Abstract
The standard extract of Ginkgo biloba leaves (EGb761) is used clinically in Europe for the symptomatic treatment of impaired cerebral function in primary degenerative dementia syndromes, and the results of numerous in vivo and in vitro studies have supported such clinical use. The abnormal production and aggregation of amyloid β peptide (Aβ) and the deposition of fibrils in the brain are regarded as key steps in the onset of Alzheimer’s Disease (AD), and the inhibition of Aβ aggregation and destabilization of the preformed fibrils represent viable approaches for the prevention and treatment of AD. Flavonoid glycosides and terpene trilactones (TTLs) are the two main components of EGb761 which represent 24 and 6% of the overall content, respectively. In our research, seven abundant flavonoid glycosides 1–7 were isolated from the extract of Ginkgo biloba leaves and characterized by spectroscopic analysis. Furthermore, an ultra-high performance liquid chromatography method was established for the simultaneous quantification of these seven flavonoids. The inhibitory activities of these flavonoids, as well as four TTLs, i.e., ginkgolides A, B, and C and bilobalide (compounds 8–11), were evaluated towards Aβ42 fibril formation using a thioflavin T fluorescence assay. It was found that three flavonoids 1, 3 and 4 exhibited moderate inhibitory activities, whereas the other four flavonoids 2, 5, 6 and 7, as well as the four terpene trilactones, showed poor activity. This is the first report of the inhibition of Aβ fibril formation of two characteristic acylated flavonoid glycosides 6, 7 in Ginkgo leaves, on the basis of which the structure-activity relationship of these flavonoids 1–7 was discussed.
Highlights
Alzheimer’s disease (AD) is the main type of senile dementia, and is characterized by a range of pathological features, including the formation of senile plaques and neurofibrillary tangles
We developed an ultra-high performance liquid chromatography (UPLC)-UV method for the quantitative analysis of these compounds, which allowed for the quantification of these seven Flavonoid glycosides (FGs) as well as the four main terpene trilactones (TTLs) components in the extracts and preparations of Ginkgo biloba leaves
We confirmed that four TTLs exhibited no inhibitory activity towards Aβ42 fibril formation
Summary
Alzheimer’s disease (AD) is the main type of senile dementia, and is characterized by a range of pathological features, including the formation of senile plaques and neurofibrillary tangles. There has been an increase in the number of reports identifying amyloid β peptide (Aβ) as a primary pathological factor in the occurrence of AD, with gradual changes in the balance between the state of Aβ production and clearance leading to the accumulation of aggregated Aβ. This accumulation of Aβ triggers a series of complex reactions that lead to neuronal death and cognitive dysfunction [1]. The results of a large number of in vivo and in vitro studies have provided strong evidence in support of the clinical use of EGb761 [3]
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