Cranberry extract is an effective treatment for cystitis in humans as it contains compounds which stop the offending bacteria adhering to the lining of the bladder - they have a similar effect on dental bacteria. I can tell you from personal experience that it does work and there are also studies supporting it's efficacy. I believe some of the compounds are antioxidants (same type as cherries and red wine) so there are indications of anti cancer and cardio-protective properties in humans.
According to James Wellbeloved:
"We add Yucca extract to all our cat products. This is an ingredient that is added as it has a number of potential benefits. Firstly it is a natural deodoriser and can help to reduce faecal odour, which is of benefit to owners whose cats live entirely indoors or use litter trays. It is also a source of saponin and is thought to help flush out pathogenic bacteria from the digestive tract and increase the absorption of nutrients."
