Identification of Sarmentosin as a Key Bioactive from Blackcurrants (Ribes nigrum) for Inhibiting Platelet Monoamine Oxidase in Humans.

Previous clinical studies indicate that monoamine oxidase-B (MAO-B) inhibition by blackcurrants must be predominantly attributed to bioactives other than anthocyanins. In this natural products discovery study, MAO-A/B inhibitory phytochemicals were isolated from blackcurrants, and a double-blind crossover study investigated the efficacy of freeze-dried whole-fruit blackcurrant powder in inhibiting MAO-B compared with blackcurrant juice in healthy adults. Platelet MAO-B inhibition was comparable between powder (89% ± 6) and juice (91% ± 4), and it was positively correlated with MAO-modulated plasma catecholamines, subjective alertness, and reduced mental fatigue, assessed using the Bond-Lader questionnaire. Sarmentosin, a nitrile glycoside, and its hydroxycinnamoyl esters were identified as novel MAO-A/B inhibitors from blackcurrant in vitro, and sarmentosin was demonstrated to inhibit platelet MAO-B activity in vivo. These findings confirm sarmentosin as the primary bioactive for MAO-A/B inhibition in blackcurrants, as well as its bioavailability and stability during freeze-drying, and suggest that consuming blackcurrant powder and juice may positively affect mood in healthy adults.