If you are growing Saponaria officinalis (soapwort) in your alpine garden (it’s a purple, spring-blooming, easy perennial) then you ‘may’ have the beginnings of a slug repellent.
Extract of saponaria was mixed with methanol and brushed on leaves (they used rapeseed plants) and found that slugs avoided the brushed leaves
So what we have here is a need to create a strong saponaria “juice” or simply pick the leaves, brew a strong tea and see what happens with a spray. It may be worth messing about with this if you have a very bad slug problem and the organic iron-based substances (Sluggo etc) don’t work for you
The problem lies in getting enough leaves for the size of your garden and in brewing a strong enough tea. But again, if you’re adventurous and have the plant you just never know
Reported in Annals of Applied Biology from Barone and Frank (Swiss researchers)