Cyclodextrins (CD) is formed by cyclodextrin glycosyltransferases (CGTases) acting on starch which is a polymer of glucose. CD was first discovered in 1891. Over the past 100 years, many scientists have made contributions to the research into CDs. Taking a look at the research work done over the past century can help us better understand CD, and the following provides a brief overview of CD history through two aspects: stages of CD development and evolution of CD nomenclature.
Stages of CD Development
The development of CD can be briefly summarized into three stages. The first stage is the discovery of CD, the second stage is the exploration of CD, and the third stage refers to the maturation or commercialization of CD [1].
The key stage in CD's history is from 1891 to 1911, which covers its discovery and characterization. CD was first discovered in 1891 by Villiers from the Bacillus amylobacter digest of potato starch. Schardinger subsequently observed α-CD and β-CD, and depicted the preparation and isolation of these two compounds in detail for the first time.
Between 1935 and 1950, Freudenberg and French explored CDs extensively, achieving numerous results on CD's molecular structure. In 1936, Freudenberg proposed the cyclic structures of α- and β-CDs, and in 1942, French described a new protocol for preparing high-purity CDs and published the correct molecular weights of α-CD and β-CD. In 1948, Freudenberg discovered γ-CD compound.
From 1950 to 1980 was the mature stage for CD's development. The discovery of inclusion complexes by Cramer in 1956 led to extensive research into CDs in food, medicine, cosmetics, and other areas. Since Japan conducted CD pilot-scale production in 1960, CD has entered the industrial production stage. In the mid-1980s, CDs were mass-produced and commercialized at a reasonable price.
Evolution of CD Nomenclature
1891CD was first discovered by Villiers was named "cellulosine" in 1891. Schardinger discovered the formation of two "krystallisiertes dextrins" and named them crystallized dextrin-α and crystallized dextrin-β in 1903, since their properties were similar to known partial degradation products of starch.
1910sThe German chemist and biochemist Hans Pringsheim thought that the compounds discovered by Schardinger arose through the bacterial depolymerization of starch (amylose and amylopectin fraction) into the fundamental units, so named them"krystallisiertes polyamylosen".
1920sThe German chemist Karl Johann Freudenberg used the name "Sardinger dextrins" in tribute to Schardinger's work, and referred to α-series and β-series compounds as "α-dextrins" and "β-dextrins". This nomenclature was used almost until the 1970s.
1942The American chemist Dexter French named these compounds discovered by Schardinger "cycloamyloses" in 1942, and Freudenberg named them "cycloglucanes" in 1943. The latter chemist proposed a nomenclature based on cycloglucane, for example, cyclohexaglucane α(1→4), cycloheptaglucane α(1→4) and cyclooctaglucane α(1→4).
1949The German chemist Friedrich Cramer first proposed the cyclo-based nomenclature and introduced the term "cyclodextrins". He proposed that cyclic oligosaccharides consisting of 6, 7 or 8 d-glucose units linked by α-(1→4) bonds are called α-, β- and γ-cyclodextrins, respectively.
1997
To provide further information on the bonding between sugar units, the term "cyclomaltohexaose" was proposed in 1997. The name consists of the term "cyclo" and another term indicating the type of linkage.
In summary, although there are several nomenclatures for CDs, the most common nomenclature is the one proposed by Cramer, based on "cyclodextrins". Because of its relative simplicity, it was quickly accepted by the public and remains the most common in today's literature.
Reference
- Nadia. M,-C.; et al. 130 years of cyclodextrin discovery for health, food, agriculture, and the industry: a review. Environmental Chemistry Letters. 2021, 19: 2581–2617.
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