Secondary metabolites from the Actinomadura sp. and their cytotoxic activity

Actinomadura sp., which is usually found in muddy habitats, produces various secondary metabolites with biological activities. In this study, five new compounds named formosensin A (1), formosensin B (2), oxanthroquinone-3-O-α-d-mannose (8), oxanthromicin A (9), and oxanthromicin B (10) were isolated from the culture of Actinomadura sp. together with five known compounds (3-7). Their structures were elucidated by extensive spectroscopic methods including NMR and MS. In particular, the absolute configurations of compounds 1 and 2 were determined using computational methods. Moreover, compounds 1-2 and 8-10 were screened for cytotoxic activity using a panel of human tumor cell lines. Compound 9 induced significant cytotoxicity in five human tumor cell lines (HL-60, A-549, SMMC-7721, MCF-7, and SW480) with IC50 values of 8.7, 17.5, 15.0, 17.8, and 14.6 μM, respectively. These findings suggested that compound 9 could provide therapeutic benefits in the treatment of tumor-related diseases.

Two undescribed benzopyran derivatives from Ranunculus sceleratus L. with their in vitro anti-inflammatory activity in lipopolysaccharide-activated RAW 264.7 cells

Previous studies on Ranunculus sceleratus L. have shown the existence of coumarins and their anti-inflammatory effect. Phytochemical work was conducted to investigate the bioactive compounds, leading to the isolation of two undescribed benzopyran derivatives, namely ranunsceleroside A (1) and B (3), together with two known coumarins (2, 4) from the whole plant of R. sceleratus L. All compounds were structurally identified by extensive spectroscopic analysis and then investigated for their inhibitory effect on nitric oxide (NO), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6) production induced by lipopolysaccharide (LPS) in RAW 264.7 murine macrophages, repectively. As a result, compound 1-4 presented inhibitory effects on the production of NO, TNF-α, IL-1β, and IL-6 in a concentration-dependent manner, which provides a potential chemical basis for the traditional use of R. sceleratus L. as an anti-inflammatory plant.

The intramolecular SN2 reaction tautomeric ent-Kauranoids isolated from the aerial parts of Isodon amethystoides

As our ongoing searching for the bioactive natural terpenoids, nine ent-kauranoids (1-9), including three previously undescribed ones (1, 2, and 9), were isolated from the aerial parts of Isodon amethystoides. Their structures were elucidated on the basis of spectroscopic data analysis, including NMR, MS, and ECD. Compounds 1 and 2 were a pair of tautomeric compounds, which was confirmed by the HPLC analysis and low temperature NMR testing. The underlying mechanism of the tautomer was proposed as an intramolecular SN2 reaction, which was explained by quantum chemical calculation. The HOMO-LUMO gap and the free energy revealed the spontaneous of the tautomeric of the 1 and 2. Additionally, the similar phenomena were also found in the two groups of known compounds 3 and 4 and 6 and 7, respectively. Apart from the tautomer, compounds 3 and 4 can be hydrolyzed into 5 through ester hydrolysis in CDCl3, while compounds 6, 7 can be hydrolyzed into 8 through ester hydrolysis. These phenomena were also confirmed through HPLC analysis and low temperature nuclear magnetic resonance tests and the mechanism was studied using quantum chemical calculation.

Anti-Inflammatory Peroxidized Chlorahololide-Type Dimers Are Artifacts of Shizukaol-Type Dimers: From Phenomena Discovery and Confirmation to Potential Underlying Mechanism

In our research on naturally occurring sesquiterpenes, eight shizukaol-type dimers, one chlorahololide-type dimer, and one sarcanolide-type dimer were isolated from the roots of Chloranthus fortunei. As the project was implemented, we accidentally discovered that shizukaol-type dimers can be converted into peroxidized chlorahololide-type dimers. This potential change was discovered after simulations of the changes in corresponding shizukaols showed that three peroxide products were generated (1-3), indicating that peroxidation reactions occurred. HPLC-HR-MS analysis results obtained for the shizukaol derivatives further demonstrate that the reaction occurred, and the type of substituent of small organic ester moieties at positions C-15' and C-13' of unit B were not decisively related to the reaction. Quantum chemical calculations of the mode dimer further demonstrated this phenomenon. The highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy of the precursor and production revealed the advantageous yield of 4β-hydroperoxyl production. Additionally, the potential reaction mechanism was speculated and validated using the free energy in the reaction which successfully explained the feasibility of the reaction. Finally, the anti-inflammatory activity of the precursors and products was evaluated, and the products of peroxidation showed better anti-inflammatory activity.

Structure-diversified terpenoids from Salvia prattii and their protective activity against alcoholic liver diseases

Eleven previously unreported compounds (1-11), including five diterpenoids (1-5) and six sesquiterpenoids (6-11), together with two known diterpenoids (12-13), have been isolated from the roots of Salvia prattii. Their structures were comprehensively elucidated through spectroscopic methods, and their configurations were established using computational 13C nuclear magnetic resonance and electronic circular dichroism. Compound 1 was found to be an abietane-type diterpenoid with a novel rearrangement generated from the cleavage of the C-4/5 chemical bond, 20-methyl shift, and the rearrangement of the C-10 side chain. Compounds 2-3 were the third and fourth examples of arrangement seco-norabietanes with a spiro-lactone ring. We evaluated all compounds for their protective effects against alcoholic liver diseases (ALD). Compound 2 exhibited potential protective activity and hence can be used as a novel anti-ALD candidate.

Chemical Constituents of Thesium chinense Turcz and Their In Vitro Antioxidant, Anti-Inflammatory and Cytotoxic Activities

Three novel compounds (1–3) along with twenty-six known compounds, two known steroids (4–5) and twenty-four known phenylpropanoids (6–29) were isolated from the whole plant of Thesium chinense Turcz. The structures of the three new compounds were elucidated on the basis of ESI-MS, HR-ESIMS, 1D and 2D NMR, IR, UV spectroscopic data. The absolute stereochemistry of compound 1 was determined by the Gauge-Including Atomic Orbitals (GIAO) method. The in vitro antioxidant, anti-inflammatory and cytotoxic activities of the isolated compounds were evaluated by DPPH radical-scavenging assay, LPS-activated RAW 264.7 cells model and CCK-8 kit, respectively. Compound 11 showed high antioxidant activity with an SC50 value of 16.2 ± 1.6 μM. Compound 21 showed considerable anti-inflammatory activity with an IC50 value of 28.6 ± 3.0 μM. Compounds 4 and 5 displayed potent cytotoxic activity against human NCI-H292, SiHa, A549, and MKN45 cell lines, with the compound 4 having IC50 values of 17.4 ± 2.4, 22.2 ± 1.1, 9.7 ± 0.9, 9.5 ±0.7 μM, and the compound 5 having all IC50 values less than 0.1 μM in vitro.

Anthraquinones from the Aerial Parts of Rubia cordifolia with Their NO Inhibitory and Antibacterial Activities

The present study aimed to identify the composition of the aerial parts of Rubia cordifolia L. A chemical investigation on the EtOAc extracts from the aerial parts of Rubia cordifolia resulted in the isolation of four new anthraquinones, namely Cordifoquinone A-D (1-4), along with 16 known anthraquinones. Their structures were elucidated on the basis of NMR and HR-ESIMS data. All isolates were assessed for their inhibitory effects on NO production in LPS-stimulated RAW 264.7 macrophage cells. Compounds 1, 3 and 10 exhibited significant inhibitory activities with IC₅₀ values of 14.05, 23.48 and 29.23 μmol·L^-1, respectively. Their antibacterial activities of four bacteria, Escherichia coli (ATCC 25922), Staphylococcus aureus subsp. aureus (ATCC 29213), Salmonella enterica subsp. enterica (ATCC 14028) and Pseudomonas aeruginosa (ATCC 27853), were also evaluated. Our results indicated that the antibacterial activity of these compounds is inactive.

Structure Revision of Four Classes of Prenylated Aromatic Natural Products Based on a Rule for Diagnostic 13C NMR Chemical Shifts

Errors in elucidating the structures of four natural classes of prenylated aromatic compounds with 2,3-epoxy, 2,3-dihydroxy, and cyclization with an ortho-phenolic hydroxyl to give a pyran or furan ring moiety are frequent and inevitable. Based on rigorous literature research and a series of chemical transformation experiments, a rule for the rapid determination of these four classes of prenylated derivates based on ¹³C NMR data was formulated, and 57 corrections featuring these fragments were accordingly reported.

Antibacterial Prenylated p-Hydroxybenzoic Acid Derivatives from Oberonia myosurus and Identification of Putative Prenyltransferases

Twelve hitherto unknown tandem prenylated p-hydroxybenzoic acid derivatives, namely, oberoniamyosurusins A-L, together with five known derivatives, were isolated from an EtOH extract of the whole parts of the plant Oberonia myosurus. Compounds 10, 13, and 17 exhibited moderate inhibitory activity against Staphylococcus aureus subsp. aureus ATCC29213 with MIC₅₀ values ranging from 7.6 to 23 μg/mL. To determine the biosynthetic pathway of this class of tandem prenyl-substituted compounds, the full-length transcriptome of O. myosurus was sequenced, yielding 19.09 Gb of clean data and 10 949 nonredundant sequences. Two isoforms of p-hydroxybenzoic acid prenyltransferases were annotated and functionally characterized as the enzymes that might be involved in the biosynthesis of nervogenic acid (13) in Pichia pastoris.

Total Synthesis of Gastrodinol via Photocatalytic 6π Electrocyclization

The first total synthesis of gastrodinol, an unprecedented poly-p-cresol-substituted natural product with a rearranged and reconstructed C ring moiety, is reported. Our synthesis features a convergent fragment approach. The Sonogashira coupling reaction forges the two segments together to furnish the conjugated ene-yne. Photocatalytic 6π electrocyclization followed by spontaneous aromatization is used to construct the tetrasubstituted B ring at the late stage. Further study shows that gastrodinol exhibits significant cytotoxic activity against five human cancer cell lines in vitro (IC₅₀ 2.5-3.8 μM).

13,27-Cycloursane, ursane and oleanane triterpenoids from the leaves of Lucuma nervosa

One hitherto unknown 24-nor-13,27-cycloursane-type triterpenoid, lucumic acid A (1), one new 24-nor-ursane triterpenoid, lucumic acid B (2), along with six known triterpenoids were isolated from the ethanol extract of the leaves of Lucuma nervosa. Their structures were established on the basis of spectroscopic data interpretation. Lucumic acid A (1) is the first example of a 24-nor-triterpenoid with a 13,27-cyclopropane ring.

Prenylated 2-Phenoxychromones and Flavonoids from Epimedium brevicornum and Revised Structures of Epimedonins A and B

Six hitherto unknown prenylated 2-phenoxychromones, epimedonin G (1), 7-O-methylepimedonin G (2), and epimedonins H-K (3-6), and two new prenylflavonoids, epimedonin L (7) and 3″-O-desmethylspinorhamnoside (8), were isolated from an ethanol extract of the aerial parts of Epimedium brevicornum. Their structures were established on the basis of spectroscopic data interpretation. Compound 7 exhibited cytotoxic activity when evaluated against four human cancer cell lines (HL-60, A-549, MCF-7, and SW-480), with IC₅₀ values of <10 μM. In addition, the structures of epimedonins A and B (9a, 10a), recently isolated from E. koreanum, were corrected by reanalysis of the published NMR data.

Design, synthesis and structure–activity relationships of mangostin analogs as cytotoxic agents

A series xanthone derivatives were synthesized and cytotoxicity results indicated that the isopentene group at C-8 is essential.

Polysubstituted Isoflavonoids from Spatholobus suberectus, Flemingia macrophylla, and Cudrania cochinchinensis

Four hitherto unknown polysubstituted isoflavonoids, including three isoflavans: 7,4'-dihydroxy-8,2',3'-trimethoxyisoflavan (1), 7,2',4'-trihydroxy-8,3'-dimethoxyisoflavan (2), and 7,2',4'-trihydroxy-5-methoxyisoflavan (3), and one prenylated isoflavone cudraisoflavone M (4) were isolated from the ethanol extracts of Spatholobus suberectus (for 1 and 2), Flemingia macrophylla (for 3), and Cudrania cochinchinensis (for 4), respectively. Their structures were established on the basis of extensive spectroscopic analysis. Compounds 1 and 4 exhibited weak cytotoxic activity against five human cancer cell lines (HL-60, A-549, SMMC-7721, MCF-7, and SW-480).

Derrisisoflavones H-K and One Isoflavan Derivative from Derris robusta

Four hitherto unknown prenylated isoflavonoids, named derrisisoflavones H-K (1-4) and one new isoflavan, namely 6-hydroxyisosativan (5), were isolated from the ethanol extract of Derris robusta. Their structures were elucidated on the basis of extensive spectroscopic studies. To our knowledge, derrisisoflavones J (3) and K (4) are the first examples of hydroxyethylated isoflavonoid.

Pterocarpadiols A-D, Rare 6a,11b-Dihydroxypterocarpans from Derris robusta

Four hitherto unknown 6a,11b-dihydroxypterocarpans, namely pterocarpadiols A-D (1-4), were isolated from the ethanol extract of the twigs and leaves of Derris robusta. Their structures were elucidated on the basis of extensive spectroscopic analysis. Pterocarpadiols A-D are a kind of very rare 6a,11b-dihydroxypterocarpans, and their presence as markers may be helpful in chemotaxonomical classification.

Lanostane-Type Triterpenoids from Scilla scilloides and Structure Revision of Drimiopsin D

Two hitherto unknown lanostane-type triterpenoids, namely scillascillol (1) and scillascillone (2), and a hitherto unknown norlanostane-triterpene glycoside, namely scillascilloside B-1 (3), were isolated from the ethanol extract of the whole plants of Scilla scilloides. Their structures were elucidated on the basis of extensive spectroscopic studies. In addition, the structure of drimiopsin D (6a) has been revised as 2,5-dimethoxy-8-methyl-1,3,6-trihydroxyxanthone (6) by reanalysis of the spectroscopic data.

Hybridaphniphyllines A and B, Daphniphyllum alkaloid and iridoid hybrids suggestive of Diels-Alder cycloaddition in Daphniphyllum longeracemosum

Two Daphniphyllum alkaloid and iridoid hybrids with the hitherto unknown decacyclic fused skeletons, hybridaphniphyllines A and B, along with one diamino Daphniphyllum alkaloid, daphnicyclidin I, were isolated from dried stems and leaves of Daphniphyllum longeracemosum. Their structures were elucidated on the basis of extensive spectroscopic analysis, and the absolute configuration of daphnicyclidin I was deduced by the CD exciton chirality method. A biogenetic pathway for 1 and 2 involving natural Diels-Alder cycloaddition is proposed.

New isoflavonoids from Erythrina arborescens and structure revision of anagyroidisoflavone A

Five hitherto unknown isoflavonoids, namely erythrinins D-H (1–5), were isolated from the ethanol extract of Erythrina arborescens. Their structures were elucidated on the basis of extensive spectroscopic studies. In addition, the structure of anagyroidisoflavone A (6a) has been revised as 1″-O-methylerythrinin F (6) by re-analysis of the original spectroscopic data.

ent-Kaurane diterpenoids from the plant Wedelia trilobata

Four new ent-kaurane diterpenoids, namely, 3α-tigloyloxypterokaurene L₃ (1), ent-17-hydroxy-kaura-9(11),15-dien-19-oic acid (2), and wedelobatins A (3) and B (4), together with 11 known ent-kaurane diterpenoids (5-15), were isolated from the ethanol extract of Wedelia trilobata. All the structures of 1–15 were elucidated on the basis of spectroscopic studies.

Chlorantholides A-F, eudesmane-type sesquiterpene lactones from Chloranthus elatior

Six eudesmane-type sesquiterpene lactones, named chlorantholides A-F, were isolated from the ethanol extract of Chloranthus elatior (Chloranthaceae) together with 12 known compounds. Their structures were elucidated on the basis of extensive spectroscopic analysis, and their absolute configurations were studied by the CD exciton chirality method. The structure of a recently reported eudesmanolide from Chloranthus anhuiensis: 8β-hydroxy-1-oxoeudesma-3,7(11)-dien-12,8-olide, was also revised as 8β-hydroxy-2-oxoeudesma-3,7(11)-dien-12,8-olide (chlorantholide D).

Pterisolic acids A-F, new ent-kaurane diterpenoids from the fern Pteris semipinnata

Six new ent-15-oxokauran-19-oic acid derivatives, named pterisolic acids A-F (1-6), were isolated from the ethanol extract of the fern Pteris semipinnata (Pteridaceae), and the structures of these new ent-kauranoids were elucidated on the basis of extensive spectroscopic studies and single crystal X-ray diffraction analysis.

Scutebarbatines W-Z, new neo-clerodane diterpenoids from Scutellaria barbata and structure revision of a series of 13-spiro neo-clerodanes

Four new neo-clerodane diterpenoids, scutebarbatines W-Z (1-4), were isolated from the ethanol extract of Scutellaria barbata (Labiatae), and their structures were elucidated on the basis of extensive spectroscopic studies. In addition, the proposed structures of at least seven 13-spiro subtype neo-clerodanes: scutehenanine B (5), scutebarbatine G (6), 6-O-nicotinoylscutebarbatine G (7), barbatin A (8), 6,7-di-O-nicotinoylscutebarbatine G (9), 6-O-nicotinoyl-7-O-acetylscutebarbatine G (10), and scutebarbatine F (11), reported by Dai and co-workers from the same species, were incorrectly assigned and have been revised by reanalysis of the published NMR data.

Alstonic acids A and B, unusual 2,3-secofernane triterpenoids from Alstonia scholaris

2,3-Secofernane triterpenoids, alstonic acids A (1) and B (2), were isolated from the leaves of Alstonia scholaris together with an indole alkaloid, N(1)-methoxymethyl picrinine (3). Their structures were established from MS and NMR spectroscopic analyses and confirmed by single crystal X-ray diffraction analysis.