Antidepressant Effect of Extracts from Ginkgo biloba Leaves in Behavioral Models

Abstract

In recent years, depression has become recognized as a major public health problem. It is estimated that in the US approximately 20% of the population has some depressive symptoms, and around 2-5% are thought to suffer from severe forms of depression.1) Understanding how to prevent and treat depression is therefore an urgent subject. Although the mechanism provoking depression has not been clearly elucidated, the main trigger is known to be exposure to chronic stress.2,3) Many types of antidepressant drugs such as tricyclic antidepressants, and selective serotonin reuptake inhibitors (SSRI), as well as antidepressant herbal medicines like St. John's wort are used to treat depression. However, most of the synthetic drugs are not without side effects. 4)Furthermore disturbance of the drug metabolizing enzyme systems were revealed with St. John's wort, 5) and thus, the search for a new antidepressant herb without side effects is deemed important.The Ginkgo biloba tree has been used as a traditional Chinese herbal medicine for thousands of years.6) Several research groups have shown that extracts from the green leaves of the G. biloba tree (EGB) have diverse effects on improvement of mood and cognitive performance, protection of memory deficits and central nervous system (CNS) disorders, and alleviation of the symptoms of mild to moderate Alzheimer-type dementia.7-12) Until now, no antidepressant effect of EGB has yet been revealed. EGB is thought to possess anti-stress properties, 13) and is safe to use without distinct side effects. 8,14) EGB might be a useful option for the prevention and treatment for stress-induced disorders such as depression. In the present study, we evaluated the antidepressant effect of EGB using two behavioral models for screening antidepressants, the forced swimming test (FST) in rats and tail suspension test (TST) in mice. MATERIALS AND METHODS ChemicalsThe EGB used in the present study was Ginkgolon-24 from Tokiwa Phytochemical Co., Ltd. (Chiba, Japan), which was 75% ethanol extracts from the leaves of Japanese G. biloba tree. This product contains 25.5% of flavonoid glycosides, including more than 8.2% quercetin glycosides, more than 6.4% kaempferol glycosides, 1.6% methylmyricetin glycosides and 1.3% isorhamnetin glycosides, and 6.5% of terpenoids in the form of 2.98% bilobalide, 1.59% ginkgolide A, 1.16% ginkgolide B, and 0.75% ginkgolide C. The antidepressant drug imipramine (hydrochloride form) was purchased from Sigma-Aldrich Co. (St. Louis, MO, U.S.A.).Animals Male CD rats (240-260 g; Charles River Japan, Inc., Yokohama, Japan) and male C57BL/6J mice (22-26 g; SLC, Inc., Hamamatsu, Japan) were used in the FST and TST, respectively. All animals were housed in a controlled room (temperature, 25Ϯ1°C; humidity, 45-50%; light-dark cycle, 12 h each) with free access to laboratory chow (MF; Oriental Yeast Co., Ltd., Tokyo, Japan) and tap water. Rodents were divided randomly into control and experimental groups. This study was performed according to the guidelines for the care and use of...

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Antidepressant properties of aqueous acerate from <i>Gladiolus Dalenii</i> corms

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