Lun Wang

Cytotoxic Phorbol Esters of Croton tiglium

Chemical investigation of the seeds of Croton tiglium afforded eight new phorbol diesters (three phorbol diesters, 1-3, and five 4-deoxy-4α-phorbol diesters, 4-8), together with 11 known phorbol diesters (nine phorbol diesters, 9-17, and two 4-deoxy-4α-phorbol diesters, 18 and 19). The structures of compounds 1-8 were determined by spectroscopic data information and chemical degradation experiments. The cytotoxic activities of the phorbol diesters were evaluated against the SNU387 hepatic tumor cell line, and compound 3 exhibited the most potent activity (IC50 1.2 μM).

Cytotoxic Sesquiterpene Lactones from Aerial Parts of Xanthium sibiricum

Chemical investigation of the aerial parts of Xanthium sibiricum led to the isolation of four new xanthanolide-type sesquiterpene lactones, including two xanthanolide dimers, pungiolide D (1) and pungiolide E (2), and two xanthanolide monomers, 8-epi-xanthatin-1α,5α-epoxide (3) and 1β-hydroxyl-5α-chloro-8-epi-xanthatin (4), together with four known compounds, pungiolide A (5), 8-epi-xanthatin-1β,5β-epoxide (6), xanthatin (7), and 11α,13-dihydro-8-epi-xanthatin (8). The structures of these compounds were elucidated on the basis of spectroscopic data analysis. Pungiolide D (1) displayed an unusual structure featuring a 5/5/6-fused tricyclic system in the unit B. Compound 4 was shown to be a rare sesquiterpene lactone containing halogen, and its absolute configuration was determined by X-ray crystallographic analysis. The evaluation of the cytotoxic activities of the isolated new compounds against the SNU387 liver and A-549 lung human cancer cell lines showed that compound 4 possessed significant in vitro cytotoxicity with an IC50 value of 5.1 µM against SNU387 liver cells.

Phenolic antioxidants from Rosa soulieana flowers

Rosa soulieana has been widely used in traditional medicine to treat cardiovascular disorders. In this study, antioxidant activity-guided fractionation and purification of the methanol extract from the flowers of R. soulieana has led to the isolation of nine phenolic antioxidants, which were identified as catechin (1), tiliroside (2), astragalin (3), isoquercitrin (4), nicotiflorin (5), eugenol 4-O-β-d-(6′-O-galloyl) glucoside (6), michehedyosides D (7), citrusin C (8) and strictinin (9), respectively. Among them, compounds 5–9 were reported from the genus Rosa for the first time. All the compounds were also assayed by in vitro ABTS [2,2′-azinobis(3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt] radical cation scavenging activity. Among these bioactive isolates (1–9), compounds 1, 6, 7 and 9 exhibited strong scavenging activity in ABTS (SC50 = 10.17, 7.38, 8.60, 4.72 μmol/L, respectively) compared with the positive control l-ascorbic acid (SC50 = 15.97 μmol/L).

Neolignans, lignans and glycoside from the fruits of Melia toosendan

Four new neolignans, meliasendanins A-D (1-4), and a new glycoside, toosenoside A (5), together with ten known ones (6-15), were isolated from a n-BuOH partition of the fruits of Melia toosendan. Their structures were elucidated by analyses of extensive spectroscopic data and comparison of the NMR data with those reported previously. Meliasendanin A (1) was a rare neolignan containing isochroman moiety, and its absolute configuration was determined using a CD spectrum. Toosenoside A (5) was an unusual glycoside with a rare naturally occurring aglycone and its structure was confirmed by X-ray single crystal diffraction analysis. The antioxidant activity of the isolated neolignans and lignans was evaluated by ABTS radical-scavenging assay. Compounds 1 and 13 exhibited strong antioxidant activity, with IC₅₀ values of 62.8 and 45.1 μM, respectively.

Meroterpenoids and a naphthoquinone from Arnebia euchroma and their cytotoxic activity.

Four new meroterpenoids, arnebinols A-D (1-4), and one new prenylated naphthoquinone, 5,8-O-dimethyl-11-deoxyalkannin (5), together with seven known meroterpenoids (6-12) were isolated from the roots of Arnebia euchroma. The structures of the isolated compounds were elucidated unambiguously by spectroscopic data analysis, as well as X-ray-single crystal diffraction analysis. Arnebinol A (1) and B (2) are rare meroterpenoids possessing a 6/10/5 tricyclic ring system. Compounds 1-12 were evaluated for their cytotoxicities against MG-63 and SNU387 human cancer cell lines. Compound 5 exhibited the most potent activity with IC50 values of 2.69 µM and 6.08 µM, respectively.

Flavonoid glycosides isolated from Epimedium brevicornum and their estrogen biosynthesis-promoting effects

Epimedium brevicornum Maxim has a long history of use in the treatment of estrogen deficiency-related diseases. However, the chemical constituents and mechanism of action of this medicinal plant are not fully understood. In the present study, we isolated four new isoprenylated flavonoid glycosides, as well as 16 known flavonoids (13 isoprenylated flavonoids), from this plant. The chemical structures of the new flavonoid glycosides were elucidated by extensive spectroscopic analysis. The new compounds 1–4 were potent promoters of estrogen biosynthesis in human ovarian granulosa-like KGN cells. ZW1, an isoprenylated flavonoid analogue and a specific inhibitor of phosphodiesterase 5 (PDE5), was synthesized and used to explore the mechanism of the isoprenylated analogues on estrogen biosynthesis. ZW1 treatment increased estrogen production by upregulation of aromatase mRNA and protein expression. ZW1 increased the phosphorylation of cAMP response element-binding protein (CREB). Further study showed that the inhibition of PDE5 by ZW1 increased estrogen biosynthesis partly through suppression of phosphodiesterase 3 (PDE3). Our results suggested that the isoprenylated flavonoids from E. brevicornum may produce beneficial health effects through the promotion of estrogen biosynthesis. PDE5 warrants further investigation as a new therapeutic target for estrogen biosynthesis in the prevention and treatment of estrogen-deficiency related diseases.

Flavonoid glycosides and alkaloids from the embryos of Nelumbo nucifera seeds and their antioxidant activity

Chemical investigation of the embryos of Nelumbo nucifera afforded four new flavone C-glycosides, named nelumbosides A-D (1-4), together with nine known ones, comprising five flavonoids (5-9) and four alkaloids (10-13). The chemical structures of the new compounds were elucidated by 1D, 2D-NMR and HR-ESI-MS techniques, together with chemical methods. Nelumbosides A-D (1-4) are rarely present in naturally occurring flavone C-glycosides featuring a 4-hydroxystyrene unit connected to the flavonoid skeleton. Compounds 2-13 were evaluated for their antioxidant activity by ABTS and DPPH radical-scavenging assay. Among them, compounds 2, 6, 7 and 11 exhibited strong scavenging activity with SC50 values ranging from 12.07 to 25.68μM compared with the positive control l-ascorbic acid.

Cucurbitane glycosides from the fruit of Siraitia grosvenori and their effects on glucose uptake in human HepG2 cells in vitro

The mogrosides in the fruit of Siraitia grosvenori can serve as a sugar substitute for diabetics due to their sweetness, low calorie and positive effects on blood glucose level control. The present study was to purify the mogrosides from the fruit of S. grosvenori and evaluate their enhancement of glucose uptake rate in HepG2 cells in vitro. As a result, eighteen mogrosides were isolated, including six new ones and a known but new naturally occurring compound. The chemical structures of the new compounds were identified by 1D, 2D-NMR and HR-ESI-MS techniques, together with chemical methods. Compared to the positive control (metformin), all the obtained mogrosides showed equivalent or more potent effects on the glucose uptake in HepG2 cells in vitro. These results suggested the mogrosides in the fruit of S. grosvenori were worthy of further research to confirm their potential benefits for obese and diabetic patients.

C21 steroidal glycosides and oligosaccharides from the root bark of Periploca sepium

Four new C21 steroidal glycosides (1-4), named perisepiumosides FI (1-4) together with six known steroidal glycosides (5-10) and four oligosaccharides (11-14), were isolated from the root bark of Periploca sepium. Their structures were characterized on the basis of 1D and 2D-NMR spectroscopic data as well as HR-ESI-MS analysis. The evaluation of inhibition activity against human A-549 and HepG2 cell lines indicated that compounds 2, 8, 10 and 13 showed different levels of cytotoxic activities with IC50 values ranging from 0.61 to 7.86μM.

Two new polyacetylene glycosides from the roots of Codonopsis tangshen Oliv.

Abstract Two new polyacetylene glycosides, tangshenyne A (1) and tangshenyne B (2), along with six known polyacetylenes were isolated from an 85% MeOH extract of the roots of Codonopsis tangshen Oliv. The chemical structures of the new compounds were determined on the basis of extensive spectroscopic analyses, including UV, IR, 1D and 2D NMR (1H–1H COSY, HSQC and HMBC) and HR-ESI-MS.