Daphmacrimines A-K, Daphniphyllum alkaloids from Daphniphyllum macropodum Miq.

Daphmacrimines A-K (1-11) were isolated from the leaves and stems of Daphniphyllum macropodum Miq. Their structures and stereochemistries were determined by extensive techniques, including HRESIMS, NMR, ECD, IR, and single-crystal X-ray crystallography. Daphmacrimines A-D (1-4) are unprecedented Daphniphyllum alkaloids with a 2-oxazolidinone ring. Daphmacrimine I (9) contains a nitrile group, which is relatively rare in naturally occurring alkaloids. The abilities of daphmacrimines A-D and daphmacrimines G-K to enhance lysosomal biogenesis were evaluated through LysoTracker Red staining. Daphmacrimine K (11) can induce lysosomal biogenesis and promote autophagic flux.

Dual Effects of 3-epi-betulin from Daphniphyllum glaucescens in Suppressing SARS-CoV-2-Induced Inflammation and Inhibiting Virus Entry.

The continuous emergence of SARS-CoV-2 variants has led to a protracted global COVID-19 pandemic with significant impacts on public health and global economy. While there are currently available SARS-CoV-2 vaccines and therapeutics, most of the FDA-approved antiviral agents directly target viral proteins. However, inflammation is the initial immune pathogenesis induced by SARS-CoV-2 infection, there is still a need to find additional agents that can control the virus in the early stages of infection to alleviate disease progression for the next pandemic. Here, we find that both the spike protein and its receptor CD147 are crucial for inducing inflammation by SARS-CoV-2 in THP-1 monocytic cells. Moreover, we find that 3-epi-betulin, isolated from Daphniphyllum glaucescens, reduces the level of proinflammatory cytokines induced by SARS-CoV-2, consequently resulting in a decreased viral RNA accumulation and plaque formation. In addition, 3-epi-betulin displays a broad-spectrum inhibition of entry of SARS-CoV-2 pseudoviruses, including Alpha (B.1.1.7), Eplison (B.1.429), Gamma (P1), Delta (B.1.617.2) and Omicron (BA.1). Moreover, 3-epi-betulin potently inhibits SARS-CoV-2 infection with an EC50 of <20 µM in Calu-3 lung epithelial cells. Bioinformatic analysis reveals the chemical interaction between the 3-epi-betulin and the spike protein, along with the critical amino acid residues in the spike protein that contribute to the inhibitory activity of 3-epi-betulin against virus entry. Taken together, our results suggest that 3-epi-betulin exhibits dual effect: it reduces SARS-CoV-2-induced inflammation and inhibits virus entry, positioning it as a potential antiviral agent against SARS-CoV-2.

Total Synthesis of Four Classes of Daphniphyllum Alkaloids.

The macrodaphniphyllamine-type, calyciphylline A-type, daphnilongeranin A-type, and daphnicyclidin D-type alkaloids are four structurally related classes of Daphniphyllum alkaloids. On the basis of a systematic analysis of the biogenetic network of these classes, we developed synthetic strategies centered on the C4-N and C1-C8 bonds of calyciphylline A, which took full advantage of the suitable substrates, reactions, and pathways that are altered from their counterparts in the postulated biogenetic network. Through this generalized biomimetic approach, we achieved the first synthesis of 14 Daphniphyllum alkaloids from the four subfamilies.

Genetic differentiation and evolution of broad-leaved evergreen shrub and tree varieties of Daphniphyllum macropodum (Daphniphyllaceae).

Tree form evolution is an important ecological specialization for woody species, but its evolutionary process with adaptation is poorly understood, especially on the microevolutionary scale. Daphniphyllum macropodum comprises two varieties: a tree variety growing in a warm temperate climate with light snowfall and a shrub variety growing in a cool temperate climate with heavy snowfall in Japan. Chloroplast DNA variations and genome-wide single-nucleotide polymorphisms across D. macropodum populations and D. teijsmannii as an outgroup were used to reveal the evolutionary process of the shrub variety. Population genetic analysis indicated that the two varieties diverged but were weakly differentiated. Approximate Bayesian computation analysis supported a scenario that assumed migration between the tree variety and the southern populations of the shrub variety. We found migration between the two varieties where the distributions of the two varieties are in contact, and it is concordant with higher tree height in the southern populations of the shrub variety than the northern populations. The genetic divergence between the two varieties was associated with snowfall. The heavy snowfall climate is considered to have developed since the middle Quaternary in this region. The estimated divergence time between the two varieties suggests that the evolution of the two varieties may be concordant with such paleoclimatic change.

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Analyzing the pattern of altitudinal variation in the leaf traits and their networks of a particular tree species of similar age and its influencing factors could contribute to understanding the impacts of environmental factors on leaf traits and excluding the interference of genetic factors. We investigated the stomatal, structural, chemical, and vein traits of Daphniphyllum macropodum leaves in middle-aged forests, following the altitudinal gradient (1100, 1500, and 1900 m) on Mao'er Mountain. The objectives of this study were to reveal patterns in leaf trait and leaf trait networks variation, the life strategy of the tree species, and the major environmental factors affecting the altitudinal variations. The results showed that leaf area, specific leaf area, leaf thickness, leaf dry matter content, chlorophyll content, nitrogen content, phosphorus content, C:N, C:P, vein density, and vein diameter varied significantly across altitudes. Mean annual temperature and total radiation explained 42.1% and 16.2% of leaf-trait variation, respectively. They served as key environmental factors driving the altitudinal variation in leaf traits. Mean annual temperature exhibited the greatest influence on leaf area (R2=0.73), and total radiation exerted the most prominent effect on leaf thickness (R2=0.72). Both relationships were significantly positive. D. macropodum exhibited low leaf nitrogen and phosphorus at the low altitude of 1100 m, and the overall and local trait networks were loose, adopting a conservative resource strategy. At the medium altitude of 1500 m, leaf nutrient contents were relatively high. The overall network of leaf traits was tightly connected and local network was loose. By enhancing the dependency among leaf traits, and improving phosphorus utilization efficiency, D. macropodum could cope with competition in deciduous forests and adopt resource acquisition strategies. Further, at the highest altitude of 1900 m, D. macropodum had relatively large leaf thickness, chlorophyll content, and leaf dry matter content, but relatively small leaf area. The local network connections were tight while the overall network looseness, indicating a resource conserving strategy. The trade-off relationship between C:P and leaf phosphorus content was closely related to phosphorus use efficiency, and its variation was an important indicator for identifying life strategies of D. macropodum in different altitudes.

Construction of the [7-5-5] Tricyclic Core of Daphniphyllum Alkaloids via a Cationic Cascade Reaction.

The [7-5-5] tricyclic core of daphniphyllum alkaloids, containing contiguous stereogenic centers at C14 and C15 and a tetrasubstituted alkene moiety between C9 and C10, was constructed via a cascade reaction that involved an electrocyclic reaction of a pentadienyl cation and intramolecular interception of the resultant cyclopentenyl cation.

Total Syntheses of Daphnezomine L-type and Secodaphniphylline-type Daphniphyllum Alkaloids via Late-Stage C-N Bond Activation.

Here, we report the first total syntheses of daphnezomine L-type alkaloids daphnezomine L methyl ester and calyciphylline K via late-stage C-N bond activation. The first synthesis of secodaphniphylline-type alkaloid caldaphnidine D was also achieved via a similar strategy. Other key transformations employed in our synthesis were a facile vicinal diol olefination and an efficient radical cyclization cascade. Biological studies indicated two synthetic compounds possess promising neuroprotective activity.

Chemical and biological studies of Daphniphyllum oldhamii from Hunan Province, China.

The fruits, twigs and leaves of Daphniphyllum oldhamii (Hemsl.) K. Rosenthal, collected from Longshan County, Hunan Province, China, were chemically investigated. Three undescribed daphniphyllum alkaloids, namely longshanoldhamines A‒C, and six known related ones have been isolated from the fruits, whereas two undescribed triterpenoids and one undescribed lignan, along with six known triterpenoids, were found in the twigs and leaves. Their structures were elucidated by extensive spectroscopic analysis, X-ray diffraction analysis and comparison with the reported data.

The chemistry of Daphniphyllum alkaloids.

The triterpenoids Daphniphyllum alkaloids share the unique fused hexacyclic ring framework are isolated from the genus Daphniphyllum. These natural products possess comprehensive biological activities and exhibit excellent potential medicinal appliment. This review covers the reported isolation studies and biological activities of Daphniphyllum alkaloids spanning the period from 1966 to the beginning of 2020, In the meantime, the total synthesis of Daphniphyllum alkaloids will be emphatically summarized for supplement over this review series.

Total Synthesis of Daphniphyllum Alkaloids: From Bicycles to Diversified Caged Structures.

Native to the Asia-Pacific region and widely applied in traditional Chinese medicine, the genus Daphniphyllum has produced over 330 known Daphniphyllum alkaloids. Investigations into these alkaloids have shown an exceptional range of interesting bioactivities. Challenging and caged polycyclic architectures and the promising biological profiles make Daphniphyllum alkaloids intriguing synthetic targets. Based on their backbones, these alkaloids can be categorized into 13-35 structurally distinct subfamilies. In addition to our work, almost 30 impressive total syntheses of Daphniphyllum alkaloids from seven subfamilies, namely, daphniphylline-type, secodaphniphylline-type, daphnilactone A-type, bukittinggine-type, daphmanidin A-type, calyciphylline A-type, and calyciphylline B-type alkaloids, have been reported by 11 research groups. However, many Daphniphyllum alkaloid subfamilies remain inaccessible by chemical synthesis.In this Account, we summarize our recent endeavors in the total synthesis of Daphniphyllum alkaloids commencing from simple chiral bicyclic synthons. Daphniphyllum alkaloids with diversified skeletons from four different subfamilies, namely, calyciphylline A-type, daphnezomine A-type, bukittinggine-type, and yuzurimine-type alkaloids, have been achieved. Furthermore, the tricyclic core structure of daphniglaucin C-type alkaloids daphnimacropodines was also synthesized. First, we describe a 14-step synthesis of calyciphylline A-type alkaloid (-)-himalensine A, which features a mild Cu-mediated nitrile hydration, an intramolecular Heck reaction to assemble the pivotal 2-azabicyclo[3.3.1]nonane moiety, and a Meinwald rearrangement to introduce the critical oxidative state into the skeleton. We then introduce the synthesis of daphnezomine A-type alkaloid dapholdhamine B, which possesses a unique aza-adamantane core. This target molecule was fabricated using key reactions including Huang's amide-activation-annulation. An unexpected radical detosylation during the synthesis of dapholdhamine B further inspired an ambitious radical cyclization cascade strategy, which eventually led to an efficient total synthesis of bukittinggine-type alkaloid (-)-caldaphnidine O. This highly chemo-, regio-, and stereoselective radical reaction cascade also shed light on the synthetic strategy of other alkaloids with caged structures. We next describe the first total synthesis of yuzurimine-type alkaloid (+)-caldaphnidine J. The key steps in our approach include a Pd-catalyzed regioselective hydroformylation and a novel Swern oxidation/ketene dithioacetal Prins reaction cascade. The work has achieved the first synthesis of a member of the largest subfamily of Daphniphyllum alkaloids. Finally, we show our efforts toward the total synthesis of daphniglaucin C-type alkaloids. Overall, we hope that the interesting strategies and synthetic methods demonstrated in our efforts could inspire a wide variety of additional applications to natural product synthesis.

FengLiao affects gut microbiota and the expression levels of Na+/H+ exchangers, aquaporins and acute phase proteins in mice with castor oil-induced diarrhea.

The severe side effects of chemosynthetic anti-diarrhea drugs have created an interest in low-toxic alternative plant-derived compounds. FengLiao consists of Polygonum hydropiper Linn. and Daphniphyllum calycinum Bench., and is widely used in China to treat diarrhea due to low levels of toxicity. In this study, the effects of FengLiao were analyzed in a castor oil-induced diarrhea model, using the anti-diarrhea drug, loperamide, as the positive control. The effects were evaluated using stool characteristics and the expression levels of various diarrhea-related factors in the jejunum and liver, as well as changes in the microbiota of the jejunum. The symptoms of diarrhea and stool consistency were improved through FengLiao and loperamide treatment. Furthermore, FengLiao down-regulated alpha 1-acid glycoprotein (AGP) and C-reactive protein (CRP) levels, and up-regulated transferrin (TRF) mRNA levels in the liver, and down-regulated Aquaporin 3 (AQP3) and Na+/H+ exchanger isoform 8 (NHE8) expression in the epithelial cells of the jejunum. It also increased the relative abundance of Bifidobacterium, Aerococcus, Corynebacterium_1 and Pseudomonas, and lowered the Firmicutes/Bacteroidetes (F/B) ratio, which maintained the balance between immunity and intestinal health. Taken together, FengLiao alleviated castor oil-induced diarrhea by altering gut microbiota, and levels of jejunum epithelial transport proteins and acute phase proteins.

Asymmetric total synthesis of yuzurimine-type Daphniphyllum alkaloid (+)-caldaphnidine J.

Ever since Hirata's report of yuzurimine in 1966, nearly fifty yuzurimine-type alkaloids have been isolated, which formed the largest subfamily of the Daphniphyllum alkaloids. Despite extensive synthetic studies towards this synthetically challenging and biologically intriguing family, no total synthesis of any yuzurimine-type alkaloids has been achieved to date. Here, the first enantioselective total synthesis of (+)-caldaphnidine J, a highly complex yuzurimine-type Daphniphyllum alkaloid, is described. Key transformations of this approach include a highly regioselective Pd-catalyzed hydroformylation, a samarium(II)-mediated pinacol coupling, and a one-pot Swern oxidation/ketene dithioacetal Prins reaction. Our approach paves the way for the synthesis of other yuzurimine-type alkaloids and related natural products.

Daphnillonins A and B: Alkaloids Representing Two Unknown Carbon Skeletons from Daphniphyllum longeracemosum.

Two highly rearranged daphniphyllum alkaloids, daphnillonins A (1) and B (2), were isolated from Daphniphyllum longeracemosum and structurally characterized by a combination of diverse methods, including the calculation of electronic circular dichroism. Compound 1 possesses an unprecedented carbon architecture with a very unique 8-methyl-6-azabicyclo[3.2.1]octane moiety, and compound 2 represents a new carbon skeleton with an uncommon 7/6/5/7/5/5-fused ring system. The biosynthetic pathways for the two alkaloids were proposed with the concurrent major alkaloids as the precursors.

Construction of the Tetracyclic Core of Calyciphylline B-Type Daphniphyllum Alkaloids.

A double cyclization strategy was developed to construct the common tetracyclic core of calyciphylline B-type alkaloids. Key features of the synthesis included asymmetric Evans alkylation, ring-closing metathesis reaction, intermolecular amidation, intramolecular aza-Michael addition, and aldol condensation reactions. This strategy may be applied to the total syntheses of this type of natural product.

Structural Revision of Macropodumine A and Structure of 2-Deoxymacropodumine A, Daphniphyllum Alkaloids with 11-Membered Macrolactone Rings.

An unusual Daphniphyllum alkaloid, 2-deoxymacropodumine A (1), possessing an 11-membered macrolactone ring, was obtained from an extract of the stems of Daphniphyllum angustifolium. The structure of 1 was elucidated by 1D and 2D NMR spectroscopic methods and chemical calculations. Based on a comparison of the experimental and calculated NMR data, the structure of macropodumine A (2'), an analogue of 1, was also revised.

Glaulactams A-C, daphniphyllum alkaloids from Daphniphyllum glaucescens.

Glaulactams A-C (1-3), which possess a novel skeleton, as well as the known compound daphmanidin B (4), were isolated from the leaves of Daphniphyllum glaucescens and separated using ion-exchange chromatography aided by NMR fingerprinting. Their structures, including their absolute configurations, were elucidated by spectroscopic analyses and time-dependent density-functional-theory-calculated electronic circular dichroism spectra; the data were subsequently analyzed to gain insight into the respective biogenetic relationships between the isolates, which exhibited anti-H1N1 and immunosuppressive activities.

Synthesis of the [7-5-5] tricyclic core of Daphniphyllum alkaloids.

The [7-5-5] tricyclic core of the Daphniphyllum alkaloids was constructed, featuring a Claisen-Ireland rearrangement to install the two contiguous stereogenic centers, E1cB elimination to form the tetrasubstituted C-C double bond, and a 2,3-Wittig rearrangement to construct the quaternary carbon. Ring-closing metathesis and an intramolecular carbonyl ene reaction were employed for construction of the requisite ring system.