Isoflavone aglycons-sulfobutyl ether-β-cyclodextrin inclusion complexes: in solution and solid state studies

Abstract

The effect of a polyanionic variably substituted sulfobutyl ether-b-cyclodextrin (SBE-b-CyD), complexation on the UV absorption of genistein (Gen) and daidzein (Dai) was studied in pure water. A phase solubility study was performed, according to the method reported by Higuchi and Connors, to evaluate the changes of isoflavones in the complexation state and type-A L solubility diagrams for both isoflavones were obtained suggesting that they form complexes with 1:1 molar ratio. These results were confirmed by Job's plot method. Complexation strongly increases the water solubility of isoflavones. The in vitro dissolution of isoflavones entrapped into SBE-b-CyD significantly surpassed that of the free isoflavones (over 90 % of the loaded Gen and Dai dissolved in 15 and 30 min, respectively). Finally, 1:1 molar ratio solid complexes were prepared by the kneading method and characterized in solid state by FTIR-ATR spectroscopy, with particular regard to O-H and C=O stretching vibrations, achieving structural information on the modifications induced by complexation on the H-bond scheme, also by applying band decomposition and curve-fit.

Temperature-Dependent Dynamical Evolution in Coum/SBE-β-CD Inclusion Complexes Revealed by Two-Dimensional FTIR Correlation Spectroscopy (2D-COS)

“…As far as the ~(1637,1624) cm −1 and ~(1724,1624) cm −1 CPs (black circles in Figure 5 c) are concerned, the following sequence can be recognized: contribution at ~1624 cm −1 , assigned to the phenyl C=C stretching vibrations of guest molecules, dynamically change upon increase in T , prior both the δ-HOH bending vibrations of crystallization water molecules directly attached to SBE-β-CD toroid (~1637 cm −1 ), and H-bonded carbonyl stretching of ketones groups of Coum (i.e., (C=O) complexed ). In apparent contradiction with what has been stated in the case of the 2D-COS analysis of the ~(1724,1712) cm −1 CP, the phenyl ring C=C groups, which are believed to participate to the complexation phenomenon as well [ 39 , 42 , 43 , 44 , 45 , 46 ], are the first groups to experience dynamical changes in this chronological progression. Such discrepancy finds an explanation if we consider the most probable inclusion geometry exhibited by the investigated Coum/SBE-β-CD system.…”

“…Briefly, by recalling well-known assignments already reported in the literature [ 39 , 42 , 43 , 44 , 45 , 46 ], the 900–1450 cm −1 wavenumber region (see Figure 2 b) shows contributions at ~990 cm −1 (shoulder), ~1020 cm −1 , ~1080 cm −1 and ~1150 cm −1 , ascribed to the =CH bending (of terminal moieties), C–O stretching, C–O–C stretching and C–H stretching vibrations of the SBE-β-CD macrocycle, respectively. Furthermore, peaks at ~1260 cm −1 , ~1305 cm −1 , ~1370 cm −1 and ~1436 cm −1 can be ascribed to the C–O stretching, C–O–C stretching, C–OH bending and C–C skeletal stretching vibrations of Coum molecules.…”

“…A first inspection of Figure 6 a,b reveals, for both the Coum/SBE-β-CD inclusion complex and Coum+SBE-β-CD physical mixture, the presence of a broad AP centered at ~(3370,3370) cm −1 . Briefly, since the static variations of the O–H stretching band upon heating are well-documented [ 20 , 45 , 54 , 55 ], the difference in the observed synchronous intensity can be ascribed to the establishment, upon complexation, of inter-mode correlations involving hydroxyl groups of both individual components. It is worth noting, however, that extended high-intensity APs, like those observed in 2DSMs, develop only in the case of the absence of simultaneous variations of correlated spectral intensities.…”

Physicochemical Characterization and Antioxidant Activity Evaluation of Idebenone/Hydroxypropyl-β-Cyclodextrin Inclusion Complex †

“…A widely recognized approach to satisfactorily account for, in a quantitative way, such modifications of the H-bond network in cyclodextrin-based systems [54,57,58] is to perform, after a proper subtraction of the overlapping C–H vibrational mode [59], a curve-fitting procedure of the O–H stretching band into six components accounting for interstitial ( ω 3 ~3360 cm −1 , ω 6 ~3084 cm −1 ) and intracavity ( ω 1 ~3525 cm −1 ) water molecules, primary ( ω 2 ~3439 cm −1 ) and secondary (ω 5 ~3191 cm −1 ) OH groups of HP- β -CD, and OH groups of IDE ( ω 4 ~3277 cm −1 ). The analysis is supported by the calculation of the second derivative of the IR spectra, furnishing a first indication of the number of sub-bands and their center-frequencies.…”

Rutin-Loaded Solid Lipid Nanoparticles: Characterization and In Vitro Evaluation

“…The main reason is their antioxidant, anti-inflammatory, anti-mutagenic anti-cancer, anti-Alzheimer, anti-arthritic, and anti-diabetic activity, which makes them indispensable components in numerous applications. In particular, flavonoids as antioxidant agents, free radical scavengers, and singlet oxygen quenchers have been, and still are, widely investigated [ 26 , 27 , 28 , 29 , 30 ]. Among them, rutin (3,3’,4’,5,7-pentahydroxyflavone-3-rhamnoglucoside, RT), is present in many medicinal herbs, fruits, vegetables, and other plants and is considered beneficial due to its potential protective role for multiple diseases related to oxidative stress [ 31 , 32 , 33 ].…”