Sapindus, saponins, toxicity & why nature isn’t always best

horsechestnuts aesculus hippocastanum fruit
Aesculus hippocastanum, more commonly known as the horse chestnut. Contains high concentrations of the saponin aescin, which has proved useful in the treatment of inflammatory and venous ailments.

After yesterday’s post about sapindus and soap nuts, I thought it important to write a short aside about why natural is not always best, even if this runs contrary to the modern mantra. Yesterday evening, I received a message from a dear friend of mine, who also happens to be a biophysicist.

Whilst I knew that saponins were renowned for their frothing properties, I was not familiar with some of their other attributes. As my friend put it, saponins are made up of amphiphilic molecules – half of the molecule likes to be in water, whilst the other likes to be in lipids. This allows them to solubilize lipids and oils, cleaning up grease”. Great. What these chemicals are also capable of doing, however, is destroying cells by altering their membranes. As said friend affirms, “they are probably used by the plant in defence against bacteria and fungi” and, like other soap-like chemicals, are a bit toxic to the environment. In fact, so effective are some saponins at killing fish, that they are employed by indigenous peoples for fishing to this day, in places ranging from Guyana to the Indian subcontinent.

So where does this leave us on the subject of soap nuts as an alternative to washing detergent? Well, firstly, I would be interested in running a comparative toxicity test to determine whether all things are equal. Presuming that they are, as my friend says, I can still see advantages in soap nuts, not only for their affordability, but also for their reduction in processing, packaging, and the possibility of composting them once spent. I presume that not all saponins are made equal, and that interesting, more local alternatives could be found in soapwort, saponaria officinalis, or the humble horse chestnut, aesculus hippocastanum (yes, I was glad to find out that they were good for something, too!). So I have some experimenting to do.

Despite issues with toxicity, saponins do have their uses as short-term, external treatments to some ailments, as well as being useful for cleaning. For instance, horse chestnut can also be used in the treatment for inflammation, varicose veins, and chronic venous insufficiency, due to its aescin content. Aescin is a saponin renowned for its anti-inflammatory, vasoconstrictor and vasoprotective qualities. Happily, these effects have been noted in high-quality clinical trials, demonstrating “definite clinical benefit in patients with clinical conditions resulting in CVI, haemorrhoids or peripheral oedema formation”. It looks like I have some more experimenting to do, but I am happy to continue using soap nuts in the interim.

For those interested, you can pick up your own bag of soap nuts here.


One thought on “Sapindus, saponins, toxicity & why nature isn’t always best

  1. Hi,
    Thank you for your interesting article.

    I am curious as to the environmental impact of using
    saponins soap nuts add washing machine detergent particularly regarding fish.

    Any update to what you’ve found out?

    Kind regards,

    Liked by 1 person

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