BackgroundCistanche tubulosa (Schenk) R. Wight (CT) is commonly used to treat forgetfulness by traditional Chinese physicians. This study presents the ameliorating effects of CT extract which was quantified with three phenylpropanoid glycosides in Alzheimer’s disease (AD)-like rat model.MethodsAmyloid β peptide 1-42 (Aβ 1-42) intracisternally infused to rats by osmotic pump (Alzet 2002) was used as an AD-like rat model. The major pathological makers were measured including Aβ 1-42 immunohistochemical stain, behavioral tests (inhibitory avoidance task and Morris water maze) and central neurotransmitter functions.ResultsAβ 1-42 caused the cognitive deficits, the increase in the amyloid deposition and acetylcholinesterase activities, and the decrease in the levels of brain’s acetylcholine and dopamine. Daily administration of CT extract throughout Aβ 1-42 infusion periods ameliorated the cognitive deficits, decreased amyloid deposition and reversed cholinergic and hippocampal dopaminergic dysfunction caused by Aβ 1-42. Donepezil also ameliorated the cognitive dysfunction, but only blocked the amyloid deposition and cholinergic dysfunction caused by Aβ 1-42.ConclusionsWe suggest that CT extract, containing enough echinacoside and acteoside, ameliorated the cognitive dysfunction caused by Aβ 1-42 via blocking amyloid deposition, reversing cholinergic and hippocampal dopaminergic neuronal function.

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Acteoside and isoacteoside, two phenylethanoid glycosides, coexist in some plants. This study investigates the memory-improving and cytoprotective effects of acteoside and isoacteoside in amyloid β peptide 1-42 (Aβ 1-42)-infused rats and Aβ 1-42-treated SH-SY5Y cells. It further elucidates the role of amyloid cascade and central neuronal function in these effects. Acteoside and isoacteoside ameliorated cognitive deficits, decreased amyloid deposition, and reversed central cholinergic dysfunction that were caused by Aβ 1-42 in rats. Acteoside and isoacteoside further decreased extracellular Aβ 1-40 production and restored the cell viability that was decreased by Aβ 1-42 in SH-SY5Y cells. Acteoside and isoacteoside also promoted Aβ 1-40 degradation and inhibited Aβ 1-42 oligomerization in vitro. However, the memory-improving and cytoprotective effects of isoacteoside exceeded those of acteoside. Isoacteoside promoted exploratory behavior and restored cortical and hippocampal dopamine levels, but acteoside did not. We suggest that acteoside and isoacteoside ameliorated the cognitive dysfunction that was caused by Aβ 1-42 by blocking amyloid deposition via preventing amyloid oligomerization, and reversing central neuronal function via counteracting amyloid cytotoxicity.

Echinacoside is a phenylethanoid glycoside and possesses neuroprotective activity in vitro and in vivo. This study investigates the role of the amyloid cascade and central neuronal function on the protective effects of echinacoside in amyloid β peptide 1-42 (Aβ 1-42)-treated SH-SY5Y cells and an Aβ 1-42-infused rat. Echinacoside inhibited Aβ 1-42 oligomerization in vitro and restored the cell viability that was reduced by Aβ 1-42 in SH-SY5Y cells. Intracisternal infusion with Aβ 1-42 by an osmotic pump caused cognitive deficits, an increase in amyloid deposition and acetylcholinesterase activities, and a decrease in the brain's levels of acetylcholine and dopamine. Echinacoside reduced the cognitive deficits and amyloid deposition, and it reversed the cortical cholinergic dysfunction that was caused by Aβ 1-42 in rats. Echinacoside further reversed the memory impairment in the Morris water maze task caused by scopolamine in mice. Therefore, we suggest that echinacoside ameliorated cognitive dysfunction that was caused by Aβ 1-42 by blocking amyloid deposition via inhibiting amyloid oligomerization and reversing the cortical cholinergic neuronal function via decreasing amyloid neurotoxicity.

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A known biotransformed compound, 6,7,4'-trihydroxyisoflavone, was identified as a potent tyrosinase inhibitor. It inhibited mushroom tyrosinase with an IC50 value of 9.2 microM, which is six times the anti-tyrosinase activity of kojic acid (IC50 = 54.4 microM). The inhibition kinetics, analyzed by Lineweaver-Burk plots, indicated 6,7,4'-trihydroxyisoflavone to be a competitive inhibitor of tyrosinase when L-tyrosine was used as a substrate. Its biosynthesis precursors and analogs, including glycitein, daidzein, and genistein, showed little anti-tyrosinase activity. The results suggest that hydroxyl groups at the C-6 and C-7 positions of the isoflavone skeleton might play an important role in the expression of tyrosinase inhibitory activity.

A new iridoid, gardaloside (1), and a new safranal-type monoterpene, jasminoside G (2), together with 10 known compounds including nine iridoids and a second safranal-type monoterpene, were isolated from the fruits of Gardenia jasminoides. The structures of 1 and 2 were established on the basis of spectroscopic evidence. Of these compounds, geniposide (3), 6alpha-hydroxygeniposide (5), ixoroside (7), and shanzhiside (8) showed significant inhibition of IL-2 secretion by phorbol myristate acetate and anti-CD28 monoclonal antibody co-stimulated activation of human peripheral blood T cells.