Studies On The Selective Extraction And Stability Of Ginkgolide A From Ginkgo Biloba L.

Ginkgo biloba L. is one of the oldest remained tree species of gymnosperm. The major bioactive ingredients of Ginkgo leaf are diterpene lactones and flavonoids, which show obvious bioactivities including antioxidant, promoting blood circulation, scavenging free radicals and against cardiovascular disease. Similar molecular structure of these diterpene lactones makes ginkgo lactone A、B、C、J、M difficult to separate. Separation methods for these gingko lactones include HPLC, high speed countercurrent chromatography and preparing column chromatography, that are complex in equipment and time consuming. In order to find a more convenient and effective method to separate these bioactive ginkgo lactones, a method was developed in our recent works. Ginkgolide A was enriched in a small fraction of the extract of Ginkgo leaf by using a selective extraction system which consisted of aqueous polyethylene glycol, ethanol, ethyl acetate and petroleum ether.1. Ginkgo biloba was extracted with 95% ethanol under the condition of ultrasonic. Extracting conditions of the pretreatment process was as follow:extracts residue of Ginkgo leaf dissolved in ethanol solution (50%) and then was extracted with petroleum ether for 3 times with an ethanol solution obtained. The ethanol solution was extracted by using an organic solvent (ethyl acetate:petroleum ether=40:60(v/v)) twice. Then the organic solution was extracted with 0.1% NaOH solution twice and concentrated to give an enriched fraction of ginkgolide A which content increased from 1% to about 30%.2. There were two methods to separate the Ginkgolide A in polyethylene glyeol system. One was the enriched fraction of Ginkgolide A dissolved in an aqueous solution (PEG aqueous solution-ethanol), and then extracted with organic solvent from the aqueous solution in Ginkgolide A about 46%. Another was the enriched fraction of Ginkgolide A dissolved in organic solvent, and extracted with aqueous solution (PEG aqueous solution-ethanol). The aqueous phase was extracted with another organic solvent to give a more enriched Ginkgolide A fraction. Effects on selectivity of extraction systems were investigated and optimized by orthogonal experiment where content and yield of Ginkgolide A acted as indexes. In our work, residue in the organic solvent (ethyl acetate:petroleum ether=28:72(v/v)) was extracted with aqueous solution (6% (w/w) PEG aqueous solution: ethanol=7:3(v/v)) to give aqueous phase, then the aqueous phase was extracted with another organic solvent (ethyl acetate:petroleum ether= 15:85(v/v)) to give Ginkgolide A product (79% in purity) in yield of Ginkgolide A 22%.3. Stability of Ginkgolide A was investigated. The results indicated that Ginkgolide A was unstable under basic condition or at high temperature (>80 ℃). When increasing basicity or temperature, stability of Ginkgolide A decreased. The stability also slightly decreased with acidity increasing. Coexistence of basic condition and high temperature great damaged to the stability of Ginkgolide A.