Discovery of guaiane-type sesquiterpenoids from the roots of Daphne genkwa with neuroprotective effects

Target isolation of diverse sesquiterpenoid from the stems of Daphne genkwa based on molecular networking

Guiding by LC-MS/MS analysis and the Global Natural Products Social (GNPS) Molecular Networking, three undescribed sesquiterpenoids, stedapgens A-C, and two known analogues were discovered in the barks of Daphne genkwa Sieb. et Zucc. The structures were determined by analysis of their spectroscopic data and quantum-chemical calculations. All the isolated novel compounds were tested for their acetylcholinesterase inhibitory activities with IC50 = 0.754 ± 0.059, 0.696 ± 0.026, and 0.337 ± 0.023 μg/ml. Among them, stedapgen A displayed promising inhibitory activities against AChE, and the binding sites were predicted by molecular docking.

Expanded Application of Piper nigrum: Guided Isolation of Alkaloids with Inhibitory Activities of AChE/BuChE and Aβ Aggregation

Piper nigrum is a popular crop that can be used as seasoning or as an additive but its active ingredients also have an effect on the nervous system. Nineteen new amide alkaloids (1a/1b, 2-5, 6a/6b, 7, 8a/8b, 9, 10a/10b, 11a-11b, 12-14) were isolated from P. nigrum, guided by inhibitory activity of AChE and LC-MS/MS based on GNPS. The configurations were determined by extensive spectral analysis, Bulkiness rule, and NMR calculations. The inhibitory activities of AChE/BuChE and Aβ aggregation were tested, and the results showed compounds 2, 7, and 12 had significant inhibitory activities. These components were identified in the crude fraction and their relative quantities were tested, which suggested that compound 2 was the index component in the active site from P. nigrum.

Meroterpenoids from Daphne genkwa shows promising in vitro antitumor activity via inhibiting PI3K/Akt/mTOR signaling pathway in A549 cells

Phytochemical investigation into the leaves and branches of Daphne genkwa afforded 25 meroterpenoids (1-16) including nine pairs of enantiomers (1a/1b-8a/8b and 12a/12b), among which 20 compounds have been reported in the present work for the first time. The structures with absolute configurations of the new molecules (excluding 10-13) were established via comprehensive spectroscopic analyses especially electronic circular dichroism (ECD) and Mosher's methods. A preliminary in vitro cell viability assay revealed remarkable cytotoxicities of selective compounds against A549 (lung), Hela (cervical), MDA-MB231 (breast) and MCF-7 (breast) cancer cells, and compound 8a showed the best inhibitory activity with IC50 values in the range of 3.12-4.67 μM toward the four cell lines. Subsequent in vitro antitumor evaluation of 8a disclosed that it could inhibit the proliferation and metastasis, as well as induce significant apoptosis and cycle arrest, of A549 cells. Further mechanistic investigations revealed that 8a could exert its antitumor activity via inhibiting the PI3K/Akt/mTOR signaling pathway.

Discovering the Mechanisms of Oleodaphnone as a Potential HIV Latency-Reversing Agent by Transcriptome Profiling

Latent HIV is a key factor that makes AIDS difficult to cure. Highly effective and specific latent HIV activators can effectively activate latent HIV, and then combined with antiretroviral therapy to achieve a functional cure of AIDS. Here, four sesquiterpenes (1-4) including a new one (1), five flavonoids (5-9) including three biflavonoid structures, and two lignans (10 and 11) were obtained from the roots of Wikstroemia chamaedaphne. Their structures were elucidated through comprehensive spectroscopic analyses. The absolute configuration of 1 was determined by experimental electronic circular dichroism. NH2 cell model was used to test the activity of these 11 compounds in activating latent HIV. Oleodaphnone (2) showed the latent HIV activation effect as well as the positive drug prostratin, and the activation effect was time- and concentration-dependent. Based on transcriptome analysis, the underlying mechanism was that oleodaphnone regulated the TNF, C-type lectin receptor, NF-κB, IL-17, MAPK, NOD-like receptor, JAK-Stat, FoxO, and Toll-like receptor signaling pathways. This study provides the basis for the potential development of oleodaphnone as an effective HIV latency-reversing agent.

New Guaiane-Type Sesquiterpenoids Biscogniauxiaols A-G with Anti-Fungal and Anti-Inflammatory Activities from the Endophytic Fungus Biscogniauxia Petrensis

Seven undescribed guaiane-type sesquiterpenoids named biscogniauxiaols A-G (1-7) were isolated from the endophytic fungus Biscogniauxia petrensis on Dendrobium orchids. Their structures were determined by extensive spectroscopic analyses, electronic circular dichroism (EC) and specific rotation (SR) calculations. Compound 1 represented a new family of guaiane-type sesquiterpenoids featuring an unprecedented [5/6/6/7] tetracyclic system. A plausible biosynthetic pathway for compounds 1-7 was proposed. The anti-fungal, anti-inflammatory and multidrug resistance reversal activities of the isolates were evaluated. Compounds 1, 2 and 7 exhibited potent inhibitory activities against Candida albicans with MIC values ranging from 1.60 to 6.30 μM, and suppressed nitric oxide (NO) production with IC50 ranging from 4.60 to 20.00 μM. Additionally, all compounds (100 μg/mL) enhanced the cytotoxicity of cisplatin in cisplatin-resistant non-small cell lung cancer cells (A549/DDP). This study opened up a new source for obtaining bioactive guaiane-type sesquiterpenoids and compounds 1, 2, and 7 were promising for further optimization as multifunctional inhibitors for anti-fungal (C. albicans) and anti-inflammatory purposes.

New Isocoumarins from the Marine Fungus Phaeosphaeriopsis sp. WP-26

Five new isocoumarins, phaeosphaerins A–E (1–5), were isolated from the fermentation broth of the marine fungus Phaeosphaeriopsis sp. WP-26, along with one known isocoumarin, 6,8-dihydroxy-7-methoxy-3-methylisocoumarin (6), and two known pimarane-type diterpenes, diaportheins A (7) and B (8). Their structures were elucidated via NMR experiments, X-ray diffraction analysis, and comparison of the experimental and computed ECD curves. Compounds 1–7 displayed weak neuroprotective effects against H2O2-induced damage in SH-SY5Y cells. Moreover, compound 8 showed cytotoxicity against BEL-7402, SGC-7901, K562, A549, and HL-60 cell lines.

Utilization of the By-Product of Corn: Guided Identification of Bioactive Terpenoids from Stigma Maydis (Corn Silk)

Stigma maydis (corn silk) (S. maydis) is a food-based by-product of maize and possesses great nutritional and pharmaceutical value. This study aimed to explore bioactive components from S. maydis. By the guidance of bioactivity-guided approach and Global Natural Products Social (GNPS) molecular networking, 12 terpenoids were discovered from S. maydis. The structures of 11 undescribed compounds (1-11) were determined by detailed spectroscopic analyses, single-crystal X-ray diffraction analysis, specific rotation calculations, electronic circular dichroism (ECD) calculations, and NMR calculations. The neuroprotective and acetylcholinesterase (AChE) inhibitory effects of 1-12 were examined, and most of them showed significant or moderate activities. The underlying neuroprotective mechanism of 4 and 5 was revealed by Hoechst 33258, AO-EB, and JC-1 staining assays. This work illustrated the potential of S. maydis as a prospective natural source of bioactive compounds in food and pharmaceutical industries.

Targeted isolation of diterpenoids and sesquiterpenoids from Daphne gemmata E. Pritz. ex Diels using molecular networking together with network annotation propagation and MS2LDA

Investigation of the whole plant of Daphne gemmata E. Pritz. ex Diels (Thymelaeaceae) using molecular networking coupled to Network Annotation Propagation (NAP) and unsupervised substructure annotation (MS2LDA) led to the discovery of five tigliane diterpenoids, 14 guaiane sesquiterpenoids, one rhamnofolane diterpenoid and three carotene sesquiterpenoids. The structures of the eight undescribed compounds, daphnorbol A and daphnegemmatoids A-G, were characterized by detailed spectroscopic analyses, NMR and ECD calculations, application of Snatzke's method and single-crystal X-ray diffraction analysis. All isolated compounds were evaluated for their cytotoxic activities against HepG2, A549, and MCF-7 cells by MTT assay. Daphnorbol A exhibited significant cytotoxic activity against HepG2 and A549 cells with IC50 values of 4.06 μM and 6.35 μM, respectively. Prostratin showed potent cytotoxic activity against HepG2 and A549 cells with IC50 values of 6.06 μM and 5.45 μM, respectively. Further Hoechst 33,258 and AO-EB staining assays indicated that daphnorbol A and prostratin could induce apoptosis in HepG2 and A549 cells.

Yuanhuacin and Related Anti-Inflammatory and Anticancer Daphnane Diterpenes from Genkwa Flos—An Overview

The dried flower buds of the plant Daphne genkwa Sieb. et Zucc. have been largely used in traditional Chinese medicine for the treatment of inflammatory diseases. Numerous diterpenoids have been isolated from the Genkwa Flos (yuanhua in Chinese), including a series of daphnane-type diterpene designated as yuanhuacin (YC, often improperly designated as yuanhuacine) and analogues with a patronymic name. The series includes ten daphnane-type diterpenes: yuanhuacin, yuanhuadin (YD), yuanhuafin (YF), yuanhuagin (YG), yuanhuahin (YH), yuanhuajin (YJ), yuanhualin (YL), yuanhuamin (YM), yuanhuapin (YP), and yuanhuatin (YT). They are distinct from the rare flavonoid yuanhuanin. The series comprises several anticancer agents, such as the lead compound YC, which has revealed potent activity in vitro and in vivo against models of lung and breast cancers. The main signaling pathways implicated in the antitumor effects have been delineated. Protein kinase C is a key factor of activity for YC, but in general the molecular targets at the origin of the activity of these compounds remain little defined. Promising anticancer effects have been reported with analogues YD and YT, whereas compounds YF and YP are considered more toxic. The pharmacological activity of each compound is presented, as well as the properties of Genkwa Flos extracts. The potential toxic effects associated with the use of these compounds are also underlined.

Three Unusual Sesquiterpenes with Distinctive Ring Skeletons from Daphne penicillata Uncovered by Molecular Networking Strategies

Daphnenoids A-C (1-3), three unusual sesquiterpenes with distinctive ring skeletons, together with a biogenetically related daphnenoid D (4) were obtained from the herb of Daphne penicillata by molecular networking strategies. Daphnenoid A (1) possesses a unique caged tetracyclo [5.3.2.0¹,⁶.0⁴,¹¹] dodecane scaffold by unexpected cyclizations of C-1/C-11 and C-2/C-14. Daphnenoids B and C (2 and 3) were the first discovered natural sesquiterpenes with unique 5/5 spirocyclic systems in nature. Their structures were determined by NMR spectroscopic analysis, computer-assisted structure elucidation methods, quantum chemical calculations, and X-ray diffraction. A hypothetical biogenetic pathway begins with typical guaiane sesquiterpene (a), including a key intermediate (4) was proposed. Daphnenoids B and C (2 and 3) exhibited potential inhibitory activities on the production of NO against LPS-induced BV2 microglial cells.

Natural products targeting mitochondria: emerging therapeutics for age-associated neurological disorders

Mitochondria are the primary source of energy production in the brain thereby supporting most of its activity. However, mitochondria become inefficient and dysfunctional with age and to a greater extent in neurological disorders. Thus, mitochondria represent an emerging drug target for many age-associated neurological disorders. This review summarizes recent advances (covering from 2010 to May 2020) in the use of natural products from plant, animal, and microbial sources as potential neuroprotective agents to restore mitochondrial function. Natural products from diverse classes of chemical structures are discussed and organized according to their mechanism of action on mitochondria in terms of modulation of biogenesis, dynamics, bioenergetics, calcium homeostasis, and membrane potential, as well as inhibition of the oxytosis/ferroptosis pathway. This analysis emphasizes the significant value of natural products for mitochondrial pharmacology as well as the opportunities and challenges for the discovery and development of future neurotherapeutics.

Guaiane-type sesquiterpenoids from the roots of Stellera chamaejasme L. and their neuroprotective activities

Nine undescribed guaiane-type sesquiterpenoids stelleraterpenoids A‒I, along with seven reported congeners, were isolated and identified from the 70% EtOH extract of the roots of Stellera chamaejasme L. Their chemical structures were elucidated on the basis of various spectral data. The relative configurations were determined by their NOESY spectra and comparison between their experimental and calculated NMR data. The absolute configurations were established by the comparison between the experimental and calculated ECD spectra and further by X-ray single-crystal diffraction analysis. The neuroprotective effects of these compounds on the H₂O₂-induced damage in human neuroblastoma SH-SY5Y cells were evaluated. Stelleraguaianone B exhibited the better activity with 71.62% cell viability compared to the positive control Trolox (65.05%) at 12.5 μM, which might be achieved by inhibiting the apoptosis of SH-SY5Y cells based on an annexin V-FITC/PI staining experiment.