BackgroundIn order to gain insight into neuroprotective effects of ECa 233, a standardized extract of Centella asiatica, previously demonstrated in animal models of memory impairment induced by transient global ischemia or intracerebroventricular injection of β-amyloid, the effect of ECa 233 on neurite outgrowth of human IMR-32 neuroblastoma cell line was investigated.MethodsCells were seeded and incubated with various concentrations of ECa 233. Morphometric analysis was carried out by a measurement of the longest neurite growth of cells at 24 and 48 h. Contributing signaling pathways possibly involved were subsequently elucidated by western blot analysis.ResultsWhile ECa 233 had only limited effects on cell viability, it significantly enhanced neurite outgrowth of IMR-32 cells at the concentrations of 1–100 μg/ml. Western blot analysis revealed that ECa 233 significantly upregulated the level of activated ERK1/2 and Akt of the treated cells suggesting their involvement in the neuritogenic effect observed, which was subsequently verified by the finding that an addition of their respective inhibitors could reverse the effect of ECa 233 on these cells.ConclusionsThe present study clearly demonstrated neurite outgrowth promoting activity of ECa 233. ERK1/2 and Akt signaling pathways seemed to account for the neurotrophic effect observed. In conjunction with in vivo neuroprotective effect of ECa 233 previously reported, the results obtained support further development of ECa 233 for clinical use in neuronal injury or neurodegenerative diseases.

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GABAergic intercalated neurons of amygdala (ITCs) have recently been shown to be important in the suppression of fear-like behavior. Effects of ECa233 (a standardized extract of Centella asiatica), previously demonstrated anxiolytic activity, were then investigated on ITCs. Cluster of GABAergic neurons expressing fluorescence of GFP was identified in GAD67-GFP knock-in mice. We found that neurons of medial paracapsular ITC were GABAergic neurons exhibiting certain intrinsic electrophysiological properties similar to those demonstrated by ITC neurons at the same location in C57BL/6J mice. Therefore, we conducted experiments in both C57BL/6J mice and GAD67-GFP knock-in mice. Excitatory postsynaptic currents (EPSCs) were evoked by stimulation of the external capsule during the whole cell patch-clamp recordings from ITC neurons in brain slices. ECa233 was found to increase the EPSC peak amplitude in the ITC neurons by about 120%. The EPSCs in ITC neurons were completely abolished by the application of an AMPA receptor antagonist. Morphological assessment of the ITC neurons with biocytin demonstrated that most axons of the recorded neurons innervated the central nucleus of the amygdala (CeA). Therefore, it is highly likely that anxiolytic activity of ECa233 was mediated by increasing activation, via AMPA receptors, of excitatory synaptic input to the GABAergic ITC leading to depression of CeA neurons.

Oxyresveratrol, a polyphenolic compound, has been reported as having antioxidant and anti-inflammatory effects. This study determined the neuroprotective effects of oxyresveratrol, extracted from the heartwood of Artocarpus lakoocha Roxburgh (Moraceae), on parkinsonism induced by rotenone. Male Wistar rats were divided into control, rotenone (PD), and rotenone plus oxyresveratrol (OXY) groups. The OXY rats received oxyresveratrol (300 mg/kg orally) on days 1-20. Rotenone (3 mg/kg subcutaneously) was given to PD and OXY rats on days 15, 16, 18, and 20. Motor function was determined by the rotarod test. Brains were collected to analyze dopaminergic neurons, malondialdehyde (MDA) levels, and superoxide dismutase (SOD) and catalase activities. OXY rats exhibited a longer latency to fall than PD rats in the rotarod test ( P < 0.01) on day 16. The number of dopaminergic neurons in PD rats was lower than that in controls ( P < 0.01), while that of OXY rats was not different from controls. OXY rats showed a reduction in MDA levels ( P < 0.01) and increased catalase activity ( P < 0.05), while SOD activity was unaltered. The results suggest that oxyresveratrol pretreatment ameliorates motor impairment induced by rotenone and preserves dopaminergic neurons. The neuroprotective mechanism of oxyresveratrol is involved with its antioxidant properties.

Antioxidant activity, anti-aging effects and cytotoxicity activity of cinnamon essential oils from Cinnamomum zeylanicum were investigated in this study. The antioxidant activities of the cinnamon essential oil at the concentrations of 125, 250, 500, and 1000 µg/mL were determined using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2ʹ-azino-bis (3-ethylbenzo-thiazoline-6-sulfonic acid) diammonium salt (ABTS). The inhibitory activities against collagenase, elastase and tyrosinase were evaluated for anti-aging effects. The antioxidant activity determined by DPPH and ABTS assays varied from 4.91 - 28.74% and 4.96 - 50.17%, respectively.  In addition, cinnamon essential oil at all concentrations tested (100, 200, 500, and 1000 µg/mL) inhibited tyrosinase activity by 61.68 - 93.12 %, collagenase activity by 2.83 - 30.28 % and elastase activity by 4.37 - 33.92 %.  The cytotoxicity activity determined by the diphenyltetrazolium (MTT) assay revealed that the cinnamon essential oil at the concentration less than 100 µg/mL did not exhibit cytotoxicity activity on human fibroblast cells while the percentage of cell viability decreased when exposed to this oil at the concentration higher than 150 µg/mL. These results demonstrated that the cinnamon essential oil has antioxidant, tyrosinase inhibitory, collagenase inhibitory, and elastase inhibitory activities. In addition, cinnamon essential oil at each effective concentration did not show any toxicity when tested on normal human fibroblast cell. Therefore, this essential oil could be a potential candidate for cosmetic and pharmaceutical products.