Biosynthesis of a new skyllamycin in Streptomyces nodosus: a cytochrome P450 forms an epoxide in the cinnamoyl chain

Activation of a silent gene cluster in Streptomyces nodosus leads to synthesis of a cinnamoyl-containing non-ribosomal peptide (CCNP) that is related to skyllamycins. This novel CCNP was isolated and its structure was interrogated using mass spectrometry and nuclear magnetic resonance spectroscopy. The isolated compound is an oxidised skyllamycin A in which an additional oxygen atom is incorporated in the cinnamoyl side-chain in the form of an epoxide. The gene for the epoxide-forming cytochrome P450 was identified by targeted disruption. The enzyme was overproduced in Escherichia coli and a 1.43 Å high-resolution crystal structure was determined. This is the first crystal structure for a P450 that forms an epoxide in a substituted cinnamoyl chain of a lipopeptide. These results confirm the proposed functions of P450s encoded by biosynthetic gene clusters for other epoxidized CCNPs and will assist investigation of how epoxide stereochemistry is determined in these natural products.

The genome of Acorus deciphers insights into early monocot evolution

Acorales is the sister lineage to all the other extant monocot plants. Genomic resource enhancement of this genus can help to reveal early monocot genomic architecture and evolution. Here, we assemble the genome of Acorus gramineus and reveal that it has ~45% fewer genes than the majority of monocots, although they have similar genome size. Phylogenetic analyses based on both chloroplast and nuclear genes consistently support that A. gramineus is the sister to the remaining monocots. In addition, we assemble a 2.2 Mb mitochondrial genome and observe many genes exhibit higher mutation rates than that of most angiosperms, which could be the reason leading to the controversies of nuclear genes- and mitochondrial genes-based phylogenetic trees existing in the literature. Further, Acorales did not experience tau (τ) whole-genome duplication, unlike majority of monocot clades, and no large-scale gene expansion is observed. Moreover, we identify gene contractions and expansions likely linking to plant architecture, stress resistance, light harvesting, and essential oil metabolism. These findings shed light on the evolution of early monocots and genomic footprints of wetland plant adaptations.

Revealing the Antiepileptic Effect of α-Asaronol on Pentylenetetrazole-Induced Seizure Rats Using NMR-Based Metabolomics

α-Asaronol from Acorus tatarinowii (known as "Shichangpu" in Traditional Chinese medicine) has been proved to possess more efficient antiepileptic activity and lower toxicity than α-asarone (namely "Xixinnaojiaonang" as an antiepileptic drug in China) in our previous study. However, the molecular mechanism of α-asaronol against epilepsy needs to be known if to become a novel antiepileptic medicine. Nuclear magnetic resonance (NMR)-based metabolomics was applied to investigate the metabolic patterns of plasma and the brain tissue extract from pentylenetetrazole (PTZ)-induced seizure rats when treated with α-asaronol or α-asarone. The results showed that α-asaronol can regulate the metabolomic level of epileptic rats to normal to some extent, and four metabolic pathways were associated with the antiepileptic effect of α-asaronol, including alanine, aspartate, and glutamate metabolism; synthesis and degradation of ketone bodies; glutamine and glutamate metabolism; and glycine, serine, and threonine metabolism. It was concluded that α-asaronol plays a vital role in enhancing energy metabolism, regulating the balance of excitatory and inhibitory neurotransmitters, and inhibiting cell membrane damage to prevent the occurrence of epilepsy. These findings are of great significance in developing α-asaronol into a promising antiepileptic drug derived from Traditional Chinese medicine.

Natural Products as Novel Neuroprotective Agents; Computational Predictions of the Molecular Targets, ADME Properties, and Safety Profile

Neurodegenerative diseases (NDs) are one of the most challenging public health issues. Despite tremendous advances in our understanding of NDs, little progress has been made in establishing effective treatments. Natural products may have enormous potential in preventing and treating NDs by targeting microglia; yet, there have been several clinical concerns about their usage, primarily due to a lack of scientific evidence for their efficacy, molecular targets, physicochemical properties, and safety. To solve this problem, the secondary bioactive metabolites derived from neuroprotective medicinal plants were identified and selected for computational predictions for anti-inflammatory activity, possible molecular targets, physicochemical properties, and safety evaluation using PASS online, Molinspiration, SwissADME, and ProTox-II, respectively. Most of the phytochemicals were active as anti-inflammatory agents as predicted using the PASS online webserver. Moreover, the molecular target predictions for some phytochemicals were similar to the reported experimental targets. Moreover, the phytochemicals that did not violate important physicochemical properties, including blood-brain barrier penetration, GI absorption, molecular weight, and lipophilicity, were selected for further safety evaluation. After screening 54 neuroprotective phytochemicals, our findings suggest that Aromatic-turmerone, Apocynin, and Matrine are the most promising compounds that could be considered when designing novel neuroprotective agents to treat neurodegenerative diseases via modulating microglial polarization.

Biotransformation of α-asarone by Alternaria longipes CGMCC 3.2875

Biotransformation of α-asarone by Alternaria longipes CGMCC 3.2875 yielded two pairs of new neolignans, (+) (7S, 8S, 7'S, 8'R) iso-magnosalicin (1a)/(-) (7R, 8R, 7'R, 8'S) iso-magnosalicin (1b) and (+) (7R, 8R, 7'S, 8'R) magnosalicin (2a)/(-) (7S, 8S, 7'R, 8'S) magnosalicin (2b), and four known metabolites, (±) acoraminol A (3), (±) acoraminol B (4), asaraldehyde (5), and 2, 4, 5-trimethoxybenzoic acid (6). Their structures, including absolute configurations, were determined by extensive analysis of NMR spectra, X-ray crystallography, and quantum chemical ECD calculations. The cytotoxic activity and Aβ₄₂ aggregation inhibitory activity of all the compounds were evaluated. Compound 2 displayed significant anti-Aβ₄₂ aggregation activity with an inhibitory rate of 60.81% (the positive control EGCG: 69.17%). In addition, the biotransformation pathway of α-asarone by Alternaria longipes CGMCC 3.2875 was proposed.

Bioguided isolation, identification and activity evaluation of antifungal compounds from Acorus tatarinowii Schott

ETHNOPHARMACOLOGY RELEVANCE

As a traditional folk medicine, Acorus tatarinowii Schott was used to treat digestive diseases, such as diarrhea, which may be related to Candida albicans infection; however according to literature surveys, there have been few studies of A. tatarinowii focusing on its antimicrobial activity, and almost all describe investigations using crude extracts or fractions.

AIM OF THE STUDY

The aims of the current study were to isolate and identify antifungal fractions of A. tatarinowii based on their antifungal activity, explore the preliminary mechanism of 60% ethanol elution (AT60) by metabonomics, and evaluate the antifungal activity of AT60 in vivo and in vitro, to provide natural resources against fungal infections.

MATERIALS AND METHODS

As a pilot evaluation of activity, A. tatarinowii fractions and compounds with antifungal bioactivity were isolated by bioactive-guided column chromatography, and identified by LC-QTOF-MS/MS and NMR spectroscopy. The antifungal effects of the active ingredients against resistant C. albicans were evaluated by in vivo and in vitro colony forming unit assays. The mechanism underlying the activity of AT60 against C. albicans was explored using an LC-QTOF-based metabonomics approach and fluorescence microscopy imaging.

RESULTS

AT60 showed better activity against C. albicans than the same dose of the first line antifungal drugs, fluconazole and itraconazole (positive control drugs). Subsequent phytochemical investigation of AT60 identified twenty-five known compounds, six of which were isolated: asaraldehyde (7), 1-(2,4,5-trimethoxyphenyl)-1,2-propanediol (12), α-asarone (14), β-asarone (15), γ-asarone (18), acotatarone C (19). Further, the compounds α-asarone (14) and acotatarone C (19) may be responsible for the antifungal activity, and exhibit synergistic effects. Metabonomics analysis indicated that AT60 can inhibit biofilm formation by regulating the C. albicans protein kinase C pathway.

CONCLUSIONS

Our results show that A. tatarinowii has potent bioactivity against C. albicans in vitro and in vivo, and can be considered an antifungal botanic agent.

Investigating Plant Micro-Remains Embedded in Dental Calculus of the Phoenician Inhabitants of Motya (Sicily, Italy)

Plant records reveal remarkable evidence about past environments and human cultures. Exploiting dental calculus analysis and using a combined approach of microscopy and gas chromatography mass spectrometry, our research outlines dietary ecology and phytomedicinal practices of the ancient community of Motya (Sicily, eight to sixth century BC), one of the most important Phoenician settlements in the Mediterranean basin. Micro-remains suggest use or consumption of Triticeae cereals, and animal-derived sources (e.g., milk and aquatic birds). Markers of grape (or wine), herbs, and rhizomes, endemic of Mediterranean latitudes and the East, provide insight into the subsistence of this colony, in terms of foodstuffs and phytotherapeutic products. The application of resins and wood of Gymnosperms for social and cultural purposes is hypothesized through the identification of Pinaceae secondary metabolites and pollen grains. The information hidden in dental calculus discloses the strong human-plant interaction in Motya’s Phoenician community, in terms of cultural traditions and land use.

From Folk Taxonomy to Species Confirmation of Acorus (Acoraceae): Evidences Based on Phylogenetic and Metabolomic Analyses

Plants in Acorus have been used as herbal medicine by various linguistic groups for thousands of years. Arguments of taxonomy of Acorus among scientists resulted in confusions and misuses of Acorus plants. The present study used different methods to investigate the classification of the genus, based on folk taxonomy. The relationships among Acorus species were revealed through phylogenetic analyses by constructing the Maximum Likelihood and Bayesian phylogenetic analyses based on sequences of two chloroplast regions (trnL-trnF and rbcL). All samples named with two so-called synonyms, Acorus macrospadiceus (Yamam.) F. N. Wei and Y. K. Li and Acorus tatarinowii Schott collected from different habitats, were clustered into separate groups, which revealed that they represented two independent species. Multivariate statistical analysis of metabolites from different Acorus populations were carried out based on UPLC-QTOF-MS data. Three independent analysis, principal component analysis, heat-map analysis, and hierarchical cluster analysis, showed that A. macrospadiceus and A. tatarinowii are different from two recognized species in the genus, A. calamus L. and A. gramineus Aiton. The results of phylogenetics and chemotaxonomy, together with morphological and ecological evidences, were consistent with traditional knowledge of local people related to Acorus taxa, which proved the significance of parataxonomy. Multiple evidences including morphological, ecological, folk taxonomic, phylogenetic, and chemical taxonomic results suggested that there are four species in the genus Acorus.

Anti-Amyloidogenic Effects of Asarone Derivatives From Perilla frutescens Leaves against Beta-Amyloid Aggregation and Nitric Oxide Production

Alzheimer's disease (AD) is a progressive, neurodegenerative brain disorder associated with loss of memory and cognitive function. Beta-amyloid (Aβ) aggregates, in particular, are known to be highly neurotoxic and lead to neurodegeneration. Therefore, blockade or reduction of Aβ aggregation is a promising therapeutic approach in AD. We have previously reported an inhibitory effect of the methanol extract of Perilla frutescens (L.) Britton (Lamiaceae) and its hexane fraction on Aβ aggregation. Here, the hexane fraction of P. frutescens was subjected to diverse column chromatography based on activity-guided isolation methodology. This approach identified five asarone derivatives including 2,3-dimethoxy-5-(1E)-1-propen-1-yl-phenol (1), β-asarone (2), 3-(2,4,5-trimethoxyphenyl)-(2E)-2-propen-1-ol (3), asaronealdehyde (4), and α-asarone (5). All five asarone derivatives efficiently reduced the aggregation of Aβ and disaggregated preformed Aβ aggregates in a dose-dependent manner as determined by a Thioflavin T (ThT) fluorescence assay. Furthermore, asarone derivatives protected PC12 cells from Aβ aggregate-induced toxicity by reducing the aggregation of Aβ, and significantly reduced NO production from LPS-stimulated BV2 microglial cells. Taken together, these results suggest that asarone derivatives derived from P. frutescens are neuroprotective and have the prophylactic and therapeutic potential in AD.

Bioactive Asarone-Derived Phenylpropanoids from the Rhizome of Acorus tatarinowii Schott

Eight new (1a/1b, 2a, 3a, 4a/4b, and 5a/5b) and seven known (2b, 3b, and 6-10) asarone-derived phenylpropanoids, a known asarone-derived lignan (12), and four known lignan analogues (11 and 13-15) were isolated from the rhizome of Acorus tatarinowii Schott. The structures were elucidated via comprehensive spectroscopic analyses, modified Mosher's method, and quantum chemical calculations. Compounds 1-8 were present as enantiomers, and 1-5 were successfully resolved via chiral-phase HPLC. Compounds 1a/1b were the first cases of asarone-derived phenylpropanoids with an isopropyl C-3 side-chain tethered to a benzene core from nature. Hypoglycemic, antioxidant, and AChE inhibitory activities of 1-15 were assessed by the α-glucosidase inhibitory, ORAC, DPPH radical scavenging, and AChE inhibitory assays, respectively. All compounds except 3a showed α-glucosidase inhibitory activity. Compound 3b has the highest α-glucosidase inhibitory effect with an IC₅₀ of 80.6 μM (positive drug acarbose IC₅₀ of 442.4 μM). In the antioxidant assays, compounds 13-15 exhibited ORAC and DPPH radical scavenging activities. The results of the AChE inhibitory assay indicated that all compounds exhibited weak AChE inhibitory activities.

Phenylisotertronic acids from the TCM endophytic fungus Phyllosticta sp

Four new phenylisotertronic acids (1a/1b, 2a, and 3a) were isolated from a TCM endophytic fungal strain Phyllosticta sp. J13-2-12Y obtained from the leaves of Acorus tatarinowii, along with two known ones (2b and 3b). Compounds 1-3 all existed as mixtures of enantiomers, and their corresponding optically pure enantiomers were successfully isolated by chiral HPLC. The structures of isolated compounds were determined by comprehensive spectroscopic analyses and X-ray diffraction. Their absolute configurations were determined by ECD experiments and quantum chemical calculations. In addition, the antimicrobial activities and the cytotoxicities of these three pairs of optically pure enantiomers (1a/1b, 2a/2b, and 3a/3b) had been evaluated.

Phyllomeroterpenoids A-C, Multi-biosynthetic Pathway Derived Meroterpenoids from the TCM Endophytic Fungus Phyllosticta sp. and their Antimicrobial Activities

Phyllomeroterpenoids A−C (1−3), multi-biosynthetic pathway derived meroterpenoids from amino acid/pentose phosphate/terpenoid pathways, were isolated from the TCM endophytic fungus Phyllosticta sp. J13-2-12Y, together with six biosynthetically related compounds (4−9). All structures were determined by extensive spectroscopic analysis, chemical derivatization, and ECD experiments. A plausible biosynthetic pathway of 1−3 was proposed. In addition, the antimicrobial activities of all isolated compounds were evaluated against Staphylococcus aureus 209P (bacterium) and Candida albicans FIM709 (fungus).

Chiral resolution, absolute configuration, and bioactivity of a new racemic asarone derivative from the rhizome of Acorus tatarinowii

A new asarone-derived racemate (1) was isolated from the rhizome of Acorus tatarinowii. The structure of 1 was established by comprehensive spectroscopic analyses, and it was successfully resolved by chiral HPLC, demonstrating that it is racemic. The absolute configurations of 1a [(-)-acortatarone A] and 1b [(+)-acortatarone A] were determined using quantum chemical calculations. Compounds 1a and 1b were the first cases of asarone derivatives with the 5,7-dialkyl-6-aryl-8-oxabicyclo[3.2.1]oct-3-en-2-one core. The α-glucosidase inhibitory and acetylcholinesterase (AChE) inhibitory activities of 1 were evaluated, and it exhibited α-glucosidase inhibitory activity with potency close to that of the positive control (acarbose).

Pharmacology and toxicology of α- and β-Asarone: A review of preclinical evidence

BACKGROUND

Asarone is one of the most researched phytochemicals and is mainly present in the Acorus species and Guatteria gaumeri Greenman. In preclinical studies, both α- and β-asarone have been reported to have numerous pharmacological activities and at the same time, many studies have also revealed the toxicity of α- and β-asarone.

PURPOSE

The purpose of this comprehensive review is to compile and analyze the information related to the pharmacokinetic, pharmacological, and toxicological studies reported on α- and β-asarone using preclinical in vitro and in vivo models. Besides, the molecular targets and mechanism(s) involved in the biological activities of α- and β-asarone were discussed.

METHODS

Databases including PubMed, ScienceDirect and Google scholar were searched and the literature from the year 1960 to January 2017 was retrieved using keywords such as α-asarone, β-asarone, pharmacokinetics, toxicology, pharmacological activities (e.g. depression, anxiety).

RESULTS

Based on the data obtained from the literature search, the pharmacokinetic studies of α- and β-asarone revealed that their oral bioavailability in rodents is poor with a short plasma half-life. Moreover, the metabolism of α- and β-asarone occurs mainly through cytochrome-P450 pathways. Besides, both α- and/or β-asarone possess a wide range of pharmacological activities such as antidepressant, antianxiety, anti-Alzheimer's, anti-Parkinson's, antiepileptic, anticancer, antihyperlipidemic, antithrombotic, anticholestatic and radioprotective activities through its interaction with multiple molecular targets. Importantly, the toxicological studies revealed that both α- and β-asarone can cause hepatomas and might possess mutagenicity, genotoxicity, and teratogenicity.

CONCLUSIONS

Taken together, further preclinical studies are required to confirm the pharmacological properties of α-asarone against depression, anxiety, Parkinson's disease, psychosis, drug dependence, pain, inflammation, cholestasis and thrombosis. Besides, the anticancer effect of β-asarone should be further studied in different types of cancers using in vivo models. Moreover, further dose-dependent in vivo studies are required to confirm the toxicity of α- and β-asarone. Overall, this extensive review provides a detailed information on the preclinical pharmacological and toxicological activities of α-and β-asarone and this could be very useful for researchers who wish to conduct further preclinical studies using α- and β-asarone.

Anti-neuroinflammatory asarone derivatives from the rhizomes of Acorus tatarinowii

A novel 7-O-7′ type mesomeric neolignan,meso-asarolignan A (1), six pairs of new neolignan enantiomers, (±)-asarolignan B–G (2a/2b,3a/3b,4–6,7a/7b), along with 16 known analogues (8–23) were isolated from the rhizomes ofAcorus tatarinowii.