(+)- and (-)-Xanthostones A-D: Four Pairs of Enantiomeric Cinnamoyl-ß-Triketone Derivatives from Xanthostemon chrysanthus.

Four pairs of cinnamoyl-ß-triketone derivative enantiomers, (+)- and (-)-xanthostones A-D ((+)- and (-)-1-4), were isolated from Xanthostemon chrysanthus. Compounds 1 and 2 feature a new rearranged cinnamoyl-phloroglucinol scaffold fused with a cinnamyl-ß-triketone framework. Compounds 1, 3, and 4 are the first examples of natural products with a peculiar phenethyl-pyranone acid unit. Their structures with absolute configurations were determined by spectroscopic data, X-ray diffraction analysis and electronic circular dichroism (ECD) calculation. Interestingly, these novel compounds showed a tautomeric behavior in solution, which was revealed by NMR spectroscopy and density functional theory calculation. A plausible biosynthetic pathway toward xanthostones A-D was proposed. Additionally, the anti-inflammatory and antibacterial activities of xanthostones A-D were evaluated.

Monoterpenoid indole alkaloids from the fruits of Gelsemium elegans and their anti-inflammatory activities.

Two novel monoterpenoid indole alkaloids (MIAs), gelsechizines A-B (1-2), along with four known ones (3-6) were isolated from the fruits of Gelsemium elegans. Compound 1 features a new carbon skeleton with two additional carbon atoms forming a 4-methylpyridine unit. Their structures with absolute configurations were elucidated by NMR, MS, X-ray diffraction and electronic circular dichroism (ECD) calculations. Compounds 1-3 showed significant anti-inflammatory effects in vivo and in vitro, which may be related to the inhibition of the trecruitment of neutrophils and macrophages as well as the secretion of TNF-α and IL-6. Preliminary structure-activity relationship analysis revealed that the ß-N-acrylate moiety plays an important role in the anti-inflammatory effect.

Dimeric Acylphloroglucinol Derivatives with New Skeletons from Leptospermum scoparium.

Leptosparones A-F (1-6), six new dimeric acylphloroglucinol derivatives with unprecedented skeletons, were isolated from Leptospermum scoparium. Compounds 1-3 and 5-6 are phenylpropanoyl-phloroglucinol dimers, while 4 is a phenylpropanoylphloroglucinol-isovalerylphloroglucinol hybrid. Structurally, these compounds represent the first examples of dimeric phloroglucinols with unprecedented C(7')-C(8) linkage between the phloroglucinol core and the acyl side chain. Their structures were elucidated by comprehensive analyses of spectroscopic data, single crystal X-ray diffraction and chemical calculations. In addition, all compounds showed inhibitory effects against α-glucosidase with IC50 values ranging from 39.5 to 186.8 µM.

Myrcaulones A-C, Unusual Rearranged Triketone-Terpene Adducts from Myrciaria cauliflora.

Three rearranged triketone-terpene adducts, myrcaulones A-C (1-3), were isolated from the leaves of Myrciaria cauliflora. Myrcaulones A (1) and B (2) feature a new carbon skeleton with an unprecedented spiro[bicyclo[3.1.1]heptane-2,2'-cyclopenta[b]pyran] core. Myrcaulone C (3) possesses an unusual cyclobuta[6,7]cyclonona[1,2-b]cyclopenta[e]pyran backbone. Their structures with absolute configurations were elucidated by NMR spectroscopy, X-ray diffraction, and electronic circular dichroism calculations. A plausible biogenetic pathway for myrcaulones A-C involving the rearrangement of a triketone unit is also proposed. In addition, myrcaulones A (1) and B (2) exhibited inhibitory effects against tumor necrosis factor-α and nitric oxide generation induced by lipopolysaccharide in RAW 264.7 macrophages.

Phloroglucinol Derivatives from Myrtus communis 'Variegata' and Their Antibacterial Activities.

Myrtucomvalones D-F, three new triketone-phloroglucinol-triketone adducts, and three known ones (myrtucommulone E, myrtucommulone D and callistenone D) were obtained from Myrtus communis 'Variegata'. Myrtucomvalone D is a pair of enantiomers which was further resolved into (+)-myrtucomvalone D and (-)-myrtucomvalone D by chiral HPLC. Their structures and complete stereochemistry were established from interpretation of NMR and crystallographic data and chemical calculations. Myrtucomvalone F, myrtucommulone D and callistenone D showed significant antibacterial activities.

Chiral Isolation and Absolute Configuration of (+)- and (-)-Xanchryones F and G from Xanthostemon chrysanthus.

(+)- and (-)-Xanchryones F and G ((+)- and (-)-1 and 2) were isolated from the plant Xanthostemon chrysanthus by chiral separation. Compounds 1 and 2 featured a new carbon skeleton with cinnamoyltriketone-flavone adducts. Their structures with absolute configurations were elucidated by detailed spectroscopic analyses and chemical calculations. The antibacterial and anti-inflammatory activities of (+)- and (-)-1 and 2 were evaluated.

Antibacterial Triketone-Phloroglucinol-Triketone Adducts from Myrtus communis.

Myrtucyclitones A-C ((+)- and (-)-1-3), three pairs of new triketone-phloroglucinol-triketone hybrids were isolated from the plant Myrtus communis. Their structures with absolute configurations were established by NMR analysis and chemical calculations. Myrtucyclitones B and C exhibited remarkable antibacterial effect.

Xanthchrysones A-C: Rearranged Phenylpropanoyl-Phloroglucinol Dimers with Unusual Skeletons from Xanthostemon chrysanthus.

Three pairs of dimeric phenylpropanoyl-phloroglucinol enantiomers, (+)- and (-)-xanthchrysones A-C [(+)- and (-)-1-3], as well as their postulated biosynthetic precursors, were isolated and identified from the leaves of Xanthostemon chrysanthus. Compound 1 featured an unprecedented bis-phenylpropanoyl-benzo[b]cyclopent[e] oxepine tricyclic backbone. Compounds 2 and 3 represent the first examples of 1-(cyclopentylmethyl)-3-(3-phenylpropanoyl)benzene scaffold. The structures and absolute configurations of 1-3 were determined by spectroscopic and X-ray diffraction analysis as well as electronic circular dichroism (ECD) calculation. Both (+)-2 and (-)-2 showed moderate antibacterial activities including several multidrug-resistant strains.

Gelsecorydines A-E, Five Gelsedine-Corynanthe-Type Bisindole Alkaloids from the Fruits of Gelsemium elegans.

Five monoterpenoid bisindole alkaloids with new carbon skeletons, gelsecorydines A-E (1-5), together with their biogenetic precursors were isolated from the fruits of Gelsemium elegans. Compounds 1-5 represent the first examples of heterodimeric frameworks composed of a gelsedine-type alkaloid and a modified corynanthe-type one. Notably, compound 2 featured an unprecedented caged skeleton with a 6/5/7/6/5/6 heterohexacyclic ring system, which possessed a pyridine ring that linked the two monomers. Their structures and absolute configurations were elucidated by spectroscopic analysis, X-ray diffraction, and electronic circular dichroism (ECD) calculation. A plausible biosynthetic pathway for compounds 1-5 is proposed. Compounds 1, 3, 4, and 5 exhibited a significant inhibitory effect against nitric oxide (NO) production in macrophages.

Antiviral Triketone-Phloroglucinol-Monoterpene Adducts from Callistemon rigidus.

Callistrilones F - K (1 - 6), six new triketone-phloroglucinol-monoterpene hybrids were isolated from the twigs and leaves of Callistemon rigidus. Their structures with absolute configurations were established by a combination analysis of NMR spectra, X-ray diffraction, and electronic circular dichroism (ECD) calculations. Compounds 3 and 4 exhibited moderate inhibitory activities against herpes simplex virus (HSV-1) with IC50 values of 10.00 ± 2.50 and 12.50 ± 1.30 µm, respectively.

Acronyrones A-C, unusual prenylated acetophenones from Acronychia pedunculata.

Two novel prenylated acetophenones with new carbon skeletons, acronyrones A and B (1 and 2), and a new analogue, acronyrone C (3), together with two known compounds (4 and 5) were isolated from the leaves of Acronychia pedunculata. Their structures with absolute configurations were identified by interpretation of spectroscopic data, single crystal X-ray diffraction, and electronic circular dichroism (ECD) calculations. Compounds 1 and 2 represent the first example of prenylated acetophenones possessed a C7 (1) and a C6 (2) side chain, forming a 4-isobutylchroman-2-one unit and a 3-(2-methylpropylidene)benzofuran-2(3H)-one moiety with the acetophenone core, respectively. In addition, compound 4 exhibited significant dose-dependent transcriptional activation effect against retinoid X receptor-α (RXRα), and could be regarded as a new type of non-classical RXR ligand.

Four New Phloroglucinol-Terpene Adducts from the Leaves of Myrciaria cauliflora.

Myrcauones A-D (1-4), four new phloroglucinol-terpene adducts were isolated from the leaves of Myrciaria cauliflora. Their structures with absolute configurations were elucidated by combination of spectroscopic analysis, single crystal X-ray diffraction, and electronic circular dichroism (ECD) calculations. Compound 1 was a rearranged isobutylphloroglucinol-pinene adduct featuring an unusual 2,3,4,4a,10,11-hexahydro-1H-3,11a-methanodibenzo[b,f]oxepin backbone. Compound 4 showed moderate antibacterial activity against Gram-positive bacteria including multiresistant strains.

Leptosperols A and B, Two Cinnamoylphloroglucinol-Sesquiterpenoid Hybrids from Leptospermum scoparium: Structural Elucidation and Biomimetic Synthesis.

Leptosperols A and B (1 and 2), two cinnamoylphloroglucinol-sesquiterpenoid hybrids featuring unprecedented 1-benzyl-2-(2-phenylethyl) cyclodecane and 2-benzyl-3-phenylethyl decahydronaphthalene backbones, along with their biosynthetic precursor (3), were isolated from Leptospermum scoparium. Compounds 1 and 2 represent the first example of phloroglucinol derivatives biogenetically constructed by a De Mayo reaction. The biomimetic synthesis of leptosperol B (2) was achieved using the proposed biosynthetic pathway. In addition, compounds 1 and 2 showed significant anti-inflammatory effects in zebrafish acute inflammatory models.

Four new cinnamoyl-phloroglucinols from the leaves of Xanthostemon chrysanthus.

Four new cinnamoyl-phloroglucinols (1-4) were isolated from the leaves of Xanthostemon chrysanthus. Compounds 1 and 2 represent the first example of natural phloroglucinols with an oxazole unit. Their structures were elucidated on the basis of NMR spectroscopic data and single crystal X-ray diffraction. Compound 3 showed moderate cytotoxic activity against MDA-MB-231 and SGC-7901 cells with IC50 values of 25.26 ±â€¯0.35 µM and 31.2 ±â€¯0.94 µM, respectively.

Gelsekoumidines A and B: Two Pairs of Atropisomeric Bisindole Alkaloids from the Roots of Gelsemium elegans.

Two pairs of atropisomeric bisindole alkaloids, gelsekoumidines A (1) and B (2), with a new carbon skeleton, were isolated from the roots of Gelsemium elegans. Compounds 1 and 2 represent the first examples of seco-koumine-gelsedine type alkaloids, which feature an unprecedented 20,21-seco-koumine scaffold fused with a gelsedine framework via a double bond. Their structures including absolute stereochemistry were elucidated by spectroscopic data, single-crystal X-ray diffraction, and electronic circular dichroism (ECD) calculation. A plausible biogenetic pathway for the new compounds is also proposed. Compound 2 exhibited a moderate inhibitory effect against nitric oxide (NO) production.

Five new koumine-type alkaloids from the roots of Gelsemium elegans.

Five new koumine-type alkaloids (1-5) along with six known ones were isolated from the roots of Gelsemium elegans. Their structures with absolute configurations were elucidated on the basis of NMR spectroscopy and electronic circular dichroism spectral analyses. The inhibitory effects of compounds 1-11 on the viability of three tumor cell lines (A-649, HepG2, and HuH7) were evaluated by the MTT assay.