Lauinoids A-X: Labdane-type diterpenoids with anti-inflammatory activity from Croton laui

Croton laui (Euphorbiaceae) is a traditional medicinal plant used by the Li ethnic group in China to treat headaches, stomachaches, and diphtheria. To understand the pharmacological basis of its medicinal use, an extensive investigation of the ethanolic extract of the bark of C. laui was performed. After repeated chromatography, twenty-four undescribed labdane-type diterpenoids, lauinoids A-X (1-24), and five known analogs (25-29) were isolated. Their structures and absolute configurations were established using a combination of spectroscopic analyses, electronic circular dichroism, nuclear magnetic resonance calculations, and single-crystal X-ray diffraction. Among them, compounds 1-3 exhibited an 11(12 → 13)-abeo-16-nor-labdane skeleton, which originated putatively from 9 through a plausible pathway that involves a semipinacol rearrangement process. Compounds 11 and 12 belong to the rare class of 14,15-dinor-labdane diterpenoids. Compounds 18 and 28 exhibited substantial inhibitory effects by suppressing lipopolysaccharide-induced NO production in RAW 264.7 macrophages, with IC50 values of 3.37 ± 0.23 and 5.82 ± 0.28 μM, respectively. This study has greatly expanded the chemical diversity of labdane diterpenoids from C. laui and will guide future research on this ethnomedicinal plant.

Crotonoids A-H, Labdane-Type Diterpenoids with Anti-Inflammatory Activity from Croton sublyratus

Croton sublyratus (Euphorbiaceae) is a traditional medicinal plant used by the Thai populace to treat helminthic infections and dermatologic conditions. In present study, eight new labdane-type diterpenoids, crotonoids A-H (1-8) and one known analogue (9) were isolated from the aerial parts of C. sublyratus. Compounds 6 and 7 belong to the rare class of 14,15-dinor-labdane diterpenoids. Compound 8 exhibited a rare 14,15,17-trinor-labdane skeleton. The structures of all these diterpenoids were elucidated by spectroscopic data analysis, electronic circular dichroism calculations, and single-crystal X-ray diffraction analysis. Compound 9 exhibited moderate anti-inflammatory activity via the inhibition of NO production in lipopolysaccharide-induced RAW 264.7 cells.

Highly modified cephalotane-type diterpenoids from Cephalotaxus fortunei var. alpina and C. sinensis

Cephalotanes are a rare class of diterpenoids occurring exclusively in Cephalotaxus plants. The intriguing structures and promising biological activities for this unique compound class prompt us to investigate C. fortunei var. alpina and C. sinensis, leading to the isolation of six undescribed cephalotane-type diterpenoids and/or norditerpenoids, ceforloids A-F (1-6). Their structures were elucidated by comprehensive analysis of spectroscopic data, including ECD and single-crystal X-ray diffraction studies, as well as quantum chemical calculations. Compound 1 possesses an unprecedented norditerpenoid skeleton featuring an unusual acetophenone moiety, and originated putatively from a disparate biogenetic pathway. Compounds 4 and 5 incorporate a unique 12,13-p-hydroxybenzylidene acetal motif. Compound 6 is a rare cephalotane-type diterpenoid glycoside. Immunosuppressive assays showed that compounds 2 and 6 exhibited mild suppressive activity against the activated T and B lymphocytes proliferation. These findings not only expanded the structural diversity of this small group of diterpenoids, but also explored their potential as novel structures for the development of immunosuppressive agents.

Anti-Inflammatory Salicin Derivatives from the Barks of Salix tetrasperma

The genus Salix L. is traditionally used in folk medicine to alleviate pain caused by various kinds of inflammation. In the present study, 10 undescribed salicin derivatives along with 5 known congeners were isolated from the barks of Salix tetrasperma, and their structures were elucidated by spectroscopic analyses, single-crystal X-ray diffraction, electronic circular dichroism (ECD) calculations, and chemical conversions. Compounds 4-6 significantly inhibited NO production in lipopolysaccharide (LPS)-induced RAW 264.7 macrophages, and the most active 4 obviously suppressed the production of IL-1β and IL-6 and decreased iNOS and COX-2 expression in a dose-dependent manner. Further Western blotting analysis revealed that the anti-inflammatory mechanism of 4 is possibly mediated through the MAPK and NF-κB signaling pathways.

Monoterpenoid indole alkaloids from Alstonia scholaris and their Toxoplasma gondii inhibitory activity

Nine previously unreported various types of monoterpenoid indole alkaloids, together with seven known analogues were isolated from the stem barks of Alstonia scholaris through a silica gel free methodology. The structures of 1-9 were elucidated by spectroscopic data analysis, electronic circular dichroism calculations, and single-crystal X-ray diffraction. Compound 1 is a modified echitamine-type alkaloid with a novel 6/5/5/7/6/6 hetero hexacyclic bridged ring system, and 8 and 9 exist as a zwitterion and trifluoroacetate salt, respectively. The anti-Toxoplasma activity of all isolates on infected Vero cells were evaluated, which revealed that compound 14 at 0.24 μM displayed potent activity. This study expanded the structural diversity of alkaloids of A. scholaris, and presented their potential application in anti-Toxoplasma drug development.

Diterpenoids from Euphorbia peplus possessing cytotoxic and anti-inflammatory activities

Phytochemical investigation into the medium polar fraction of the ethanol extract of Euphorbia peplus led to the identification of 32 diterpenoids with five structural types. Compounds 1-5 and 7-11 are reported for the first time, while the configuration of 6,7-epoxy group of 6 was revised to be β-oriented. Compounds 1-5 feature a rare structural variation of the double bond at Δ1 migrating to Δ1(10) in the tigliane-type diterpenoid family. Biologically, compound 21 was found to be the only one to show moderate cytotoxic activity, associated with the presence of a benzoyloxy residue at C-16. Besides, compounds 4, 8, 12, 13, 16, and 19 show significant inhibitory activities against NO production induced by LPS in RAW264.7 macrophage cells, with IC50 values within 2-5 μM. Structure-activity relationship (SAR) analysis revealed that the ingenane-type diterpenoids have the best anti-inflammatory activity, and the esterification at 3-OH or 5-OH is crucial. Further biological researches demonstrated that 13, the predominant metabolite in this plant, exerts anti-inflammatory effects by blocking the activation of NF-κB and MAPK signaling pathways.

Sesquiterpenoids and Cytochalasins with Immunosuppressive Activity from Sonchus wightianus

The plant species, Sonchus wightianus DC., was historically used in China for both medicinal and dietary uses. In present study, seven new guaiane sesquiterpenoids (1-7) and one cytochalasin (8), along with five known guaianes (9-13) and two known cytochalasins (14 and 15), were isolated from the whole plants of S. wightianus. These guaianes showed structural variations in the substituents at C-8 and/or C-15, and compounds 6 and 7 are two sesquiterpenoid glycoside derivatives. Their structures were determined by extensive analysis of spectroscopic, electronic circular dichroism, and X-ray diffraction data, and chemical method. Biological tests revealed that compounds 5 and 8 are potent and selective immunosuppressive reagents.

Design and Synthesis of Cyclolipopeptide Mimics of Dysoxylactam A and Evaluation of the Reversing Potencies against P-Glycoprotein-Mediated Multidrug Resistance

Inspired by the structure of dysoxylactam A (DLA) that has been demonstrated to reverse P-glycoprotein (P-gp)-mediated multidrug resistance (MDR) effectively, 61 structurally simplified cyclolipopeptides were thus designed and synthesized via an effective method, and their reversing P-gp-mediated MDR potentials were evaluated, which provided a series of more potent analogues and allowed us to explore their structure-activity relationship (SAR). Among them, a well-simplified compound, 56, with only two chiral centers that all derived from amino acids dramatically reversed drug resistance in KBV200 cells at 10 μM in combination with vinorelbine (VNR), paclitaxel (PTX), and adriamycin (ADR), respectively, which is more promising than DLA. The mechanism study showed that 56 reversed the MDR of tumor cells by inhibiting the transport function of P-gp rather than reducing its expression. Notably, compound 56 effectively restored the sensitivity of MDR tumors to VNR in vivo at a dosage without obvious toxicity.

Unprecedented sesterterpenoids, orientanoids A-C: discovery, bioinspired total synthesis and antitumor immunity

Sesterterpenoids are a very rare class of important natural products. Three new skeletal spiro sesterterpenoids, named orientanoids A-C (1-3), were isolated from Hedyosmum orientale. Their structures were determined by a combination of spectroscopic data, X-ray crystallography, and total synthesis. To obtain adequate materials for biological research, the bioinspired total syntheses of 1-3 were effectively achieved in 7-8 steps in overall yields of 2.3-6.4% from the commercially available santonin without using any protecting groups. In addition, this work also revised the stereochemistry of hedyosumins B (6) and C (10) as 11R-configuration. Tumor-associated macrophages (TAMs) have emerged as important therapeutic targets in cancer therapy. The in-depth biological evaluation revealed that these sesterterpenoids antagonized the protumoral and immunosuppressive functional phenotype of macrophages in vitro. Among them, the most potent and major compound 1 inhibited protumoral M2-like macrophages and activated cytotoxic CD8+ T cells, and consequently inhibited tumor growth in vivo.

Densely Functionalized Macrocyclic Sesquiterpene Pyridine Alkaloids from Maytenus austroyunnanensis

Eleven densely functionalized new dihydro-β-agarofuran sesquiterpenoid derivatives, named maytenoids A-K (1-11), as well as one known analog, were isolated and characterized from Maytenus austroyunnanensis. Their structures were assigned based on analysis of spectroscopic data and X-ray crystallography. Compounds 1-9 are macrocyclic sesquiterpene pyridine alkaloids generated by the respective acylation of the hydroxy groups at C-3 and C-13 of dihydro-β-agarofuran sesquiterpenoids via diverse pyridine dicarboxylic acids. Compounds 1, 2, 5-10, and 12 exhibited significant inhibitory effects on NO production at 10 μM in lipopolysaccharide (LPS)-stimulated BV2 cells.

Highly Modified Sesquiterpene Lactones with Cytotoxic Activities from Strobocalyx chunii

Three new germacranolide sesquiterpene lactones (SLs), strochunolides A-C (1-3, respectively), and a new guaianolide SL, strochunolide D (4), were isolated from Strobocalyx chunii and structurally characterized. Compound 1 is the first example of a dihomo-germacranolide SL, characterized by an unprecedented 6/10/5 tricyclic scaffold incorporating an additional fused δ-lactone C-ring. The structure of a known germacranolide SL, spicatolide C (5), was revised as its 8-epimer. Compound 3 exhibited potent in vitro cytotoxic activity against the HL-60 cell line, with an IC50 value of 0.18 ± 0.01 μM.

A new class of potent liver injury protective compounds: Structural elucidation, total synthesis and bioactivity study

A new class of potent liver injury protective compounds, phychetins A-D (1-4) featuring an unique 6/6/5/6/5 pentacyclic framework, were isolated and structurally characterized from a Chinese medicinal plant Phyllanthus franchetianus. Compounds 2-4 are three pairs of enantiomers that were initially obtained in a racemic manner, and were further separated by chiral HPLC preparation. Compounds 1-4 were proposed to be originated biosynthetically from a coexisting lignan via an intramolecular Friedel-Crafts reaction as the key step. A bioinspired total synthesis strategy was thus designated, and allowed the effective syntheses of compounds 2-4 in high yields. Some of compounds exhibited significant anti-inflammatory activities in vitro via suppressing the production of pro-inflammatory cytokine IL-1β. Notably, compound 4, the most active enantiomeric pair in vitro, displayed prominent potent protecting activity against liver injury at a low dose of 3 mg/kg in mice, which could serve as a promising lead for the development of acute liver injury therapeutic agent.

Triterpenoids with multi-skeletons as 11 β -HSD1 inhibitors from Euphorbia sikkimensis

An exploration for 11β-HSD1 inhibitors from the whole plant of Euphorbia sikkimensis led to the identification of 10 undescribed triterpenoids 1-10, as well as 7 known triterpenoids (11-17). Their structures were determined by a combination of spectrum elucidations, conformational analyses and quantum chemical calculations. (23E)-25-methoxy-eupha-14,23-diene-3β,7α-diol (1) and (23E)-3β-dihydroxy-27-noreupha-7,23-diene-25-one (2) are two rare cases that feature a rearrangement of Me-30 (14 → 8) and a degradation of Me-27, respectively, in the euphane-type triterpenoid family. It is an interesting phenomenon that (23E)-3β-hydroxy-25-methoxy-eupha-8,23-diene-7-one (4) and (23E)-3β-hydroxy-25-methoxy-lanost-8,23-diene-7-one (5) coexist in the same plant, sharing the same planar structure but belonging to different structural types of triterpenoids. Compounds 3-5 and 14 show significant inhibitory activity against 11β-HSD1 with IC₅₀ values of 6.50 ± 0.22, 1.31 ± 0.34, 9.38 ± 0.64, and 8.27 ± 0.33 μM, respectively. The structure-activity relationship study shows that the euphane-type triterpenoids exhibit the best inhibitory activity, which is in accord with the fact of the euphane-type triterpenoids having the best ability to bind to the active pocket of 11β-HSD1 in the molecular docking experiments.

Sumatranins A-J: Lignans with Immunosuppressive Activity from Cleistanthus sumatranus

Chemical investigation of the twigs of Cleistanthus sumatranus (Phyllanthaceae) led to the isolation of 10 undescribed lignans, sumatranins A-J (1-10). Compounds 1-4 are unprecedented furopyran lignans characterized by a unique 2,3,3a,9a-tetrahydro-4H-furo[2,3-b]chromene heterotricyclic framework. Compounds 9 and 10 are rare 9'-nor-dibenzylbutane lignans. Structures were established based on analyses of spectroscopic data, X-ray crystallographic data, and experimental ECD spectra. Immunosuppressive assays revealed compounds 3 and 9 displayed moderate inhibitory effects with good selectivity indexes against LPS-induced B lymphocyte proliferation.

Diterpenoids from Euphorbia lactea and their anti-HIV-1 activity

Nine undescribed diterpenoids, euphlactenoids A-I (1-9), including four ingol-type diterpenoids (1-4) with a 5/3/11/3-tetracyclic framework and five ent-pimarane-type diterpenoids (5-9), together with thirteen known diterpenoids (10-22), were identified from the leaves and stems of Euphorbia lactea Haw. The structures and absolute configurations of compounds 1-9 were unequivocally elucidated on the basis of spectroscopic analysis, ECD calculations and single crystal X-ray diffraction. Compounds 3 and 16 showed anti-HIV-1 effects with IC₅₀ values of 1.17 μM (SI = 16.54) and 13.10 μM (SI = 1.93), respectively.

Laeviganoids A-T, ent-Clerodane-Type Diterpenoids from Croton laevigatus

Laeviganoids A-T (1-20), 20 new ent-clerodane-type diterpenoids featuring a 2-furanone (1-3) or a furan (4-20) ring, as well as six analogues (21-26), were isolated from the roots of Croton laevigatus. Their structures were determined by spectroscopic data analysis, experimental electronic circular dichroism measurements, and X-ray crystallographic studies. Compounds 4-6, 16, 21-24, and 26 could influence the anti-inflammatory protumoral phenotype of macrophages. Among these compounds, 21 and 26 are the most potent, as evidenced by consistently downregulating the classic anti-inflammatory cytokine IL-10 and upregulating the classic pro-inflammatory cytokine TNF-α on the secretion level in RAW 264.7 cells.

Allylic hydroxylation of enones useful for the functionalization of relevant drugs and natural products

Enones are privileged structural motifs in bioactive natural products and pharmaceuticals, but the γ-hydroxylation of enones is challenging. Here we show a mild and efficient method for the direct C(sp³)-H hydroxylation of enones via visible-light-induced hydrogen-atom transfer (HAT), which facilitates γ-hydroxylation of primary, secondary, and tertiary C-H bonds of different enones without involving metal and peroxide. The mechanism study shows that Na₂-eosin Y serves as both the photocatalyst and the source of catalytic bromine radical species in the HAT-based catalytic cycle, and finally sacrifices itself completely by oxidative degradation to produce bromine radical and a major product phthalic anhydride in an environmentally friendly way. This scalable method was demonstrated by plenty of substrates (41 examples) including 10 clinical drugs and 15 natural products to be useful for the late-stage functionalization of enone-containing compounds, and, in particular, has potential application in industry for large-scale production.

Sarglamides A-E, Indolidinoid-Monoterpenoid Hybrids with Anti-neuroinflammatory Activity from a Sarcandra Species

Sarglamides A-E (1-5), representing the first example of heterodimers of a trans-N-cinnamoylindolidinoid and α-phelladrene derivatives, were isolated from Sarcandra glabra subsp. brachystachys. Particularly, compounds 4 and 5 possess unprecedented cagelike 6/6/5/6/5- and 6/6/6/6/5-fused pentacyclic scaffolds, respectively. Their structures were established by spectroscopic analysis, X-ray crystallography, quantum-chemical calculations, and chemical conversions. Plausible biosynthetic pathways of 1-5 involving the coisolated enantiomers 6a and 6b were proposed. Compounds 3-7 showed inhibitory activity against lipopolysaccharide-induced inflammation in BV-2 microglial cells.

Dichapetalins from the Twigs of Dichapetalum longipetalum with Cytotoxic Activities

Continued efforts to expand the structural diversity of dichapetalins and explore further the cytotoxic structure-activity relationships have led to the isolation of 17 undescribed analogues, dichapelonins A-Q (1-17), and three known compounds (18-20) from the twigs of Dichapetalum longipetalum. Compounds 1-17 comprise five compound classes as classified by varied C6-C2 conjugates at the A ring of the 13,30-cyclodammarane skeleton, and their structures were determined by spectroscopic data analysis, experimental electronic circular dichroism measurements, and X-ray crystallography. Biological tests revealed compounds 1-7 with a phenyl-butadiene appendage to be the most potent cytotoxic compound type of those evaluated.

Baccaramiones A-D, Four Highly Oxygenated and Rearranged Trinorditerpenoids from Baccaurea ramiflora

Baccaramiones A-D (1-4), four highly oxygenated and rearranged trinorditerpenoids, were isolated from Baccaurea ramiflora. Compound 1 is a 1(10 → 5)-abeo-15,16,17-trinor-ent-abietane featuring a unique 5/6/6 spirocyclic scaffold, and 2-4 are the first example of a novel 20(10 → 5)-abeo-15,16,17-trinor-ent-abietane skeleton. Their structures were established by spectroscopic analysis, X-ray crystallography, and electronic circular dichroism calculations. A plausible biosynthetic pathway for 1-4 was proposed. Interestingly, compounds 3 and 4 exhibited significant immunosuppressive activities against concanavalin A-induced T cell proliferation and lipopolysaccharide-induced B cell proliferation in vitro.

Natural products are the treasure pool for antimalarial agents

Despite the success in malaria control, it remains a life-threatening infectious disease due mainly to the persistent emergence of drug resistance. Sharpened insight into the historical achievements and current trends in antimalarial drug discovery provides more hopes and advantages on natural products for the development of the next antimalarial treatment.

Antimicrobial abietane-type diterpenoids from Torreya grandis

Twelve undescribed abietane-type diterpenoids, along with ten known analogues were isolated from the twigs and leaves of Torreya grandis var. merrillii Hu. Their structures were characterized by spectroscopic data analyses, single-crystal X-ray diffraction, and ECD spectra. Torgranols A-C possess three different architectures shaped via a common 6,7-seco-procedure and subsequent ring formations. In particular, torgranol A represents the first example of a 6,7-seco-abietane diterpenoid featuring a unique oxygen bridge between C-3 and C-6. The biosynthetic pathways for torgranols A-C were proposed. Some compounds displayed antimicrobial activities against Mycobacterium tuberculosis and/or Staphylococcus aureus.

Spicatulides A-G, Phenolic-Monoterpenoid Hybrids from Chloranthus spicatus

Spicatulides A-G (1-7), seven new phenolic-monoterpenoid hybrid molecules, along with two known compounds, 8 and 9, were isolated and identified from Chloranthus spicatus. Compound 1 represents an unprecedented skeleton featuring an aryl-fused 2-oxabicyclo[4.3.1]decane moiety, and compound 2 is the first example of a denudaquinol-normonoterpenoid adduct. Their structures with absolute configurations were elucidated on the basis of spectroscopic data analyses and TDDFT-ECD calculations. Compounds 3, 5, 6, and 9 exhibited the activity of reducing lipogenesis in HepG2 cells in a dose-dependent manner.

Ursane and 24-Noroleanane-Type Triterpenoids with Anti-HIV Activity from the Twigs and Leaves of Antirhea chinensis

Investigations on the twigs and leaves of Antirhea chinensis have led to the discovery of two undescribed pentacyclic triterpenoids ( 1 and 2 ) and nine known analogues. Compounds 1 and 2 , each assigned as the ursane and 24-noroleanane-type triterpenoids, featuring similar oxidation pattern of 3 β ,6 β ,19 α -trihydroxy-28-carboxyl. Their structures were elucidated via comprehensive analyses of spectroscopic data. Compound 1 displayed potent anti-HIV activity (EC 50 = 1.24 μ M) and high selectivity index (SI > 32.3).

Dolabrane-Type Diterpenoids with Immunosuppressive Activity from Koilodepas hainanense

Thirteen new dolabrane-type diterpenoids, koilodenoids A-M (1-13), including a chlorinated congener (2), along with six known analogues, were isolated from Koilodepas hainanense. The structures were determined by analysis of spectroscopic data, ECD spectra, and X-ray crystallographic studies. The absolute configuration of C-15 in the 15,16-diol unit of compounds 4 and 5 was established by using the dimolybdenum tetraacetate [Mo₂(AcO)₄]-induced ECD method. Compounds 4, 7, 16, 17, and 19 showed moderate to significant immunosuppressive activities against the proliferation of T and B lymphocytes in vitro, with compound 16 being the most potent (IC₅₀ 0.86 and 0.29 μM, respectively).

Phorneroids A-M, diverse types of diterpenoids from Euphorbia neriifolia

A chemical investigation on the aerial parts of Euphorbia neriifolia led to the identification of thirteen undescribed diterpenoids, phorneroids A-M, including ent-abietane (A-D), ent-kaurane (E-G), ent-atisane (H-K), and ent-isopimarane (L and M) types, together with three known compounds. Phorneroid A represents the first example of 8-spiro-fused 9,10-seco-ent-abietane diterpenoid lactone featuring a unique 6/5/6/5 spirocyclic framework. Biological assays showed that some of the compounds displayed moderate cytotoxicity against two human tumor cell lines, A549 and HL-60.

Diterpenoids from Sauropus spatulifolius Leaves with Antimicrobial Activities

As a plant used in both food and medicine, Sauropus spatulifolius is consumed widely as a natural herbal tea, food source, and Chinese medicine. Inspired by its extensive applications, we conducted a systematic phytochemical study of the leaves of S. spatulifolius. Thirteen new diterpenoids, sauspatulifols A-M (1-13), including four ent-cleistanthane-type diterpenoids (1-4), eight 15,16-di-nor-ent-cleistanthane-type diterpenoids (5-12), and one 17-nor-ent-pimarane-type diterpenoid (13) as well as one known diterpenoid, cleistanthol (14), were isolated. All of these diterpenoids feature a 2α,3α-dihydroxy unit within the A ring, and their structures were elucidated by spectroscopic data analysis, electronic circular dichroism calculations, and single-crystal X-ray diffraction analysis. Compound 14 displayed moderate inhibitory activity against Staphylococcus aureus, Staphylococcus epidermidis, Bacillus subtilis, and Shigella flexneri with the same minimum inhibitory concentration value of 12 μg/mL as well as activity against vesicular stomatitis virus and influenza A virus.

Quinoline alkaloids with anti-inflammatory activity from Zanthoxylum avicennae

Zanthoxylum avicennae fruits were traditionally used to treat many inflammatory-related diseases, such as icterohepatitis, nephritis and colitis, which inspired us to explore the active chemicals and pharmacological activity. As a result, ten quinoline alkaloids, including six new ones, avicenines A-F (1-6), were isolated and structurally characterized by solid data. Compounds 1, 7 and 8 were identified as three pairs of enantiomers by chiral HPLC separation, of which 1 was an unusual 6/6/5/5-fused quinoline alkaloid bearing a unique cis-hexahydrofuro[3,2-b]furan moiety. The putative biosynthetic pathway for enantiomeric compounds was also proposed. In addition, compound 6 significantly suppressed the gene expression and secretion of pro-inflammatory cytokines IL-1β and IL-6 in macrophages.

Cephalotane-type C20 diterpenoids from Cephalotaxus fortunei var. alpina

Seventeen new cephalotane-type diterpenoids were isolated from Cephalotaxus fortunei var. alpina. Compounds 14 and 15 contain an unusual 7-oxabicyclo[4.1.1]octane moiety.

Sublyratins A-O, Labdane-Type Diterpenoids from Croton sublyratus

Fifteen new labdane-type diterpenoids, sublyratins A-O (1-15), along with four known analogues (16-19) were isolated from the aerial parts of Croton sublyratus. Their structural assignments were challenging due to the stereoisomeric features evident and were achieved by analyzing comprehensively the spectroscopic data and electronic circular dichroism spectra and using X-ray crystallographic analysis. Compounds 9 and 16-18 displayed cytotoxic activity against the HL-60 cell line with IC₅₀ values of 1.5-2.8 μM.

Quassinoids with Inhibitory Activities against Plant Fungal Pathogens from Picrasma javanica

A bioactivity-guided study on the leaves of Picrasma javanica led to the isolation of 19 quassinoids, including 13 new compounds. The structures of the new compounds were elucidated by a combination of spectroscopic data analysis, X-ray crystallography studies, and electronic circular dichroism (ECD) data interpretation. Compounds 1-7 are rare examples of quassinoids with a keto carbonyl group at C-12. The biological activities of 11 of the more abundant isolates were evaluated against five phytopathogenic fungi in vitro, and several of them including 6 and 15 showed moderate inhibitory effects that were comparative to those of the positive control, carbendazim. In addition, the preliminary structure-activity relationships (SARs) of these quassinoids were also investigated.

Discovery of four modified classes of triterpenoids delineated a metabolic cascade: compound characterization and biomimetic synthesis

Chemical studies on Dichapetalum gelonioides have afforded 18 highly modified complex triterpenoids belonging to four compound classes as defined by the newly adapted functional motifs associated with the A ring of the molecules. Their structures were determined by solid data acquired by diverse methods. The biosynthetic pathway for the four compound classes was rationalized via cascade modifications involving diverse chemical events. The subsequent biomimetic syntheses afforded all the desired products, including compounds 16 and 19 that were not obtained in our purification, which validated the proposed biosynthetic pathway. Besides, some compounds exhibited strong cytotoxic activities, especially 2 and 4 showed nanomolar potency against the NAMALWA tumor cell line, and a gross structure–activity relationship (SAR) of these compounds against the tested tumor cell lines was delineated.

Characterization of four classes of highly modified triterpenoids from Dichapetalum gelonioides sheds light on an unprecedented biosynthetic cascade, which was validated by the subsequent biomimetic syntheses. Moreover, some isolates exhibited nanomolar cytotoxic activities.

Horienoids A and B, Two Heterocoupled Sesquiterpenoid Dimers from Hedyosmum orientale

Two eudesmane-guaiane/lindenane heterocoupled sesquiterpenoid dimers, horienoids A (1) and B (2) with new carbon skeletons, from Hedyosmum orientale were characterized by a combined method. Compound 1 featured a unique 2,10-dioxabicyclo[6.2.1]undecane core moiety with an anti-Bredt bridgehead double bond. Their biogenetic pathways were proposed to involve Diels-Alder and cascade rearrangement reactions as the key steps. Compound 2 exhibited a potent anti-inflammatory effect on LPS-induced BV-2 microglial cells.

Cephalodiones A-D: Compound Characterization and Semisynthesis by [6+6] Cycloaddition

Cephalodiones A-D (1-4), the first example of C₁₉ -norditerpenoid dimers, were isolated and fully characterized from a Cephalotaxus plant. These new skeletal natural products shared a unique tricyclo[6.4.1.1^2,7 ]tetradeca-3,5,9,11-tetraene-13,14-dione core that was capped in both ends with rigid multicyclic ring systems either C₂ -symmetrically or asymmetrically. Compounds 1-4 were proposed to be biosynthetically produced by the [6+6]-cycloaddition of two identical C₁₉ -norditerpenoid troponoids, which was validated by the semisyntheses of dimers 2-4. Moreover, some compounds showed significant inhibition on Th17 cell differentiation.

Trichloranoids A–D, antimalarial sesquiterpenoid trimers from Chloranthus spicatus

Four new anti-malarial sesquiterpenoid trimers including two rearranged skeletons were isolated from Chloranthus spicatus. The structurally different but biogenetically related compounds 1, 2 and 5 rationalized the biradical pathway, and vice versa.

Resistance to Some But Not Other Dimeric Lindenane Sesquiterpenoid Esters Is Mediated by Mutations in a Plasmodium falciparum Esterase

Unique lindenane sesquiterpenoid dimers from Chloranthecae spp. were recently identified with promising in vitro antiplasmodial activity and potentially novel mechanisms of action. To gain mechanistic insights to this new class of natural products, in vitro selection of Plasmodium falciparum resistance to the most active antiplasmodial compound, chlorajaponilide C, was explored. In all selected resistant clones, the half-maximal effective concentration (EC50) of chlorajaponilide C increased >250-fold, and whole genome sequencing revealed mutations in the recently discovered P. falciparum prodrug activation and resistance esterase (PfPARE). Chlorajaponilide C was highly potent (mean EC50 = 1.6 nM, n = 34) against fresh Ugandan P. falciparum isolates. The analysis of the structure-resistance relationships revealed that in vitro potency of a subset of lindenane sesquiterpenoid dimers was not mediated by PfPARE mutations. Thus, chlorajaponilide C, but not some related compounds, required parasite esterase activity for in vitro potency, and those compounds serve as the foundation for development of potent and selective antimalarials.

Diverse Types of Diterpenoids with an Aromatized C Ring from the Twigs of Podocarpus imbricatus

An ethanol extract of the powdered twigs of Podocarpus imbricatus afforded 14 new diterpenoids (1-14), which all share an aromatized C ring. These isolates belong to five diterpenoid types that include abietanes (1-3), semperviranes (4-9), totaranes (10-12), a C-17 norabietane (13), and an icetexane (14). Their structures were assigned mainly by analysis of the spectroscopic data, and the absolute configuration of 1 was determined by X-ray crystallography. A biosynthetic pathway for five of the biogenetically related types of diterpenoids was proposed. Compound 7 showed moderate inhibitory activity against Zika virus with an IC₅₀ value of 2.5 μM.

Limonoids from Cipadessa baccifera

Eighteen new limonoids, including eight methyl angolensates (1-8) and 10 cipadesins (9-18), were isolated from the leaves of Cipadessa baccifera. Their structures were characterized by means of spectroscopic data analyses, single-crystal X-ray diffraction, and quantum chemistry computational methods. The C-6 configurations in those compounds possessing a C-6 hydroxy group were all assigned as S regardless of the magnitude of J_5,6, and the C-2' configuration in those bearing a 2-methylbutyryl residue was defined by single-crystal X-ray diffraction and NMR data. Compounds 1, 5, 6, 7, 11, and 12 showed moderate antimalarial activities with IC₅₀ values ranging from 12 to 28 μM.

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.

Crokonoids A-C, A Highly Rearranged and Dual-Bridged Spiro Diterpenoid and Two Other Diterpenoids from Croton kongensis

Crokonoid A (1), a highly rearranged diterpenoid featuring a dual-bridged tricyclo[4.4.1.1^1,4]dodecane-2,11-dione ring system and its two possible ent-kaurene diterpenoid precursors (2 and 3), was isolated and structurally characterized by solid data from Croton kongensis. Compound 1 exhibited significant cytotoxicity against HL-60 and A-549 cell lines with IC₅₀ values of 1.24 ± 0.56 and 1.92 ± 0.60 μM, respectively.

Chemical constituents from Vernonia bockiana

A new sesquiterpenoid and two pregnane steroids, named vernobockolide C (1) and vernobockones A and B (2 and 3), respevtively, along with a known sesquiterpenoid, 7, 10-epoxy-11-hydroxy-bisabol-2-en-15-al, were isolated from the aerial part of Vernonia bockiana. Their structures were elucidated on the basis of extensive spectroscopic data analysis, especially 2D NMR (HSQC, HMBC, and ROESY). This study further expands the chemical space of this underexplored species.

Integrating yeast chemical genomics and mammalian cell pathway analysis

Chemical genomics has been applied extensively to evaluate small molecules that modulate biological processes in Saccharomyces cerevisiae. Here, we use yeast as a surrogate system for studying compounds that are active against metazoan targets. Large-scale chemical-genetic profiling of thousands of synthetic and natural compounds from the Chinese National Compound Library identified those with high-confidence bioprocess target predictions. To discover compounds that have the potential to function like therapeutic agents with known targets, we also analyzed a reference library of approved drugs. Previously uncharacterized compounds with chemical-genetic profiles resembling existing drugs that modulate autophagy and Wnt/β-catenin signal transduction were further examined in mammalian cells, and new modulators with specific modes of action were validated. This analysis exploits yeast as a general platform for predicting compound bioactivity in mammalian cells.