15
French’s results had for many years been regarded as dubious since they were not
able to experimentally distinguish the large cyclodextrins from branched derivatives. As late as 1988, Szejtli expressed his doubts, in his monograph Cyclodextrin
Technology, to whether cyclodextrins larger than γ-cyclodextrin exist (Szejtli 1988).
In fact, higher cyclic cyclodextrins than the three native cyclodextrins, reported in
the 1960s, were probably so-called branched derivatives such as branched
diglucosyl- cyclodextrins. When a section of the amylopectin molecule containing a
branching point was incorporated into a cyclic structure, one or two glucosyl or
maltosyl side chains were attached by α-(1→6) linkages to the ring formed
(Frömming and Szejtli 1994). During the production of native cyclodextrins, these
branched cyclodextrins were also produced. It was only during the mid-1990s that
the existence of the large cyclodextrins has been fully proven (Miyazawa et al.
1995; Endo et al. 1997, 1999; Larsen 2002; Qi et al. 2004; Taira et al. 2006;
Crini 2014).
1.3.3 Cyclodextrin Chemistry
For over 20 years, Pringsheim and his various collaborators penned an abundant
literature on dextrins. Indeed, Pringsheim is considered to be the first researcher to
have published prolifically on their preparation and chemistry (Pringsheim and
Langhans 1912; Pringsheim and Eissler 1913, 1914; Pringsheim 1915, 1919, 1922,
1924, 1925, 1926, 1927, 1928a, b, 1931a, b, 1932; Pringsheim and Lichtenstein
1916; Pringsheim and Persch 1921, 1922; Pringsheim and Dernikos 1922;
Pringsheim and Goldstein 1922, 1923; Pringsheim and Beiser 1924, 1932; Irvine
et al. 1924; Pringsheim and Leibowitz 1924, 1925a, b, 1926a, b; Pringsheim and
Steingroever 1924, 1926; Pringsheim and Wolfsohn 1924; Pringsheim and Schapiro
1926; Pringsheim and Meyersohn 1927; Irvine et al. 1929; Pringsheim et al. 1930,
1931a, b). However, these studies suffered from numerous errors due to the use of
dextrins that were not pure and to problems arising from separation of the fractions
and from the use of unsuitable analytical methods, e.g., determination of the masses
by cryoscopy (Freudenberg and Jacobi 1935; Samec and Blinc 1941; French 1957a;
Thoma and Stewart 1965; Caesar 1968). In 1935, Freudenberg dismissed the work
of Pringsheim as practically valueless, since “most of it was based upon work with
dextrin mixtures and upon serious misconceptions relating to the structural principles of high polymers” (Freudenberg and Jacobi 1935). French (1957a) also wrote:
“Pringsheim’s literature was voluminous but much of it was repetitive, controversial, or based on erroneous concepts.”
From 1910, Pringsheim repeated Schardinger’s experiments. He reported higher
yields of β-dextrin from glycogen crude preparations of amylopectin, and this is the
reason why he postulated that amylose was polymerized α-diamylose and amylopectin and glycogen were polymerized β-triamylose. Like Schardinger, Pringsheim
observed that the relative proportions of α- and β-dextrins depended on the different
substrates used (Pringsheim and Langhans 1912). Pringsheim described the
1 History of Cyclodextrins
French’s results had for many years been regarded as dubious since they were not
able to experimentally distinguish the large cyclodextrins from branched derivatives. As late as 1988, Szejtli expressed his doubts, in his monograph Cyclodextrin
Technology, to whether cyclodextrins larger than γ-cyclodextrin exist (Szejtli 1988).
In fact, higher cyclic cyclodextrins than the three native cyclodextrins, reported in
the 1960s, were probably so-called branched derivatives such as branched
diglucosyl- cyclodextrins. When a section of the amylopectin molecule containing a
branching point was incorporated into a cyclic structure, one or two glucosyl or
maltosyl side chains were attached by α-(1→6) linkages to the ring formed
(Frömming and Szejtli 1994). During the production of native cyclodextrins, these
branched cyclodextrins were also produced. It was only during the mid-1990s that
the existence of the large cyclodextrins has been fully proven (Miyazawa et al.
1995; Endo et al. 1997, 1999; Larsen 2002; Qi et al. 2004; Taira et al. 2006;
Crini 2014).
1.3.3 Cyclodextrin Chemistry
For over 20 years, Pringsheim and his various collaborators penned an abundant
literature on dextrins. Indeed, Pringsheim is considered to be the first researcher to
have published prolifically on their preparation and chemistry (Pringsheim and
Langhans 1912; Pringsheim and Eissler 1913, 1914; Pringsheim 1915, 1919, 1922,
1924, 1925, 1926, 1927, 1928a, b, 1931a, b, 1932; Pringsheim and Lichtenstein
1916; Pringsheim and Persch 1921, 1922; Pringsheim and Dernikos 1922;
Pringsheim and Goldstein 1922, 1923; Pringsheim and Beiser 1924, 1932; Irvine
et al. 1924; Pringsheim and Leibowitz 1924, 1925a, b, 1926a, b; Pringsheim and
Steingroever 1924, 1926; Pringsheim and Wolfsohn 1924; Pringsheim and Schapiro
1926; Pringsheim and Meyersohn 1927; Irvine et al. 1929; Pringsheim et al. 1930,
1931a, b). However, these studies suffered from numerous errors due to the use of
dextrins that were not pure and to problems arising from separation of the fractions
and from the use of unsuitable analytical methods, e.g., determination of the masses
by cryoscopy (Freudenberg and Jacobi 1935; Samec and Blinc 1941; French 1957a;
Thoma and Stewart 1965; Caesar 1968). In 1935, Freudenberg dismissed the work
of Pringsheim as practically valueless, since “most of it was based upon work with
dextrin mixtures and upon serious misconceptions relating to the structural principles of high polymers” (Freudenberg and Jacobi 1935). French (1957a) also wrote:
“Pringsheim’s literature was voluminous but much of it was repetitive, controversial, or based on erroneous concepts.”
From 1910, Pringsheim repeated Schardinger’s experiments. He reported higher
yields of β-dextrin from glycogen crude preparations of amylopectin, and this is the
reason why he postulated that amylose was polymerized α-diamylose and amylopectin and glycogen were polymerized β-triamylose. Like Schardinger, Pringsheim
observed that the relative proportions of α- and β-dextrins depended on the different
substrates used (Pringsheim and Langhans 1912). Pringsheim described the
1 History of Cyclodextrins