Neuroprotective Activity of Some Marine Fungal Metabolites in the 6-Hydroxydopamin- and Paraquat-Induced Parkinson's Disease Models

A review on nonviral, nonbacterial infectious agents toxicity involved in neurodegenerative diseases

Neuronal death, decreased activity or dysfunction of neurotransmitters are some of the pathophysiological reasons for neurodegenerative diseases like Alzheimer's, Parkinson's and multiple sclerosis. Also, there is evidence for the role of infections and infectious agents in neurodegenerative diseases and the effect of some metabolites in microorganisms in the pathophysiology of these diseases. In this study, we intend to evaluate the existing studies on the role of infectious agents and their metabolites on the pathophysiology of neurodegenerative diseases. PubMed, Scopus, Google Scholar and Web of Science search engines were searched. Some infectious agents have been observed in neurodegenerative diseases. Also, isolations of some fungi and microalgae have an improving effect on Parkinson's and Alzheimer's.

The Metabolite Profiling of Aspergillus fumigatus KMM4631 and Its Co-Cultures with Other Marine Fungi

An Aspergillus fumigatus KMM 4631 strain was previously isolated from a Pacific soft coral Sinularia sp. sample and was found to be a source of a number of bioactive secondary metabolites. The aims of this work are the confirmation of this strain' identification based on ITS, BenA, CaM, and RPB2 regions/gene sequences and the investigation of secondary metabolite profiles of Aspergillus fumigatus KMM 4631 culture and its co-cultures with Penicillium hispanicum KMM 4689, Amphichorda sp. KMM 4639, Penicillium sp. KMM 4672, and Asteromyces cruciatus KMM 4696 from the Collection of Marine Microorganisms (PIBOC FEB RAS, Vladivostok, Russia). Moreover, the DPPH-radical scavenging activity, urease inhibition, and cytotoxicity of joint fungal cultures' extracts on HepG2 cells were tested. The detailed UPLC MS qTOF investigation resulted in the identification and annotation of indolediketopiperazine, quinazoline, and tryptoquivaline-related alkaloids as well as a number of polyketides (totally 20 compounds) in the extract of Aspergillus fumigatus KMM 4631. The metabolite profiles of the co-cultures of A. fumigatus with Penicillium hispanicum, Penicillium sp., and Amphichorda sp. were similar to those of Penicillium hispanicum, Penicillium sp., and Amphichorda sp. monocultures. The metabolite profile of the co-culture of A. fumigatus with Asteromyces cruciatus differed from that of each monoculture and may be more promising for the isolation of new compounds.

In vitro studies on the pharmacological potential, anti-tumor, antimicrobial, and acetylcholinesterase inhibitory activity of marine-derived Bacillus velezensis AG6 exopolysaccharide

In the current study, Bacillus velezensis AG6 was isolated from sediment samples in the Red Sea, identified by traditional microbiological techniques and phylogenetic 16S rRNA sequences. Among eight isolates screened for exopolysaccharide (EPS) production, the R6 isolate was the highest producer with a significant fraction of EPS (EPSF6, 5.79 g L-1). The EPSF6 molecule was found to have a molecular weight (Mw) of 2.7 × 104 g mol-1 and a number average (Mn) of 2.6 × 104 g mol-1 when it was analyzed using GPC. The FTIR spectrum indicated no sulfate but uronic acid (43.8%). According to HPLC, the EPSF6 fraction's monosaccharides were xylose, galactose, and galacturonic acid in a molar ratio of 2.0 : 0.5 : 2.0. DPPH, H2O2, and ABTS tests assessed EPSF6's antioxidant capabilities at 100, 300, 500, 1000, and 1500 μg mL-1 for 15, 60, 45, and 60 minutes. The overall antioxidant activities were dose- and time-dependently increased, and improved by increasing concentrations from 100 to 1500 μg mL-1 after 60 minutes and found to be 91.34 ± 1.1%, 80.20 ± 1.4% and 75.28 ± 1.1% respectively. Next, EPSF6 displayed considerable inhibitory activity toward the proliferation of six cancerous cell lines. Anti-inflammatory tests were performed using lipoxygenase (5-LOX) and cyclooxygenase (COX-2). An MTP turbidity assay method was applied to show the ability of EPSF6 to inhibit Gram-positive bacteria, Gram-negative bacteria, and antibiofilm formation. Together, this study sheds light on the potential pharmacological applications of a secondary metabolite produced by marine Bacillus velezensis AG6. Its expected impact on human health will increase as more research and studies are conducted globally.

Endophytic fungi: a potential source for drugs against central nervous system disorders

Neuroprotection is one of the important protection methods against neuronal cells and tissue damage caused by neurodegenerative diseases such as Alzheimer's, Parkinson's, Huntington's, and multiple sclerosis. Various bioactive compounds produced by medicinal plants can potentially treat central nervous system (CNS) disorders. Apart from these resources, endophytes also produce diverse secondary metabolites capable of protecting the CNS. The bioactive compounds produced by endophytes play essential roles in enhancing the growth factors, antioxidant defence functions, diminishing neuroinflammatory, and apoptotic pathways. The efficacy of compounds produced by endophytic fungi was also evaluated by enzymes, cell lines, and in vivo models. Acetylcholine esterase (AChE) inhibition is frequently used to assess in vitro neuroprotective activity along with cytotoxicity-induced neuronal cell lines. Some of drugs, such as tacrine, donepezil, rivastigmine, galantamine, and other compounds, are generally used as reference standards. Furthermore, clinical trials are required to confirm the role of these natural compounds in neuroprotection efficacy and evaluate their safety profile. This review illustrates the production of various bioactive compounds produced by endophytic fungi and their role in preventing neurodegeneration.

Marine-Derived Components: Can They Be a Potential Therapeutic Approach to Parkinson's Disease?

The increase in the life expectancy average has led to a growing elderly population, thus leading to a prevalence of neurodegenerative disorders, such as Parkinson's disease (PD). PD is the second most common neurodegenerative disorder and is characterized by a progressive degeneration of the dopaminergic neurons in the substantia nigra pars compacta (SNpc). The marine environment has proven to be a source of unique and diverse chemical structures with great therapeutic potential to be used in the treatment of several pathologies, including neurodegenerative impairments. This review is focused on compounds isolated from marine organisms with neuroprotective activities on in vitro and in vivo models based on their chemical structures, taxonomy, neuroprotective effects, and their possible mechanism of action in PD. About 60 compounds isolated from marine bacteria, fungi, mollusk, sea cucumber, seaweed, soft coral, sponge, and starfish with neuroprotective potential on PD therapy are reported. Peptides, alkaloids, quinones, terpenes, polysaccharides, polyphenols, lipids, pigments, and mycotoxins were isolated from those marine organisms. They can act in several PD hallmarks, reducing oxidative stress, preventing mitochondrial dysfunction, α-synuclein aggregation, and blocking inflammatory pathways through the inhibition translocation of NF-kB factor, reduction of human tumor necrosis factor α (TNF-α), and interleukin-6 (IL-6). This review gathers the marine natural products that have shown pharmacological activities acting on targets belonging to different intracellular signaling pathways related to PD development, which should be considered for future pre-clinical studies.

Discovery of a natural small-molecule AMP-activated kinase activator that alleviates nonalcoholic steatohepatitis

Non-alcoholic steatohepatitis (NASH) is a primary cause of cirrhosis and hepatocellular carcinoma. Unfortunately, there is no approved drug treatment for NASH. AMP-activated kinase (AMPK) is an important metabolic sensor and whole-body regulator. It has been proposed that AMPK activators could be used for treating metabolic diseases such as obesity, type 2 diabetes and NASH. In this study, we screened a marine natural compound library by monitoring AMPK activity and found a potent AMPK activator, candidusin A (CHNQD-0803). Further studies showed that CHNQD-0803 directly binds recombinant AMPK with a KD value of 4.728 × 10-8 M and activates AMPK at both molecular and intracellular levels. We then investigated the roles and mechanisms of CHNQD-0803 in PA-induced fat deposition, LPS-stimulated inflammation, TGF-β-induced fibrosis cell models and the MCD-induced mouse model of NASH. The results showed that CHNQD-0803 inhibited the expression of adipogenesis genes and reduced fat deposition, negatively regulated the NF-κB-TNFα inflammatory axis to suppress inflammation, and ameliorated liver injury and fibrosis. These data indicate that CHNQD-0803 as an AMPK activator is a novel potential therapeutic candidate for NASH treatment.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42995-023-00168-z.

Mactanamide and lariciresinol as radical scavengers and Fe2+ ion chelators - A DFT study

A DFT based kinetic study of OOH radical scavenging potency of mactanamide (MA) and lariciresinol (LA), two natural polyphenols, indicates their nearly equal potential via the proton coupled electron transfer (PCET) mechanism in lipid media. Contribution of C-H bond breaking to this potency is negligible compared to O-H bond breaking, contrary to recent claims. The predicted potency of both compounds is not sufficient to protect biological molecules from oxidative damage in lipid media. In aqueous media, the scavenging potency of MA and LA phenoxide anions via the single electron transfer (SET) mechanism is much higher and may contribute to the protection of lipids, proteins, and DNA from OOH radical damage. Also, MA and LA have the potential to chelate catalytic Fe2+ ions, thus suppressing the formation of dangerous OH radicals via Fenton-type reactions. The monoanionic species of MA and LA show stronger monodentate chelating ability with Fe2+ ion compared to its neutral form. The dianionic specie LA2- exhibited the highest chelation ability with Fe2+ ion via bidentate 1:2 coordination. However, direct radical scavenging and metal chelation could be rarely operative in vivo because MA and LA presumably achieve very low concentrations in systemic circulation.

Cytoprotective Polyketides from Sponge-Derived Fungus Lopadostoma pouzarii

The new polyketides lopouzanones A and B, as well as the new 1-O-acetyl and 2-O-acetyl derivatives of dendrodochol B, were isolated from the sponge-derived marine fungus Lopadostoma pouzarii strain 168CLC-57.3. Moreover, six known polyketides, gliorosein, balticolid, dendrodolide G, dihydroisocoumarine, (-)-5-methylmellein, and dendrodochol B, were identified. The structures of the isolated compounds were determined by a combination of NMR and ESIMS techniques. The absolute configurations of the lopouzanones A and B were determined using the Mosher's method. The cytotoxicity of the isolated compounds against human prostate cancer cells PC-3 and normal rat cardiomyocytes H9c2 was investigated. Gliorosein showed weak DPPH radical-scavenging activity and in vitro cardioprotective effects toward rotenone toxicity and CoCl2-mimic hypoxia.

Biodiversity and Bioprospecting of Fungal Endophytes from the Antarctic Plant Colobanthus quitensis

Microorganisms from extreme environments are considered as a new and valuable reservoir of bioactive molecules of biotechnological interest and are also utilized as tools for enhancing tolerance to (a)biotic stresses in crops. In this study, the fungal endophytic community associated with the leaves of the Antarctic angiosperm Colobanthus quitensis was investigated as a new source of bioactive molecules. We isolated 132 fungal strains and taxonomically annotated 26 representative isolates, which mainly belonged to the Basidiomycota division. Selected isolates of Trametes sp., Lenzites sp., Sistotrema sp., and Peniophora sp. displayed broad extracellular enzymatic profiles; fungal extracts from some of them showed dose-dependent antitumor activity and inhibited the formation of amyloid fibrils of α-synuclein and its pathological mutant E46K. Selected fungal isolates were also able to promote secondary root development and fresh weight increase in Arabidopsis and tomato and antagonize the growth of pathogenic fungi harmful to crops. This study emphasizes the ecological and biotechnological relevance of fungi from the Antarctic ecosystem and provides clues to the bioprospecting of Antarctic Basidiomycetes fungi for industrial, agricultural, and medical applications.

Kunitz-Type Peptides from Sea Anemones Protect Neuronal Cells against Parkinson's Disease Inductors via Inhibition of ROS Production and ATP-Induced P2X7 Receptor Activation

Parkinson’s disease (PD) is a socially significant disease, during the development of which oxidative stress and inflammation play a significant role. Here, we studied the neuroprotective effects of four Kunitz-type peptides from Heteractis crispa and Heteractis magnifica sea anemones against PD inductors. The peptide HCIQ1c9, which was obtained for the first time, inhibited trypsin less than other peptides due to unfavorable interactions of Arg17 with Lys43 in the enzyme. Its activity was reduced by up to 70% over the temperature range of 60–100 °C, while HCIQ2c1, HCIQ4c7, and HMIQ3c1 retained their conformation and stayed active up to 90–100 °C. All studied peptides inhibited paraquat- and rotenone-induced intracellular ROS formation, in particular NO, and scavenged free radicals outside the cells. The peptides did not modulate the TRPV1 channels but they affected the P2X7R, both of which are considered therapeutic targets in Parkinson’s disease. HMIQ3c1 and HCIQ4c7 almost completely inhibited the ATP-induced uptake of YO-PRO-1 dye in Neuro-2a cells through P2X7 ion channels and significantly reduced the stable calcium response in these cells. The complex formation of the peptides with the P2X7R extracellular domain was determined via SPR analysis. Thus, these peptides may be considered promising compounds to protect neuronal cells against PD inductors, which act as ROS production inhibitors and partially act as ATP-induced P2X7R activation inhibitors.

Marine Indole Alkaloids-Isolation, Structure and Bioactivities

Indole alkaloids are heterocyclic natural products with extensive pharmacological activities. As an important source of lead compounds, many clinical drugs have been derived from natural indole compounds. Marine indole alkaloids, from unique marine environments with high pressure, high salt and low temperature, exhibit structural diversity with various bioactivities, which attracts the attention of drug researchers. This article is a continuation of the previous two comprehensive reviews and covers the literature on marine indole alkaloids published from 2015 to 2021, with 472 new or structure-revised compounds categorized by sources into marine microorganisms, invertebrates, and plant-derived. The structures and bioactivities demonstrated in this article will benefit the synthesis and pharmacological activity study for marine indole alkaloids on their way to clinical drugs.

Neuroprotective Effect of 1,4-Naphthoquinones in an In Vitro Model of Paraquat and 6-OHDA-Induced Neurotoxicity

Targeted screening using the MTT cell viability test with a mini-library of natural and synthetic 1,4-naphthoquinones and their derivatives was performed in order to increase the survival of Neuro-2a neuroblastoma cells in in vitro paraquat and 6-hydroxydopamine models of Parkinson’s disease. As a result, 10 compounds were selected that could protect neuronal cells from the cytotoxic effects of both paraquat and 6-hydroxydopamine. The five most active compounds at low concentrations were found to significantly protect the activity of nonspecific esterase from the inhibitory effects of neurotoxins, defend cell biomembranes from lytic destruction in the presence of paraquat and 6-hydroxydopamine, and normalize the cell cycle. The protective effects of these compounds are associated with the suppression of oxidative stress, decreased expression of reactive oxygen species and nitric oxide formation in cells and normalization of mitochondrial function, and restoration of the mitochondrial membrane potential altered by neurotoxins. It was suggested that the neuroprotective activity of the studied 1,4-NQs is attributable to their pronounced antioxidant and free radical scavenging activity and their ability to reduce the amount of reactive oxygen species formed by paraquat and 6-hydroxydopamine action on neuronal cells. The significant correlation between the neuroprotective properties of 1,4-naphthoquinones and Quantitative Structure–Activity Relationship descriptors describing the physicochemical properties of these compounds means that the hydrophobicity, polarity, charge, and shape of the molecules can be of decisive importance in determining the biological activity of studied substances.

Acetylcholine esterase inhibitory activity of green synthesized nanosilver by naphthopyrones isolated from marine-derived Aspergillus niger

Aspergillus niger metabolites exhibited a wide range of biological properties including antioxidant and neuro-protective effects and some physical properties as green synthesis of silver nanoparticles AgNP. The present study presents a novel evidence for the various biological activities of green synthesized AgNPs. For the first time, some isolated naphtho-γ-pyrones from marine-derived Aspergillus niger, flavasperone (1), rubrofusarin B (2), aurasperone A (3), fonsecinone A (4) in addition to one alkaloid aspernigrin A (7) were invistigated for their inhibitory activity of acetylcholine esterase AChE, a hallmark of Alzheimer’s disease (AD). The ability to synthesize AgNPs by compounds 3, 4 and 7 has been also tested for the first time. Green synthesized AgNPs were well-dispersed, and their size was ranging from 8–30 nm in diameter, their morphology was obviously spherical capped with the organic compounds. Further biological evaluation of their AChE inhibitory activity was compared to the parent compounds. AgNps dramatically increased the inhibitory activity of Compounds 4, 3 and 7 by 84, 16 and 13 fold, respectively to be more potent than galanthamine as a positive control with IC₅₀ value of 1.43 compared to 0.089, 0.311 and 1.53 of AgNPs of Compounds 4, 3 and 7, respectively. Also compound 2 showed moderate inhibitory activity. This is could be probably explained by closer fitting to the active sites or the synergistic effect of the stabilized AgNPs by the organic compouds. These results, in addition to other intrinsic chemical and biological properties of naphtho-γ-pyrones, suggest that the latter could be further explored with a view towards other neuroprotective studies for alleviating AD.

Cytoprotective Activity of p-Terphenyl Polyketides and Flavuside B from Marine-Derived Fungi against Oxidative Stress in Neuro-2a Cells

The influence of p-terphenyl polyketides 1-3 from Aspergillus candidus KMM 4676 and cerebroside flavuside B (4) from Penicillium islandicum (=Talaromyces islandicus) against the effect of neurotoxins, rotenone and paraquat, on Neuro-2a cell viability by MTT and LDH release assays and intracellular ROS level, as well as DPPH radical scavenging activity, was investigated. Pre-incubation with compounds significantly diminished the ROS level in rotenone- and paraquat-treated cells. It was shown that the investigated polyketides 1-3 significantly increased the viability of rotenone- and paraquat-treated cells in two of the used assays but they affected only the viability of paraquat-treated cells in the LDH release assay. Flavuside B statistically increased the viability of paraquat-treated cells in both MTT and LDH release assays, however, it increased the viability of rotenone-treated cells in the LDH release assay. Structure-activity relationships for p-terphenyl derivatives, as well as possible mechanisms of cytoprotective action of all studied compounds, were discussed.

Recent updates on the bioactive compounds of the marine-derived genus Aspergillus

The genus Aspergillus is widely distributed in terrestrial and marine environments. In the marine environment, several Aspergillus species have proved their potential to produce a plethora of secondary metabolites including polyketides, sterols, fatty acids, peptides, alkaloids, terpenoids and miscellaneous compounds, displaying a variety of pharmacological activities such as antimicrobial, cytotoxicity, anti-inflammatory and antioxidant activity. From the beginning of 2015 until December 2020, about 361 secondary metabolites were identified from different marine Aspergillus species. In our review, we highlight secondary metabolites from various marine-derived Aspergillus species reported between January 2015 and December 2020 along with their biological potential and structural aspects whenever applicable.

Disclosing the potential of eleganolone for Parkinson's disease therapeutics: Neuroprotective and anti-inflammatory activities

The treatment of Parkinson´s disease (PD) has benefited from significant advances resulting from the increasing research efforts focused on new therapeutics. However, the current treatments for PD are mostly symptomatic, alleviating disease symptoms without reversing or retarding disease progression. Thus, it is critical to find new molecules that can result in more effective treatments. Within this framework, this study aims to evaluate the neuroprotective and anti-inflammatory effects of three compounds (eleganolone, eleganonal and fucosterol) isolated from the brown seaweed Bifurcaria bifurcata. In vitro neuroprotective effects were evaluated on a PD cellular model induced by the neurotoxin 6-hydroxydopamine (6-OHDA) on SH-SY5Y human cells, while lipopolysaccharide (LPS) - stimulated RAW 264.7 macrophages were used to evaluate the anti-inflammatory potential. Additionally, the underlying mechanisms of action were also investigated. Compounds were isolated by preparative chromatographic methods and their structural elucidation attained by NMR spectroscopy. Among the tested compounds, eleganolone (0.1-1 µM; 24 h) reverted the neurotoxicity induced by 6-OHDA in about 20%. The neuroprotective effects were mediated by mitochondrial protection, reduction of oxidative stress, inflammation and apoptosis, and inhibition of NF-kB pathway. The results suggest that eleganolone may provide advantages in the treatment of neurodegenerative conditions and, therefore, should be considered for future preclinical studies.

Sea Anemone Kunitz-Type Peptides Demonstrate Neuroprotective Activity in the 6-Hydroxydopamine Induced Neurotoxicity Model

Kunitz-type peptides from venomous animals have been known to inhibit different proteinases and also to modulate ion channels and receptors, demonstrating analgesic, anti-inflammatory, anti-histamine and many other biological activities. At present, there is evidence of their neuroprotective effects. We have studied eight Kunitz-type peptides of the sea anemone Heteractis crispa to find molecules with cytoprotective activity in the 6-OHDA-induced neurotoxicity model on neuroblastoma Neuro-2a cells. It has been shown that only five peptides significantly increase the viability of neuronal cells treated with 6-OHDA. The TRPV1 channel blocker, HCRG21, has revealed the neuroprotective effect that could be indirect evidence of TRPV1 involvement in the disorders associated with neurodegeneration. The pre-incubation of Neuro-2a cells with HCRG21 followed by 6-OHDA treatment has resulted in a prominent reduction in ROS production compared the untreated cells. It is possible that the observed effect is due to the ability of the peptide act as an efficient free-radical scavenger. One more leader peptide, InhVJ, has shown a neuroprotective activity and has been studied at concentrations of 0.01–10.0 µM. The target of InhVJ is still unknown, but it was the best of all eight homologous peptides in an absolute cell viability increment on 38% of the control in the 6-OHDA-induced neurotoxicity model. The targets of the other three active peptides remain unknown.

Marine natural products

This review covers the literature published between January and December in 2018 for marine natural products (MNPs), with 717 citations (706 for the period January to December 2018) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1554 in 469 papers for 2018), together with the relevant biological activities, source organisms and country of origin. Reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. The proportion of MNPs assigned absolute configuration over the last decade is also surveyed.

Loliolide, a New Therapeutic Option for Neurological Diseases? In Vitro Neuroprotective and Anti-Inflammatory Activities of a Monoterpenoid Lactone Isolated from Codium tomentosum

Parkinsons Disease (PD) is the second most common neurodegenerative disease worldwide, and is characterized by a progressive degeneration of dopaminergic neurons. Without an effective treatment, it is crucial to find new therapeutic options to fight the neurodegenerative process, which may arise from marine resources. Accordingly, the goal of the present work was to evaluate the ability of the monoterpenoid lactone Loliolide, isolated from the green seaweed Codium tomentosum, to prevent neurological cell death mediated by the neurotoxin 6-hydroxydopamine (6-OHDA) on SH-SY5Y cells and their anti-inflammatory effects in RAW 264.7 macrophages. Loliolide was obtained from the diethyl ether extract, purified through column chromatography and identified by NMR spectroscopy. The neuroprotective effects were evaluated by the MTT method. Cells' exposure to 6-OHDA in the presence of Loliolide led to an increase of cells' viability in 40%, and this effect was mediated by mitochondrial protection, reduction of oxidative stress condition and apoptosis, and inhibition of the NF-kB pathway. Additionally, Loliolide also suppressed nitric oxide production and inhibited the production of TNF-α and IL-6 pro-inflammatory cytokines. The results suggest that Loliolide can inspire the development of new neuroprotective therapeutic agents and thus, more detailed studies should be considered to validate its pharmacological potential.

Marine-derived fungi as a source of bioactive indole alkaloids with diversified structures

Marine-derived fungi are well known as rich sources of bioactive natural products. Growing evidences indicated that indole alkaloids, isolated from a variety of marine-derived fungi, have attracted considerable attention for their diverse, challenging structural complexity and promising bioactivities, and therefore, indole alkaloids have potential to be pharmaceutical lead compounds. Systemic compilation of the relevant literature. In this review, we demonstrated a comprehensive overview of 431 new indole alkaloids from 21 genera of marine-derived fungi with an emphasis on their structures and bioactivities, covering literatures published during 1982-2019.

Neuroprotective Metabolites from Vietnamese Marine Derived Fungi of Aspergillus and Penicillium Genera

Low molecular weight secondary metabolites of marine fungi Aspergillus flocculosus, Aspergillus terreus and Penicillium sp. from Van Phong and Nha Trang Bays (Vietnam) were studied and a number of polyketides, bis-indole quinones and terpenoids were isolated. The structures of the isolated compounds were determined by 1D and 2D NMR and HR-ESI-MS techniques. Stereochemistry of some compounds was established based on ECD data. A chemical structure of asterriquinone F (6) was thoroughly described for the first time. Anthraquinone (13) was firstly obtained from a natural source. Neuroprotective influences of the isolated compounds against 6-OHDA, paraquat and rotenone toxicity were investigated. 4-Hydroxyscytalone (1), 4-hydroxy-6-dehydroxyscytalone (2) and demethylcitreoviranol (3) have shown significant increasing of paraquat- and rotenone-treated Neuro-2a cell viability and anti-ROS activity.

Biologically Active Echinulin-Related Indolediketopiperazines from the Marine Sediment-Derived Fungus Aspergillus niveoglaucus

Seven known echinulin-related indolediketopiperazine alkaloids (1–7) were isolated from the Vietnamese sediment-derived fungus Aspergillus niveoglaucus. Using chiral HPLC, the enantiomers of cryptoechinuline B (1) were isolated as individual compounds for the first time. (+)-Cryptoechinuline B (1a) exhibited neuroprotective activity in 6-OHDA-, paraquat-, and rotenone-induced in vitro models of Parkinson’s disease. (−)-Cryptoechinuline B (1b) and neoechinulin C (5) protected the neuronal cells against paraquat-induced damage in a Parkinson’s disease model. Neoechinulin B (4) exhibited cytoprotective activity in a rotenone-induced model, and neoechinulin (7) showed activity in the 6-OHDA-induced model.

Amelioration of Mitochondrial Quality Control and Proteostasis by Natural Compounds in Parkinson's Disease Models

Parkinson’s disease (PD) is a well-known age-related neurodegenerative disorder associated with longer lifespans and rapidly aging populations. The pathophysiological mechanism is a complex progress involving cellular damage such as mitochondrial dysfunction and protein homeostasis. Age-mediated degenerative neurological disorders can reduce the quality of life and also impose economic burdens. Currently, the common treatment is replacement with levodopa to address low dopamine levels; however, this does not halt the progression of PD and is associated with adverse effects, including dyskinesis. In addition, elderly patients can react negatively to treatment with synthetic neuroprotection agents. Recently, natural compounds such as phytochemicals with fewer side effects have been reported as candidate treatments of age-related neurodegenerative diseases. This review focuses on mitochondrial dysfunction, oxidative stress, hormesis, proteostasis, the ubiquitin‒proteasome system, and autophagy (mitophagy) to explain the neuroprotective effects of using natural products as a therapeutic strategy. We also summarize the efforts to use natural extracts to develop novel pharmacological candidates for treatment of age-related PD.

Biologically Active Metabolites from the Marine Sediment-Derived Fungus Aspergillus flocculosus

Four new compounds were isolated from the Vietnamese marine sediment-derived fungus Aspergillus flocculosus, one aspyrone-related polyketide aspilactonol G (2), one meroterpenoid 12-epi-aspertetranone D (4), two drimane derivatives (7,9), together with five known metabolites (1,3,5,6,8,10). The structures of compounds 1–10 were established by NMR and MS techniques. The absolute stereoconfigurations of compounds 1 and 2 were determined by a modified Mosher’s method. The absolute configurations of compounds 4 and 7 were established by a combination of analysis of ROESY data and coupling constants as well as biogenetic considerations. Compounds 7 and 8 exhibited cytotoxic activity toward human prostate cancer 22Rv1, human breast cancer MCF-7, and murine neuroblastoma Neuro-2a cells.

Marine-Derived Natural Compounds for the Treatment of Parkinson's Disease

Parkinson’s disease (PD) is a neurodegenerative disorder caused by the loss of dopaminergic neurons, leading to the motor dysfunctions of patients. Although the etiology of PD is still unclear, the death of dopaminergic neurons during PD progress was revealed to be associated with the abnormal aggregation of α-synuclein, the elevation of oxidative stress, the dysfunction of mitochondrial functions, and the increase of neuroinflammation. However, current anti-PD therapies could only produce symptom-relieving effects, because they could not provide neuroprotective effects, stop or delay the degeneration of dopaminergic neurons. Marine-derived natural compounds, with their novel chemical structures and unique biological activities, may provide anti-PD neuroprotective effects. In this study, we have summarized anti-PD marine-derived natural products which have shown pharmacological activities by acting on various PD targets, such as α-synuclein, monoamine oxidase B, and reactive oxygen species. Moreover, marine-derived natural compounds currently evaluated in the clinical trials for the treatment of PD are also discussed.