It's like vitamin C as a substance should not be capitalized but all words in a brand name of a product such as Chewable Vitamin C or Vicks Vitamin C Drops should be capitalized.

Should chemical names be capitalized?

Chemical names

The names of chemicals are not capitalized unless they are the first word of a sentence. In such a case, the first letter of the syllabic portion is capitalized, not the descriptor or prefix. Note that prefixes such as Tris- and Bis- (which are not commonly italicized) are considered part of the name.

Should products be capitalized?

In the content marketing world, that means any brand names or product names should be capitalized, unless of course, the company has a registered trademark style of lowercase, like “iPod.”