Preliminary assay for extraction of saponins from Styrax Officinalis and characterization of emulsifying properties of their extract

Abstract

An extraction protocol for saponins of Styrax Officinalis plant was adopted, modified and successfully applied. The extract obtained was tested by stabilizing Oil-in-Water emulsions. Ethanol extraction and successful one-step partial purification using AB-8 adsorption column chromatography yielded positive colorimetric (Vanillin – Sulfuric Acid) TLC results. The 3D structure of the four Styrax Officinalis saponins reported in the literature were rendered for the first time, and their partitioning properties exclusively acquired using Marvin Sketch chemical drawing software. 10% w/w Sunflower Oil emulsions were prepared using our Styrax saponins extract and their properties compared to similar emulsions stabilized by analytical grade Acacia Gum. The saponins extract outperformed the Acacia Gum by making much smaller (180 ~ 900 nm compared to 5 ~ 1 μm for Acacia) and lower charged particles (ζ-potential ~ - 90mV) as measured by Dynamic Light Scattering. However, Styrax emulsion particles showed bimodal distribution and broader particle size DLS peaks (PDI ~ 0.4, compared to PDI ~ 0.1 for Acacia Gum). These results can be linked to the fact that the Styrax extract contains four different saponins as reported in the literature, each with its own emulsification properties. An attempt at assessing the antioxidant effect of the saponin extract of styrax and acacia gum on oil particles was made using the Rancimat method (accelerated ageing test). The preliminary results obtained showed that the Styrax extract would have good encapsulating effect on the droplets yielding by longer induction times. However the induction times obtained had no direct correlation with emulsifier concentration. The oxidative stability experiments of Styrax Officinalis saponins are worth further investigations.