IMPRINTED POLYMERS FOR COFFEE TERPENES

Coffea canephora and Coffea Arabica are industrially the widest used species of coffee. The price of C. arabica is, due to its high quality, nearly twice the price of C. canephora¹, which increases the frequency of fraudulent behaviour, influencing the quality of the end product. To avoid it, a simple way to distinguish between the two species is desired. An interesting deviation between the contents of cafestol and 16-O-methylcafestol (Figure 1) in coffee beans and brews of both species has been reported - the beans of both species contain almost equal amounts of cafestol, whereas 16-O-methylcafestol is found in greater amounts in the beans of C. canephora and minor amounts in C. arabica², and has thus been accepted as a specific marker.³

While both molecules are pentacyclic kaurene diterpenes, the only difference between them is the methoxylated hydroxy group on the atom C₁₆ of 16-O-methylcafestol. As molecular imprinting technology provides us with the possibility of creating a polymeric system with highly specific molecular recognition properties,⁴ we predict that creation of MIP-based sensors via covalent imprinting could lead to a sufficient differentiation between the two molecules. In cafestol the vicinal hydroxy groups can be selectively esterified with boronic acids to form boronic esters, whereas in 16-O-methylcafestol it is possible to esterify the hydroxy group and form a π-methyl interaction between an aromatic ring and the methoxy group.

In the poster, presented on the 9^th International conference of molecular imprinting, isolation of both diterpenes was shown, and selection of most appropriate functional monomers for the two molecules was described.⁵

In this poster we introduce synthesis of the polymerizable derivatives and molecularly imprinted polymers for both diterpenes.

References

[1] Jeszka-Skowron M et al. (2015) Analytical methods applied for the characterization and the determination of bioactive compounds in coffee. Braz. J. Plant Physiol. 240: 19-31.

[2] Gunning Y et al. (2018)v16-O-methylcafestol is present in ground roast Arabica coffees: Implications for authenticity testing. Food Chemistry 248:52-60.

[3] De Lucia M et al. (2009) Differential Reactivity of Purified Bioactive Coffee Furans, Cafestol and Kahweol, with Acidic Nitrite: Product Characterization and Factors Controlling NitrosationVersus Ring-Opening Pathways. Chem. Res. Toxicol. 22: 1922-1928.

[4] Kriz D et al. (1997) MOLECULAR IMPRINTING: New Possibilities for Sensor Technology. Analytical Chemistry News & Features A: 345-349.

[5] Oreški A et al. (2016) Coffee Terpenes: Extraction and selection of functional monomers. Poster presented at the 9^th international conference on molecular imprinting. Lund, Sweden.