I agree with Dave about sphingolin. It seems to be a product extracted from cow brains which is advocated on many comp/alt med sites. The biggest risk with it is that if any of those cows were infected with the pathological form of prion protein (none of the comp/alt sites comment on whether this has been tested), it will kill you. There is nothing in any serious site (eg, PubMed) which suggests that sphingolin is of any clinical benefit. I would not touch it with the proverbial barge-pole.

Inosine is less clear. It is a nucleoside which is usually made from another nucleoside called adenosine. There are (very rare) conditions in which it may be indicated but if they do not apply to you and if you eat in a healthy way (your GP should be able to help here), I see no reason to eat it. Unless the evidence suggests otherwise, I think it a waste of money.