Inclusion complex of β-cyclodextrin with coffee chlorogenic acid: new insights from a combined crystallographic and theoretical study

Abstract

This work reports the elusive structural evidence for the [4]pseudorotaxane of β-cyclodextrin (β-CD) with coffee chlorogenic acid (CGA), a conjugate of caffeic acid (CFA) and quinic acid (QNA). A single-crystal X-ray structure analysis of the inclusion complex β-cyclodextrin–chlorogenic acid–water (2/2/17), 2C42H70O35·2C16H18O9·17H2O, reveals that CGA threads through β-CD and assembles via O—H...O hydrogen bonds and parallel-displaced π–π interactions in the twofold symmetry-related dimer yielding a [4]pseudorotaxane, which is crystallographically observed for the first time in CD inclusion complexes. The encapsulation of the aromatic ring and C=C—C(=O)O chain in the β-CD dimeric cavity indicates that the CFA moiety plays a determinant role in complexation. This is in agreement with the DFT-derived relative thermodynamic stabilities of the trimodal β-CD–CGA inclusion complexes, that is, β-CD complexed with different CGA components: C=C—C(=O)O chain > cyclohexane ring > aromatic ring. The complexation stability is further enhanced in the dimeric β-CD–CGA complex, with the CFA moiety totally enclosed in the β-CD dimeric cavity.

Structural Insights into the Host–Guest Complexation between β-Cyclodextrin and Bio-Conjugatable Adamantane Derivatives

“…As depicted in Figure 3 , in the structures of 1 , 2 , 4 , and 5 , the β-CD host exclusively forms a pair via the hydrogen bonding interactions between the –OH groups on C2/C3 with their equivalents (symmetry codes: x , y , z for 1 ; x , – y – 1, – z – 2 for 2 ; – x + 1, y , – z + 3/2 for 3 ; x + 1/2, y + 1/2, z for 4 ; x , y , z for 5 ; x , y , z for 6 ) to give a truncated-cone-like cavity. Such dimeric form dominates the host–guest complexes of β-CD with very limited exceptions [ 66 , 67 , 68 , 69 , 70 ]. As shown in Figure 3 a, a pair of adm-1-OH in the cavity of 1 features a back-to-back conformation.…”

Development of Potential Therapeutic Agents from Black Elderberries (the Fruits of Sambucus nigra L.)

“…Quinic acid and chlorogenic acid are also major components of elderberries, with their content in elderberry wine having been reported as 1674.77 µg/mL and 17.67 µg/mL, respectively [13]. The structures of these compounds were confirmed by single-crystal X-ray diffraction data collected from crystals of the complexes of these compounds as well as from β-cyclodextrin, and their absolute configurations were determined based on those reported for β-cyclodextrin [63,64] (Figure 3).…”

Current Status of Quantum Chemical Studies of Cyclodextrin Host–Guest Complexes

“…A separate group consists of substances that could be defined as functionalized food (Table 1C). In those cases, CDs serve to protect or even increase the antioxidative capacity of the substances in question, for example (−)-gallocatechin, (−)-catechin gallate and (−)-gallocatechin present in tea [102][103][104], or to reduce the bitter taste of coffee [105,106]. Moreover, CDs can be used as chiral selectors, and this has its reflection in the DFT articles (Table 1D).…”