The demand for crops grown in a pesticide-free environment remains on the increase as consumers demand purer, untainted herbs and foods but the potential for fraud is also high. This type of organic crop is generally more expensive so there is money to be made by falsely selling “regular” food as organic food. One such example is ginseng, popular around the world, but especially in the far East, as a herbal medicine.
Several scientific techniques have been developed to determine the geographical origin and cultivation age of ginseng, based on its ginsenoside profile and the content of carbohydrates, amino acids and organic acids. Now, scientists in South Korea have turned once again to organic acids to see whether they can be predictors of the cultivation method. Man-Jeong Paik and colleagues from Sunchon National University, Chungbuk National University, Kyung See University, Amorepacific R&D Unit, Yongin, and Osulloc Farm Co., Ltd., Seogwipo-si, employed GC/MS in a profiling procedure for organic acids.
Ginseng testing
Ginseng was collected from five different farms at which conventionally farmed and pesticide-free crops were grown in neighbouring sites. The roots were homogenised in water and the organic acids were converted to the methoxime-tert-butyldimethylsilyl derivatives with standard reagents to render them amenable to GCMS. They were analysed following electron ionisation in full-scan and selected ion monitoring mode.
A total of 17 organic acids were detected in ginseng and their limits of quantification were 0.009-0.208 µg under SIM. The analytical criteria such as repeatability, accuracy and linearity were all at acceptable levels, so the researchers looked more closely at the individual organic acids to see if the levels could provide any indication of the farming conditions during growth.
Isocitric acid biomarker
Citric acid was the most abundant organic acid in most of the cropped ginseng regardless of the farming method. Several acids, namely 2- and 3-hydroxybutyric, pyruvic, oxaloacetic and 4-hydroxyphenylacetic acid, were promising biomarker candidates because they were at reduced levels in four- and five-year-old ginseng grown under environmentally conditions compared with conventional ginseng. However, for six-year-old roots the levels were higher than those in conventionally grown plants.
The best biomarker was isocitric acid. It was found at increased levels in all of the pesticide-free crops in amounts relative to the conventionally grown ginseng that make it easy to distinguish the two. The levels of all the organic acids were normalised against those from the conventional plants and presented as star pattern plots which helped to visualise the data. Plots for the 17 organic acids showed a more distorted pattern for the environmentally grown crops compared with the conventional ones.
This preliminary study on ginseng metabolites has highlighted isocitric acid as a potential indicator that ginseng has been grown under environmentally conditions in the absence of pesticides. If validated on a larger set of samples, it could be introduced into food monitoring programs because the GC/MS derivatisation and analysis regime is routine and amenable to automation.
Related Links
Bulletin of the Korean Chemical Society 2018, 39, 1449-1454: “Monitoring of Organic Acids in Ginseng Roots Produced by Conventional and Environmentally Friendly Farming by Gas Chromatography–Mass Spectrometry”
Source: Spectroscopy Now
