Black Currant, 1 lb. The Black Currant fruit have a high natural vitamin C content. Like the other true currants, it is classified in the genus Ribes. In addition to the high levels of vitamin C, studies have also shown concentrated blackcurrant to be an effective Monoamine oxidase inhibitor (Bormann, et al. 1993). Fifty grams of 5.5X concentrate was found to inhibit 92% of the Monoamine oxidase enzymes. Blackcurrant seed oil is a rich source of gamma-linolenic acid (GLA), a very rare essential fatty acid.