Secondary Metabolites From Eucalyptus Robusta Smith Endophytic Fungi And Their Bioactivities

Our country is rich in forest resources. The effect of anti-adversity of woody plants is much higher than that of herbaceous plants. It has great potential for the development of endophytic fungi. In rescent years, the research of antimicrobial activity of the metabolites becomes more and more important, and there is vast prospect to develop new antimicrobial natural medicines from the endophytic fungi. In this paper, Eucalyptus species were screened for resistance to bacterial wilt and the endophytic fungi from two resistant Eucalyptus species Eucalyptus exserta F.V. Muell. and Eucalyptus citriodora Hook. F. along with the detection on their steroidal and antimicrobial components was studied in this thesis. The main results are as follows.1. E. exserta, E. citriodora, E. robusta Smith, E. torelliana and E. urophyllas were screened for resistance to bacterial wilt. The resistance of them were: E. exser ta > E. Citriodora > E. torelliana > E. robusta Smith > E. urophyllas. Hence, we choose E. exserta. and E. citriodora as candidates to isolated endophytic fungi.2. About 45 fungal endophytic isolates were isolated and purified from the branches and seeds of E. exserta and E. citriodora. According to their colony morphological charaters in petri dish, as well as the microscopic charaters of the mycelia, sporophores and spores, 21 representative isolates were selected for further characterications on their taxnomical identification mainly based on their morphological characters and r-DNA ITS sequences. There were 20 genera in the 21 isolates. Of them, they were belonged to Phoma sp, Colletotrichum gloeosporioides, Fusarium equiseti, Lophiostoma sp, Cladosporium cladosporioides, Dinemasporium sp, Rhytidhysteron sp, Colletotrichum boninense.,Leptostroma sp, Campylocarpon fasciculare, Guiqnardia manqiferae, Teratosphaeria zuluensis, Eutypella sp, Lophiostoma sp, Aquanectria submerse, Pestalotiopsis diploclisia.Chaetomium brasiliense. It demonstrated the biological diversity of E. exserta and E.citriodora.3. All endophytic fungi were fermentation in rice culture medium, an ethyl acetate extract from the supernatant of methanolic extracts were prepared and both exhibited certain antibacterial activity against 7 bacteria. In E. exserta, the fungus Eef-B5?Eef-B14?Eef-S1?Eef-S10 showed strong antibacterial activity, and in E. citriodora is Ecf-B5?Ecf-B10?Ecf-B23?Ecf-B24.4. The anti-oxidative activity of all endophytic fungus was detected. In E. exserta, the fungus Eef-B5 ? Eef-B14 ? Eef-S10 showed strong anti-oxidative activity, and in E.citriodora is Ecf-B5?Ecf-B10?Ecf-B23.This study showed that the branches and seeds of both E. exserta and E. citriodora contained abundant endophytic fungi, and some of them have a variety of antibacterial and antioxidant components. It demonstrated the ability to produce bioactive agents with pharmaceutical potential, and may provide a new lead in the pursuit of new biological sources of drug candidates.