Macroscopic Analysis of Commercial Supplies of Seeds and Fruits Used in Traditional Chinese Medicine

Reviewed: Van der Valk JMA, Leon CJ, Nesbitt M. Macroscopic authentication of Chinese materia medica (CMM): A UK market study of seeds and fruits. J Herbal Med. 2017;8:40-51.

Keywords: Astragalus complanatus, Carpesium abrotanoides, fruit, macroscopic analysis, seed, traditional Chinese medicine, Ziziphus jujuba var. spinosa

In this study, 23 fruit or seed samples listed in the Chinese Pharmacopoeia and regularly used in traditional Chinese medicine (TCM) were macroscopically evaluated for identity and purity. A total of 211 samples representing the 23 species were obtained from commercial suppliers in the United Kingdom, and were compared to vouchered TCM reference drugs at the herbarium of the Royal Botanical Garden, Kew, UK, other herbarium specimens, and drawings in the published literature.

The species selection was based on answers from a use questionnaire by British herbal practitioners and criteria established by the authors, such as fruit/seed size <10 mm. To complement the identification expertise of the authors, each sample was also compared to specimens deposited in Kew’s vouchered TCM materia medica reference collection and in other herbaria, and to TCM identification guides, key Chinese trade authentication studies,^1,2 and a core reference text on the practice of Chinese herbal medicine in Western countries.³ The evaluation was carried out using the naked eye, a hand lens, or a stereomicroscope with a light source. Sample purity assessment was based on the amount of foreign plant matter, soil, or stones: contents <2% were deemed ‘acceptable’, those with 2-5% and >5% of foreign matter were considered to contain ‘minor contamination’ or ‘major contamination’, respectively. Of the 211 samples, 20 (9.5%) did not contain the labeled material at all, 5 (2.4%) displayed major contamination, and 12 (5.7%) exhibited minor contamination. One-hundred-seventy-three (82.4%) proved to be authentic and acceptable in terms of the presence of foreign organic matter.

Among the 23 fruit and seed species, three stood out as being adulterated particularly often. Of the eight samples of Astragalus complanatus (syn. Phyllolobium chinense, Fabaceae) seed, only three were authentic, while the remainder was composed of seeds from unidentified species, but likely seeds from other Astragalus species. The authors write “Given that Phyllolobium chinense is wild-harvested in many Chinese provinces and its source plants as well as seed are easily confused with those of species in the ubiquitous genus Astragalus, identification confusion at source is likely to account for the high levels of seed contamination.”

High adulteration rates were also found with Ziziphus jujuba var. spinosa (Rhamnaceae) fruit, where 7 of 12 samples were not authentic. These seeds were substituted with seeds from Z. mauritiana, probably as a low-cost look-alike of the official plant according to the authors. The third species where a majority of the materials were mislabeled, the fruit of Carpesium abrotanoides (Asteraceae), had a small number of samples. Only two samples labeled to contain C. abrotanoides were obtained, but both contained the fruit of Torilis japonica (Apiaceae). The adulteration of C. abrotanoides with T. japonica has been described previously,^3,4 and is believed to be because of the similarity of the common names he shi (C. abrotanoides) and hua nan he shi (T. japonica) or permissible interchangeable use in certain regions in China.

Incorrect species were also found in two of six samples of Schisandra chinensis (Schisandraceae), two of 10 samples of Vitex trifolia (Lamiaceae), one of 12 samples of Cullen corylifolium (Fabaceae), and one of 12 samples of Plantago spp. (P. asiatica or P. depressa, Plantaginaceae).

Not surprisingly, wild harvested materials showed higher rates of accidental contamination relative to materials obtained from cultivation. Bassia, Cnidium, and Leonurus fruits were all present as contaminants in several samples of each of the respective herbs. The authors list species differences among official and local compendia, local availability of plants, confusion of common and scientific names, morphological similarity, human error during collection or processing, accidental contamination during harvest, or intentional adulteration for financial gain as some of the causes for the identity and purity issues.

Comment: This paper exemplifies the wealth of information that can be obtained by thorough macroscopic evaluation of crude plant materials. The authors intentionally chose small-sized fruits and seeds for their work since adulteration and contamination are less likely to be obvious at first sight. While some of the substitutions, e.g., the sale of T. japonica fruit instead of C. abrotanoides fruit, are readily detected, others require a high level of expertise to enable a distinction among the plant of interest and closely related species. Nevertheless, the results of this paper show that a hand lens and a stereomicroscope are worthy and necessary investments for a quality control laboratory.

The purported adulterant of S. chinensis (bei wu wei zi), S. sphenanthera (nan wu wei zi), has been given a separate entry in the Chinese Pharmacopoeia (PPRC) in 2000. Traditionally, both species were acceptable as “wu wei zi”, and are still often used interchangeably due to their similar pharmacological actions. Of the thirteen suppliers from which schisandra samples were requested, five did not distinguish the two species and simply supplied fruits labeled as wu wei zi; these five samples were identified as S. sphenanthera. Three samples of S. sphenanthera were found to be treated with a red dye, likely to make them visually more similar to the more expensive S. chinensis seeds, which have a more pronounced red color. Since the red dye is water soluble, its presence is easily detected by adding a few seeds into a small amount of water.

References

1. Zhang J. Genuine or Fake Chinese Medicinal Material Distinguish Atlas (Vol. 3). Common Seed and Fruit Medicinal Materials. [in Chinese]. Guangzhou, China: Guangdong Science & Technology Publishing House. 2002.
2. Ho Y-L, Lin I-H, Chang Y-S. Illustration of Commonly Misused Chinese Drug Species in Taiwan [in Chinese], Taiwan’s Chinese Medicine Medication Safety Environment Regulations Series. Taipei, Taiwan: Committee on Chinese Medicine and Pharmacy, Department of Health, Executive Yuan. 2006.
3. Bensky D, Clavey S, Stöger E. Chinese Herbal Medicine: Materia Medica, 3rd ed. Seattle. Eastland Press. 2004.
4. Zhao ZZ, Xiao PG. Encyclopedia of Medicinal Plants. Shanghai, China: World Publishing Corporation. 2010.