Abstract
The limited bioavailability of the highly hydrophobic natural compound, curcumin with wide range of beneficial bioactivity is still a challenge. Self-association type systems of polyethylene oxide-polypropylene oxide-polyethylene oxide block copolymers (Pluronic) were applied to enhance the aqueous solubility of curcumin. Comparison of four Pluronics (94, 105, 127,108) with different compositions led to the conclusion that solubilization capacity is maximum for Pluronic 105 with intermediate polarity (hydrophilic/lipophilic balance (HLB) = 15) possessing the optimum balance between capacity of hydrophobic core of the micelle and hydrophilic stabilizing shell of the associate. Curcumin concentration in aqueous solution was managed to increase 105 times up to 1–3 g/L applying Pluronic at 0.01 mol/L. Formation of a host–guest complex of cyclodextrin as another way of increasing the curcumin solubility was also tested. Comparing the(2-hydroxypropyl)-α, β and γ cyclodextrins (CD) with 6, 7 and 8 sugar units and their polymers (poly-α-CD, poly-β-CD, poly-γ-CD) the γ-CD with the largest cavity found to be the most effective in curcumin encapsulation approaching the g/L range of concentration. The polymer type of the CDs presented prolonged and pH dependent release of curcumin in the gastrointestinal (GI) system modelled by simulated liquids. This retarding effect of polyCD was also shown and can be used for tuning in the combined system of Pluronic micelle and polyCD where the curcumin release was slower than from the micelle.
Highlights
Curcumin is a well-known traditional medicine with wide scale of beneficial bioactivity from powerful anti-inflammatory effect to remarkable antioxidant property [1]
Main properties of the Pluronics, structure, critical micellar concentration, hydrophilic/lipophilic balance (HLB) are summarized in Methanol, ethanol, dimethyl-sulfoxide (DMSO) and acetone were of laboratory grade from Molar Chemicals Kft. (Budapest, Hungary) while sodium chloride, sodium hydroxide, potassium dihydrogen phosphate, disodium hydrogen phosphate and sodium dodecylsulfate (SDS) from Sigma-Aldrich
Enhanced solubility of curcumin in aqueous medium was planned to achieve by its solubilization in tri-block copolymer (Pluronic) micelles
Summary
Curcumin is a well-known traditional medicine with wide scale of beneficial bioactivity from powerful anti-inflammatory effect to remarkable antioxidant property [1]. By modulating the activation of various transcription factors, curcumin regulates the expression of inflammatory enzymes, cytokines, adhesion molecules, and cell survival proteins. Polymers 2020, 12, 2167 of cancer prevention and treatment (pancreatic, colon cancer, etc.), reducing the risk of diabetes and various skin diseases, for example psoriasis [2]. It has a beneficial effect applied in nanofibrous scaffold for chronic wound treatments [3]. The very poor aqueous solubility of curcumin (
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