Genetic Authentication of Commercial Sea Buckthorn Berry Products Sold in Markets and Stores in China

Reviewed: Liu Y, Xiang L, Zhang Y, et al. DNA barcoding based identification of Hippophae species and authentication of commercial products by high resolution melting analysis. Food Chem. 2018;42:62-67.

Keywords: Adulteration, DNA barcoding, high resolution melting, Hippophae rhamnoides, sea buckthorn

Due to their contents of nutritious substances, sea buckthorn (Hippophae rhamnoides, syn. Eleagnus rhamnoides, Eleagnaceae) berries have gained popularity as ingredients in food, beverages, dietary supplements, and cosmetic products. In China, the berries are on the List of Medicinal and Edible Plants in China; however, local customs and availability, and the same vernacular name applied to different species has led to the use of a number of different Hippophae species throughout China. In addition, morphologically similar berries are commonly added to commercial sea buckthorn products.

The identity of 10 commercial products labeled to contain dried sea buckthorn (without species information) berries from major herb markets and stores in Anhui, Hebei, Inner Mongolia, Liaoning, Qinghai, Sichuan, Xinjiang, and Yunnan provinces was verified by DNA barcoding and high-resolution melting (Bar-HRM). Five varieties of botanically authenticated sea buckthorn and six additional Hippophae species were used as reference materials.

High-resolution melting is a genetic analysis technology that relies on dyes which emit high fluorescence when bound to double-stranded DNA, and low fluorescence with single-stranded DNA. The double-stranded DNA fragment of interest is submitted to increasing heat, and eventually separates (‘melts’) into single-stranded DNA. During this process, the fluorescence intensity is measured. Small changes in the DNA composition will lead to differences in the melting temperature and thus the fluorescence signal. These differences can be measured to detect genetic variations and thus can help to identify materials based on comparison of the melting curves with those of authentic samples.

Four HRM curves of the commercial samples lined up with those of the H. rhamnoides var. turkestanica, while one corresponded to H. rhamnoides var. sinensis. The remaining five commercial products showed clear differences in their HRM curves. The identity of these five samples was determined by comparison of the sequence of the Internal Transcribed Spacer 2 (ITS2) region with sequences deposited in GenBank. Adulterating materials reported included the berries of Nitraria tangutorum (Nitrariaceae), N. sibirica, Sorbus pohuashanensis (Rosaceae) and Berberis vulgaris (Berberidaceae).

Comment: The results of this investigation show that a number berries that look similar to sea-buckthorn are sold in major herbal markets in China. All the substitute materials have recorded medicinal and food uses and are believed to be safe if consumed in appropriate amounts. When sold as the whole dry berry, sea buckthorn is readily distinguished from the adulterants described in this paper. However, distinction from closely-related Hippophae species may be more challenging. For the purpose of the study, both genetic tests are useful to determine the presence/absence of sea buckthorn. The DNA barcoding approach has the advantage of enabling to identify the adulterants providing that the sequences obtained through the BLAST search in GenBank are correct.