Lipoic acid absorption maximum

Another result of the ring strain is that the reduction potential E° (pH 7, 25°C), is -0.30 V, almost the same as that of reduced NAD (-0.32V). Thus, reoxidation of reduced lipoic acid amide by NAD+ is thermodynamically feasible. Yet another property attributed to the ring strain in lipoic acid is the presence of an absorption maximum at 333 nm. 

---