Investigation of Bioactive Complexes of Chitosan and Green Coffee Bean or Artichoke Extracts

The formation of water-insoluble complexes between chitosan (ChS) and caffeoylquinic acid (CQ) derivatives present in artichoke (AE) and green coffee bean (GCBE) extracts was investigated by the equilibrium adsorption method. The UPLC/HPLC analysis revealed that the phenolic compounds accounted for 8.1% and 74.6% of AE and GCBE respectively, and CQ derivatives were the predominant compounds. According to the applied Langmuir adsorption model, anionic compounds present in natural extracts were adsorbed onto the active centers of ChS, i.e., primary amino groups. The driving forces of adsorption were electrostatic interactions between cationic groups of ChS and anionic compounds of natural extracts. Chromatographic analysis revealed that not only CQ derivatives, but also other phenolic compounds of natural extracts were attached to ChS. The release of adsorbed compounds into different media as well as the bioactive properties of complexes were also studied. With the immobilization of bioactives onto ChS, increased and prolonged ABTS^•+ radical scavenging activity and decreased antifungal activity against Fusarium graminearum and Botrytis cinerea were observed compared to those of ChS. The findings of the current study highlight that the adsorption approach could be used to successfully prepare water-insoluble complexes of ChS and components of natural extracts with prolonged antioxidant activity.

Interaction between cross-linked cationic starch microgranules and chlorogenic acid isomers in artichoke and green coffee bean aqueous extracts

In the present study, the adsorption of phenolic compounds, first of all, chlorogenic acid isomers (chlorogenic, neo-chlorogenic and crypto-chlorogenic acids) predominant in the artichoke (AE) or green coffee bean (GCBE) extracts on cross-linked cationic starch having quaternary ammonium groups (CCS) has been investigated. The equilibrium adsorption studies showed that adsorption closely followed the Langmuir adsorption model, i.e. anionic substances of the extracts were interacting with quaternary ammonium groups of CCS. The UPLC-UV-MS/MS analysis showed that 8% and 17% of chlorogenic acid isomers of the total amount of adsorbed phenolics form AE and GCBE, respectively, were immobilized on CCS. The desorption study of phenolics from AE/CCS and GCBE/CCS complexes revealed that amount of desorbed AE or GCBE phenolics depended on the desorption medium. The antioxidant activity investigation showed that the immobilization of active components of extracts on CCS prevented the rapid loss of antioxidant activity. The results suppose that adsorption on modified starch technique can be successfully employed to remove important amounts of bioactive compounds from plant extracts by employing effective, sustainable and environmental friendly procedures.