Complexing of chlorogenic acid with β-cyclodextrins: Inclusion effects, antioxidative properties and potential application in grape juice

Highlights

• The structure characteristics of HP-β-CD caused the better inclusion effect.

• The antioxidant activity of CGA/HP-β-CD complex was better than CGA/β-CD.

• The copigmentation effect of CGA/HP-β-CD was better than CGA/β-CD.

Abstract

Chlorogenic acid (CGA) is a polyphenol commonly existed in fruits and vegetables with a variety of bioactivities. To increase its stability and potential broader industrial application, CGA/cyclodextrin (CD) complexes were prepared using β-cyclodextrin (β-CD) and its derivative (2-hydroxypropyl)-β-cyclodextrin (2-HP-β-CD). Their inclusion complexation behavior and characterization were investigated by FT-IR, XRD, SEM, and ¹H NMR spectroscopy. The morphologic and spectral studies indicated the formation of inclusion complexes. Moreover, spatial arrangements of inclusion complexes were proposed based on ¹H NMR results. The antioxidant activities of the complexes were improved compared with the CGA without inclusion, and the CGA/HP-β-CD complexes showed the highest antioxidant activity. In addition, the CGA/CD complexes were added in grape juice to explore the potential on the preservation of anthocyanin and color quality. Results showed that the degradation of anthocyanins was reduced when CGA and CGA/CDs inclusions were added in grape juice due to copigmentation effect, and their copigmentation strength showed in an order of CGA/HP-β-CD complex > CGA/β-CD complex > free CGA.

Introduction

Chlorogenic acid (CGA) is a polyphenol derivative existed widely in fruits, vegetables, black teas, soy beans, and wheat (Wang, Wang, & Yang, 2007). Our previous work also demonstrated that the major phenolic compound in Eucommia ulmoides Oliver (Du-Zhong in Chinese, a traditional Chinese medicine) leaf is CGA (Shao, Hong, Liu, He, & Sun, 2011). CGA possesses well documented bioactivities such as antioxidant activity (Sato et al., 2011), antimicrobial properties (Puupponen-Pimia et al., 2001, Zhu et al., 2004), and anxiolytic activity (Bouayed, Rammal, Dicko, Younos, & Soulimani, 2007). However, CGA is easily to be oxidized and sensitive to heat and light (Chao, Wang, Zhao, Zhang, & Zhang, 2012), which restricts its application in industries.

Encapsulation of polyphenols has been proposed as an alternative to improve their stability, bioactivity and extend its application (Fang & Bhandari, 2010). Inclusion complexation with cyclodextrins (CDs) has been evidenced to be a good encapsulation technology (Davis and Brewster, 2004, Loftsson and Duchene, 2007). CDs are a series of water-soluble cyclic oligomers consisting of six to eight d-glucose monomers linked by α (1→4) glycosidic bonds, which form hydrophobic central cavities with hydrophilic external walls (Del Valle, 2004, Hamilton et al., 2000, Szejtli, 2004). Hence, CDs are able to interact with a variety of hydrophobic compounds to form inclusion complexes (Ambrus et al., 2011, Karathanos et al., 2007, Zielenkiewicz et al., 2010). When CDs form inclusion complex with guest molecules, the physicochemical properties of the guest molecules could be positively modified, such as enhancing the solubility and stability of the guest molecules (Caliceti et al., 2003, Yang et al., 2010), reducing the drug bitterness and decreasing tissue irritation (Carrier et al., 2007, Misiuk and Zalewska, 2009, Roik and Belyakova, 2011).

Among the natural CDs, β-cyclodextrin (β-CD) is particularly useful in the pharmaceutical industry because of its high encapsulation efficiency, suitable cavity dimensions, and low cost (Sancho, Gasull, Blanco, & Castro, 2011). In addition, its modified derivative of hydroxypropyl-β-cyclodextrin (HP-β-CD) is well studied in drug encapsulation because of its good inclusion capacity as well as high water solubility, non-toxicity and biocompatibility (Eid et al., 2011, Stella and He, 2008).

The addition of phenolic compounds to prevent anthocyanin degradation due to copigmentation effect has been widely recognized (Chen and Hrazdina, 1981, Mazza and Brouillard, 1987, Mazza and Miniati, 1993). Earlier studies also demonstrated that CGA could be applied as a copigment to enhance the color stability and intensity of cyanidin-3-glucoside (Bakowska, Kucharska, & Oszmianski, 2003). However, to our knowledge, no literature is available on utilization of inclusion complexed polyphenols as copigments of anthocyanins. Therefore, the aim of this study was to prepare inclusion complexes between CGA and two different CDs, namely β-CD and 2-HP-β-CD, to investigate their effects on preservation of anthocyanins and color quality of grape juice. The obtained complexes were characterized by FT-IR, XRD, SEM, and ¹H NMR spectroscopy and their physical, chemical and biological properties were compared. This study may expand the industrial applications of CGA inclusion complexes as enhanced antioxidants and provide a new method to improve the color stability of anthocyanin rich products through copigmentation with encapsulated polyphenols.