β‐cyclodextrin encapsulated polyphenols as effective antioxidants

Abstract

Formation of dityrosine (DT) cross-linkages in proteins is one of the most widely used markers of oxidative stress. Ribonuclease A (RNase A) has 6 Tyr residues and shows a characteristic DT fluorescence peak upon oxidation in addition to major changes in its secondary structure. DT formation can be prevented by using polyphenols (GA, ECG, and EGCG) which are known to have strong antioxidant activity. However, it has been observed that ECG and EGCG initiate protein oligomerization due to protein-polyphenol cross-linkages. To prevent the formation of such crosslinkages we have used b-cyclodextrin (b-CD) to encapsulate the polyphenols and studied its antioxidant properties along with that of free polyphenols. The polyphenol/b-cyclodextrin (b-CD) inclusion complexes not only prevent DT formation but also reduce protein oligomerization. This may be attributed to the fact that the quinone forming rings of ECG and EGCG become encapsulated in the cavity of b-CD and are no longer available for protein cross-linking.b-cyclodextrin encapsulation, dityrosine, oxidative stress, polyphenols, protein oligomerization | I N TR ODU C TI ONBiological aging in mammalian cells is a direct indication of oxidative stress in proteins. [1] These oxidatively modified forms of proteins are generated due to the presence of reactive oxygen species (ROS) such as hydroxyl and superoxide free radicals. [2,3] Persulfates, a key ingredient in flour, are a source of sulfate (SO 2 4 ) free radicals under neutral pH. [4,5] Due to the higher oxidizing power of the sulfate radical (E 0 5 12.60 V) and longer half-life period over the OH radical, it has drawn attention in recent times as a powerful oxidizing agent. [6][7][8] Many chemical and cosmetic industries require persulfates as their key components [9] and workers often suffer from skin and respiratory diseases due to hypersensitive reactions. [10] Generally, the lower thermal energy at room temperature (25-508C) is not sufficient enough to activate persulfate, but generation of SO 2 4 radical is facilitated in presence of metal cations. Since proteins tend to lose their structure and function at high temperatures, [11] we have carried out the oxidation of ribonuclease A (RNase A) in presence of persulfate using cobalt (II) ion at 378C. [12] Cobalt is an integral component of vitamin B12 and thus physiologically found in most tissues mainly in liver and kidney. [13,14] Gill et al., reported the formation of oligomeric species (dimer, trimer, tetramer) when RNase A was exposed to KHSO 5 in presence of metal ions such as Ni 21 and Cu 21 and the high molecular weight species were identified using SDS-PAGE. [12] An important biomarker of oxidative stress is the dityrosine moiety generated due to the covalent linkage of two Tyr residues. [15] Dityrosine bond formation is an indication of aging, and disease related problems since it generally occurs during amyloid fibril formation, [16] Parkinson disease, [17] cerebrospinal fluid damage, [18] and also in the cataract of the eye lens. [19,20] D...

Preparation and Characterisation of Polyphenol-HP-β-Cyclodextrin Inclusion Complex that Protects Lamb Tripe Protein against Oxidation

“…Figure 5 shows the effects of GSE on DPPH radical scavenging activity, which were ordered HP-β-CD/GSE (1:2) > HP-β-CD/GSE (1:1) > HP-β-CD/GSE (1:0.5) > GSE. This could be because catechins of the inclusion polyphenol and the two hydroxyl groups at the rim of β-CD engage in hydrogen bonding interactions, and the OH groups in the β-CD wall may be shielded by catechins, which stabilises them and makes them more resistant to oxidation [23]. The result was consistent with that of a previous study [37] in which the antioxidant activity of the rosmarinic acid (RA):HP-β-CD freeze-dried complex was higher than that of RA.…”

“…Researchers have studied various applications of HP-β-CD, including encapsulation of polyphenols [1,21,22]. For example, polyphenol-cyclodextrin inclusion complexes not only prevent dityrosine cross-linkage, but also reduce protein oligomerisation [23], and they can reduce the partial degradation of essential amino acids, thereby decreasing adverse interactions between proteins and polyphenols [24]. Thus, the naturally unstable antioxidant improves antioxidant effects and bioavailability through inclusion.…”

Interactions between β-cyclodextrin and tea catechins, and potential anti-osteoclastogenesis activity of the (−)-epigallocatechin-3-gallate–β-cyclodextrin complex

“…[15][16][17]21,38,39 Tea catechins, including EGCG, GCG, ECG, EGC, EC, and GA, have been shown to form stable inclusion complexes with the encapsulating material b-CD, which are demonstrated by using different techniques and theoretical approaches. [15][16][17]21,22,[38][39][40] Despite this, data on the intrinsic molecular interactions of b-CD with these tea catechins assessed using novel biomolecular interaction technology are still relatively limited. In addition, tea catechins, especially EGCG, are easily oxidized and unstable at high pH or on prolonged exposure to high temperature.…”

“…17 In addition, extensive experiments have been performed to illuminate the interactions between individual catechins and b-CD using a number of techniques. 7,[15][16][17][20][21][22] Based on the distinctive characteristics of b-CD, it has also been successfully used to extract EGCG and ECG from tea leaves. 23,24 However, to the best of our knowledge, fundamental data on the real-time interactions between b-CD and EGCG, ECG, EGC and EC are still relatively limited.…”

Inclusion complexes of tea polyphenols with HP‐β‐cyclodextrin:Preparation, characterization, molecular docking, and antioxidant activity

“…Therefore, hydroxypropyl‐β‐cyclodextrin (HP‐β‐CD) as a derivative of β‐CD has gained increasing attention due to its low toxicity, improved aqueous solubility, and flexible cavity (Dreassi et al., 2010; Liu et al., 2013; Tang et al., 2016). Previous studies found that polyphenols have high activity in cyclodextrin, thereby inhibiting polyphenol‐induced protein aggregation (Budryn, Zaczyńska, Rachwa‐Rosiak, & Oracz, 2015; Niccoli, Oliva, & Castronuovo, 2017; Roy, Dinda, Chaudhury, & Dasgupta, 2017). Therefore, the above research inspires the testing of HP‐β‐CD to improve the loading capacity of TP due to the interference of protein–polyphenol interaction.…”