Cytotoxic azaphilone alkaloids from Chaetomium globosum TY1

Three novel azaphilone alkaloids, namely chaetomugilides A–C (1–3), together with three related compounds (4–6) were isolated from the methanol extract of Chaetomium globosum TY1, an endophytic fungus isolated from Ginkgo biloba. Their structures were elucidated on the basis of extensive 1D and 2D NMR as well as HRESI-MS spectroscopic data analysis. The isolated compounds exhibited highly cytotoxic activities against human cancer cell line HePG2 with the IC₅₀ values range from 1.7 to 53.4 μM.     

Phytochemical and chemotaxonomic study on Dictamnus angustifolius G. Don ex Sweet (Rutaceae)

A phytochemical investigation of Dictamnus angustifolius led to the isolation of 14 compounds, including six furoquinoline alkaloids (1–6), two sesquiterpenoids (7, 8) and six flavonoids (9–14). The structures of these compounds were identified by spectroscopic methods and a comparison of their data with those reported in the literature. This is the first report of three furoquinoline alkaloids 1–3 and six flavonoids 9–14 from the genus Dictamnus and the first isolation of compounds 4–8 from D. angustifolius. The chemotaxonomic significance of furoquinoline alkaloids and sesquiterpenoids has also been summarized.     

Prenylated indole alkaloids from the stem bark of Hexalobus monopetalus

Seven new prenylated indole alkaloids (1–7) together with two known compounds (8–9) were isolated from the stem bark of Hexalobus monopetalus. Their structures were established on the basis of comprehensive spectroscopic analysis, including HR-MS, 1D and 2D NMR and by comparison of their spectral data with those reported in literature. The new compounds were tested for antimicrobial activity against selected pathogenic bacteria and fungi but showed no activity. The marked presence of prenylated indole alkaloids in Hexalobus and closely related genera makes them useful chemotaxonomic markers.     

New furanopyridine alkaloids from the leaves of Glycosmis pentaphylla

Three new furanopyridine alkaloids, namely glypenfurans A–C (1–3), were isolated from the leaves of Glycosmis pentaphylla together with six known furoquinoline alkaloids. Their structures were determined by extensive spectral analysis (UV, IR, MS, 1D and 2D NMR).     

Chemical constituents of Melodinus hemsleyanus diels

Phytochemical investigation on the aerial parts of Melodinus hemsleyanus diels (Jahrb, Syst, 1995) led to the isolation and identification of 27 compounds, including fifteen aspidosperma-type alkaloids (1–15), four quinoline-type alkaloids (16–19), three quebrachamine-type alkaloids (20–22), and five eburna-type alkaloids (23–27). The structure of compound 1 was elucidated by means of spectroscopic analysis, including HRESIMS, and 1D and 2D NMR experiments. Compounds 1–2, 6, 10, 12, 13, 15, 16 and 20–27 are herein reported for the first time from the studied plant, while the compounds 1–2 and 21 have not previously been recorded in the genus Melodinus. The aspidosperma-type monoterpenoid indole alkaloids in M. hemsleyanus could serve as chemotaxonomic markers.     

Chemical constituents of Gardneria ovata wall

A phytochemical investigation on the aerial parts of Gardneria ovata Wall resulted in the isolation and identification of 14 compounds, including three gardneria glycoalkaloids (1–2 and 6), seven gardneria alkaloids (3–5 and 7–10), and four oxindole alkaloids (11–14). The structure of compound 1 was elucidated by means of spectroscopic analysis, including HRESIMS together with 1D and 2D NMR experiments. Compounds 1–2 and 11–14 are the first time reported from of G. ovate, while the compounds 3–4, 6, and 8 are also the characteristic secondary metabolites of the title plant. The chemotaxonomic significance and distribution of these monoterpenoid indole alkaloids in Gardneria genus are discussed.     

Indole alkaloids from Ervatamia chinensis

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.     

Carbazole alkaloids and coumarins from Clausena lansium roots

Two new carbazole alkaloids, mafaicheenamines D (1) and E (2), together with twelve known compounds (3–14) were isolated from the roots of Clausena lansium. Spectroscopic methods, including NMR, UV, IR, and MS spectral data were used for structural characterization. Some of isolates were evaluated for their cytotoxicity against three human cancer cell lines (KB, MCF-7, and NCI-H187).     

Monoterpenoid indole alkaloids from Kopsia hainanensis Tsiang

A phytochemical investigation on the twigs and leaves of Kopsia hainanensis Tsiang resulted in the isolation and identification of 18 alkaloids, including two sarpagine type alkaloids (1 and 2), five eburnane type alkaloids (3–7), three aspidofractinine type alkaloids (8–10), one vincadine type alkaloid (11), three akuammiline type alkaloids (12–13 and 15), one corynanthean type alkaloid (14), two ajmalicine-like type alkaloids (16 and 17), and one aspidospermine type alkaloid (18). The new structure of compound 1 was elucidated by means of spectroscopic analysis, including HRESIMS, and 1D and 2D NMR experiments. Compounds 1–2, 4–5, 7, and 10–17 are herein reported for the first time from this plant, while the compounds 1, 2, 7, and 12–17 have not been previously recorded in the Kopsia genus. The chemotaxonomic significance and distribution of these monoterpenoid indole alkaloids in Kopsia genus are discussed.     

Chemical Constituents of Dactylicapnos torulosa and Their Antithrombotic Activities

Dactylicapnos torulosa (D. torulosa) has been traditionally used as a therapeutic remedy. Here, a combined strategy using both phytochemical and biological approaches was conducted to discern the effective components of D. torulosa. Three new alkaloids, namely, (1–3), Torulosine A, 1-Methoxypseudoprotopine and 1,14-Dimethoxyprechilenine together with 33 (4–36) known compounds were isolated. The structures of the new compounds were fully established by extensive analysis of HR-ESI-MS NMR and CD spectroscopic data. These compounds were then screened using zebrafish bioassay methods for antithrombotic activities. Compounds 5 and 7 had the best antithrombotic effect with prevention rates of 100% at 50 μM, and Compounds 8, 4, 9 and 11 at 50 μM had prevention rates of 81.3%, 79.4%, 84.4% and 79.3%, respectively. The antithrombotic effect of compounds may be related to their inhibitory effect on platelet aggregation. The present study contributes to the diverse chemical and bioactivity data of the Dactylicapnos genus.     

Chemical constituents from the fruits of Zanthoxylum bungeanum and their chemotaxonomic significance

The phytochemical study of the fruits of Zanthoxylum bungeanum Maxim led to the isolation of sixteen compounds, including a new compound zantharin (1) and fifteen other known compounds, which consist of ten coumarins (2–11), three alkaloids (12–14), and two phenols (15–16). Their structures were elucidated based on extensive spectroscopic methods (1D and 2D NMR, HRESIMS, UV, and IR experiments) and by comparison with literature data. In this work, all the compounds were isolated from Z. bungeanum for the first time, in which, compounds 5 and 13–16 were reported for the first time from the genus Zanthoxylum and the Rutaceae family, respectively. Moreover, the chemotaxonomic significance of isolated compounds is discussed.     

Tetrahydro-β-Carboline alkaloids from Carthamus tinctorius L. with tyrosinase inhibitory activity

Phytochemical research on the dry flower of Carthamus tinctorius L. led to the isolation of two new epimeric tetrahydro-β-carboline alkaloids (1 and 2), together with three known analogues (3–5). Their planar structures were determined by comprehensive 1D, 2D-NMR, and HR-ESI–MS spectroscopic data analyses. The absolute configurations of alkaloids 1 and 2 were assigned by comparing their experimental electronic circular dichroism (ECD) curves with the calculated ECD data. To investigate their impact on melanogenesis, all of the alkaloids isolated were tested for their tyrosinase inhibitory activity and alkaloid 4 was found to inhibit tyrosinase with an IC₅₀ value of 0.17 mM, compared with 0.18 mM for arbutin. The putative binding interactions between the compounds and tyrosine were studied by molecular docking to provide an explanation for their inhibitory activities, and the results obtained indicated that hydrophobic interactions played a very significant role in the combination.     

Five new C19-diterpenoid alkaloids from Aconitum carmichaeli

Five new aconitine-type C₁₉-diterpenoid alkaloids, namely, carmichaenine A–E (1–5), and six known diterpenoid alkaloids, namely, 14-benzoylneoline (6), neoline (7), 10-hydroxyneoline (8), neolinine (9), songoramine (10), and songorine (11), were isolated from the aerial parts of Aconitum carmichaeli. Their structures were determined by extensive spectroscopic methods, especially 2D NMR analyses. Compounds 8 and 9 were isolated for the first time from A. carmichaeli.     

Two new alkaloid metabolites produced by endophytic fungus Stagonosporopsis oculihominis isolated from Dendrobium huoshanense

Two new alkaloids (1–2), together with six known compounds (3–8), were isolated from cultures of the endophytic fungus Stagonosporopsis oculihominis. Their structures were elucidated through extensive spectroscopic methods including 2D NMR and HRMS analyses. The absolute configurations of 1 was determined by the comparison of experimental and theoretical electronic circular dichroism spectra. The new compounds were investigated for their cytotoxicity against five human cancer cell lines.     

Venezuelines A–G,new phenoxazine-based alkaloids and aminophenols from Streptomyces venezuelae and the regulation of gene target Nur77

Five new phenoxazine-based alkaloids venezuelines A–E (1–5) and two new aminophenols venezuelines F–G (6–7), as well as three known analogues exfoliazone, chandrananimycin D and carboxyexfoliazone were isolated from the fermentation broth of the marine-derived bacterium Streptomyces venezuelae. The structures of new compounds were determined on the basis of extensive spectroscopic analysis. The cytotoxic activity of these compounds against a panel of tumor cell lines were tested, while the regulation of gene target Nur77 of 2 and exfoliazone (8) were evaluated.     

Alkaloids from the mangrove endophytic fungus Diaporthe phaseolorum SKS019

Six new alkaloids including four new chromeno[3,2-c]pyridines, diaporphasines A-D (1–4), and two new isoindolinones, meyeroguillines C and D (6–7), as well as three known compounds meyeroguilline A (5), 5-deoxybostrycoidin (8), and fusaristatin A (9), were isolated from an endophytic fungus Diaporthe phaseolorum SKS019. Their structures were determined by analysis of 1D and 2D NMR and mass spectroscopic data. Compounds 1–9 are alkaloid components reported for the first time from the Diaporthe sp., and diaporphasines A-D (1–4) are the third examples of alkaloids possessing the unique chromeno[3,2-c]pyridine nucleus. All isolated compounds 1–9 were evaluated for their cytotoxic activity in vitro using MDA-MB-435, HepG2, MCF10A, HCT116, and NCI-H460 human cell lines. Compound 8 exhibited cytotoxicity against MDA-MB-435 and NCI-H460 human cancer cell lines with IC₅₀ values of 5.32 and 6.57 μM, respectively, and compound 9 showed growth-inhibitory activity against MDA-MB-435 human cancer cell line with IC₅₀ value of 8.15 μM.     

Three new alkaloids from the twigs of Cassia siamea and their bioactivities

Three new tricyclic alkaloid, siamalkaloids A–C (1–3), together with three known alkaloids (3–6) were isolated from the twigs of Cassia siamea. Their structures were determined by means of HRESIMS and extensive 1D and 2D NMR spectroscopic studies. Compounds 1–6 were tested for their anti-tobacco mosaic virus (anti-TMV) activity, and compound 3 exhibited high anti-TMV activity with inhibition rate of 34.5%. This rate is higher than that of positive control. In addition, the cytotoxicity of compounds 1–6 were also tested, and compounds 2–6 showed weak activity with IC₅₀ values ranging from 2.8 to 9.4 μM for some tested human tumor cell lines.     

Chemical constituents of Uncaria rhynchophylloides How and their chemotaxonomic significance

One undescribed 1,4-diazaindan-type alkaloid, namely howlumine (1), along with seventeen known compounds, including a known analogue, agrocybenine (2), three iridoid glycosides (3–5), four megastigmane glycosides (6–9), two benzoic acid derivatives (10–11), two phenylpropanoids (12–13), and five flavonoids (14–18), were isolated from the 95% EtOH extract of the aerial parts of Uncaria rhynchophylloides How. The structures of these compounds were elucidated by spectroscopic analyses. All compounds were isolated from this plant for the first time. Howlumine and agrocybenine represent the first report of 1,4-diazaindan-type alkaloids from the genus Uncaria. Furthermore, the chemotaxonomic significance of the isolates was also discussed.     

New purine alkaloids from the Red Sea marine tunicate Symplegma rubra

Investigation of the Red Sea marine tunicate Symplegma rubra Monniot, 1972 gave three new purine alkaloids namely 6-methoxy-7,9-dimethyl-8-oxoguanine (1), 6-methoxy-9-methyl-8-oxoguanine (2), and 2-methoxy-7-methyl-8-oxoadenine (4) together with seven known compounds: 6-methoxy-7-methyl-8-oxoguanine (3), 9-methyl-8-oxoadenine (5), 7-methyl-8-oxoadenine (6), 8-oxoadenine (7), 3-methylxanthine (8), inosine (9), and homarine (pyridinium-2-carboxylic acid-1-methyl) (10). Compound 6 was reported here for the first time from a natural source. The structure determination of the compounds was accomplished by extensive interpretation of their spectroscopic data including 1D (¹H and ¹³C) and 2D (¹H–¹H COSY, HSQC, and HMBC) NMR and high-resolution mass spectral data. The isolated compounds were evaluated for their protein kinase inhibitory activity against different kinases (CDK5, CK1, DyrK1A, and GSK3) at 10 μg/mL. The compounds showed moderate activity against these kinases.     

Chemical constituents from Melodinus cochinchinensis (Lour.) Merr. and their chemotaxonomic significance

A phytochemical investigation on the twigs and leaves of Melodinus cochinchinensis (Lour.) Merr. resulted in the isolation and identification of 22 compounds, including seven sesamin-type lignans (1–7), three pentacyclic triterpenes (8–10), one anthraquinone (11), one flavanone (12), two phenolic compounds (13 and 14), five aspidosperma-type indole alkaloids (15–19), and three eburnan-type indole alkaloids (20–22). The structures of these compounds were elucidated by means of spectroscopic analysis, including HREIMS together with 1D and 2D NMR experiments, and comparison with reported data. Among them, compounds 1/4, 2/5, and 3/6 are three pairs epimers at C-7''. Compounds 1–6, 8 and 11 were firstly isolated from the family Apocynaceae, whereas 17 was isolated from Melodinus species for the first time. Compound 8 was only found in Juglans hopeiensis, while 11 was only found in roots of Rubia cordifolia. Compounds 1–6, 8, 11 and 15–22 could be considered as chemotaxonomic markers for M. cochinchinensis. Furthermore, the chemotaxonomic significance and distribution of these isolates in Melodinus genus are discussed in detail.