Kaempferol-3-O-(2″-O-galloyl-ß-D-glucopyranoside): a novel neuroprotective agent from Diospryros kaki against cerebral ischemia-induced brain injury.

Our previous study demonstrated neuroprotective and therapeutic effects of a standardized flavonoid extract from leaves of Diospyros kaki L.f. (DK) on middle cerebral artery occlusion-and-reperfusion (MCAO/R)-induced brain injury and its underlying mechanisms. This study aimed to clarify flavonoid components responsible for the effects of DK using in vitro and in vivo transient brain ischemic models. Organotypic hippocampal slice cultures (OHSCs) subjected to oxygen- and glucose-deprivation (OGD) were performed to evaluate in vitro neuroprotective activity of DK extract and nine isolated flavonoid components. MCAO/R mice were employed to elucidate in vivo neuroprotective effects of the flavonoid component that exhibited the most potent neuroprotective effect in OHSCs. DK extract and seven flavonoids [quercetin, isoquercetin, hyperoside, quercetin-3-O-(2″-O-galloyl-ß-D-galactopyranoside), kaempferol, astragalin, and kaempferol-3-O-(2″-O-galloyl-ß-D-glucopyranoside) compound (9)] attenuated OGD-induced neuronal cell damage and compound (9) possessed the most potent neuroprotective activity in OHSCs. The MCAO/R mice showed cerebral infarction, massive weight loss, characteristic neurological symptoms, and deterioration of neuronal cells in the brain. Compound (9) and a reference drugs, edaravone, significantly attenuated these physical and neurological impairments. Compound (9) mitigated the blood-brain barrier dysfunction and the change of glutathione and malondialdehyde content in the MCAO mouse brain. Edaravone suppressed the oxidative stress but did not significantly affect the blood-brain barrier permeability. The present results indicated that compound (9) is a flavonoid constituent of DK with a potent neuroprotective activity against transient ischemia-induced brain damage and this action, at least in part, via preservation of blood-brain barrier integrity and suppression of oxidative stress caused by ischemic insult.

Therapeutic effects of a standardized-flavonoid Diospyros kaki L.f. leaf extract on transient focal cerebral ischemia-induced brain injury in mice.

This study aimed to investigate the neuroprotective and therapeutic effects of Diospyros kaki L.f. leaves (DK) on transient focal cerebral ischemic injury and underlying mechanisms using a middle cerebral artery occlusion (MCAO) model of mice. The animals received the MCAO operation on day 0. The daily administrations of DK (50 and 100 mg/kg, p.o) and edaravone (6 mg/kg, i.v), a reference drug with radical scavenging activity, were started 7 days before (pre-treatment) or immediately after the MCAO operation (post-treatment) and continued during the experimental period. Histochemical, biochemical, and neurological changes and cognitive performance were evaluated. MCAO caused cerebral infarction and neuronal cell loss in the cortex, striatum, and hippocampus in a manner accompanied by spatial cognitive deficits. These neurological and cognitive impairments caused by MCAO were significantly attenuated by pre- and post-ischemic treatments with DK and edaravone, suggesting that DK, like edaravone, has therapeutic potential for cerebral ischemia-induced brain damage. DK and edaravone suppressed MCAO-induced changes in biomarkers for apoptosis (TUNEL-positive cell number and cleaved caspase-3 protein expression) and oxidative stress (glutathione and malondialdehyde contents) in the brain. Interestingly, DK, but not edaravone, mitigated an increase in blood-brain permeability and down-regulation of vascular endothelial growth factor protein expression caused by MCAO. Although the exact chemical constituents implicated in the effects of DK remain to be clarified, the present results indicate that DK exerts neuroprotective and therapeutic activity against transient focal cerebral ischemia-induced injury probably by suppressing oxidative stress, apoptotic process, and mechanisms impairing blood-brain barrier integrity in the brain.