Secondary metabolites from endophytic fungi: isolation, purification, characterization and bioassay

Abstract

Drug-resistance of pathogens causing fatal diseases has increased in recent years, which is a prime aspect to be addressed by researchers. Evidently, scientists have provided the public health cause with many effective drugs and vaccines, but the battle against these witty microbes is still far from over. Diseases caused by microbes (bacteria, viruses, fungi, protozoans and prokaryotes) such as respiratory infections, HIV/ AIDS, tuberculosis and malaria and diseases such as cancer account for many infections deaths. These microbes obtained resistance to many of the first-line drugs used for the treatment. Resistance to these first-line drugs has forced to change the treatment to more expensive second- or third-line agents. If resistances to these drugs also emerge, we would run out of treatment options. An intensive search for newer and more effective agents to deal with these problems is now underway. One such renewable source apart from the medicinal plants is endophytic microbes, which reside in the tissues between living plant cells. Some of the interesting compounds produced by endophytic microbes are taxol, cryptocin, cryptocandin, jesterone, oocydin, isopestacin, the psuedomycins and ambuic acid. The reason endophytes mimic the chemistry of their respective hosts and make the same bioactive natural products or derivatives has been attributed to the possible intergenericgenetic exchange between higher plants and the endophytic microbe. Usually the host endophyte associations are symptom-less, as the latter do not interfere with the host biological or physiological affairs. In some cases, especially in grasses, it is observed that secondary metabolites produced by the inhabitant endophytes show beneficial effects on the growth of the host. Plants infected by some endophtyes which produce alkaloids have also been found to be pest-resistant.