Complexation of curcumin with Lepidium sativum protein hydrolysate as a novel curcumin delivery system
Introduction
In the past decade, complexations between proteins and lipophilic molecules, especially polyphenolic compounds, have attracted attention of many researchers and nutraceutical industries. The increased interest is mainly due to the ability of formed complexes to enhance water solubility, stability and bioavailability of the bioactive compounds with a targetted release in the GI tract (Ahmed, Li, McClements, & Xiao, 2012). Curcumin [1,7-bis(4-hydroxy-3-methoxyphenyl)1,6-heptadiene-3,5-dione], an important lipophilic polyphenol, is found in the rhizome of turmeric (Curcuma longa) and the crude extract is used indigenously in numerous herbal medicines; it is commonly comprised of three key compounds: curcumin, demethoxy-curcumin, and bisdemethoxycurcumin (Chen, Li, & Tang, 2015). Among the three, curcumin is the major active constituent that contributes to several biological and pharmacological activities, such as anti-inflammatory, antioxidant, anti-cancer, antiproliferative, antimicrobial and antiangiogenic properties (Bhatia et al., 2016). However, the applications of curcumin in functional food and nutraceutical formulations are limited due to its limited water solubility and poor bioavailability.
Many studies have shown the potential of animal-derived protein molecules to act as a carrier to improve the solubility and bioavailability of curcumin. Previous reports concluded that casein (Rahimi Yazdi and Corredig, 2012, Sahu et al., 2008), β-lactoglobulin nanoparticle (Sneharani, Karakkat, Singh, & Rao, 2010), β-casein micelle (Esmaili et al., 2011, Pan et al., 2013) and bovine serum albumin (Yang, Wu, Li, Zhou, & Wang, 2013) increased the solubility of various molecules by balancing the ratio of hydrophilic-to-hydrophobic amino acids with a peculiar micellar structure that aids complexation. Beside the animal-derived proteins, plant-based proteins are also regarded as safe and economical with significant health benefits (Satija & Hu, 2018). The complexation with soy protein isolate (Chen et al., 2015, Tang and Li, 2013, Tapal and Tiku, 2012), pea protein (Donsì, Senatore, Huang, & Ferrari, 2010), flaxseed hydrolysate (Akbarbaglu et al., 2019) and zein colloidal particles (Patel, Hu, Tiwari, & Velikov, 2010) has demonstrated the improvement in solubility and stability of curcumin. However, many of these proteins in native form failed to show proper functional characteristics for food applications. Therefore, the natural proteins are modified by various methods, such as enzymatic hydrolysis, to improve their solubility, emulsification capability and foaming capacity (Akbarbaglu et al., 2019).
The plant-based proteins are environmentally sustainable dietary sources of proteins and their demand from vegans is increasing, with only limited experimental results available to address the possible application of the proteins in this respect (Karaca, Low, & Nickerson, 2011). In our study, Lepidium sativum seed protein isolates were used as the carrier for curcumin complexation. Lepidium sativum, a shrub native to the Indian subcontinent, belongs to the Cruciferae family and is a cheap and abundant renewable source of proteins. The object of our research was to evaluate the feasibility of molecular weight-based Lepidium sativum protein hydrolysate fractions as potential complexation agents for curcumin. This study systematically investigated the preparation, characterization and functional evaluation of protein-based curcumin complex as an effective nutraceutical and functional food ingredient.
Section snippets
Material
Curcumin (CUR, 95%) was purchased from ICN Biomedicals, Inc. (Aurora, Ohio). Lepidium sativum seeds were purchased from APMC market, Mumbai. 2,2-Diphenyl-1-picrylhydrazyl, 2,4,6-Tris(2-pyridyl)-s-triazine (TPTZ), was from Sigma Aldrich and the rest of the chemicals were of analytical grade from the Merck Company.
Production of enzymatic hydrolysate
To prepare LSPH/CUR complex, a freeze-dried Lepidium sativum protein hydrolyzed molecular fraction was used. Prior to enzymatic hydrolysis, defatted Lepidium sativum seedcake was
Complexation of curcumin with LSPI
Curcumin (diferuloylmethane), a lipophilic polyphenol found in turmeric (Curcuma longa), exhibits potential biological and pharmacological activities. However, its applicability as a health-promoting agent in various formulation developments is often limited due to its poor water-solubility and chemical instability, as well as low and variable bioavailability. In this study, we used LSPH (MWCO > 30 kDa, 10–30 kDa, 5–10 kDa and <5 kDa) as an emulsifier and stabilizer at pH 3.0, 3.5 and 4.0 to
Conclusion
This study has shown that the LSPH (10–30 kDa) fraction can undergo a compact complexation with curcumin at pH 3.0 that significantly improves its solubility (in the aqueous phase), stability and even bioaccessibility. The functional attributes of the LSPH/CUR complex, especially the foam and emulsion forming capacities, were promising for its applications in food product formulations. Furthermore, the antioxidant activity of LSPH increased after complexation with curcumin. The present work
Declaration of Competing Interest
None declared.
Acknowledgment
The authors are thankful for the Basic Scientific Research Fellowship in Sciences by the University Grants Commission, Government of India, for providing financial assistance (Grant number: 2812/UGC-SAP) during this investigation.
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