The Naturoli company sells liquid soapnut detergent formulated from soapnuts by their own in-house chemist. I used to sell this liquid detergent.
However, soapnuts are a fruit, and the liquid detergent is thus a fruit juice. Fruit juice needs a preservative if it’s not vacuum packed. Soapnut detergent is not vacuum packed, and even if it was, once opened I would think it would have to be refrigerated. So a little amount of food grade preservative is added to the detergent to keep it fresh.
In a bid to be the most natural possible, a few years ago Naturoli switched to using grapeseed extract as a preservative.
This presents a Kashrus concern. Just like wine needs Kosher supervision, grapeseed extract requires supervision in order to derive benefit from it.
To avoid this concern, we sell the Naturoli soapnut powder which is ground from soapnuts with nothing added. We also sell what is left of our Kosher stock of liquid detergent.