Investigation Using DNA Barcoding Confirms Authenticity of Maca Products Sold in China

Reviewed: Chen J-J, Zhao Q-S, Liu Y-L, Zha S-H, Zhao B. Identification of maca (Lepidium meyenii Walp.) and its adulterants by a DNA-barcoding approach based on the ITS sequence. Chin J Nat Med. 2015;13(9):653-659.

The recent surge of maca (Lepidium meyenii, Brassicaceae), particularly in China, has led to large-scale efforts to grow the crop within China, especially in higher elevations in the Yunnan province. Despite the availability of China-grown maca, reports have indicated that materials labeled to contain powdered maca root are partly or entirely substituted with turnip (Brassica rapa, Brassicaceae), radish (Raphanus raphanistrum subsp. sativus, syn. R. sativus, Brassicaceae), potato (Solanum tuberosum, Solanaceae), or corn (Zea mays, Poaceae).¹ The authors evaluated the ITS sequence of maca, corn, potato, radish, turnip, and 15 Lepidium species (the ITS sequences for the four potential adulterants and 15 Lepidium species were obtained from the GenBank database) and found that the genetic variability was high enough to distinguish maca from the other species.

Using the ITS sequence, the authenticity of 43 maca samples was examined, including four powders imported from Peru, eight fresh roots, 12 dried slices, four samples of dried fruit, and 15 tablets originating from different locations in China. The presence of maca was further evaluated by high-performance liquid chromatography (HPLC) analysis of macamides, which are alkylamides characteristic for maca; however, the details of the chemical analysis and its exact results were not provided in the paper. The ITS sequence was successfully extracted and amplified from all the samples, and in every case corresponded to the sequence of authentic L. meyenii.

Comment: The results of this investigation into the authenticity of maca products on the Chinese markets may indicate that adulteration of this popular herb is not widespread, although a larger sample size needs to be assessed for a more definitive conclusion. Care needs to be taken when talking about “potential adulterants,” which, according to the authors, included the 15 Lepidium species where ITS sequences were listed in GenBank. Most of these Lepidium species are not likely to be used as adulterants, since they grow, e.g., in Australia, North America, or Europe, outside the area where maca is typically harvested or sourced. A comparison between this paper and the paper by Han et al. (reviewed above) also reveals differences among DNA barcoding tests, such as the need to rely on different loci to distinguish species, or the use of sequence data from a number of different databases. A harmonization of DNA barcoding practices would be helpful to make it a more consistent approach, and to avoid a proliferation of methods, which is often seen with chemical methods for herbal ingredient analysis, in particular with liquid chromatography.

References

1. Jin W, Zhang Y, Mei S, Xiong Y, Yang Q, Yu L. Identification of Lepidium meyenii (Walp.) based on spectra and chromatographic characteristics of its principal functional ingredients. J Sci Food Agric. 2007;87(12):2251-2258.