Wormlike Micellar Aggregates of Saponins from Ilex paraguariensis A. St. Hil. (mate): A Characterisation by Cryo-TEM, Rheology, Light Scattering and Small-Angle Neutron Scattering

• Published in: Journal of pharmaceutical sciences 2011-02, Vol.100 (2), p.536-546
• Main Authors: Peixoto, Maria Paula G., Treter, Janine, de Resende, Pedro Ernesto, da Silveira, Nádya Pesce, Ortega, George G., Lawrence, M. Jayne, Dreiss, Cécile A.
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Cryoelectron Microscopy; encapsulation; Fruit - chemistry; General pharmacology; Ilex paraguariensis - chemistry; Medical sciences; micelle; Micelles; Microscopy, Electron, Transmission; Neutron Diffraction; Pharmaceutical technology. Pharmaceutical industry; Pharmacology. Drug treatments; Rheology; saponins; Saponins - chemistry; Saponins - isolation & purification; Scattering, Small Angle; Solubility; Surface-Active Agents - chemistry; Surface-Active Agents - isolation & purification; surfactants
• ISSN: 0022-3549; 1520-6017
• DOI: 10.1002/jps.22283

This work reports the physico-chemical characterisation of the micellar structures formed by a saponin fraction obtained from an important South American species, Ilex paraguariensis (mate). The mate saponin-enriched fraction (MSF) mainly comprises triterpenic glycosides and was obtained from mate green fruits through solid-phase extraction. The physico-chemical studies focused on the determination of the critical micellar concentration (CMC), the size and shape of the micelles, using conventional transmission electronic microscopy (TEM), as well as Cryo-TEM, light scattering and small-angle neutron scattering. The rheological behaviour of the solutions up to 4wt% was also determined using a controlled-strain rheometer. Finally, the MSF ability to solubilise poorly water-soluble drugs was assayed using carbamazepine and flurbiprofen as basic and weak acidic drug models. Small spherical micelles of around 20 Å radius were observed in the presence of elongated structures with lengths of more than 500nm, possessing a well-defined CMC of 0.41g/L. MSF solutions ranging from 0.25 to 4% (w/v) demonstrated a viscoelastic behaviour independent of the concentration. MSF could improve the solubility of carbamazepine in the range of 0.13 to 1.5% (w/v)