A SKIN serum hailed as the "holy grail" of anti-ageing started flying off the shelves yesterday.

Forever Youth Liberator from Yves Saint Laurent had already racked up more than 5,000 pre-orders.

In a trial of 50 women, nine out of ten said their skin looked more luminous after using the lotion, while 72 per cent said fine lines were less visible.

The range contains synthetic versions of glycans, naturally occurring sugars in the skin.

Science writer and broadcaster Vivienne Parry says: "Glycobiology is going to change the world in many areas and it is a very important development in skincare too.

"Glycans are complicated sugars that play a key role in the structure of the skin.

"They also sit on the surface of cells and transmit messages to them. Glycans reduce with age. These glycans can make skin cells act as they would have when in a younger body."

A study of the technique in the journal Technology Review in 2003 said the discovery was "one of the ten emerging technologies that would change the world."

YSL worked with Professor Peter Seeberger, of Germany's Max Planck Institute, to develop the serum.

He said: "I was surprised YSL was interested in my work. I'm interested in health, not face paint. Still, we were able to apply our existing techniques to glycans in skin."