**1. Introduction**

In the history of humanity, plants have always been present as a source of health. The knowledge of the various healing properties of plants has been transmitted in an empirical way. However, over time, man has been interested in knowing where the properties of plants come from. In the process of knowledge generation, man has developed many methodologies to know the structures of organic compounds responsible for the healing properties of plants. This is the birth of phytochemistry that is defined as the science responsible for the study of

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

the compounds contained in plants. In this field, various techniques have been developed, ranging from the preparation of the plant tissue sample to sophisticated techniques for the elucidation of organic structures. The search for new products for the pharmaceutical and agrochemical industries is an ongoing process that requires continual optimization [1]. Previously, the screening of 10,000 natural products resulted in one commercial product. In the advent of combinatorial chemistry, this relationship changed. Presently, the screening of 100,000 structures day−1 from combinatorial chemistry together with the natural products screened yields less than one commercial product year−1 (F. Hansske, pers. comm.). Its development takes approximately 12 years and costs ~\$350 M [2]. Considering that 6 out of 20 of the most commonly prescribed medications are of fungal origin [3] and only ~5% of the fungi have been described [4], fungi offer an enormous potential for new products.

novo fashion [17]. At that time, there were few reports describing the chemistry of plant endophytes, although there was a rich literature cataloguing the secondary metabolism of plant pathogenic fungi and bacteria. Phytotoxins, secondary metabolites produced by plant pathogenic microorganisms, have been studied for almost a century as virulence factors and the initiators of diseases in susceptible plants. Three well-known examples are the host-specific toxins produced by three different *Cochliobolus* species, all of which caused severe blight diseases of economically important crops [18]. *C. carbonum* (*Helminthosporium carbonum*) produces host-specific HC-toxin, which causes Northern leaf blight of maize and inhibits maize histone deacetylase [18]. *C. heterostrophus* (H. maydis) produces T-toxin which caused Southern Corn Leaf Blight, one of the worst plant disease epidemics in modern history, and which was especially virulent toward maize carrying Texas male sterile cytoplasm [18]. *C. victoriae* produces victorin which caused a devastating epidemic in the Victoria race of oats that was developed

Introduction to Phytochemicals: Secondary Metabolites from Plants with Active Principles…

http://dx.doi.org/10.5772/intechopen.78226

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by plant breeders in an effort to produce oats that were resistant to crown rust [18].

and the anticancer agent calicheamycin are produced by actinomycetes [22].

**2. Metabolism**

Plant endophytes are subtler, however, rarely causing problems and coexisting with their hosts under most circumstances. Hirsch and Braun provided an inclusive and widely accepted definition of endophytes: "microbes that colonize living, internal tissues of plants without causing any immediate, overt negative effects" [19, 20]. They are generally nonpathogenic in nature, but may produce secondary metabolites that enable them to survive in the competitive world of plant interstitial space without harming their host. Microorganisms in most ecosystems establish and define their ecological niches by their ability to control fellow microbes with only their cell walls or membranes and chemical arsenals to defend them. But these chemical arsenals have provided many of the important chemotherapeutics used to date. The potent antifungal agent griseofulvin is of fungal origin [21] and both the antibiotic streptomycin [21]

Plant endophytes, however, received less attention until the discovery of a Taxol-producing fungus in the bark and needles of the Northwest Pacific yew tree. In 2011, we published a review of cytotoxic or anticancer compounds produced by plant endophytes [23]. Over 100 compounds with demonstrated cytotoxicity or anticancer activity had been isolated from endophytic fungi including several compounds originally isolated from higher plants [8]. Less than 10% of these compounds were isolated from coniferous species [24]. Our own work with the fungal endophytes of conifers has shown them to be rich producers of bioactive secondary metabolites.

Two reasons led us to start this research project: produce secondary metabolites of pharmaceutical application to reduce a type of cancer and reduce the cutting of trees and apply biotechnology to produce taxanes by endophytic microorganisms. The main aim of this book chapter is to present case studies of isolation, characterization and application of secondary metabolites: Taxoles.

Metabolism is a set of chemical reactions carried out by the cells of living beings, to synthesize complex substances from simpler ones, or to degrade complexes and obtain simple ones [25]. Plants, autotrophic organisms, have two metabolisms, the primary metabolism present in

Endophytic fungi, a polyphyletic group of highly diverse, primarily ascomycetous fungi defined functionally by their occurrence within asymptomatic tissues of plants, are found in aboveground tissues of liverworts, hornworts, mosses, lycophytes, equisetopsids, ferns, and seed plants from the arctic to the tropics, and from agricultural fields to the most biotically diverse tropical forests. Their cryptic lifestyle, ubiquity and richness within individual plants, coupled with emerging evidence of their often overlooked ecological importance, have inspired growing enthusiasm regarding these little known fungi over the past four decades. In particular, David Hawksworth's much discussed estimates of fungal diversity at a global scale [4, 5] engendered tremendous enthusiasm for understanding endophyte diversity. Comprising interactions that range from mutualism to antagonism, fungal symbioses with plants are key determinants of biomass, nutrient cycling and ecosystem productivity in terrestrial habitats from the poles to the equator [6, 7]. Most plantassociated fungi catalogued to date have been recognized because of the fruitbodies they produce in association with their hosts (e.g., plant pathogens, mycorrhizal fungi). Yet plants in all major lineages, including liverworts, mosses, seed free vascular plants, conifers, and angiosperms, also form cryptic symbioses with fungi that penetrate and persist within healthy aboveground tissues such as leaves. Foliar fungal endophytes (i.e., endophylls or mycophyllas) are a fundamental but frequently overlooked aspect of plant biology: all plant species surveyed thus far harbor one or more endophytic symbionts in their photosynthetic tissues [8]. Plants live in association with microorganisms with different levels of interaction. This assumption stimulates insights on plant microbiome, intended as the collective genome of microorganisms living in contact with plants [9], and new concepts in plant evolution have been developed considering a basic role of the associated fungal endophytes [10]. Regarded as an underexplored niche of chemo diversity [11], endophytic fungi have a recognized ability to produce bioactive compounds which may play a role in plant protection against pathogens and pests [12, 13]. Colonization by endophytes may offer significant benefits to their host plants by producing various metabolites that protect against pathogen attack, promote plant (or vegetative) growth, improve crop yields, show herbicide activity and induce resistance. Fungal natural products are currently used in agriculture as active ingredients of different bioformulates [14] and several endophytes are known to have anti-insect properties [15]. Although bioinsecticides currently occupy only a small amount of the market, these compounds are very interesting and their use is constantly increasing [16].

In 1991, researchers began studying the microbial endophytes of the Northwest Pacific yew tree *Taxus brevifolia*, in search for a fungus or bacterium that could produce paclitaxel in de novo fashion [17]. At that time, there were few reports describing the chemistry of plant endophytes, although there was a rich literature cataloguing the secondary metabolism of plant pathogenic fungi and bacteria. Phytotoxins, secondary metabolites produced by plant pathogenic microorganisms, have been studied for almost a century as virulence factors and the initiators of diseases in susceptible plants. Three well-known examples are the host-specific toxins produced by three different *Cochliobolus* species, all of which caused severe blight diseases of economically important crops [18]. *C. carbonum* (*Helminthosporium carbonum*) produces host-specific HC-toxin, which causes Northern leaf blight of maize and inhibits maize histone deacetylase [18]. *C. heterostrophus* (H. maydis) produces T-toxin which caused Southern Corn Leaf Blight, one of the worst plant disease epidemics in modern history, and which was especially virulent toward maize carrying Texas male sterile cytoplasm [18]. *C. victoriae* produces victorin which caused a devastating epidemic in the Victoria race of oats that was developed by plant breeders in an effort to produce oats that were resistant to crown rust [18].

Plant endophytes are subtler, however, rarely causing problems and coexisting with their hosts under most circumstances. Hirsch and Braun provided an inclusive and widely accepted definition of endophytes: "microbes that colonize living, internal tissues of plants without causing any immediate, overt negative effects" [19, 20]. They are generally nonpathogenic in nature, but may produce secondary metabolites that enable them to survive in the competitive world of plant interstitial space without harming their host. Microorganisms in most ecosystems establish and define their ecological niches by their ability to control fellow microbes with only their cell walls or membranes and chemical arsenals to defend them. But these chemical arsenals have provided many of the important chemotherapeutics used to date. The potent antifungal agent griseofulvin is of fungal origin [21] and both the antibiotic streptomycin [21] and the anticancer agent calicheamycin are produced by actinomycetes [22].

Plant endophytes, however, received less attention until the discovery of a Taxol-producing fungus in the bark and needles of the Northwest Pacific yew tree. In 2011, we published a review of cytotoxic or anticancer compounds produced by plant endophytes [23]. Over 100 compounds with demonstrated cytotoxicity or anticancer activity had been isolated from endophytic fungi including several compounds originally isolated from higher plants [8]. Less than 10% of these compounds were isolated from coniferous species [24]. Our own work with the fungal endophytes of conifers has shown them to be rich producers of bioactive secondary metabolites.

Two reasons led us to start this research project: produce secondary metabolites of pharmaceutical application to reduce a type of cancer and reduce the cutting of trees and apply biotechnology to produce taxanes by endophytic microorganisms. The main aim of this book chapter is to present case studies of isolation, characterization and application of secondary metabolites: Taxoles.
