Methoxycinnamidopropyl Hydroxysultaine

A colorless, odorless liquid that works as a water-soluble UVB filter with a peak protection of 306 nm. Chemical sunscreen agents are typically oil-soluble so being water-soluble is unique and it makes it possible to create cosmetically elegant, non-oily, non-tacky, silky and smooth feeling formulas. It is also used as a color protectant in hair care formulations.

We could not figure out its regulatory status as a sunscreen agent, though. Its manufacturer only says it's registered "as a new cosmetic ingredient in the EU", but it is probably not an officially approved sunscreen filter (yet).