Qing-Bo Liu

Antioxidant and anti-inflammatory active dihydrobenzofuran neolignans from the seeds of Prunus tomentosa.

Prunus tomentosa seeds were researched for antioxidant and anti-inflammatory constituents. By activity-guided fractionation of P. tomentosa seed extract, six new dihydrobenzofuran neolignans, prunustosanans AI-IV (1-4) and prunustosanansides AI and AII (5 and 6), together with 10 known compounds (7-16) were isolated from bioactive fraction. The structures were determined by spectroscopic analyses, especially NMR, HRESIMS, and CD spectra. The antioxidant activity was greatest for 5, 10, and 12 against DPPH radical and for 8, 9, and 13 against ABTS radical. Moreover, compounds 7 and 11 exhibited much stronger inhibitory activity on nitric oxide (NO) production in murine microglia BV-2 compared with positive control minocycline (IC50 = 19.7 ± 1.5 μM). The results show that P. tomentosa seeds can be regarded as a potential source of antioxidants and inflammation inhibitors.

Cytotoxic triterpenoid glycosides (saikosaponins) from the roots of Bupleurum chinense.

As a part of our ongoing studies on cytotoxic triterpenoid saponins from herbal medicines, phytochemical investigation of the roots of Bupleurum chinense DC. afforded four new saikosaponins (1-4), along with 16 known ones (5-20). Their structures were established by direct interpretation of their spectral data, mainly HR-ESI-MS, 1D NMR and 2D NMR, and by comparison with literature data. Among them, compound 20 was isolated from the natural product for the first time. The cytotoxicities of all compounds against five selected human cancer cell lines (A549, HepG2, Hep3B, Bcap-37 and MCF-7) were assayed. In general, a number of the isolated compounds exhibited potent cytotoxic activities against the five selected human cancer cell lines. In particular, compounds 3, 8-9, 11-13, 16 and 20 showed more potent cytotoxic activities against the HepG2 and A549 cell lines than the positive control 5-fluorouracil. Based on the primary screening results, the preliminary structure-activity relationship (SAR) studies were also discussed. The SAR results suggest that the 13,28-epoxy bridge, the orientation of the hydroxyl group and the type of the sugar units are important requirements for cytotoxicity and selectivity.

Two new glycosides from the fruits of Forsythia suspense.

Two new glycosides suspensaside C (1) and 2,3,5,6-tetrahydro-jacaranone-4-O-β-d-glucopyranoside (2), together with four known compounds suspensaside A (3), rengynic acid-1′-O-β-d-glucopyranoside (4), forsythoside A (5), and rengynic acid (6), were isolated from the fruits of Forsythia suspense (Thunb.) Vahl. The structures of 1 and 2 were elucidated on the basis of chemical and spectral analysis, including 1D, 2D NMR analyses and HR-ESI-MS. All isolates were tested for their cytotoxicities against five human cancer cell lines (A549, Colo-205, Hep-3B, HL60, and KB). Compound 3 exhibited cytotoxicity against HL-60, Hep-3B, and A549 cancer cell lines.

Secondary metabolites from the flower buds of Lonicera japonica and their in vitro anti-diabetic activities

Four new compounds (1, 2, 7 and 8) and twenty known compounds were isolated from the flower buds of Lonicera japonica. Their structures were determined by extensive NMR and HR-ESIMS spectroscopic data analyses. Among them, compounds 1 and 2 are a pair of diastereoisomers possessing a rare chemical structure, and their absolute configurations were determined by comparing their experimental and calculated ECD spectra. Furthermore, all the isolates were evaluated for their inhibitory effects on α-glucosidase and protein tyrosine phosphatase 1B (PTP1B), especially 1 and 2, which displayed both significant inhibitions. In addition, the possible action mechanism of the active compounds was also explored by using molecular docking studies.

Steroidal saponins from Anemarrhena asphodeloides

Two new steroidal saponins, named anemarnoside A (1) and anemarnoside B (2), along with three known compounds, timosaponin J (3), timosaponin B II (4), and timosaponin B (5), have been isolated from Anemarrhena asphodeloides. Their structures were established by spectroscopic techniques (IR, MS, 1D NMR, and 2D NMR) and by comparison with published data.

Neogenkwanines A–H: daphnane-type diterpenes containing 4,7 or 4,6-ether groups from the flower bud of Daphne genkwa

Neogenkwanines A–H (1–8), eight daphnane-type diterpenes possessing new skeletons with 4,7- or 4,6-ether groups, along with seven known ones (10–16), were isolated from Daphne genkwa. Their structures and absolute configurations were established by analysis of their NMR, X-ray crystallography, CD exciton chirality data and hydrolysis experiments. In addition, an MTT assay was used to examine the growth-inhibitory effects of all the new isolates on HL-60, Hep3B, and U87 cells; compounds 3, 4 and 5 exhibited significant inhibitory effects against Hep3B cell lines with IC50 values of 7.61, 8.16 and 8.35 μM, respectively.

Anti-inflammatory sesquiterpene pyridine alkaloids from Tripterygium wilfordii

During a screening procedure involving higher plants to find novel candidates for use as anti-inflammatory agents, Tripterygium wilfordii Hook. f. was shown to exhibit considerable inhibitory activity. Five new sesquiterpene pyridine alkaloids, tripterygiumines S-W (1-4,15), along with 14 known dihydroagarofuran derivatives, were isolated from the roots of the T. wilfordii Hook. f. Their structures were established by extensive use of spectroscopic techniques, including 1D and 2D NMR spectroscopy and high-resolution mass spectrometry. All compounds were evaluated for their anti-inflammatory activity by measuring the nitric oxide production by the LPS-induced murine macrophage cell line RAW264.7. It was found that 1, 5, and 19 possessed potent nitric oxide inhibitory activity with IC50 values ranging from 2.99 to 28.80 μM, without any effect on the cell viability of RAW264.7 cells. Accordingly, compounds 1, 5, and 19, especially 5, were identified as promising candidates for further scientific investigation of their potential use as anti-inflammatory agents.

Neuroprotective oleanane triterpenes from the roots of Bupleurum chinense

The discovery of new natural compounds with pharmacological properties is an increasingly important field, and a continuous phytochemical investigation of the roots of Bupleurum chinense D.C. has led to the isolation of 17 triterpenoids, including three new oleanane triterpenes (1-3) together with 14 known ones. Their structures were determined on the basis of 1D and 2D NMR spectra as well as HR-ESI-MS data. The cytotoxicities of all compounds against five selected human cancer cell lines were assayed. Only compounds 9 and 14 exhibited moderate activities. Recently, a number of investigations have focused on the neuroprotective properties of triterpenoids in B. chinense. In order to expand our knowledge about this herb, the neuroprotective effects of compounds 1-17 against hydrogen peroxide (H2O2)-induced neuronal cell damage in human neuroblastoma SH-SY5Y cells were evaluated. Compounds 1-3, 6-7 showed significant neuroprotective effects against H2O2-induced SH-SY5Y cell death. Preliminary structure-activity relationships (SARs) between neuroprotective effects and the isolates were also discussed.

Tomensides A–D, new antiproliferative phenylpropanoid sucrose esters from Prunus tomentosa leaves

To search for novel cytotoxic constituents against cancer cells as lead structures for drug development, four new 3-phenylpropanoid-triacetyl sucrose esters, named tomensides A-D (1-4), and three known analogs (5-7) were isolated from the leaves of Prunus tomentosa. Their structures were elucidated by spectroscopic analyses (1D, 2D NMR, CD and HRESIMS). The cytotoxic activities of all isolates against four human cancer cell lines (MCF-7, A549, HeLa and HT-29) were assayed, and the results showed that these isolates displayed stronger inhibitory activities compared with positive control 5-fluorouracil. Tomenside A (1) was the most active compound with IC50 values of 0.11-0.62 μM against the four tested cell lines. The structure-activity relationship (SAR) of the isolates was also discussed. The primary screening results indicated that these 3-phenylpropanoid-triacetyl sucrose esters might be valuable source for new potent anticancer drug candidates.

Three new lignan glycosides from the fruits of Forsythia suspense

Two new lignan glycosides forsythiayanoside A (1) and forsythiayanoside B (2), one new stereoisomer of lignan glycoside (+)-8-hydroxyepipinoresinol-4-O-β-d-glucopyranoside (3), together with seven known compounds (4–10), were isolated from the fruits of Forsythia suspense (Thunb.) Vahl. Compounds 4 and 10 were isolated from this species for the first time. The structures of 1–3 were elucidated on the basis of chemical and spectral analyses, including 1D and 2D NMR data and HR-ESI-MS. The absolute configurations were determined by the circular dichroism method. All isolates were tested for their cytotoxicities against five human cancer cell lines (A549, Colo-205, Hep-3B, HL60, and KB). In particular, compound 3 showed significant cytotoxicity with IC50 values of 9.48, 7.75, 0.59, 4.06, and 38.38 μM, respectively.