Seven new sesquiterpene glycosides from the root bark of Dictamnus dasycarpus

From the water-soluble constituents of the root bark of Dictamnus dasycarpus, six new eudesmane-type sesquiterpene glycosides, dictamnosides H-M (1-6), and a new trinorguaiane-type sesquiterpene glycoside, dictamnoside N (7), together with four known sesquiterpene glycosides, dictamnosides A (8), B (9), D (10), and G (11), were isolated. Their structures were elucidated by spectroscopic analyses and chemical evidence. In vitro tests for immunological activity showed dictamnoside A (8) to possess remarkable activity in stimulating the proliferation of T-cells.

Salvianolate inhibits proliferation and endothelin release in cultured rat mesangial cells

AIM

To study the effects of salvianolate, an aqueous extract of Radix Salviae Miltiorrhizae, on the proliferation and endothelin release of cultured rat mesangial cells.

METHODS

The proliferation of mesangial cells was determined in terms of [3H]thymidine uptake. The concentration of endothelin was measured by radioimmunoassay. The cytotoxicity of salvianolate was tested by tetrazolium (MTT) and lactic dehydrogenase (LDH) assay.

RESULTS

Lipopolysaccharide (LPS) 10 mg/L increased the proliferation and endothelin release in cultured mesangial cells. When mesangial cells pretreated with 3, 10, and 30 mg/L of salvianolate were incubated for 4 h with LPS, salvianolate exhibited a concentration dependent inhibitory effect on proliferation and endothelin levels in the mesangial cells induced by LPS. Furthermore, the increased basal levels of mesangial cells proliferation and the endothelin release were also effectively inhibited by salvianolate 30 mg/L at 4, 8, and 12 h. Besides, no cytotoxicity of salvianolate was observed.

CONCLUSION

These results indicate that salvianolate can inhibit mesangial cells proliferation, which may be related to the decrease of endothelin release.

Effects of magnesium lithospermate B on aggregation and 5-HT release in rabbit washed platelets

AIM

To study the effects and mechanism of magnesium lithospermate B(MLB) on rabbit platelet aggregation and 5-HT release.

METHODS

The platelet aggregation was determined by Born's method. Release of serotonin (5-HT) and formation of thromboxane A2 (TXA2) were measured by fluorophotometry and radioimmunoassay (RIA) respectively. Cytoplasmic free Ca2+ concentration ([Ca2+]i) in platelets was measured by Fura 2-AM fluorescence technique.

RESULTS

In washed platelets, thrombin (200 U/L) or arachidonic acid (AA) (30 mumol/L)-induced aggregation was inhibited by MLB 50-800 mg/L in a concentration-dependent manner. In addition, MLB had more inhibitory effects on platelet aggregation in the absence of extracellular calcium with IC50 of 102 mg/L than in the presence of CaCl2 1 mmol/L with IC50 of 194 mg/L. MLB concentration-dependently decreased the thrombin-activated release of 5-HT, whereas it did not affect the formation of TXA2 in platelets. Furthermore, MLB not only inhibited the rise of [Ca2+]i in thrombin stimulated platelets, but decreased the [Ca2+]i in resting platelets.

CONCLUSION

MLB inhibited the aggregation and 5-HT release in rabbit platelets and it is probably by attenuating intracellular calcium concentration.

Free radical scavenging and inhibition of lipid peroxidation by magnesium lithospermate B

AIM

To study the effect of magnesium lithospermate B (MLB) on the lipid peroxidation and on its free radical scavenging activity.

METHODS

MLB was incubated in rat tissue homogenate or in a free radical generating system. MLB induced inhibition of lipid peroxidation and its scavenging activity on superoxide anions and hydroxyl radicals was studied using colorimetric estimation.

RESULTS

MLB inhibited the lipid peroxidation induced by either an auto-oxidant or Fe2+/VitC in vitro, in the liver homogenate, the inhibitory rate of MLB (10 mg/L) being 69.2% and 57.7%, respectively. MLB (25 and 50 mg/kg) decreased the amount of thiobarbituric acid reactive substances (TBARS) in rat serum, liver, kidney, and heart. However, it did not inhibit the lipid peroxidation of brain homogenate ex vivo. MLB scavenged superoxide anions generated from xanthine/xanthine oxidase system and iron-dependent hydroxyl radicals.

CONCLUSION

MLB is an inhibitor of lipid peroxidation and scavenge superoxide anions and hydroxyl radicals both in vitro and ex vivo.

Solakhasoside, a novel steroidal saponin from Solanum khasianum

Solakhasoside (1), a novel steroidal saponin, was isolated from the fruit of Solanum khasianum. Its structure was determined as (23S, 25S)-spirot-5-en-3beta,17alpha, 23-triol-3-O-[alpha-L-rhamnopyranosyl-(1-->2)[beta-D-xylopyranosyl-(1 -->3)]-beta-D-galactopyranoside] (1) by spectroscopic analysis.

Three diterpene dilactone glycosides from Podocarpus nagi

Three water-soluble constituents, nagilactosides C-E, were isolated from Podocarpus nagi. Their structures were determined by chemical and spectroscopic methods, respectively. Nagilactoside C was identified as 1-deoxy-nagilactone A-2 alpha-O-beta-D-glucopyranosyl-(1-->3)-beta-D-glucopyranoside, nagilactoside D as 1-deoxy-nagilactone A-2 alpha-O-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranoside, and nagilactoside E as nagilactone A-1 beta-O-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyransoide.