Saponins

Saponins are plant-based compounds with properties similar to soap – they foam in water, cleanse, and emulsify oil into tiny droplets.

To understand how and why they work we’ll have to take a look at their chemical structure.

The molecule of a saponin has two parts: one is an oil-soluble, big, bulky molecule very similar to cholesterol (this one is called a sapogenin or saponin aglycone), while the other part is made of sugars linked together to form a sugar chain attached to the sapogenin. This is very water-soluble, sometimes with multiple sugar chains attached to the sapogenin.

When you put this molecule in the water, it will always orient itself on the surface between water and air (sugar part into the water, sapogenin into the air). The same thing happens in the oil-water emulsion – the molecules of the saponin help to stabilize tiny oil droplets by orienting themselves on the oil-water interface.

If you see this ingredient on your skincare product’s ingredients list, you will most likely not be able to find out exactly which saponins are used, or which plant they were extracted from.

Saponins can be found in many different plants. They get their name from the common soapwort, Saponaria officinalis, whose root contains up to 20% of saponins. The plant can be used to make a gentle cleansing solution.

Another example is the soapbark tree, Quillaia saponaria. The saponins from these plants can be used as cleansers and emulsifying agents. They are safe to use by humans, but are toxic to fish and other aquatic animals in high concentrations.

Several saponins have unique biological activities, such as ginsenosides from ginseng root (anti-inflammatory), glycyrrhizin from licorice root (anti-inflammatory and sweet-tasting), aescin from horse chestnut seeds (strengthens capillary walls), asiaticoside from Gotu kola (wound healing and anti-wrinkle), or calendulosides from marigold flowers (wound healing and soothing).

Their properties are so unique that they will be probably written on the label separately.