Glycerin can be dissolved into water or alcohol, but not oils. On the other hand, many things will dissolve into glycerin easier than they do into water or alcohol. So it is a good solvent. Glycerin is also highly "hygroscopic" which means that it absorbs water from the air.
Because alpha-lipoic acid is an unproven treatment, there is no established dose. However, studies have used between 600-1,200 milligrams daily for diabetes and neuropathy; one review concluded that the evidence is convincing for the use of 600 milligrams daily for three weeks on symptoms of diabetic neuropathy.