Beta-secretase (BACE1)-inhibiting stilbenoids from Smilax Rhizoma.

In the course of searching for BACE1 (beta-secretase) inhibitors from natural products, the ethyl acetate soluble fraction of Smilax Rhizoma (the dried rhizomes of Smilax china L.) showed potent inhibitory activity. The active compounds were identified as a trans/cis-resveratrol mixture, oxyresveratrol, veraphenol, and cis-scirpusin A. They were shown to non-competitively inhibit BACE1 with the Ki values of 5.4 x 10(-6), 5.4 x 10(-6), 3.4 x 10(-6), and 5.4 x 10(-6)M and IC(50) values of 1.5 x 10(-5), 7.6 x 10(-6), 4.2 x 10(-6), and 1.0 x 10(-5)M, respectively. The active compounds were less inhibitory to alpha-secretase (TACE) and other serine proteases such as chymotrypsin, trypsin, and elastase, suggesting that they were relatively specific inhibitors of BACE1.

Lactate elicits vascular endothelial growth factor from macrophages: a possible alternative to hypoxia.

Macrophages respond to various stimuli to produce angiogenic factors but few mechanistic details are known. We examined the effects of hypoxia, lactate and nicotinamide on the expression of vascular endothelial growth factor by cultured macrophages. These agents were chosen because they down-regulate polyadenosine diphosphoribose levels. Following exposure, conditioned media were analyzed for vascular endothelial growth factor protein. Nicotinamide adenine dinucleotide, polyadenosine diphosphoribose, and vascular endothelial growth factor mRNA were measured in the cellular fraction. Angiogenic capacity of the conditioned media was tested in rabbit corneas and Matrigel implants. All three agents, hypoxia, lactate and nicotinamide, elicited significantly increased levels of vascular endothelial growth factor mRNA and vascular endothelial growth factor in the conditioned media, and these levels were paralleled by their angiogenic activity. Polyadenosine diphosphoribose in the cellular fraction was correspondingly depressed. Anti-vascular endothelial growth factor antibody inhibited most of the angiogenic response whereas anti-basic fibroblast growth factor antibody had little effect. We propose that redox changes associated with the alteration of cellular nicotinamide adenine dinucleotide and polyadenosine diphosphoribose are involved in lactate-mediated VEGF expression.

Biological and pharmacological effects of pinusolide, a novel platelet activating factor antagonist.

Pinusolide, a potent platelet activating factor (PAF) receptor binding antagonist, inhibited PAF-induced aggregation of rabbit platelets with an IC50 value of 5 microM, whereas no inhibitory effects on the aggregation induced by ADP, thrombin, and collagen were observed. Pinusolide protected the mice from PAF-induced lethality with ED50 values of 1.1 mg/kg, i.v. and 69 mg/kg, p.o. Topically given pinusolide at 2 mg/ear effectively inhibited croton oil induced mouse ear edema. All the pinusolide treated ears recovered to normal healthy appearance in a sharp contrast to totally necrotized untreated ears. These results indicated that pinusolide is a potent and specific PAF antagonist in all experimental models as shown in vitro, in vivo, and in animal tests.

Isolation and characterization of platelet-activating factor receptor binding antagonists from Biota orientalis.

The leaf extract of Biota orientalis showed potent PAF receptor binding antagonistic activity in our previous screening studies on 234 Korean medicinal plants using rabbit platelet receptor binding tests. The activity-guided purification of the plant extract resulted in the isolation of six compounds, including two active substances. The chemical structures of the compounds isolated were established by chemical and spectrometric analyses as dotriacontane, totarol, 8 beta-hydroxy-3-oxopimar-15-ene, cedrol (IC50 = 1.3 x 10(-5) M), pinusolide (IC50 = 2.52 x 10(-7) M), and 5-hydroxy-7,4'-dimethoxyflavone.