Nicotinamide-adenine dinucleotide phosphate, reduced (NADPH) is the reduced form of the electron acceptor NADP+ and acts as an electron donor in various biological reactions. In plants, NADPH is produced by ferredoxin-NADP+ reductase in the last step of the electron chain during photosynthesis. In animals it is predominantly produced by the pentose phosphate pathway, but it is also generated by key mitochondrial enzymes. NADPH provides the reducing equivalents for biosynthetic reactions and the oxidation-reduction involved in protecting against the toxicity of reactive oxygen species. It is also used for the synthesis of lipids and cholesterol and during the process of fatty acid chain elongation. β-Nicotinamide adenine dinucleotide 2′-phosphate (NADP+) and β-Nicotinamide adenine dinucleotide 2′-phosphate, reduced (NADPH) comprise a coenzyme redox pair (NADP+:NADPH) involved in a wide range of enzyme catalyzed oxidation reduction reactions. The NADP+/NADPH redox pair facilitates electron transfer in anabolic reactions such as lipid and cholesterol biosynthesis and fatty acyl chain elongation. The NADP+/NADPH redox pair is used in a variety of antioxidation mechanism where it protects agains reactive oxidation species accumulation. NADPH protects against redox stress by providing reducing equivalents to antioxidants such as glutathione and thioredoxin. NADPH levels decline with aging in several tissues, but whether this is a major driving force for the aging process has not been well established. Both NADPH and NAD+ have been reported to have potent neuroprotective effects against ischemic neuronal injury. The combination of NADPH and NAD+ may provide a novel effective therapy for ischemic stroke.