insecticidal activity at 100 ppm, with the corrected mortality 79.1% and 60.6%, respectively.

Phytochemical study of the roots of Trigonostemon thyrsoideum led to the isolation of four new oxygenated daphnane-type diterpenoids, trigonosins A−D (1−4), and two new modified daphnanes, trigonosins E and F (5 and 6). The structures and relative configurations were elucidated on the basis of extensive spectroscopic analysis, including 1D and 2D NMR experiments. All compounds isolated were evaluated for their cytotoxicity against HL-60, A549, and MCF-7 human cancer cell lines.

Seven new neoclerodane diterpenoids, scutebatas A−G (1−7), have been isolated from Scutellaria barbata. Compounds 1−3 possess a rare α-hydroxy group in their α,β-unsaturated lactone rings. Their structures were elucidated by spectroscopic analysis, and the relative configuration of scutebata A was deduced using ROESY data and the computational DFT method. Compounds 1, 2, 4, 5, and 6 were evaluated for in vitro cytotoxicity against six human cancer cell lines: HL-60, SMMC-7721, A-549, SK-BR-3, CACO-2, and PANC-1. Scutebata A (1) showed weak cytotoxicity against SK-BR-3 with an IC50 value of 15.2 μM.

Two novel monoterpenoid indole alkaloids, aminocadambines A (1) and B (2), characterized by tetrahydrofuran and 1,2,3,4-tetrahydropyridine rings, were isolated from the leaves of Neolamarckia cadamba. Their structures were elucidated on the basis of spectroscopic and computational methods. The absolute configuration of 1 was established by CD analysis. A plausible biosynthetic pathway for 1 and 2 is proposed.

A new isoflavonolignan has been isolated from the Pueraria alopecuroides Craib. The structure was elucidated by the combination of 1D, 2D NMR analysis and mass spectrometry.