Zhifang Xu

Two new prenylated xanthones and a new prenylated tetrahydroxanthone from the pericarp of Garcinia mangostana

Two new prenylated xanthones and a new prenylated tetrahydroxanthone, garcimangosxanthone A-C (1-3), along with fourteen known xanthones were isolated from the pericarp of Garcinia mangostana. Their structures were elucidated on the basis of spectroscopic data. Compounds 1 and 2 exhibited in vitro cytotoxicity against A549, LAC and A375 cell lines with IC(50) values of 5.7-24.9 microM, which were comparable to those of doxorubicin.

Isolation, synthesis, and biological activity of tomentosenol A from the leaves of Rhodomyrtus tomentosa

Tomentosenol A (1), along with a pair of epimers, 4S-focifolidione (2) and 4R-focifolidione (3), were isolated from the leaves of Rhodomyrtus tomentosa. 1 was the first example of a new meroterpenoid class with a unique skeleton that contained a free syncarpic acid coupled with a terpenoid unit, and showed excellent antimicrobial and cytotoxic activities. The absolute configuration of 1 was unambiguously determined by a chemical conversion between 1 and the predetermined 2. In contrast to the common hetero Diels–Alder cycloaddition embodied in previously reported meroterpenoid biosynthesis, an Alder-ene reaction was proposed as the key transformation to account for the biosynthesis of 1, which was confirmed by a biomimetic total synthesis.

Callviminols A-E, new terpenoid-conjugated phloroglucinols from the leaves of Callistemon viminalis.

Callviminols A-E (1-5), five rare phloroglucinols bearing a framework embodying a hexahydrodibenzo[b,d]furan or 2-phenylcyclohexanol nucleus derived from a phloroglucinol-monoterpene adduct, were isolated from the leaves of Callistemon viminalis. Their structures were established via extensive spectroscopic measurements, with the absolute configuration of 5 determined by electronic circular dichroism (ECD) calculations. The plausible biogenetic pathway suggested that a unique oxidative radical addition and classic cationic cyclization were key biosynthetic steps.

Polyprenylated isoflavanone and isoflavonoids from Ormosia henryi and their cytotoxicity and anti-oxidation activity.

A rare naturally-occurring polyprenylated isoflavanone, designated ormosinol (1), and a new isoflavonoid glycoside, named ormosinoside (2), along with 21 known compounds were isolated from the root bark of Ormosia henryi Prain. The structures of compounds 1 and 2 were determined as 5,7,2,4-tetrahydroxyl-6,8,5-tri-(γ,γ-dimethylallyl)isoflavanone and isoprunetin-7-O-β-D-xylopyranosyl-(1 → 6)-β-D-glucopyranoside on the basis of a combination of 1D-, 2D-NMR and mass spectroscopic measurements. Compound 1 showed significant anti-oxidation activity against DPPH radicals (IC(50) 28.5 μM) and cancer cell line (A549, LAC, and HepG2) growth inhibitory activity with IC(50) ranging from 4.25 to 7.09 μM, while compound 2 found to be inactive to both testing systems.

A new quassinoid from fruits of Brucea javanica

A new minor quassinoid named bruceine M (1), together with 12 known quassinoids (2–13), was isolated from the fruits of Brucea javanica (Simaroubaceae). Their structures were determined by interpretation of NMR and HR-ESI-MS data. The structures of the known compounds were confirmed by comparison of their spectral data with those reported in the literatures. In vitro cytotoxicity of the isolated compounds against cancer cell lines Bel-7404, MCF-7 and A549 was evaluated. Compounds 4, 6 and 9 exhibited significant growth inhibitory activity against three cancer cell lines.

Anti-inflammatory and antimicrobial coumarins from the stems of Eurya chinensis

Abstract Two new coumarins, named (±)-euryacoumarin A (1) and 6-demethylobtusinin (2), and one new natural coumarin, named euryacoumarin B (3), along with two known compounds, scopoletin (4) and obtusinol (5), were isolated from the stems of Eurya chinensis. Their structures were elucidated by means of extensive spectroscopic methods and comparison with data reported in the literatures. Compound 1 exhibited significant inhibition of LPS-induced nitric oxide (NO) production in RAW264.7 cells with IC50 value of 35.64 ± 1.73 μM, and showed marginal antibacterial activities against Bacillus subtilis and B. cereus with MIC values of 50.59 ± 2.12 and 35.42 ± 0.96 μM, respectively.

Euryachins A and B, a new type of diterpenoids from Eurya chinensis with potent NO production inhibitory activity

Euryachins A (1) and B (2), a new type of tetracyclic diterpenoid named a euryamane type, were isolated from the branches of Eurya chinensis. Their structures were elucidated through extensive spectroscopic analysis with the absolute configuration of 1 determined by single crystal X-ray diffraction analysis. A biogenetic pathway was proposed to account for the formation of this new type of diterpenoid. Both 1 and 2 exhibited anti-inflammatory activities with potencies comparable to the positive control L-NMMA, as evaluated against NO production in LPS-stimulated RAW264.7 cells.

Callistemenonone A, a novel dearomatic dibenzofuran-type acylphloroglucinol with antimicrobial activity from Callistemon viminalis

A new acylphloroglucinol with a novel architecture including an unprecedented dearomatic dibenzofuran core, named callistemenonone A (1), was isolated from the leaves of Callistemon viminalis (Myrtaceae). The structure was fully characterized on the basis of extensive spectroscopic analysis, including UV, HRESIMS, as well as 1D and 2D NMR spectral data (HSQC, HMBC, and ROESY). The deduced structure represents the first example of a natural dibenzofuran with two phenyl moieties coupling through tertiary hydroxy and ketal carbons. A plausible biogenetic pathway involving oxidative coupling and dearomatization as key steps is proposed to account for the biosynthesis of this novel class of dibenzofuran. Moreover, antimicrobial assays, in conjunction with the time-killing and biophysical studies, revealed that 1 exerted potent bactericidal activity against a panel of methicillin resistant pathogenic microbes with a unique mechanism.

Yangonindimers A-C, three new kavalactone dimers from Piper methysticum (kava)

Abstract Three new kavalactone dimers, designated as yangonindimers A-C (1–3), along with one known analogue were isolated from the roots of Piper methysticum. Their structures were elucidated via extensive analysis of their 1D, 2D NMR and mass spectroscopic data. All these dimers possess a skeleton featuring a cyclobutane ring connecting two kavalactone units. Compounds 1–4 were evaluated for their cytotoxic activities against human tumour cell lines NCI-H46, SW480 and HepG2, but none showed significant activity.

A New Isoprenylated Flavanone from Cajanus cajan

A new isoprenylated flavanone, naringenin-3′-isoprenyl-7-methyl ether, was isolated from the chloroform extract of the leaves of Cajanus cajan. Its structure was eluciated by spectral analysis, mainly 1D and 2D NMR.