Effects of resveratrol, syringic acid, gallic acid, o-coumaric acid, and rutin on mitochondrial content (a,b) mitochondrial enzyme activities (c,d), and intracellular ATP levels (e) in C2C12 myotubes. C2C12 myotubes were incubated with 50 μM resveratrol, syringic acid, gallic acid, o-coumaric acid, and rutin for 24 h at 37 °C in a humidified 5% CO2 incubator. Representative NAO dye and DAPI staining of the C2C12 myotubes are shown at 200× magnification. For intracellular ATP levels, C2C12 myotubes were incubated with 25 and 50 μM of resveratrol, gallic acid, o-coumaric acid, and rutin for 24 h at 37 °C in 5% CO2 incubator. ATP concentrations were normalized to control. The enzyme activities of citrate synthase and cytochrome c oxidase are expressed as a percentage, with the value of control set at 100%. The reported values are the means ± SD (n = 3). Mean values with different letters were significantly different (p < 0.05).