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In response to increasing natural surfactant demand and environmental concerns, natural plant-based surfactants have been replacing synthetic ones. Saponins belong to a class of plant metabolites with surfactant properties that are widely distributed in nature. They are eco-friendly because of their natural origin and biodegradable. To date, many plant-based saponins have been investigated for their surface activity. An overview of saponins with a particular focus on their surface-active properties is presented in this article. For this purpose, works published in the past few decades, which report better surfactant relevant properties of saponins than synthetic ones, were extensively studied. The investigations on the potential surfactant application of saponins are also documented. Moreover, some biological activities of saponins such as antimicrobial activity, antidiabetic activity, adjuvant potentials, anticancer activity, and others are reported. Plants rich in saponins are widely distributed in nature, offering great potential for the replacement of toxic synthetic surfactants in a variety of modern commercial products and these saponins exhibit excellent surface and biological activities. New opportunities and challenges associated with the development of saponin-based commercial formulations in the future are also discussed in detail.

Design and synthesis of enzyme mimic with programmed molecular interaction among several building blocks including metal complexes and metal chelators is of intellectual and practical significance. The preparation of artificial enzymes that mimic the natural enzymes such as hydrolases, phosphatases, etc. remains a great challenge in the field of supramolecular chemistry. Herein we report on the design and synthesis of asymmetric (nonsymmetric) supermolecules by the 2:2:2 self-assembly of an amphiphilic zinc(II)−cyclen complex containing a 2,2′-bipyridyl linker and one long alkyl chain (Zn 2 L 3 ), barbital analogues, and Cu 2+ as model compounds of an enzyme alkaline phosphatase that catalyzes the hydrolysis of phosphate monoesters such as mono(4nitrophenyl)phosphate at neutral pH in two-phase solvent system (H 2 O/CHCl 3 ) in pH 7.4 and 37 °C. Hydrolytic activity of these complexes was found to be catalytic, and their catalytic turnover numbers are 3−4. The mechanistic studies based on the UV/vis and emission spectra of the H 2 O and CHCl 3 phases of the reaction mixtures suggest that the hydrophilicity/ hydrophobicity balance of the supramolecular catalysts is an important factor for catalytic activity.

The effect of β-sitosteryl sulfate (PSO 4) on the liposomal size, stability, fluidity, and dispersibility of DPPC liposomes prepared by vortex mixing, bath-sonication, and probe-sonication has been studied. PSO 4 significantly decreases the particle size of the multilamellar liposomes (MLVs). The sizes of the vortexmixed and the bath-sonicated liposomes vary as a function of PSO 4 concentration. On the other hand, PSO 4 has only little effect on the particle sizes of probe sonicated liposomes. In some cases, the liposomal stability at higher PSO 4 concentrations depends on the preparation method. PSO 4 improves the dispersibility of the DPPC liposomes and enhances their hydration. It also increases the fluidity of the liposomes prepared by each method. Our results suggest that liposomes consisting of DPPC and PSO 4 can be suitable as a cosmetic or pharmaceutical ingredient for the effective delivery of the active components into the body.

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The micellar solution and the lyotropic liquid crystalline phases formed by gemini surfactants containing morpholinium headgroups are investigated for their self-aggregation and physicochemical properties in water. These gemini surfactants demonstrated good surface activity because they are able to undergo micellization at lower concentration and form nanosized micellar aggregates in dilute aqueous solution. The binary mixture of the morpholinium gemini surfactant–water system is investigated over a wide range of concentrations. The micellar solution of the morpholinium gemini surfactants demonstrated Newtonian fluidlike behavior between 10 and 50 wt % as the observed viscosities were independent of the applied shear rate. At higher concentration, morpholinium geminis formed self-assembled lyotropic phases in water. These liquid crystalline phases were characterized by small-angle X-ray scattering and polarized optical microscopy techniques.

We investigated the hydration behavior of dipalmitoylphosphatidylcholine (DPPC) bilayers containing sodium β-sitosteryl sulfate (PSO). PSO was found to enhance hydration in the headgroup region of DPPC bilayers. Therefore, with the incorporation of PSO into DPPC membranes, the amount of water required to reach the fully hydrated state was enhanced as indicated by the constant values of the main phase transition temperature (T) and the bilayer repeat distance (d). For example, with the addition of 20 mol% of PSO, the saturation point was shifted to ~70 wt% water compared to ~40 wt% for pure DPPC and 47 wt% for DPPC-cholesterol. The effectiveness of PSO in fluidizing the membrane and enhancing its hydration state can be useful in the pharmaceutical and cosmetic industries.