Investigation of the Interactions in Complexes of Low Molecular Weight Chitosan with Ibuprofen

Complexation between ibuprofen and low molecular weight chitosan (LMWC) was studied. LMWC was prepared from high molecular weight chitosan using the acid hydrolysis method. The complexes were investigated by using DSC, FT-IR and liquid-state ¹H-NMR. Molecular mechanics (MM) calculations were used to give insight into the stoichiometry of the interaction of chitosan with ibuprofen. The results showed that complexation of ibuprofen with LMWC involves ionic interaction between the ammonium group of LMWC and the carboxylate anion of ibuprofen. It was also shown that it is more efficient to prepare the complexes using lower concentration solutions of the polymer. These results were supported by molecular mechanics calculations. The experimental results may explain the discrepancies in the literature where, in many studies, the concentration of chitosan and its low average molecular weight were not considered to be important factors in the complexation process.     

Some Physico-Chemical Properties of Low Molecular Weight Chitosans and their Relationship to Conformation in Aqueous Solution

Depolymerization for different time intervals of high molecular weight chitosan using 2 mol⋅L⁻³ HCl resulted in low molecular weight (LMW) chitosan of 6, 10, 13, 18, and 30 kDa. These were studied using the FT-IR which indicated that the depolymerization process did not influence the chemical structure. LMW chitosan increases the surface tension of water but adjusting the ionic strength (1% NaCl) caused LMW chitosan to reduce the water surface tension. The zeta potential increased with increasing concentration up to a maximum in 1% NaCl solutions. Particle size showed a reduction in size with increasing concentration. This behavior in reduction of particle size was similar to that for the stiffness parameters. These physico-chemical properties showed that LMW chitosan was present in low concentration in its extended form while in higher concentrations it adopted a more contracted form. This change in conformation was confirmed by using molecular modeling where LMW chitosan is ribbon-like to rod-like in solution but becomes rod-like to spherical at the gas–liquid interface.     

LC-MS/MS Screening,Total Phenolic,Flavonoid and Antioxidant Contents of Crude Extracts from Three Asclepiadaceae Species Growing in Jordan

This study aimed to evaluate the antioxidant activity and total phenolic content (TPC) and total flavonoid content (TFC) of crude extracts obtained from three Asclepiadaceae species, namely, Calotropis procera L., Peruglaria tomentosa L., and Pentatropis spiralis (Forsk.) Decne. Both butanol and aq. methanol extracts of the three species showed the highest amount of phenol and flavonoid contents, which exhibited the greatest antioxidant activity in the scavenging of 2,2-diphenyl-2-picrylhydrazyl free radical (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt radical cation (ABTS), ferrous chelating effect (FIC), and hydroxyl radical (HDR) assays. Phytochemical screening of the extracts revealed the presence of alkaloids, tannins, sponins, flavonoids, terpenoids, and glycosides. LC-MS analysis was carried out to identify the major compounds from each crude extract. A total of 12 phenolic compounds in the extracts of the 3 species were identified and quantified, including 9 flavonoids, 2 hydroxybenzoic acids, and 3 hydroxycinnamic acids. The current study also revealed a good correlation between total phenolic contents and the observed antioxidant activity of the crude extracts.