MAO inhibitor

9-Me-BC is a β-carboline — the same tryptophan-derived ring system found in cooked meat, coffee and tobacco smoke, and in human blood and brain. Most members of that family damage dopaminergic neurons, which is why they have been investigated as causes of Parkinson's disease; 9-Me-BC does the opposite in cell culture and in one rat study, raising tyrosine hydroxylase, inducing neurotrophic factors and restoring dopamine after a neurotoxin. Ten days of treatment also improved maze learning in rats and thickened dendrites in the dentate gyrus. No human has been studied at any dose.

Selegiline (L-deprenyl) is an irreversible MAO-B inhibitor created in Joseph Knoll's Budapest laboratory in the 1960s and prescribed for Parkinson's disease and, as a skin patch, for major depression. In early Parkinson's disease 10 mg a day delayed the need for levodopa by about nine months, though whether that was protection or symptom relief was never settled; the patch beat placebo modestly in adult depression and not at all in adolescents. It is broken down to l-methamphetamine and l-amphetamine. Its reputation as an anti-aging drug rests on rat longevity studies that replicated inconsistently, and a Cochrane review found no clinically meaningful benefit in Alzheimer's disease.