In vivo antiosteoporotic activity of a fraction of Dioscorea spongiosa and its constituent, 22-O-methylprotodioscin.

The antiosteoporotic activity of the 90 % EtOH fraction of the water extract of rhizomes of Dioscorea spongiosa and methylprotodioscin, its major constituent, were examined in the model of postmenopausal bone loss using ovariectomized (OVX) rats or mice. After 6 weeks treatment, the proximal tibia of rats or mice and the distal femora of mice were scanned by peripheral quantitative computed tomography (pQCT). Both the 90 % EtOH fraction (100 mg/kg/d) and methylprotodioscin (50 mg/kg/d) significantly inhibited bone loss in bone mineral content (BMC) and bone mineral density (BMD) in total, cancellous and cortical bones, and the decrease in bone strength indexes induced by OVX, without side effect on the uterus.

Secoisolariciresinol and isotaxiresinol inhibit tumor necrosis factor-alpha-dependent hepatic apoptosis in mice.

The effects of secoisolariciresinol (1) and isotaxiresinol (2), two major lignans isolated from the wood of Taxus yunnanensis, on tumor necrosis factor-alpha (TNF-alpha)-dependent hepatic apoptosis induced by D-galactosamine (d-GalN)/lipopolysaccharide (LPS) were investigated in mice. Co-administration of d-GalN (700 mg/kg) and LPS (10 microg/kg) resulted in a typical hepatic apoptosis characterized by DNA fragmentation and the formation of apoptotic bodies. Serum glutamic pyruvic transaminase (sGPT) and glutamic oxaloacetic transaminase (sGOT) levels were also raised at 8 h after d-GalN/LPS intoxication due to a severe necrosis of hepatocytes. Pre-administration of 1 or 2 (50, 10 mg/kg, i.p.) 12 and 1 h before d-GalN/LPS significantly reduced DNA fragmentation and prevented chromatin condensation, apoptotic body formation and hepatitis. Pro-inflammatory cytokines such as TNF-alpha and interferon-gamma (IFN-gamma) secreted from LPS-activated macrophages are important mediators of hepatocyte apoptosis in this model. Pre-treatment with 1 or 2 significantly inhibited the elevation of serum TNF-alpha and IFN-gamma levels. In a separate experiment, both lignans had a significant dose-dependent protective effect on d-GalN/TNF-alpha-induced cell death in primary cultured mouse hepatocytes and TNF-alpha-mediated cell death in murine L929 fibrosarcoma cells. These results indicated that 1 and 2 prevent d-GalN/LPS-induced hepatic injury by inhibiting hepatocyte apoptosis through the blocking of TNF-alpha and IFN-gamma production by activated macrophages and direct inhibition of the apoptosis induced by TNF-alpha.

Hepatoprotective effect of taxiresinol and (7'R)-7'-hydroxylariciresinol on D-galactosamine and lipopolysaccharide-induced liver injury in mice.

The hepatoprotective effect of taxiresinol ( 1) and (7' R)-7'-hydroxylariciresinol ( 2), two tetrahydrofuran-type lignans isolated from the wood of Taxus yunnanensis, were investigated on D-galactosamine ( D-GalN)/lipopolysaccharide (LPS)-induced hepatic liver injury in mice. Pre-administration of 1 or 2 at doses of 50 and 10 mg/kg ( i. p.) at 12 and 1 h before D-GalN/LPS injection significantly inhibited hepatocyte DNA fragmentation and apoptotic body formation. Pre-treatment of these two lignans further suppressed hepatic necrosis which occur at later stage of D-GalN/LPS intoxication as demonstrated by the significant and dose-dependent reduction in serum glutamic pyruvic transaminase (sGPT) and serum glutamic oxaloacetic transaminase (sGOT) at 8 h after intoxication. The elevation of serum tumor necrosis factor-alpha (TNF- alpha) level by D-GalN/LPS toxication was significantly inhibited by 1 or 2 at doses of 50 and 10 mg/kg. Moreover, both of these lignans significantly protected hepatocytes from D-GalN/TNF- alpha-induced cell death in primary cultured mouse hepatocytes. These results suggested that 1 and 2 had protected the hepatocytes from apoptosis via an inhibition of TNF- alpha production by activated macrophages and a direct inhibition of apoptosis induced by TNF- alpha in D-GalN/LPS-treated mice.

New diarylheptanoids from the rhizomes of Dioscorea spongiosa and their antiosteoporotic activity.

Bioassay-guided fractionation of the water extract of the rhizomes of Dioscorea spongiosa led to the isolation and identification of new diarylheptanoids, diospongins A - C, together with three known lignans. Their structures, including absolute stereochemistry, were determined by analyses of NMR data, chemical conversions and CD spectrum. The isolated compounds, except for diospongin A, exerted potent inhibitory activities on bone resorption induced by parathyroid hormone in a bone organ culture system.

Chemical constituents and biological activities of Vietnamese medicinal plants.

Every country has its own traditional medicine system originated from ancient times. Vietnam, a Southeast Asian country, has a unique traditional medicine system. Several medicinal plants are still used by different ethnic societies of Vietnam for treating several diseases due to their easy availability. Combretum quadrangulare, Panax vietnamensis (Vietnamese Ginseng), Dracaena angustifolia (Nam Ginseng) and Orthosiphon stamineus are among the popular medicinal plants used in Vietnamese traditional medicine for curing various diseases and to improve physical strength. In this review article, we discuss the chemical analysis as well as biological activities of these Vietnamese medicinal plants in order to establish the relation between their therapeutic uses and scientific findings.

Antiproliferative activity of Vietnamese medicinal plants.

Methanol, methanol-water (1:1) and water extracts were prepared from seventy-seven Vietnamese medicinal plants and tested for their antiproliferative activities against human HT-1080 fibrosarcoma cells. Among them, fifteen extracts including seven methanol extracts of Caesalpinia sappan, Catharanthus roseus, Coscinium fenestratum, Eurycoma longifolia, Hydnophytum formicarum and Streptocaulon juventas (collected at two areas), six methanol-water (1:1) extracts of Cae. sappan, Cat. roseus, Co. fenestratum, H. formicarum and S. juventas (at two areas), and two water extracts of Cae. sappan and S. juventas exhibited antiproliferative activities in a concentration-dependent manner. Their antiproliferative activities against human cervix HeLa adenocarcinoma, human lung A549 adenocarcinoma, murine colon 26-L5 carcinoma, murine Lewis lung carcinoma (LLC) and murine B16-BL6 melanoma cells were then examined. Co. fenestratum showed selective activity against lung carcinoma and/or lung metastatic cell lines, A549, LLC and B16-BL6, while H. formicarum and S. juventas showed selective activity against human tumor cell lines, HeLa and A549. Characteristic morphological change and DNA fragmentation indicated the antiproliferative activity to be due to the induction of apoptosis.