Ginkgo biloba

The leaves of Ginkgo biloba L. (Ginkgoaceae) have been used in TEM for respiratory and circulatory disorders, and its extract has been therapeutically used for several decades to increase peripheral and cerebral blood flow as well as for the treatment of dementia. G. biloba extract EGb761, a standardized extract of G. biloba leaves, contains about 24% flavonoid glycosides, primarily quercetin, kaempferol, isorhamnetin, 6% terpene lactones, 2.8 to 3.4% ginkgolides A, B, and C, and 2.6 to 3.2% bilobalide. EGb761 has shown favorable effects on cerebral circulation and neuronal cell metabolism [36, 37] and also exhibited antioxidant activity [38, 40].

EGb761 is neuroprotective against amyloid- and NO-induced toxicity in vitro. G. biloba extracts attenuate scopolamine-induced amnesia in rats [41], enhance memory retention in young and old rats [42], and improve short-term memory in mice [43]. G. biloba attenuates delayed neuronal death in the CA1 of the hippocampus in Mongolian gerbils [44] and is also associated with reduced stroke infarct volume in mice subjected to 45 min of tMCAo [45].

Bilobalide (Fig. 16.1), a sesquiterpene trilactone constituent of G. biloba, reduces cerebral edema produced by triethyltin through preventing the uncoupling of oxida-tive phosphorylation. Pretreatment with bilobalide reduced the cerebral infarct area in MCAo mice [46]. Bilobalide protected the slices against hypoxia-induced phos-pholipid breakdown [47]. Bilobalide inhibited NMDA-induced phospholipase A2 activation and phospholipid breakdown in rat hippocampal slices [48]. Ginkgolides also had protective effects on focal cerebral ischemia, and its mechanism may be relative to its inhibition of platelet-dependent thrombosis and amelioration of hemarhe-ological partments [49].

Cumulative evidence indicates that G. biloba may have neuroprotective effects in brain ischemia rodent models, and bilobalide may be one of the main compounds responsible for this effect. There is no convincing evidence from trials of sufficient methodological quality to support the routine use of G. biloba extract to promote recovery after stroke [50]. High-quality and large-scale randomized controlled trials are needed to test its efficacy.

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