Miscibility ofQuillajaSaponins with other Co-surfactants under Different pH Values

Development of a water-in-oil-in-water adjuvant for foot-and-mouth disease vaccine based on ginseng stem-leaf saponins as an immune booster

There has been an increasing interest in finding new formulations that qualify as vaccine adjuvants, which must be safe, stable, and have the capacity to stimulate a strong immune response. In this study, a basic formulation of a water-in-oil-in-water (W/O/W) adjuvant CV13 was developed, and ginseng stem-leaf saponins (GSLS) were added as an immune booster into oil phase. The physicochemical properties of the adjuvant were tested. Furthermore, the immune activity and the adjuvant effects, as indicated by the foot-and-mouth disease virus (FMDV) antigen were evaluated. The results showed that CV13 was similar in appearance to ISA 206 and could package FMDV antigen into a stable W/O/W emulsion. The FMD vaccine prepared with CV13 alone or CV13 containing GSLS achieved pharmaceutical characteristics comparable to a vaccine prepared with ISA 206, moreover the structural stability of the CV 13 vaccine was found to be better. Mice that were immunized with the FMD vaccine prepared with CV13 containing GSLS presented a significantly higher LPBE antibody titer and splenocyte proliferation rate than those immunized with a vaccine prepared with CV13 alone (p < 0.05). In addition, there was no significant difference between the groups that were immunized with FMD vaccine prepared with CV13 containing GSLS and ISA206 in terms of cellular and humoral immune response. In this paper, CV13 containing GSLS shows excellent immunologic adjuvant effect in mice model, and this new adjuvant may provide a potential choice for FMD vaccine production in the future.

Formation and stability of emulsions stabilized by Quillaja saponin-egg lecithin mixtures

Knowledge of binary emulsifiers' influence on the formation and stability of emulsion-based products is still limited. The aim of this study was to investigate the emulsifying properties of Quillaja saponin-egg lecithin mixtures at different concentration ratios (r = 5:0, 4:1, 3:2, 2:3, 1:4, and 0:5) with total emulsifier concentration set to 0.5% or 1.0% (w/w). For this, oil-in-water emulsions (10% oil, pH 7) were prepared via high-pressure homogenization. Furthermore, emulsion stability against different environmental stresses was tested. All the binary emulsifier mixtures formed submicron sized emulsions upon homogenization. The most stable emulsions among the mixed emulsifiers were obtained at low Quillaja saponin concentration at r = 1:4 that showed similar physical stability over time to emulsions stabilized by Quillaja saponins and egg lecithin alone. The data suggested that the mixtures of Quillaja saponins and egg lecithins built mixed interfacial layers that were prone to changes over time. Emulsions stabilized by the binary mixtures were in general less stable against changes in pH and ionic strength than the emulsions stabilized by the individual emulsifiers. An exception were the emulsions at r = 1:4 that showed improved stability at pH 2 over the phase separated Quillaja saponin-stabilized emulsions at the same pH. Moreover, all the emulsions were heat stable up to 90 °C. On the other hand, none of the emulsions were stable upon freeze-thawing. These results increase our understanding of technofunctionality of binary emulsifier systems. PRACTICAL APPLICATION: Food-grade and natural emulsifier mixtures composed of Quillaja saponins and egg lecithin may be used in selected emulsion-based food or personal care product applications to replace synthetic surfactants due to issues with consumer acceptance and regulatory restrictions.

Formation and Stability of Emulsions Prepared with a Water-Soluble Extract from the Microalga Chlorella protothecoides

Unicellular microalgae are a valuable source of macro- and micronutrients. They contain, for example, proteins that are potentially useful as new emulsifiers. The aim of this study was to investigate the emulsifying properties of a less-refined lyophilized crude water-soluble extract (WSE), obtained from the heterotrophically cultivated microalga Chlorella protothecoides. Interfacial tension measurements indicated that mainly the proteins in the extract showed interfacial activity. O/W emulsions were prepared by high-pressure homogenization (1 000 bar, 3 passes) with 5.0 wt % of oil and 2.5 wt % of protein from Chlorella protothecoides, resulting in emulsions having a volume-based mean droplet diameter of d₄₃ ≤ 1 μm and being stable for at least 7 days. Two different stress tests showed that ( i) protein-stabilized emulsions were resistant to very high salt concentrations (up to 500 mM NaCl), and ( ii) emulsions were stable over a very broad pH range of 2-9, with only minor changes in the particle size d₄₃ (e.g. with an increase of only 300 nm when the pH was lowered from 5 to 4) compared to whey protein-stabilized emulsions. All WSE emulsions had monomodal particle size distributions and were macro- and microscopically stable during a storage of up to 7 days. The results indicate that the WSE of Chlorella protothecoides has remarkably good emulsifying properties and might be of use as a new emulsifier in various applications in which emulsions are exposed to a broad range of ionic strengths and pH values.

Foamy matters: an update on Quillaja saponins and their use as immunoadjuvants

Immunoadjuvant Quillaja spp. tree saponins stimulate both cellular and humoral responses, significantly widening vaccine target pathogen spectra. Host toxicity of specific saponins, fractions and extracts may be rather low and further reduced using lipid-based delivery systems. Saponins contain a hydrophobic central aglycone decorated with several sugar residues, posing a challenge for viable chemical synthesis. These, however, may provide simpler analogs. Saponin chemistry affords characteristic interactions with cell membranes, which are essential for its mechanism of action. Natural sources include Quillaja saponaria barks and, more recently, Quillaja brasiliensis leaves. Sustainable large-scale supply can use young plants grown in clonal gardens and elicitation treatments. Quillaja genomic studies will most likely buttress future synthetic biology-based saponin production efforts.

Quillaja Saponin Characteristics and Functional Properties

Consumer concerns about synthetically derived food additives have increased current research efforts to find naturally occurring alternatives. This review focuses on a group of natural surfactants, the Quillaja saponins, that can be extracted from the Quillaja saponaria Molina tree. Quillaja saponins are triterpenoid saponins comprising a hydrophobic quillaic acid backbone and hydrophilic sugar moieties. Commercially available Quillaja saponin products and their composition and properties are described, and the technofunctionality of Quillaja saponins in a variety of food, cosmetic, and pharmaceutical product applications is discussed. These applications make use of the biological and interfacial activities of Quillaja saponins and their ability to form and stabilize colloidal structures such as emulsions, foams, crystallized lipid particles, heteroaggregates, and micelles. Further emphasis is given to the complexation and functional properties of Quillaja saponins with other cosurfactants to create mixed surfactant systems, an approach that has the potential to facilitate new interfacial structures and novel functionalities.

Improving emulsion formation, stability and performance using mixed emulsifiers: A review

The formation, stability, and performance of oil-in-water emulsions may be improved by using combinations of two or more different emulsifiers, rather than an individual type. This article provides a review of the physicochemical basis for the ability of mixed emulsifiers to enhance emulsion properties. Initially, an overview of the most important physicochemical properties of emulsifiers is given, and then the nature of emulsifier interactions in solution and at interfaces is discussed. The impact of using mixed emulsifiers on the formation and stability of emulsions is then reviewed. Finally, the impact of using mixed emulsifiers on the functional performance of emulsifiers is given, including gastrointestinal fate, oxidative stability, antimicrobial activity, and release characteristics. This information should facilitate the selection of combinations of emulsifiers that will have improved performance in emulsion-based products.

Sugar Beet Extract (Beta vulgaris L.) as a New Natural Emulsifier: Emulsion Formation

The interfacial and emulsion-forming properties of sugar beet extract (Beta vulgaris L.) were examined and compared to a Quillaja extract that is widely used within the food industry. We investigated the influence of extract concentration on surface activity at oil-water and air-water interfaces and on the formation of oil-in-water emulsions (10% w/w, pH 7). Sugar beet extract reduced the interfacial tension up to 38% at the oil-water interface, and the surface tension up to 33% at the air-water surface. The generated emulsions were negatively charged (ζ ≈ -46 mV) and had the smallest particle sizes (d₄₃) of ∼1.3 μm at a low emulsifier-to-oil ratio of 0.75:10. Applying lower or higher extract concentrations increased the mean particle sizes. The smallest emulsions were formed at an optimum homogenization pressure of 69 MPa. Higher homogenization pressures led to increased particle sizes. Overall, sugar beet extract showed high surface activity. Furthermore, the formation of small emulsion droplets was successful; however, the droplets were bigger compared to those from the Quillaja extract. These results indicate sugar beet as an effective natural emulsifier that may be utilized for a variety of food and beverage applications.

Saponins - Self-assembly and behavior at aqueous interfaces

Saponins are interfacially active ingredients in plants consisting of a hydrophobic aglycone structure with hydrophilic sugar residues. Variations in aglycone structure as well as type and amount of sugar residues occur depending on the botanical origin. Saponins are a heterogeneous and broad class of natural substances and therefore the relationship between molecular structure and interfacial properties is complex and, yet, not completely understood. A wide range of research focused either on structural elucidation of saponins or interfacial properties. This review combines recent knowledge on structural features with interfacial properties and draws conclusions on how saponin structure affects interfacial properties. Fundamental understanding on interfacial configuration of individual saponin molecules at the interface distinctly increased. It was shown that interfacial configuration may differ depending on botanical origin and thus structure of the saponins. The formation of strong viscoelastic interfacial films by some saponins was attributed to hydrogen bonds between neighboring sugar residues. Few studies analyzed the relationship between botanical origin and interfacial rheology and derived main conclusions on important structural features. Saponins with a triterpenoid structure are most likely to form viscoelastic films, which result in stable foams and emulsions. The aglycone subtype may also affect interfacial properties as triterpenoid saponins of oleanane type formed most stable interfacial networks. But for more reliable conclusions more saponins from other aglycone subtypes (dammarane, ursolic) have to be analyzed. To-date only extracts from Quillaja saponaria Molina are approved for food products and many studies focused on these extracts. From experiments on interfacial rheology a reasonable model for supramolecular structure of Quillaja saponins was developed. It was further shown that Quillaja saponins may form micelles loaded with hydrophobic substances, nano-emulsions and stable foams. In combination proteins an increase in interfacial film stability may be observed but also negative phenomena like aggregation of oil droplets in emulsions may occur.