ALA is commonly found in dietary components such as
vegetables (spinach, broccoli, tomato) and meats, mainly
viscera and also in many dietary supplements. ALA can be
also synthesized through enzymatic reactions in plants and
animals’ mitochondria from octanoic acid and cysteine (as
a sulfur donor) [17,18]. As a sulfur containing substance,
ALA is considered a thiol compound. Mammalian cells can
synthesize ALA through the action of mitochondria lipoic
acid synthase (LASY) which can be down-regulated in
different clinical conditions [18].
ALA exists in two enantiomeric (optical isomers) forms,
R and S, (Figure 1) being the R isoform an essential cofactor
for mitochondrial enzymes of oxidative metabolism since
it is joined in amide linkage to €-amino group of lysine
residues (lipoamide) [17]. The following enzymes use
R-ALA as a cofactor: pyruvate dehydrogenase (PDH),