Macamides present in the commercial maca (Lepidium meyenii) products and the macamide biosynthesis affected by postharvest conditions

Macamides are bioactive and marker compounds of maca (Lepidium meyenii). Thirty-five commercial maca products were surveyed for macamide composition and content by HPLC-UV/MS. Significant variations of macamide content were found in these products (69-2738 g/g). Analysis of the macamide biosynthetic pathway suggests that: (a) glucosinolate catabolism, (b) lipid hydrolysis, and (c) amide formation are key steps controlling macamide accumulation in the tissues during the postharvest drying process. Therefore, we further investigated the effects of sample forms, drying temperatures, and storage times on macamide accumulation. Our results show that (1) powdered maca provided the largest macamide accumulation followed by sliced hypocotyls, while whole roots displayed a significantly reduced amide-generating potential; (2) the ideal temperature for macamide formation is about 30 degrees C; (3) macamide content increases continuously along with storage time; (4) exposure to air results in the percentage of unsaturated macamides decreasing. These findings provide useful insights which can be applied in the industrial manufacture of maca products with higher content of bioactive amides.