Evaluation of foam properties of saponin from Ilex paraguariensis A. St. Hil. (Aquifoliaceae) fruits

Gizele Scotti Do Canto,Gustavo Luís Borré,Janine Treter,George González Ortega,Maria Paula Garofo Peixoto,Samanta Yang

doi:10.1590/s1984-82502010000200010

Gizele Scotti Do Canto, Gustavo Luís Borré + Show 4 more

Open Access

https://doi.org/10.1590/s1984-82502010000200010

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Abstract

Saponins are natural compounds able to form abundant foam, a desirable quality required in some chemical, foods, cosmetic and pharmaceutical processes. Ilex paraguariensis A. St. Hil. (Aquifoliaceae) known as mate, is a South American widely cultivated specie due to the preparation of a tea-like beverage from its leaves. Moreover, its green fruits are a rich source of non-toxic and very low haemolytic saponins. In this study, mate saponin fraction (MSF) was evaluated as a foam former, focusing on its foamability, foam lifetime, and film drainage in the presence of different electrolytes (ionic strength I = 0.024 M). Sodium dodecyl sulphate (SDS) and polysorbate 80 (Poly-80) were used as reference surfactants. The critical micelle concentration (CMC), the minimum attainable surface tension (γCMC), surface excess concentration (Γ) and cross-section molecular surface (A) values of MSF were comparable to those of Poly-80. The foamability of MSF and both reference surfactants was equivalent. The addition of MgCl2 resulted in a negative effect on MSF foamability. The salts NaCl, KBr, and KNO3 exhibited a negative influence on MSF foam lifetime. Similar behavior was observed for MSF film drainage (order of activity: Na2HPO4 > MgCl2 ≈ NaCl ≈ KNO3 > KBr), where a primary fast film drainage rate was followed by film thinning stabilization after around 5 min. The behavior described above seems to be uncorrelated to the solutions' zeta potential.

Highlights

The present study aimed to evaluate the foam produced by an enriched mate saponin fraction, and to compare it to sodium dodecyl sulfate and polysorbate 80, chosen as ionic and non-ionic reference surfactants, respectively
The calculated MSF molecular cross-section (97.7 Å2) was comparable to the value reported for quilaja saponins (83 Å2), considered an unexpectedly high diameter given its hydrophilic sugar chains (Mitra, Dungan, TABLE I - Critical micelle concentration (CMC), minimum attainable surface tension, surface excess concentration (G) and molecular cross-section (A) determined for sodium dodecyl sulfate (SDS), polysorbate 80 (Poly-80) and mate saponin fraction (MSF) solutions
Studies on foam obtained from saponins are scarce, this class of natural biodegradable product is emerging as a workable alternative to synthetic surfactants

Summary

Introduction

The Brazilian crop of mate leaves attains approximately half a million tons per year (Mosele, 2002), not including mate fruits, which are discarded as a byproduct of the erva-mate production process. The stimulant action on the central nervous system of mate leaves is well established and is ascribed to their high methylxanthines content (Wichtl, 1989). The highest saponin content occurs in the unripe mate fruits rather than in its leaves or other aerial parts (Pavei, 2004). Mate saponins are bidesmosidic and monodesmosidic compounds with a prevalence of non-ionic triterpenic derivates of ursolic and oleanolic acids (Kraemer et al.,1996; Taketa, 2001; Pavei, 2004)

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