Ginkgo BilobavsSAMe

Ginkgo biloba extract (EGb 761) contains flavonoids (quercetin, kaempferol, isorhamnetin) and terpenoids (ginkgolides A, B, C, J and bilobalide). The flavonoids are potent antioxidants that scavenge superoxide, hydroxyl radicals, and peroxynitrite, and protect neurons from oxidative damage; they may also chelate iron. The terpenoids (ginkgolides and bilobalide) improve blood flow by antagonizing platelet-activating factor (PAF) at the PAF receptor, which reduces platelet aggregation, blood viscosity, and improves microcirculation in the brain. Bilobalide protects mitochondria and reduces apoptosis. Ginkgo modulates nitric oxide (NO) availability via endothelial nitric oxide synthase (eNOS) for vasodilation. It inhibits monoamine oxidase A and B (MAO-A, MAO-B), mildly elevating dopamine and serotonin. It may enhance cholinergic transmission and reduce amyloid aggregation.

SAMe serves as the principal methyl donor in over 100 transmethylation reactions catalyzed by SAM-dependent methyltransferases. In the brain, it donates methyl groups to phosphatidylethanolamine N-methyltransferase (PEMT), converting PE to phosphatidylcholine and maintaining neuronal membrane fluidity critical for receptor function. It methylates DNA via DNMT enzymes, modulating gene expression epigenetically. SAMe is essential for catechol-O-methyltransferase (COMT) activity, which metabolizes dopamine and norepinephrine, and for phenylethanolamine N-methyltransferase (PNMT), which converts norepinephrine to epinephrine. It feeds the transsulfuration pathway, producing cysteine via cystathionine beta-synthase (CBS) and cystathionine gamma-lyase, ultimately supporting glutathione synthesis for antioxidant defense. SAMe also donates methyl groups for myelin basic protein methylation, essential for myelin sheath integrity and nerve conduction velocity.