Abstract
The temperature- and pH-responsive poly(N-isopropylacrylamide-co-acrylic acid), p(NIPAM-co-AA), copolymer was synthesized by free radical polymerization and examined as a carrier for modified release of biochanin A. Biochanin A is a biologically active methoxylated isoflavone which exhibits estrogenic and other pharmacological activities. Due to its poor aqueous solubility and extensive first-pass metabolism, biochanin A has low bioavailability. The aim of this work was to incorporate biochanin A into the synthesized p(NIPAM-co-AA) copolymer and to examine its release at the body temperature and pH values that correspond to pH values of vaginal and rectal cavities. The amount of released biochanin A was monitored by the ultra-visible spectroscopy (UV-Vis) method. The structure of synthesized p(NIPAM-co-AA) copolymer and copolymer with incorporated biochanin A were characterized by using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) methods. The content of residual monomers in the synthesized copolymer was analyzed by using the high-pressure liquid chromatography (HPLC) method. The swelling behavior of p(NIPAM-co-AA) copolymer was monitored in relation to the temperature and pH values of the surrounding medium. For modelling the process of p(NIPAM-co-AA) copolymer swelling, the full three-level factorial design was applied.
Highlights
Biochanin A is a methoxylated isoflavone which can be found predominantly in plants of the Fabaceae family, primarily in red clover (Trifolium pratense L.), soybean (Glycine maxL.), alfalfa (Medicago sativa L.) and chickpea (Cicer arietinum L.) [1]
Based on the sign in front of the regression coefficients, it can be concluded that increasing the pH value causes an increase in the equilibrium swelling degree of the p(NIPAM-co-acrylic acid (AA)) hydrogel, while temperature has the opposite effect
The content of biochanin A released from a non-lyophilized copolymer p(NIPAM-coAA) in pH fluid of 7.9 at 37 ◦ C for 12 h is 50.57 mg/gxerogel (84.28%), where the content of biochanin A released from the lyophilized copolymer is 53.29 mg/gxerogel (88.83%) relative to the available amount, under pH conditions corresponding to the rectum
Summary
Biochanin A is a methoxylated isoflavone which can be found predominantly in plants of the Fabaceae family, primarily in red clover (Trifolium pratense L.), soybean (Glycine maxL.), alfalfa (Medicago sativa L.) and chickpea (Cicer arietinum L.) [1]. Due to its structural similarity to human estrogen, biochanin A can exhibit both estrogenic and antiestrogenic activity depending on the applied concentration [2]. Biochanin A has other pharmacological activities, such as anti-inflammatory, antioxidant, antimicrobial, antidiabetic, osteoprotective and anticancer activity, primarily against hormone-dependent cancers [3,4,5,6,7,8]. Due to conjugation and hydrolysis by enzymes and intestinal bacteria, biochanin A undergoes extended enterohepatic recirculation. In this way, the biochanin A ability to enter the systemic circulation is further decreased as well as its bioavailability [10]
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