Hai-Li Liu

Paracaseolide A, First α-Alkylbutenolide Dimer with an Unusual Tetraquinane Oxa-Cage Bislactone Skeleton from Chinese Mangrove Sonneratia paracaseolaris

A novel α-alkylbutenolide dimer, paracaseolide A (2), characterized by an unusual tetraquinane oxa-cage bislactone skeleton bearing two linear alkyl chains, was isolated from the mangrove plant Sonneratia paracaseolaris. The structure of 2 was elucidated by extensive spectroscopic analysis. A plausible retrosynthetic pathway for paracaseolide A (2) was proposed. Compound 2 exhibited significant inhibitory activity against dual specificity phosphatase CDC25B, a key enzyme for cell cycle progression, with an IC(50) value of 6.44 μM.

Steroids with Aromatic A-Rings from the Hainan Soft Coral Dendronephthya studeri Ridley

Eight new marine steroids, characterized by either the presence of an aromatic ring or a cross-conjugated dienone system in ring A, were isolated from the Hainan soft coral Dendronephthya studeri Ridley. Their structures were elucidated on the basis of detailed spectroscopic analysis and by comparison of their NMR data with those reported in the literature.

The growth of high-Al-content InAlGaN quaternary alloys by RF-MBE

High-Al-content InxAlyGa1-x-yN (x = 1-10%, y = 34-45%) quaternary alloys were grown on sapphire by radio-frequency plasma-excited molecular beam epitaxy. Rutherford back-scattering spectrometry, high resolution x-ray diffraction and cathodoluminescence were used to characterize the InAlGaN alloys. The experimental results show that InAlGaN with an appropriate Al/In ratio (near 4.7, which is a lattice-match to the GaN under-layer) has better crystal and optical quality than the InAlGaN alloys whose Al/In ratios are far from 4.7. Some cracks and V-defects occur in high-Al/In-ratio InAlGaN alloys. In the CL image, the cracks and V-defect regions are the emission-enhanced regions.

Bioactive polyhydroxylated steroids from the Hainan soft coral Sinularia depressa Tixier-Durivault.

Two new steroids, (2β,3β,4α,5α,8β)-4-methylergost-24(28)-ene-2,3,8-triol (1) and (3β,7α)-24-methyl-7-hydroperoxycholest-5,24(28)-diene-3-ol (2), together with 13 known analogues (3-15) were isolated from the soft coral Sinularia depressa Tixier-Durivault. The structures of the new compounds were elucidated by detailed spectroscopic analysis and comparison with reported data. In the bioassay in vitro, compounds 3a, 4, and 14 exhibited potent PTP1B inhibitory activity, being similar as that of positive control oleanolic acid. Compound 14 also displayed a notable neuroprotective activity against both amyloid-β(25-35)- and serum deprivation-induced injuries in SH-SY5Y cells while compound 11 showed a considerable antibacterial activity against Staphylococcus aureus. Preliminary structure-activity relationships of these steroids were discussed.

Ximaosteroids A-D, new steroids from the Hainan soft coral Scleronephthya sp.

One novel uncommon steroid, ximaosteroid A (1), possessing an unusual tetrahydrofuran moiety and three new pregnane steroids, ximaosteroids B-D (2-4), were isolated from the Hainan soft coral Scleronephthya sp. Their structures were elucidated on the basis of detailed spectroscopic (IR, MS, and 2D NMR) analysis and by comparison with those reported in the literature.

9,11-Secosteroids and polyhydroxylated steroids from two South China Sea soft corals Sarcophyton trocheliophorum and Sinularia flexibilis.

A new 9,11-secosteroid, 25(26)-dehydrosarcomilasterol (1), two new polyhydroxylated steroids, 7α-hydroxy-crassarosterol A (2) and 11-acetoxy-7α-hydroxy-crassarosterol A (3), together with three known related ones (4-6), were isolated from the South China Sea soft corals Sarcophyton trocheliophorum and Sinularia flexibilis, respectively. The structures of the new steroids were elucidated on the basis of extensive spectroscopic analyses, comparison with the literature data and chemical correlation. Compound 2 exhibited a moderate protein tyrosine phosphatase 1B (PTP1B) inhibitory activity with an IC50 value of 33.05μM. Compounds 1-3 showed weak in vitro cytotoxicities against the tumor cell lines K562 and HL-60.

Phragmalin limonoids from Chukrasia tabularis var. velutina.

Two new C-15-acyl phragmalin limonoids, velutinalides A and B, featuring a C-16/C-30 δ-lactone ring, and a new structurally related natural product, R310B8, were isolated from the leaves of Chukrasia tabularis var. velutina. Their structures were elucidated on the basis of extensive spectroscopic data analyses and by comparison of their NMR data with those of related known compounds.

Piperidine Alkaloids from Chinese Mangrove Sonneratia hainanensis

A new diphenacyl-piperidine alkaloid, sonneratine A (2), identified as a piperidine ring bearing two phenacyl substitutes at C-2 and C-6, and a known related derivative, (+/-)1-(2-piperidyl)-4-( P-methoxyphenyl)-butanone-2 (3), were isolated from the leaves and stems of the Hainan mangrove Sonneratia hainanensis. The structure of the new compound was determined by extensive analysis of its spectroscopic data and by comparison of its NMR data with those reported in the literature.

A New Kalihinol Diterpene from the Hainan Sponge Acanthella sp.

A new kalihinol diterpene, 10-epi-kalihinol X (1), together with two known related diterpenes (2 and 3), and two sesquiterpenes (4 and 5) were isolated from the Hainan sponge Acanthella sp. The structure of the new compound was elucidated on the basis of the detailed analysis of its spectroscopic data and by comparison of its NMR data with those of structurally related compounds. Compounds 1 and 3–5 exhibited in vitro moderate cytotoxicities against human lung adenocarcinoma cell line A549, with IC50 values of 9.30, 3.17, 2.44, and 1.98 µg/mL, respectively.

Structural and stereochemical studies of five new pregnane steroids from the stem bark of Toona ciliata var. pubescens.

Five new pregnane steroids, toonasterones A (1), B (2), (Z)-aglawone (3), (Z)-toonasterone C (4), and (E)-toonasterone C (5), were isolated from the stem bark of Toona ciliata var. pubescens. Their structures were elucidated by means of detailed spectroscopic (IR, MS, and 2D NMR) analysis, and the stereochemistry of 1 was secured by X-ray diffraction analysis. (Z)-aglawone (3) exhibited moderate inhibitory activity of protein tyrosine phosphatase 1B (PTP1B), a potential drug target for treatment of type-II diabetes and obesity, with an IC(50) value of 1.12 μg/mL.