Macamides are characteristically
found in maca (Lepidium meyenii Walper).
Fatty acid derivatives
are also an important type of constituent in maca, since they not
only relate to the biosynthesis of macamides in the postharvest process
but also possess some bioactivities. To study their comprehensive
profiles in maca tubers processed via the air-drying method, ultraperformance
liquid chromatography quadrupole time-of-flight mass spectrometry
(UPLC-QTOF-MS) analyses were performed to identify macamide and fatty
acid molecules. Their contents in maca tubers that were processed
via air drying and freeze drying, respectively, were further quantified
using high-performance liquid chromatography (HPLC) analyses comparing
with eight macamide and three fatty acid reference standards. A total
of 19 macamides (including four novel ones) and 16 fatty acid derivatives
(two found in maca for the first time) were identified. Quantification
analyses results showed the eight macamides with contents ranging
from 31.39 to 1163.19 μg/g (on dry tuber), and fatty acids from
18.71 to 181.99 μg/g in the air-dried maca, but there were only
three macamides and one fatty acid detected with very low contents
(3.97–34.36 μg/g) in the freeze-dried maca. The results
demonstrated that the air-drying method can increase the accumulations
of macamides and fatty acids in the metabolism of maca in the postharvest
process. The biosynthesis of two types of macamides, i.e., N-benzyl-oxo-octadecadienamides and N-benzyl-oxo-octadecatrienamides,
was further elucidated in detail. These results provide more valuable
insights into the phytochemicals of maca, which is helpful to explain
its health benefits.
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