Daphmacromines A-J, alkaloids from Daphniphyllum macropodum

Variation of terpene alkaloids in Daphniphyllum macropodum across plants and tissues

Daphniphyllum macropodum produces alkaloids that are structurally complex with polycyclic, stereochemically rich carbon skeletons. Understanding how these compounds are formed by the plant may enable exploration of their biological function and bioactivities. We employed multiple metabolomics techniques, including a workflow to annotate compounds in the absence of standards, to compare alkaloid content across plants and tissues. Different alkaloid structural types were found to have distinct distributions between genotypes, between tissues and within tissues. Alkaloid structural types also showed different isotope labelling enrichments that matched their biosynthetic relationships. The work suggests that mevalonate derived 30-carbon alkaloids are formed in the phloem region before their conversion to 22-carbon alkaloids which accumulate in the epidermis. This sets the stage for further investigation into the biosynthetic pathway.

Total Synthesis of Yuzurine-type Alkaloid Daphgraciline

The first total synthesis of daphgraciline has been achieved, which also represents the first example of the synthesis of Daphniphyllum yuzurine-type alkaloids (∼50 members). The unique bridged azabicyclo[4.3.1] ring system in the yuzurine-type subfamily was efficiently and diastereoselectively assembled via a mild type II [5+2] cycloaddition for the first time. The compact tetracyclic [6-7-5-5] skeleton was installed efficiently via an intramolecular Diels-Alder reaction, followed by a benzilic acid-type rearrangement. The synthetically challenging spiro tetrahydropyran moiety in the final product was installed diastereoselectively via a Ti^III-mediated reductive epoxide coupling reaction. Potential access to enantioenriched daphgraciline is presented.

New Secodaphnane-Type Alkaloids with Cytotoxic Activities from Daphniphyllum angustifolium Hutch

One new Daphniphyllum alkaloid, daphnioldhanol A (1), together with three known ones, were isolated from the stem part of Daphniphyllum angustifolium Hutch. Their structures were elucidated by spectroscopic methods and comparing with the literature data. Compound 2 is a new natural product, but known by synthesis as a racemate. Compound 1 exhibited week cytotoxic activity against Hela cell line with IC₅₀ of 31.9 μM.

Calycindaphines A–J, Daphniphyllum alkaloids from the roots of Daphniphyllum calycinum

Ten new Daphniphyllum alkaloids, calycindaphines A–J (1–10), together with seventeen known alkaloids were isolated from the roots of Daphniphyllum calycinum. Their structures were established by extensive spectroscopic methods and compared with data from literature. Compound 1 is a novel alkaloid with a new rearrangement C₂₂ skeleton with the 5/8/7/5/5 ring system. Compound 2 represents the second example of calyciphylline G-type alkaloids. Compound 10 is the first example of secodaphniphylline-type alkaloid absent of the oxygen-bridge between C-25/C-29. The possible biogenetic pathways of 1 and 2 were also proposed. All the isolated compounds were evaluated for their bioactivities in three cell models. Compounds 22, 23, and 26 showed significant NF-κB transcriptional inhibitory activity at a concentration of 50 μM. Compounds 16 and 18 exhibited significant TGF-β inhibitory activity in HepG2 cells. Compounds 24 and 26 induced autophagic puncta and mediated the autophagic marker LC3-II conversion in HEK293 cells.

Ten new Daphniphyllum alkaloids, calycindaphines A–J (1–10), were isolated from Daphniphyllum calycinum. Compound 1 possesses a unique C₂₂ skeleton with the 5/8/7/5/5 ring system and might be a key intermediate for daphhimalenine A formation.

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.

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.

An Explorer of Chemical Biology of Plant Natural Products in Southwest China, Xiaojiang Hao

Xiaojiang Hao, who obtained Master Degree from Kunming Institute of Botany (KIB), Chinese Academy of Sciences (CAS) in 1985, and Doctor in Pharmacy degree in Pharmacy from Institute for Chemical Research, Kyoto University, in 1990, was born in Chongqing in July, 1951. In 1991, he returned to KIB, CAS, as an Associate professor and served as the chair of the Department of Phytochemistry. In 1994, he was promoted to a full professor at the current institute. He served as the Deputy Director of KIB and the Director of Open Laboratory of Phytochemistry from 1995 to 1997, and the Director of KIB from 1997 to 2005. Professor Hao has published more than 450 peer-reviewed SCI papers, which have been cited over 6000 times. He has obtained one PCT patent and 23 patents in China. Due to his tremendous efforts, one candidate drug, phenchlobenpyrrone, has entered the Phase II clinical trail for the treatment of Alzheimer's disease. Moreover, he won the First Prize of Natural Sciences in Yunnan Province for three times, and Ho Leung Ho Lee Fund Science and Technology Innovation Award in 2017.

Daphniphyllum alkaloids with cytotoxic activity from Daphniphyllum angustifolium

A new Daphniphyllum alkaloid, daphnezomine W (1), together with four known ones, were isolated from the stems of Daphniphyllum angustifolium Hutch. Their structures were elucidated by spectroscopic methods and comparing with the literature data. Compound 1 was a new daphnezomine L-type alkaloid and exhibited moderate cytotoxic activity against Hela cell line with IC₅₀ of 16.0 μg/mL. A plausible biosynthetic pathway of 1 was also proposed.

Recent Progress in the Chemistry of Daphniphyllum Alkaloids †

Daphniphyllum is an evergreen species known since 1826. After initial systematic investigations, more than 320 members of this family have been isolated, which comprise complex and fascinating structures. Unique azapolycyclic architectures containing one or more quaternary stereocenters render these alkaloids synthetically challenging. This review covers efforts toward the synthesis of Daphniphyllum alkaloids spanning the period from 2005 to the beginning of 2016, including reported biological activities as well as the isolation of new members of this genus.

Cytotoxic neolignans from the traditional Chinese medicine Daphniphyllum macropodum Miq

Four new neolignans (1–4) were isolated from the seeds of Daphniphyllum macropodum Miq. and the evaluated for their antiproliferative activity showed that 2 could induced the apoptosis in A549 cells through activating the mitochondrial pathway.

Sterhirsutins A and B, two new heterodimeric sesquiterpenes with a new skeleton from the culture of Stereum hirsutum collected in Tibet Plateau

Two new heterodimeric sesquiterpenes, sterhirsutins A (1) and B (2), and two new sesquiterpenes, hirsutic acids D-E (3 and 4), were identified from the culture of Stereum hirsutum. The absolute configurations in 1 and 2 were confirmed by single-crystal X-ray diffraction experiments and electronic circular dichroism (ECD) calculations. Compounds 1 and 2 are likely biosynthesized from a hirsutane-type sesquiterpene and α-humulene by a hetero-Diels-Alder cycloaddition. Compounds 1-4 showed cytotoxicity against K562 and HCT116 cell lines.

Antimicrobial Constituents of the Mature Carpels of Manglietiastrum sinicum

Seven new compounds, including a eupodienone-type lignan (1), a dibenzocyclooctadiene-type lignan (2), three tetrahydrofuran-type lignans (3-5), and two 1-phenylbutyl benzoates (6, 7), together with six known compounds, were isolated from the mature carpels of Manglietiastrum sinicum. The structures of new compounds 1-7 were defined by spectroscopic techniques, and the absolute configuration of manglisin A (1) was determined by X-ray crystallography. Compounds 1-4 exhibited moderate antimicrobial activities (MIC values: 0.016-0.14 μM) against Staphylococcus aureus, MRSA 82(#), MRSA 92(#), MRSA 98(#), and MRSA 331(#). Compounds 2 and 3 showed weak cytotoxic activity against five human tumor cell lines.

Anti-diabetic properties of Daphniphyllum macropodum fruit and its active compound

We evaluated in vitro anti-diabetic activities of 497 native plants of Jeju Island (South Korea) by measuring the induction of adipocyte differentiation. Among the plants, Daphniphyllum macropodum fruit extract (DME) had the highest peroxisome proliferator-activated receptor γ (PPARγ) agonist activity and was therefore selected as a potential source of anti-diabetic agents. To elucidate the active components of DME, constituent compounds were purified and their effects on the adipocyte differentiation were studied. Using activity-guided fractionation, four compounds were isolated from DME and their adipogenic effects were evaluated. Among the compounds isolated, 5,7-dihydroxychromone potently induced the differentiation of mouse 3T3-L1 preadipocytes. DME and 5,7-dihydroxychromone increased PPARγ and liver X receptor α (LXRα) mRNA expression levels. To determine whether the adipogenic effects we observed might affect serum glucose levels, we undertook in vivo experiment using streptozotocin-/high-fat diet-induced type 2 diabetes mouse model. DME supplementation reduced serum glucose, total cholesterol, and triacylglycerol levels in diabetes mice. These results suggest that DME may be useful for the prevention and treatment of type 2 diabetes mellitus. Moreover, it was proposed that 5,7-dihydroxychromone isolated from DME is one of the active compounds that may contribute to regulate blood glucose levels.

In vivo antimalarial efficacy of acetogenins, alkaloids and flavonoids enriched fractions from Annona crassiflora Mart

Annona crassiflora and Annonaceae plants are known to be used to treat malaria by traditional healers. In this work, the antimalarial efficacy of different fractions of A. crassiflora, particularly acetogenin, alkaloids and flavonoid-rich fractions, was determined in vivo using Plasmodium berghei-infected mice model and toxicity was accessed by brine shrimp assay. The A. crassiflora fractions were administered at doses of 12.5 mg/kg/day in a 4-day test protocol. The results showed that some fractions from woods were rich in acetogenins, alkaloids and terpenes, and other fractions from leaves were rich in alkaloids and flavonoids. The parasitaemia was significantly (p < 0.05, p < 0.001) reduced (57-75%) with flavonoid and alkaloid-rich leaf fractions, which also increased mean survival time of mice after treatment. Our results confirm the usage of this plant in folk medicine as an antimalarial remedy.

Five new alkaloids from the stem bark of Daphniphyllum macropodum

Five new alkaloids, daphnicyclidins M and N (compounds 1 and 2) and calyciphyllines Q-S (compounds 3-5), along with four known ones, paxiphylline C (6), macropodumine B (7), macropodumine C (8) and daphnicyclidin A (9) were isolated from the stem bark of Daphniphyllum macropodum. Calyciphylline Q (3) is the first calyciphylline A derivative possessing a double bond between C-18 and C-19. Their structures and relative configurations were elucidated on the basis of spectroscopic methods, especially 2D NMR techniques. Compounds 1, 2, 8 and 9 exhibited cytotoxic activity against P-388 cells with IC₅₀ values of 5.7, 6.5, 10.3 and 13.8 µM, respectively. Compounds 1 and 2 also showed cytotoxic activity against SGC-7901 cells with IC₅₀ values of 22.4 and 25.6 µM.

Strategies towards the synthesis of calyciphylline A-type Daphniphyllum alkaloids

The Daphniphyllum alkaloids are a diverse family of natural products rich in number and structural diversity that have been known for many decades. However, the structurally unique subclass of calyciphylline A-type alkaloids has only recently been discovered and is relatively unexplored. Several noteworthy core syntheses and the development of a wide range of novel synthetic strategies have been achieved. This includes strategies based on intramolecular Michael addition, Pd-catalysis, cycloaddition, and Mannich-type reactions. This review will provide an overview of these synthetic studies.

Rapid access to the heterocyclic core of the calyciphylline A and daphnicyclidin A-type Daphniphyllum alkaloids via tandem cyclization of a neutral aminyl radical

A streamlined approach to the tertiary amine-containing core of the calyciphylline A and daphnicyclidin A-type Daphniphyllum alkaloids is presented. A known carvone derivative is converted into the core structure in only four synthetic operations, and it is well poised for further elaboration. The key enabling methodology is a radical cyclization cascade beginning with addition of a secondary, neutral aminyl radical to the β-position of an enone, followed by trapping with a pendant alkyne.

Bioactive limonoid and triterpenoid constituents of Turraea pubescens

Eleven new limonoids, turrapubins A-K (1-11), and three new triterpenoids (12-14), along with 14 known compounds, were isolated from the twigs of Turraea pubescens. The structures of 1-14 were elucidated on the basis of NMR and MS analysis. Compounds 12, 16, 18, and 19 exhibited inhibitory activities against lipopolysaccharide-induced nitric oxide production in RAW264.7 cells. In addition, compounds 2, 11, 18, and 26 exhibited inhibitory activities against brine shrimp larvae (Artemia salina) at 100 ppm with the corrected mortality ranging from 81.7% to 100%.

Daphmacromines K-O, alkaloids from Daphniphyllum macropodum

Five new yuzurimine-type Daphniphyllum alkaloids, daphmacromines K-O (1-5), were isolated from the leaves and stems of Daphniphyllum macropodum. Their structures were elucidated by extensive spectroscopic techniques, including 2D NMR spectroscopy and mass spectrometry. Daphmacromine O (5) showed moderate cytotoxic activity against brine shrimp.

Daphmacrodins A and B, alkaloids from Daphniphyllum macropodum

Two new daphnicyclidin-type Daphniphyllum alkaloids, daphmacrodins A and B (1 and 2) were isolated from the leaves and stems of Daphniphyllum macropodum. Their structures were elucidated by extensive spectroscopic techniques, including 2D NMR spectroscopy and mass spectrometry. The relative configuration of 1 was further confirmed by a single-crystal X-ray diffraction analysis. Their cytotoxic activities against five human cancer cell lines, pesticidal activities against brine shrimp (Artemia salina), and antibacterial activities against five standard bacterial and fungal strains were evaluated. The structure of 1 was successfully transformed to 2 by a chemical method.