A chemically chopped up version of normal yeast extract that works as a skin moisturizer.
It often comes to the formula as part of a moisturizing, skin smoothing complex trade named Optim Hyal. Combined with polyglucuronic acid and some helper ingredients the complex is obtained by bio-fermentation and - according to the manufacturer - it can stimulate the hyaluronic acid synthesis in the skin. (It does that by containing so-called Glycokines, specific signaling oligosaccharides that mimic the hyaluronic acid fragments in the skin.) And more hyaluronic acid means smoother, better moisturized and more supple skin.