I found a paper in which they synthesize xanthoxin from violaxanthin by incubating this compound with lipoxygenase...no idea about the yield nor the actual procedure. Actually, I also experienced problems in finding violaxanthin. Anyway.
Xanthoxin is availabel in Triveni Interchem Pvt. Ltd., India Contact No is 09227788177. It is available with 25 kg minimum quantity. I have contacted them but they are not sending the quotation for the same. Please contact them and if you purchased please provide me the same of 10 grams.