Hollywood’s best-known cougar sharpened her claws last week, fearing a sex kitten was going to tempt away her man.

Demi Moore, 47, rushed to the set of her much younger husband Ashton Kutcher’s new movie, Friends With Benefits, as he prepared to film a steamy love scene with his gorgeous 28-year-old co-star Natalie Portman.

Fearful of Natalie’s reputation after a string of published reports linking her to taken men – including the then-married Sean Penn, 49, and Black Swan choreographer Benjamin Millepied, 32, who had a girlfriend at the time – Demi clutched Ashton’s arm tightly as she marched him to his trailer.

“Demi is obsessed with the idea that Ashton might stray,” a friend told American magazine Star.

While the actress, dressed in youthful three-quarter-length leggings and a casual navy dress, may have looked a treat, her visit failed to bring a smile to her normally good-natured husband’s face.

Renowned for his cheerful disposition and wisecracking, Ashton had a face like thunder as his wife led him away after filming a scene where his character shared a long and passionate lip-lock with gorgeous Natalie, who is almost 20 years younger than Demi.

To read more about Demi's jealous ways and her plans for a baby at 47 see this week's Woman's Day, on sale May 24, 2010.