Ginkgolide B accelerates vestibular compensation of spontaneous ocular nystagmus in guinea pig following unilateral labyrinthectomy

Ginkgolides-loaded soybean phospholipid-stabilized nanosuspension with improved storage stability and in vivo bioavailability

The purpose of this study was to investigate the effects of soybean phospholipid, as a steric stabilizer, on improving dissolution rate, storage stability and bioavailability of ginkgolides. The ginkgolides coarse powder, hydroxypropyl methylcellulose (HPMC), soybean phospholipid and sodium dodecyl sulfate (SDS) were mixed and wet-milled to prepare nanosuspension S1. Nanosuspension S2 was obtained by the same technique except adding the soybean phospholipid. Results of particle size showed that particle size (D50) of S1 significantly decreased from 44.25 μm to 0.373 μm. Results of differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD) and transmission electron microscope (TEM) showed that ginkgolides in nanosuspension still maintained its crystallinity, and the nanoparticles were all nearly circular and uniformly dispersed. Then, pellets F1 and F2 were prepared by layering S1 and S2 onto the microcrystalline cellulose (MCC) spheres, respectively. The dissolution rate of ginkgolide A (GA) and ginkgolide B (GB) in F1 was 98.3% and 97.7% in 30 min, respectively. It was much higher than F2 (89.0% and 86.5%) and coarse powder of ginkgolides (22.3% and 24.6%). According to the results of stability test, the storage stability of F1 was improved compared with F2. In addition, compared with coarse powder of ginkgolides, the relative bioavailability of GA and GB in F1 were up to (221.84 ± 106.67) % and (437.45 ± 336.43) %, respectively. The above results demonstrated that soybean phospholipid added to the nanosuspension played an important role in improving drug dissolution rate, storage stability and in vivo bioavailability: (1) The amphiphilic soybean phospholipid interacted with the drug, with the hydrophobic part adsorbed on the surface of the poorly soluble drug and the hydrophilic part exposed to the aqueous medium. This increases the wettability of the nanoparticles, which ensure a good redispersibility of the drug particles. (2) It could self-assemble to form an interfacial phospholipid film by surrounding the individual nanoparticles, which can produce enough steric hindrance to prevent nanoparticles from aggregation and ensure a rapid dissolution rate. (3) Soybean phospholipid and its hydrolysate formed strong micellar solubilizing vehicles with bile salts in vivo, stimulated the absorption process of ginkgolides. Thus, soybean phospholipid was a promising steric stabilizer in nanosuspension drug delivery system.

Ginkgo biloba Extract EGb 761 Improves Vestibular Compensation and Modulates Cerebral Vestibular Networks in the Rat

Unilateral inner ear damage is followed by behavioral recovery due to central vestibular compensation. The dose-dependent therapeutic effect of Ginkgo biloba extract EGb 761 on vestibular compensation was investigated by behavioral testing and serial cerebral [¹⁸F]-Fluoro-desoxyglucose ([¹⁸F]-FDG)-μPET in a rat model of unilateral labyrinthectomy (UL). Five groups of 8 animals each were treated with EGb 761-supplemented food at doses of 75, 37.5 or 18.75 mg/kg body weight 6 weeks prior and 15 days post UL (groups A,B,C), control food prior and EGb 761-supplemented food (75 mg/kg) for 15 days post UL (group D), or control food throughout (group E). Plasma levels of EGb 761 components bilobalide, ginkgolide A and B were analyzed prior and 15 days post UL. Behavioral testing included clinical scoring of nystagmus, postural asymmetry, head roll tilt, body rotation during sensory perturbation and instrumental registration of mobility in an open field before and 1, 2, 3, 5, 7, 15 days after UL. Whole-brain [¹⁸F]-FDG-μPET was recorded before and 1, 3, 7, 15 days after UL. The EGb 761 group A (75 mg/kg prior/post UL) showed a significant reduction of nystagmus scores (day 3 post UL), of postural asymmetry (1, 3, 7 days post UL), and an increased mobility in the open field (day 7 post UL) as compared to controls (group E). Application of EGb 761 at doses of 37.5 and 18.75 mg/kg prior/post UL (groups B,C) resulted in faster recovery of postural asymmetry, but did not influence mobility relative to controls. Locomotor velocity increased with higher plasma levels of ginkgolide A and B. [¹⁸F]-FDG-μPET revealed a significant decrease of the regional cerebral glucose metabolism (rCGM) in the vestibular nuclei and cerebellum and an increase in the hippocampal formation with higher plasma levels of ginkgolides and bilobalide 1 and 3 days post UL. Decrease of rCGM in the vestibular nucleus area and increase in the hippocampal formation with higher plasma levels persisted until day 15 post UL. In conclusion, Ginkgo biloba extract EGb 761 improves vestibulo-ocular motor, vestibulo-spinal compensation, and mobility after UL. This rat study supports the translational approach to investigate EGb 761 at higher dosages for acceleration of vestibular compensation in acute vestibular loss.

[Special ginkgo extract in cases of vertigo: a systematic review of randomised, double-blind, placebo controlled clinical examinations]

BACKGROUND

The concept for the medical treatment of vertigo has changed over the last 30 years due to recognition of the dependence of the vertiginous sensation on vestibular compensation and the dependence of vestibular compensation on the state of vigilance.

METHODS

In this systematic review, experimental studies of the influence of the special ginkgo extract EGb 761 on vestibular compensation in animals and randomized, double-blind clinical studies of EGb 761 in vestibular and non-vestibular vertigo are described and critically evaluated.

RESULTS

The beneficial effect of EGb 761 on vestibular compensation has been demonstrated in preclinical and clinical studies.

CONCLUSION

Evidence of the efficacy of EGb 761 for the treatment of vertiginous syndromes is presented in the available studies.

Adrenalectomy-induced cell death in the dentate gyrus: further characterisation using TUNEL and effects of the Ginkgo biloba extract, EGb 761, and ginkgolide B

This study investigated the potential neuroprotective effects of the Ginkgo biloba extract, EGb-761, and ginkgolide B, on adrenalectomy (ADX)-induced cell death in the dentate gyrus (DG). Adrenalectomised, sham surgery-treated, and naive controls received either EGb-761 (25, 50, or 100 mg/kg), 0.9% saline vehicle control, ginkgolide B (10 or 25 mg/kg), or a polyethylene glycol vehicle control, i.p, daily for 6 days postsurgery. Cell death in the DG was determined by in situ labelling of DNA fragments, using the TUNEL method; sections were counterstained with hematoxylin. Radioimmunoassay was used to confirm a decrease in plasma corticosterone (CORT) after ADX. TUNEL-positive granule cells were observed in the DG at 1 week, but not at 24 h, post-ADX. The rate of granule cell death at this time was highest in the suprapyramidal blade and increased in a crest tip and a rostrotemporal gradient. Whereas CORT replacement completely prevented the occurrence of TUNEL-positive granule cells, EGb-761 and ginkgolide B did not, at any of the doses used. These results suggest that these drugs may not have substantial neuroprotective effects in the ADX model of neurodegeneration.

Magnesium deficiency-dependent audiogenic seizures (MDDASs) in adult mice: a nutritional model for discriminatory screening of anticonvulsant drugs and original assessment of neuroprotection properties

A great many animal models for audiogenic seizures have been described. The extent to which these models may provide insight into neuroscience fields such as abnormal locomotor behavior (wild running), seizures and anticonvulsants, and neuroinsults and neuroprotectors is examined here by our study of magnesium deficiency-dependent audiogenic seizures (MDDASs) in adult mice. MDDASs were induced in all of the eight tested adult murine strains and are presented as a sequence of four successive components (latency, wild running, convulsion, and recovery phase periods). Compared with several classic seizure tests, the nutritional MDDAS model responded to low doses of prototype antiepileptic drugs (AEDs), including phenytoin (PHT), carbamazepine (CBZ), phenobarbital (PB), valproic acid (VPA), ethosuximide (ESM), and diazepam (DZP). Modulation by AEDs of the four components of MDDAS indicated that this seizure test was discriminatory, distinguishing between phenytoinergic (PHT, CBZ), GABAergic (PB, VPA, DZP), and ethosuximide (ESM) compounds. Suitability of the MDDAS test for evaluation of neuroprotective compounds was also examined: it showed partial (melatonin) and complete (WEB2170, an anti-PAF agent) reduction of recovery phase by non-anticonvulsant doses of test compounds. These neuroprotective responses were compared with neuroprotective potentials determined in a model of neonatal cerebral injury induced by focal injection of ibotenate (a glutamate analog). WEB2170 and melatonin reduced the size of lesions in white matter, but only WEB2170 protected cortical plate against ibotenate-induced lesions. In addition to the original neuroprotective behavior of WEB2170, studies on the neuroprotectors also supported GABAergic anticonvulsant activity of melatonin in the MDDAS test.

Evidence for reduced nitric oxide synthase (NOS) activity in the ipsilateral medial vestibular nucleus and bilateral prepositus hypoglossi following unilateral vestibular deafferentation in the guinea pig

The aim of the present study was to examine, using a radioenzymatic assay technique, nitric oxide synthase (NOS) activity in the bilateral medial vestibular nuclei (MVN) and prepositus hypoglossi (PH), during the development of vestibular compensation for unilateral vestibular deafferentation (UVD) in the guinea pig. In the MVN ipsilateral to the UVD, and bilaterally in PH, NOS activity decreased following UVD compared to sham controls and did not recover significantly up to 50 h later, when a substantial degree of behavioural vestibular compensation had occurred. These results suggest that UVD causes a decrease in NOS activity in the ipsilateral MVN and the bilateral PH, and that a consequent decrease in NO may be responsible for some of the ocular motor and postural symptoms of UVD.

The effects of ginkgolide B (BN52021) on guinea pig vestibular nucleus neurons in vitro: importance of controlling for effects of dimethylsulphoxide (DMSO) vehicles

The present study investigated the effects of the platelet-activating factor (PAF) receptor antagonist, ginkgolide B, on guinea pig medial vestibular nucleus (MVN) neurons in vitro and addressed the potential problem of using dimethylsulphoxide (DMSO) as a solvent. Using DMSO as a solvent, 10(-10), 10(-8) and 10(-4) M ginkgolide B had no effect on extracellularly recorded MVN neurons in brainstem slices in vitro. Using 10(-6) M ginkgolide B, 50% (5/10) of MVN neurons exhibited a decrease in firing rate and 10% (1/10) of neurons responded with an increase in firing rate. While attempting to control for possible DMSO vehicle effects, 40% (4/10) of MVN neurons displayed a decrease in firing rate when ginkgolide B (10(-6) M) was presented before the DMSO control solution. When the DMSO vehicle was presented first, only 10% (1/10) responded similarly. In some cases the DMSO vehicle alone also produced a decrease in MVN neuron firing rate. These results emphasise the importance of using adequate DMSO control conditions in ginkgolide research.

The neuroprotective properties of the Ginkgo biloba leaf: a review of the possible relationship to platelet-activating factor (PAF)

Ginkgo biloba (Ginkgoaceae) is an ancient Chinese tree which has been cultivated and held sacred for its health-promoting properties. There is substantial experimental evidence to support the view that Ginkgo biloba extracts have neuroprotective properties under conditions such as hypoxia/ischemia, seizure activity and peripheral nerve damage. Research on the biochemical effects of Ginkgo biloba extracts is still at a very early stage. One of the components of Ginkgo biloba, ginkgolide B, is a potent platelet-activating factor (PAF) antagonist. Although the terpene fraction of Ginkgo biloba, which contains the ginkgolides, may contribute to the neuroprotective properties of the Ginkgo biloba leaf, it is also likely that the flavonoid fraction, containing free radical scavengers, is important in this respect. Taken together, the evidence suggests that Ginkgo biloba extracts are worthy of further investigation as potential neuroprotectant agents.