mRNA Expression Signatures of Human Skeletal Muscl... [Cell Metab. 2011] - PubMed result
"A natural compound enriched in apples, ursolic acid reduced muscle atrophy and stimulated muscle hypertrophy in mice. It did so by enhancing skeletal muscle insulin/IGF-I signaling and inhibiting atrophy-associated skeletal muscle mRNA expression. Importantly, ursolic acid's effects on muscle were accompanied by reductions in adiposity, fasting blood glucose, and plasma cholesterol and triglycerides. These findings identify a potential therapy for muscle atrophy and perhaps other metabolic diseases."
I remember trying to find a good ursolic acid supplement several years ago (without success) and I don't recall now why I wanted to try it.
Doesn't seem to be any more now than there were then.