I believe that 90% of all ascorbic acid is made in the lab from corn starch. I know a lot of companies put on the label no corn, but what they are saying there is no physical corn. So if says ascorbic acid as the main ingredient then its synthetic.
After learning about this and reading about how synthetic vitamins are made, I switch to natural forms of c like Camu Camu Berries powder from The Synergy Company which has about 600mg of powder per 1/4 teaspoon. But when a lab measures it they can only record ascorbic acid not the other forms of c. The Dr. who discovred vitamin C recommend nevering taking this in an isolated form and This Dr. was before Linus Pauling. I have also added 1500mg of Rosehips to my daily C intake and along with adding Goji Berries to my protein drinks. I believe your body knows what to do with whole foods compared to isolates otherwise the creator would have made ascorbic acid powder for us!