V
Preface
This textbook is based on a lecture we offer for Master of Biology students at the LudwigMaximilians-Universität in Munich, Germany. As an interdisciplinary approach between
plant and animal cell biology, it covers, on the one hand, cellular signal transduction
mechanisms in animals, concentrating on seven-transmembrane receptors (GPCRs)
and ion channels. On the other hand, it describes biosynthetic pathways and the role of
secondary metabolites in plants. The interplay between these topics is illustrated by our
elaboration on prominent plant-derived drugs that constitute potent plant toxins, pharmaceutically used drugs to treat human disease as well as so-called recreational drugs.
When we designed the lecture for the Master of Biology, we wanted to teach students
how these powerful and often well-known plant-derived drugs interact with molecular
and cellular mechanisms in animals, including humans, and how and why plants produce such compounds.
The book therefore starts in the first part with a discussion of the general function of
secondary metabolites in plants. Secondary metabolites are not always essential for plant
survival, but they play important roles in adapting a plant’s life to the microclimate at its
location, they help plants in battling with herbivores and pathogens, and they attract
pollinators and seed distributors. This part also gives a short historical account on the
use of plants as medicines and recreational drugs.
In the second part, we describe two cellular pathways in animals that together provide
the great majority of current-day pharmacological molecular targets. These involve
G-protein-coupled receptor - and ion channel-signalling. They will at first be dissected
into their molecular components and explained in a general way. Then we consider some
well-known drugs and toxins (nicotine, morphine, cannabis and many others) and elaborate on their specific target molecules in humans. We explore the role that particular
receptors play in normal human physiology and then discuss how the respective drugs
interfere with these functions.
In the third part, we look in detail into the plants that produce these compounds. We
delve into the history of many drug discoveries and describe specific applications of
plant-derived drugs, including some curiosities about their use. We also discuss how
plants themselves employ these “bestsellers” from their repertoire of secondary metabolites. Caffeine and nicotine provide two very good examples. However, in many cases,
very little is known about the role of specific substances that have become famous or
infamous for their effect on humans. In this area a lot of further research is needed to
gain an understanding of the part that these compounds play for plants.
All the compounds that we discuss in the first parts of this textbook are produced in
plants by highly conserved and tightly regulated biosynthetic pathways. These pathways are described in the fourth part. Secondary metabolites arise from primary
metabolism, for instance, amino acid synthesis and the tricarboxylic acid (TCA) cycle.
They can also be formed within pathways for the synthesis of structural plant compounds, for instance, lignin, or essential signalling molecules, like hormones. We show
Preface
This textbook is based on a lecture we offer for Master of Biology students at the LudwigMaximilians-Universität in Munich, Germany. As an interdisciplinary approach between
plant and animal cell biology, it covers, on the one hand, cellular signal transduction
mechanisms in animals, concentrating on seven-transmembrane receptors (GPCRs)
and ion channels. On the other hand, it describes biosynthetic pathways and the role of
secondary metabolites in plants. The interplay between these topics is illustrated by our
elaboration on prominent plant-derived drugs that constitute potent plant toxins, pharmaceutically used drugs to treat human disease as well as so-called recreational drugs.
When we designed the lecture for the Master of Biology, we wanted to teach students
how these powerful and often well-known plant-derived drugs interact with molecular
and cellular mechanisms in animals, including humans, and how and why plants produce such compounds.
The book therefore starts in the first part with a discussion of the general function of
secondary metabolites in plants. Secondary metabolites are not always essential for plant
survival, but they play important roles in adapting a plant’s life to the microclimate at its
location, they help plants in battling with herbivores and pathogens, and they attract
pollinators and seed distributors. This part also gives a short historical account on the
use of plants as medicines and recreational drugs.
In the second part, we describe two cellular pathways in animals that together provide
the great majority of current-day pharmacological molecular targets. These involve
G-protein-coupled receptor - and ion channel-signalling. They will at first be dissected
into their molecular components and explained in a general way. Then we consider some
well-known drugs and toxins (nicotine, morphine, cannabis and many others) and elaborate on their specific target molecules in humans. We explore the role that particular
receptors play in normal human physiology and then discuss how the respective drugs
interfere with these functions.
In the third part, we look in detail into the plants that produce these compounds. We
delve into the history of many drug discoveries and describe specific applications of
plant-derived drugs, including some curiosities about their use. We also discuss how
plants themselves employ these “bestsellers” from their repertoire of secondary metabolites. Caffeine and nicotine provide two very good examples. However, in many cases,
very little is known about the role of specific substances that have become famous or
infamous for their effect on humans. In this area a lot of further research is needed to
gain an understanding of the part that these compounds play for plants.
All the compounds that we discuss in the first parts of this textbook are produced in
plants by highly conserved and tightly regulated biosynthetic pathways. These pathways are described in the fourth part. Secondary metabolites arise from primary
metabolism, for instance, amino acid synthesis and the tricarboxylic acid (TCA) cycle.
They can also be formed within pathways for the synthesis of structural plant compounds, for instance, lignin, or essential signalling molecules, like hormones. We show