Chlorogenic acid (CGA), a natural polyphenol widespread in nature (plants, vegetables, fruits), displays several pharmacological and biological activities such as antioxidative, antibacterial, antihypertensive, antitumor, anti-inflammatory. However, its highly hydrophilic structure strongly limits its bioavailability and hinders the use into oil-based products such as cosmetic and nutraceutical preparations. To overcome this drawback, CGA can be lipophilized through esterification with a fatty alcohol. The use of heterogeneous Brønsted solid acid catalysts, such as the sulphonic resins Amberlite® IR120 and Amberlyst® 15, resulted greatly effective in the direct acylation of CGA with several fatty alcohols (2 to 18 carbon atom) in a sustainable, solvent free, one-pot reaction (Scheme 1).
Ethyl, butyl, octyl- and lauryl- chlorogenates were isolated in high yields (up to 93%) and fully characterized by NMR and LC-MS analyses. The antioxidant activity of these products, estimated through the DPPH test, was found to be higher than unsubstituted CGA (Figure 1).
V. Pappalardo et al., Antioxidants 2023, 12, 218.