Endophytic fungi or endophytes exist widely inside the healthy tissues of living plants, and are important components of plant micro-ecosystems. Over the long period of evolution, some co-existing endophytes and their host plants have established a special relationship with one and another, which can significantly influence the formation of metabolic products in plants, then affect quality and quantity of crude drugs derived from medicinal plants. This paper will focus on the increasing knowledge of relationships between endophytic fungi and medicinal plants through reviewing of published research data obtained from the last 30 years. The analytical results indicate that the distribution and population structure of endophytes can be considerably affected by factors, such as the genetic background, age, and environmental conditions of their hosts. On the other hand, the endophytic fungi can also confer profound impacts on their host plants by enhancing their growth, increasing their fitness, strengthening their tolerances to abiotic and biotic stresses, and promoting their accumulation of secondary metabolites. All the changes are very important for the production of bioactive components in their hosts. Hence, it is essential to understand such relationships between endophytic fungi and their host medicinal plants. Such knowledge can be well exploited and applied for the production of better and more drugs from medicinal plants.
The aim of this study was to investigate the antidepressant properties of stigmas and corms of Crocus sativus L. The aqueous ethanol extract of C. sativus corms was fractionated on the basis of polarity. Among the different fractions, the petroleum ether fraction and dichloromethane fraction at doses of 150, 300, and 600 mg/kg showed significant antidepressant-like activities in dose-dependent manners, by means of behavioral models of depression. The immobility time in the forced swimming test and tail suspending test was significantly reduced by the two fractions, without accompanying changes in ambulation when assessed in the open-field test. By means of a gas chromatography-mass spectrometry technique, twelve compounds of the petroleum ether fraction were identified. These data show that administration of C. sativus corms extract produces antidepressant-like effects. Aqueous stigmas extract also exerted antidepressive effects in the behavioral models. Crocin 1 and crocin 2 of the aqueous stigmas extract were identified by a reversed-phase HPLC analysis. In addition, the bioactive compound crocin 1 in this herb was quantitatively determined. The data indicate that antidepressant-like properties of aqueous stigma extracts may be due to crocin 1, giving support to the validity of the use of this plant in traditional medicine. All these results suggest that the low polarity parts of C. sativus corms should be considered as a new plant material for curing depression, which merit further studies regarding antidepressive-like activities of chemical compounds isolated from the two fractions and mechanism of action.
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