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digestible fructans among which chicory fructans play a major
role. (2200)
23. Alkaloids
Since, by definition, alkaloids are physiologically active upon
animals, and many alkaloids are important drugs, the
compounds are best known to the pharmacologist. Much of the
voluminous literature on alkaloids is the direct or indirect result
of their great economic importance. It is probable that alkaloids
are less well known to most botanists than are certain
compounds or classes of compounds that serve some structural
or obvious functional role in the plant (for example, lignin, and
plastid pigments). Consequently, a brief general discussion,
including a limited treatment of the chemical affinities of the
major classes of alkaloids will precede the section directly treat-
ing their sytematic significance. In this latter section no attempt
is made to give a comprehensive account of alkaloid distribution
or to develop any unified system of phylogenetic interpretation.
Each of a number of more natural classes of alkaloids could be
given such a treatment, and in fact some investigators have
already done so. Certain of these latter types of studies will be
described, but they have been selected mainly to provide further
insight into general principles applicable to the evaluation of the
systematic worth of alkaloids.
In general, discussion of biosynthetic mechanisms past the point
required to clarify some point of phylogenetic interpretation is
beyond the scope of this book, especially in the case of the
alkaloids, wherein many classes of compounds exist, each of
which may be formed by almost completely independent
biosynthetic routes.
The subject of alkaloid biosynthesis is rarely given
comprehensive formal review, and then one is impressed with
the incompleteness of knowledge and the prevalence of
hypotheses supported by circumstantial evidence alone. It
should be noted that numerous alkaloids show structurally a
potential relationship to one or more amino acids. Consequently,
it is generally regarded that alkaloid synthesis is related to
amino acid synthesis. This generalization has proved helpful in
seeking relationships between alkaloids otherwise difficult to
interpret. Hegnauer (1958) has placed the major alkaloid types
into amino acid "families" for purposes of disclosing useful
systematic correlations. The arbitrary basis of such schemes
should be remembered, however. The directness of the
relationship of the biosynthesis of a particular alkaloid to a
corresponding amino acid may vary greatly in different cases.
(2000).
24. The relationship between marbling and sensory
traits in beef.
Although marbling of beef is an important trait in a number of
beef markets, the relationship between marbling level and
palatability of beef is not clearly defined. Palatability of beef can
be described as a function of tenderness, juiciness and flavour
and is generally measured using one, or a combination of
objective and sensory measurements. The former includes shear
force, compression and adhesion measurements, which all
describe specific dimensions of texture. Perry et al. (2001a)
showed that these objective measurements were well related to
sensory tenderness, although they are by nature rather simplistic
measures and do not take into account the complex interactions
that occur with flavour and juiciness dimensions during the
eating process.
digestible fructans among which chicory fructans play a major The subject of alkaloid biosynthesis is rarely given
role. (2200) comprehensive formal review, and then one is impressed with
the incompleteness of knowledge and the prevalence of
23. Alkaloids hypotheses supported by circumstantial evidence alone. It
should be noted that numerous alkaloids show structurally a
Since, by definition, alkaloids are physiologically active upon potential relationship to one or more amino acids. Consequently,
animals, and many alkaloids are important drugs, the it is generally regarded that alkaloid synthesis is related to
compounds are best known to the pharmacologist. Much of the amino acid synthesis. This generalization has proved helpful in
voluminous literature on alkaloids is the direct or indirect result seeking relationships between alkaloids otherwise difficult to
of their great economic importance. It is probable that alkaloids interpret. Hegnauer (1958) has placed the major alkaloid types
are less well known to most botanists than are certain into amino acid "families" for purposes of disclosing useful
compounds or classes of compounds that serve some structural systematic correlations. The arbitrary basis of such schemes
or obvious functional role in the plant (for example, lignin, and should be remembered, however. The directness of the
plastid pigments). Consequently, a brief general discussion, relationship of the biosynthesis of a particular alkaloid to a
including a limited treatment of the chemical affinities of the corresponding amino acid may vary greatly in different cases.
major classes of alkaloids will precede the section directly treat- (2000).
ing their sytematic significance. In this latter section no attempt
is made to give a comprehensive account of alkaloid distribution
or to develop any unified system of phylogenetic interpretation. 24. The relationship between marbling and sensory
Each of a number of more natural classes of alkaloids could be
traits in beef.
given such a treatment, and in fact some investigators have
already done so. Certain of these latter types of studies will be
Although marbling of beef is an important trait in a number of
described, but they have been selected mainly to provide further
beef markets, the relationship between marbling level and
insight into general principles applicable to the evaluation of the
palatability of beef is not clearly defined. Palatability of beef can
systematic worth of alkaloids.
be described as a function of tenderness, juiciness and flavour
and is generally measured using one, or a combination of
In general, discussion of biosynthetic mechanisms past the point
objective and sensory measurements. The former includes shear
required to clarify some point of phylogenetic interpretation is
force, compression and adhesion measurements, which all
beyond the scope of this book, especially in the case of the
describe specific dimensions of texture. Perry et al. (2001a)
alkaloids, wherein many classes of compounds exist, each of
showed that these objective measurements were well related to
which may be formed by almost completely independent
sensory tenderness, although they are by nature rather simplistic
biosynthetic routes.
measures and do not take into account the complex interactions
that occur with flavour and juiciness dimensions during the
eating process.
