Stemona-amines C–E,new alkaloids from Stemona tuberosa

Three new alkaloids, stemona-amines C–E, were isolated from the roots of Stemona tuberosa Lour. (Stemonaceae). The structures of stemona-amines C and D were determined by X-ray crystallography and that of stemona-amine E was determined by interpretation of spectroscopic data. The absolute structures of stemona-amines C and D were established by VCD spectroscopy.     

Alstolactines A–C,novel monoterpenoid indole alkaloids from Alstonia scholaris

Three novel ring-fused monoterpenoid indole alkaloids, alstolactines A–C (1–3), were isolated from the long-term stored leaves of Alstonia scholaris. Their structures were identified on the basis of extensive spectroscopic data and X-ray diffractions. Moreover, the absolute configurations of these related structures were indicated by the crystal X-ray diffractions (Mo Kα) of 1a, a chlorinated derivative of 1.     

Alsmaphorazines C–E,indole alkaloids from Alstonia pneumatophora

Three novel indole alkaloids, alsmaphorazines C (1)–E (3), were isolated from the leaves of Alstonia pneumatophora (Apocynaceae) and their structures were determined on the basis of the 2D NMR and MS spectral analyses. The absolute configurations of 1 and 3 were elucidated by applying a modified Mosher’s method and CD spectral analysis. These alkaloids possessed novel ring skeletons containing an octahydropyrrolo[2,3-b]pyrrole unit.     

Fluevirines A–D,four new securinega-type alkaloids from Flueggea virosa

Four new securinega-type alkaloids, fluevirines A–D (1–4), along with ten known ones, were isolated from the twigs and leaves of Flueggea virosa. The structures of the new ones were elucidated by means of spectroscopic methods, and their absolute configurations were assigned by CD spectra. Among them, fluevirine A (1) was a novel C,C-linked dimeric indolizidine alkaloid and showed weak antimicrobial activity against Staphylococcus aureus.     

Two new indole alkaloids from Nauclea officinalis

Two new indole alkaloids,4-oxo-4,12-dihydroindolo[2,3-a]quinolizine-3-carbaldehyde(1)and 1,6,7-trihydro-indolo-[2,3- a]furan[3,4-g]quinolizine-3,4(13H)-dione(2),were isolated from Nauclea officinalis.Their structures were determined on the basis of 1D and 2D NMR spectral data.     

Topsendines A–F,new 3-alkylpyridine alkaloids from a Hainan sponge Topsentia sp.

Six new 3-alkylpyridine alkaloids, topsendines A–F (1–6), and one new naturally occurring product, 2-methyl-12-(pyridine-3-yl)dodecanal (7), were isolated from an undescribed species of Hainan sponge Topsentia. The structures of the new compounds were determined by extensive 2D NMR experiments, HR-EI/ESI-MS spectrometry measurements, and by comparison of their NMR data with those of structurally related compounds in the literature. In bioassay, compounds 1, 3, and 5 showed inhibitory actions on delayed rectifier K⁺ currents (I_K) in rat acutely dissociated hippocampal neurons at the concentration of 100 μM, with the percentage of inhibition of 85.9±3.9%, 87.1±4.4%, and 76.2±12.2%, respectively.     

Rubischumanins A–C,new cytotoxic cyclopeptides from Rubia schumanniana

Three new cyclic hexapeptides, designated as rubischumanins A–C (1–3), together with three known ones (4–6) were isolated from the roots and rhizomes of Rubia schumanniana. The structures were elucidated on the basis of extensive spectroscopic analysis. Cytotoxicity of these compounds was evaluated and compounds 1, 2, 4, and 5 showed cytotoxicity against A549, BGC-823, and Hela cell lines.     

Twelve new compounds from Ligularia melanothyrsa; isolation of melanothyrsins A–E,normelanothyrsin A,and other eremophilane sesquiterpenoids

Twelve new compounds, namely, five melanothyrsins A–E (1α-angeloyloxyeremophilenolides), normelanothyrsin A (1α-angeloyloxynoreremophilenone), and six other eremophilane-type compounds, have been isolated from Ligularia melanothyrsa Hand.-Mazz. (Asteraceae), collected in the Sichuan Province of China. Six of the compounds have a 1α-angeloyloxy moiety, while the other six have no functional group at the C-1 position. The absolute configuration was also determined using CD spectra. This is the first chemical study of compounds isolated from this species.     

Violaceimides A–E,sulfur-containing metabolites from a sponge-associated fungus Aspergillus violaceus

Five new methylsuccinimide-based sulfur-bearing compounds, namely violaceimides A–E (1–5), were isolated from the sponge-associated fungal strain Aspergillus violaceus WZXY-m64-17. Their structures were determined by analyses of the HRESIMS, 1D and 2D NMR data, along with the Mosher’s and Snatzke’s methods, experimental and calculated ECD data, as well as chemical conversion for the configurational assignment. The structures of 1–5 featured the fusion of methylsuccinimide with a modified cysteine to incorporate sulfur element, which was found from nature for the first time. The biogenetic relationship of the sulfur-containing compounds was postulated. Violaceimides A and B exerted selective inhibition against the growth of human leukemia U937 and human colorectal cancer cell HCT-8 with low cytotoxicity toward Vero cells, whereas violaceimide E showed moderate activity to inhibit U937 cells. The preliminary structure-activity relationship was discussed.     

Leucomidines A–C,novel alkaloids from Leuconotis griffithii

Two novel indole alkaloids and new quinazoline alkaloids, namely leucomidines A–C (1–3), were isolated from the barks of Leuconotis griffithii. The structures including the absolute configuration were elucidated on the basis of spectroscopic data, chemical means, and CD calculations. The quinazoline alkaloid, 3, is proposed to be derived from the same biogenetic precursor as the indole alkaloids 1 and 2.     

Lycocasuarines A–C,Lycopodium alkaloids from Lycopodiastrum casuarinoides

Three lycodine-type Lycopodium alkaloids (1–3) were isolated from Lycopodiastrum casuarinoides. Their structures were elucidated by spectroscopic analysis, single-crystal X-ray crystallography, and computational methods. Compound 1 possesses a rearranged five-membered ring D resulting from C-8/C-15 cleavage and a new C-7/C-15 linkage. Compound 2 is the first Lycopodium alkaloid found to bear an additional carbon (C-17) directly bonded to C-8, which is particularly unusual from a biogenetic point of view. Compounds 1–3 were evaluated for acetylcholinesterase inhibitory activities.     

Trigoxyphins O–T,six new heterodimers from Trigonostemon xyphophylloides

Phytochemical study of the twigs of Trigonostemon xyphophylloides led to the isolation of six new heterodimers, trigoxyphins O (1) and R–T (4–6) comprising of two different degraded diterpenoids, and trigoxyphins P (2) and Q (3) comprising a degraded diterpenoid and a phenylpropanoid, together with a known homodimer, neoboutomannin (7). The structures and relative configurations were elucidated on the basis of extensive spectroscopic analysis, including 1D and 2D NMR experiments. Compounds 1–6 were evaluated for their cytotoxicity against four human tumour cell lines by MTT assay.     

β-Carboline-type indole alkaloid glycosides from Ophiorrhiza trichocarpon

Six new β-carboline-type indole alkaloid glycosides, ophiorrhisides A–F (1–6), were isolated from Ophiorrhiza trichocarpon (Rubiaceae) collected in Thailand. Ophiorrhisides A (1) and B (2) possess a lactam function in the C ring and a unique biose residue in the molecule. Ophiorrhiside F (6) has a highly oxidized C ring with a 1,2-dicarbonyl function at C-5 and C-6 positions as well as a double bond between C-3 and C-14.     

Novel ring A rearranged isomers with γ-lactone from the fruits of Aphanamixis grandifolia

Aphagranols A (1) and B (2), a pair of isomers with a novel limonoid carbon skeleton, were isolated from the fruits of Aphanamixis grandifolia. Their structures were determined by spectroscopic analyses and further confirmed by their unique acetylated derivative aphagranol C (3). The possible equilibrium system of the enol interconversion was presented using the polarizable continuum model (PCM). The absolute configuration of 3 was established via experimental and calculated ECD spectra comparison. The γ-lactone moiety in ring A system was first found in this class of limonoids.     

New alkaloids sinomacutines A–E,and cephalonine-2-O-β-d-glucopyranoside from rhizomes of Sinomenium acutum

Phytochemical investigation on the rhizomes of Sinomenium acutum led to the isolation of new alkaloids sinomacutines A–E (1–5), and cephalonine-2-O-β-d-glucopyranoside (6), along with known tetrahydroisoquinoline alkaloids (7–9). Among them, sinomacutines A–C were new bistetrahydroisoquinoline alkaloids with morphinane–proaporphine and morphinane–benzyltetrahydroisoquinoline types, and coupled with unique C–CH₂–N unit. Their structures with absolute configuration were elucidated on the basis of 1D and 2D NMR, and ECD spectra analysis. The new compounds were evaluated for their anti-inflammatory and cytotoxic activities, and sallisonine B (2) showed moderate ability to inhibit NO production of LPS-stimulated RAW264.7 macrophages, as well as sallisonine A (1) showed weak inhibitory effects against five cancer cell lines.     

Dendronephthols A–C,new sesquiterpenoids from the Red Sea soft coral Dendronephthya sp.

Three new ylangene-type sesquiterpenoids: dendronephthol A (7,13-dihydroxy-3,4-dihydro-α-ylang-5-one) (1), dendronephthol B (6,7,13-trihydroxy-3,4-dihydro-α-ylangene) (2), and dendronephthol C (6,7,13-trihydroxy-α-ylang-5-one) (3), together with two known compounds: dendronesterone A and cholesterol were isolated from the CHCl₃ fraction of Red Sea soft coral Dendronephthya sp. (Nephtheidae). The structures of the new compounds were established on the basis of one- and two-dimensional NMR spectroscopic studies (¹H, ¹³C, DEPT, COSY, HSQC, HMBC, and NOESY) as well as MS spectroscopy and by comparison of the spectral data with those of related known compounds. Compounds 1 and 3 showed cytotoxic activity against the murine lymphoma L5187Y cancer cell line with ED₅₀ values of 8.4 and 6.8 μg/mL, respectively.     

Senedensiscins A–F: six new eudesmane sesquiterpenoid glucosides from Senecio densiserratus

Six new highly oxygenated eudesmane sesquiterpenoid glucosides, senedensiscins A–F (1–6), were isolated from the aerial parts of Senecio densiserratus. Their structures with the absolute configurations were established on the basis of spectroscopic analyses and chemical methods. These compounds represent an unprecedented type of sesquiterpenoid glucoside with the angeloyl group directly connected to the glucosyl moiety and their cytotoxicity was evaluated against the selected human cell lines, HL-60, SMMC-7721, and HeLa.     

Cytosporins F–K,new epoxyquinols from the endophytic fungus Pestalotiopsis theae

Chemical investigation of an endophytic fungus, Pestalotiopsis theae, isolated from the leaves of Turraeanthus longipes (Meliaceae) collected in Cameroon, resulted in the isolation of six new epoxyquinols, cytosporins F–K (2–7), together with the known cytosporin D (1). The structures of the new compounds were unambiguously determined by analysis of the 1D, 2D NMR, and HRMS spectra. Cytosporins G–K (3–7) are the first cytosporins with a hydroxyl substituted C₇ side chain, while cytosporins F–I (2–5) contain a 13-acetoxyl group that was not reported previously. A plausible biosynthetic pathway for the cytosporin derivatives is proposed.     

Capillosananes S–Z,new sesquiterpenoids from the soft coral Sinularia capillosa

Chemical examination of the soft coral Sinularia capillosa resulted in the isolation of eight new sesquiterpenoids named capillosananes S–Z (1–8) and six known sesquiterpenes. The structures of the new compounds were determined on the basis of extensive spectroscopic analysis, including CD effects and Mosher method for the assignment of their absolute configurations. Capillosananes S–U (1–3) presented as the novel carbon skeletons with bicyclo[3,6,0] and bicyclo[4,5,0] systems, while capillosanane V (4) was characteristic of an unprecedented tricyclic skeleton. Capillosananes W–X (5–6) were assigned to the unusual dumortane-type sesquiterpenes. In addition, the absolute configurations of the stereoisomers of isodaucene-9,14-diol were assigned for the first time.     

Daphnauranols A–C,new antifeedant sesquiterpenoids with a 5/6/7 ring system from Daphne aurantiaca

Daphnauranols A–C (1–3), three new sesquiterpenoids with an unprecedented 5/6/7 ring system, were isolated from the stems of Daphne aurantiaca Diels. Their structures were elucidated on the basis of comprehensive spectroscopic methods including MS and NMR. The absolute configuration of daphnauranol A was further confirmed by single crystal X-ray diffraction (Cu Kα). Their anti-feedant activity was tested, and the fruit fly antifeedant index (AI) were 39.8 ± 7.2%, 29.4 ± 7.2%, and 26.3 ± 6.4%, respectively.