3-Hydroxybutyric acid (or beta-hydroxybutyrate) is a ketone body. Like the other ketone bodies (acetoacetate and acetone) levels of 3-hydroxybutyrate in blood and urine are raised in ketosis. In humans 3-hydroxybutyrate is synthesized in the liver from acetyl-CoA and can be used as an energy source by the brain when blood glucose is low.

L-(+)-Arabinose inhibits intestinal sucrase activity, thereby reducing sucrose utilization, and consequently decreasing lipogenesis.

4-Methylbiphenyl is an endogenous metabolite.