title: 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.
abstract: 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 4 wt% 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 500 nm, possessing a well-defined CMC of 0.41 g/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).
authors.affiliation: Faculdade de Farmácia, Universidade Federal do Rio Grande do Sul, Porto Alegre RS, Brazil.
authors.forename: Maria Paula G
authors.initials: MP
authors.lastname: Peixoto
authors.forename: Janine
authors.initials: J
authors.lastname: Treter
authors.forename: Pedro Ernesto
authors.initials: PE
authors.lastname: de Resende
authors.forename: Nádya Pesce
authors.initials: NP
authors.lastname: da Silveira
authors.forename: George G
authors.initials: GG
authors.lastname: Ortega
authors.forename: M Jayne
authors.initials: MJ
authors.lastname: Lawrence
authors.forename: Cécile A
authors.initials: CA
authors.lastname: Dreiss
mesh_terms: D020285:Cryoelectron Microscopy; D005638:Fruit / Q000737:chemistry; D030019:Ilex paraguariensis / Q000737:chemistry*; D008823:Micelles; D046529:Microscopy, Electron, Transmission; D033363:Neutron Diffraction; D012212:Rheology; D012503:Saponins / Q000737:chemistry* / Q000302:isolation & purification; D053838:Scattering, Small Angle; D012995:Solubility; D013501:Surface-Active Agents / Q000737:chemistry* / Q000302:isolation & purification
chemical_list: D008823:Micelles; D012503:Saponins; D013501:Surface-Active Agents