2 Afra Khiralla, Rosella Spina, Sakina Yagi et al.
endophytes took a consider attention as alternative source of active
compounds produced by their host plants, however they could be an
alternative source of novel natural products for exploitation in modern
medicine, agriculture and industry.
Conclusion: The chapter sets out to present general overview of
endophytic fungi and focus on their occurrence, classification, functions
and several classes of their secondary metabolites. Finally examples are
given concerning natural products isolated from fungal endophytes with
potent biological activity.1. INTRODUCTION
The term “endophyte” is derived from the Greek, endon = within and
phyte = plant. It was first introduced in 1866 by de Bary. It was used broadly
to refer to any organism found within tissues of living plants; including
everything from virulent foliar pathogens to mycorrhizal root sombionts;
subsequent re-definitions led to confusion regarding the meaning of the term.
Modern mycologists generally agree that endophytes are organisms that
colonize internal plant tissues without causing apparent harm to their host.
Different groups of organisms such as fungi, bacteria, actinomycetes and
mycoplasma are reported as endophytes of plants (Arnold, 2007).
Collectively, more than 100 years of research suggest that most, if not all,
plants in natural ecosystems are symbiotic with mycorrhizal fungi and/or
fungal endophytes (Petrini, 1986). Unlike mycorrhizal fungi that colonize
plant roots and grow into the rhizosphere, endophytes reside entirely within
plant tissues and may grow within roots, stems and/or leaves, emerging to
often occur sparsely as hypha in the intercellular fluids and wall spaces of their
plant hosts, sporulate at plant or host-tissue senescence (Bacon and White,
2000). Studies of endophytic fungi were initiated nearly 200 years ago, when
Person in 1772 described the species Sphaeria typhena, now known as
Epichloe typhina (Pers.) Tul. (Khan, 2007). Fossils, in a 400-million-year-old,
indicated that plants have been associated with endophytes. Krings et al.,
(2007) studied petrographic thin sections of the Rhynie chert plant Nothia
aphylla, they found that three fungal endophytes occur in prostrata axes of this
plant.