Identification of three key enzymes involved in the biosynthesis of tetracyclic oxindole alkaloids in Uncaria rhynchophylla.

Tetracyclic oxindole alkaloids (TOAs), main active ingredients of Uncaria rhynchophylla (UR), has inspired the interest of pharmacologists and chemists because of its great potential in the treatment of the diseases of the nervous system and cardiovascular system and its special spirooxindole scaffold, but the biosynthetic pathway of this compounds is still unknown. In this work, the metabolomics and transcriptomics of hook, leaf and stem of UR were analyzed, and 31 alkaloids and 47,423 unigenes were identified, as well as the relative contents of these alkaloids were evaluated. Based on the above results and literatures, a proposal biosynthetic pathway for TOAs was devised. Furthermore, three unigenes were suggested mediating the biosynthesis of TOAs through the integrated analysis of metabolomics and transcriptomics, and three enzymes, tryptophan decarboxylase, strictosidine synthase and strictosidine-ß-d-glucosidase, were identified as important catalytic enzymes for the synthesis of tryptamine, strictosidine (7) and 4,21-dehydrogeissochizine, respectively, which are considered as the important precursors of TOAs.

Naphtho-γ-pyrone Dimers from an Endozoic Aspergillus niger and the Effects of Coisolated Monomers in Combination with Cisplatin on a Cisplatin-Resistant A549 Cell Line.

Chemotherapy resistance is one of the main causes of lung cancer treatment failure, and a combination regimen may be an effective way to overcome this. Here we report 5 new (1-3, 7, and 9) and 15 known polyketides, isolated from an endozoic Aspergillus niger. The structures of the new compounds were determined by the interpretation of IR, HRESIMS, NMR, and ECD spectra. The ESI-MS/MS fragmentation of the isolated naphtho-γ-pyrone isomers in positive mode is discussed. The effects of isolated compounds in combination with cisplatin (DDP) on a DDP-resistant A549 cell line (A459/DDP) are investigated. The most active compound, 12, could reduce the ratio of GSH/GSSG, promote the generation of intracellular ROS, and cooperate with DDP to down-regulated levels of Nrf2, Akt, HO-1, and NQO1, suggesting that inhibition of Nrf2 and Akt pathways might be involved in the combined effect of 12 and DDP in A549/DDP cells.

Two New Isomeric Andrographolides with Anti-Inflammatory and Cytotoxic Activity.

Two novel epimerized andrographolides, 8,17-dihydro-7,8-dehydroandrographolide and 10ß-8,17-dihydro-7,8-dehydroandrographolide, were isolated from andrographolide sulfonates. Their structures were elucidated by detailed NMR analysis, single-crystal X-ray diffraction and quantum chemical ECD calculations. In addition, these compounds exhibited suppression of NO production in LPS-stimulated RAW264.7 cells over the range of 1.564 to 25.000 µg/mL.

Effects of Picrasma quassioides and its active constituents on Alzheimer's disease in vitro and in vivo.

Alzheimer disease (AD), a prevalent neurodegenerative disorder, is one of the leading causes of dementia. However, there is no effective drug for this disease to date. Picrasma quassioides (D.Don) Benn, a Chinese traditional medicine, was used mainly for the treatment of inflammation, fever, microbial infection and dysentery. In this paper, we reported that the EtOAc extract of Picrasma quassioides stems showed potential neuroprotective activities in l-glutamate-stimulated PC12 and Aß25-35-stimulated SH-SY5Y cell models, as well as improved memory and cognitive abilities in AD mice induced by amyloid-ß peptide. Moreover, it was revealed that the anti-AD mechanism was related to suppressing neuroinflammatory and reducing Aß1-42 deposition using ELISA assay kits. To clarify the active components of the EtOAc extract of Picrasma quassioides stems, a systematic phytochemistry study led to isolate and identify six ß-carboline alkaloids (1-6), seven canthin-6-one alkaloids (7-13), and five quassinoids (14-18). Among them, four ß-carbolines (1-3, and 6) and six canthin-6-ones (7-11, and 13) exhibited potential neuroprotective activities in vitro. Based on these date, the structure-activity relationships of alkaloids were discussed. Furthermore, molecular docking experiments showed that compounds 2 and 3 have high affinity for both of dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYPKIA) and butyrylcholinesterase (BuChE).

Sesquiterpenoids from Chloranthus anhuiensis with Neuroprotective Effects in PC12 Cells.

Glutamate-induced excitotoxicity plays a vital role in neurodegenerative diseases. Neuroprotection against excitotoxicity has been considered as an effective experimental approach for preventing and/or treating excitotoxicity-mediated diseases. In the present study, six new sesquiterpenoids (1-6) and 26 known compounds of this type (7-32) were isolated and characterized from the whole plants of Chloranthus anhuiensis. Chlorantolide A (1) is the first example of a 5,6- seco-germacrane-type sesquiterpenoid, while phacadinane E (2) is a rare 4,5- seco-cadinane-type sesquiterpenoid. The structures of the new compounds were determined by spectroscopic analysis and by calculations of electronic circular dichroism (ECD) spectra. Their neuroprotective effects in mediating glutamate-induced PC12 cell apoptosis were evaluated. Compound 26 exhibited potent neuroprotective activity with an EC50 value of 3.3 ± 0.9 µM. Using Hoechst 33258 staining, a caspase-3 activity assay, and Western blot analysis it was demonstrated that this compound reduces the apoptosis of PC12 cells through inhibition of caspase-3 activity, while activating the Akt signaling pathway.

Chemical Constituents from Chloranthus anhuiensis and Their Cytotoxic Activities.

Three hiherto unknown phenylpropanoid compounds, namely (7S,8R)-1-(1-ethoxy-2-hydroxypropyl)-2-methoxy-3,4-(methylenedioxy)benzene (1), (7S,8S)-1-(1-ethoxy-2-hydroxypropyl)-2-methoxy-3,4-(methylenedioxy)benzene (2), and (7S,8R)-1-(1-methoxy-2-hydroxypropyl)-2-methoxy-3,4-(methylenedioxy)benzene (3), along with 12 known compounds (4 - 15) were obtained from the extract of whole plant of Chloranthus anhuiensis. Among them, 7 and 13 were obtained from nature for the first time. The structures of these natural compounds were characterized by extensive spectroscopic analysis and calculated electronic circular dichroism (ECD) data. Furthermore, their cytotoxic and neuroprotective activities were evaluated using MDA-MB-231, 4T1, HepG2, and PC12 cell lines. Compounds 8 and 13 exhibited moderate cytotoxic activities against MDA-MB-231 cell line with the IC50 values of 39.7 and 25.8 µm, respectively. And all the isolated compounds have no neuroprotective activities.