Elemental compositions and stable isotope signatures for determining the geographical origin of salep orchids collected from different regions of Turkey

Abstract

Salep is a highly valued natural food and medicinal commodity with strict regulations on its use and export. It is produced from tubers of orchids and consumed for its delectable and functional qualities in different parts of the world. This study aimed to identify and compare the elemental composition and isotope ratios of salep based on discrimination of geographical origins. The samples were collected from five different regions (North, Southwest, South, Southeast and East Anatolia) of Turkey. The 21 microelements (Li, Be, Ti, V, Cr, Mn, Fe, Ni, Co, Cu, Zn, Ga, Se, Rb, Sr, Mo, Sb, Cs, Ba, Tl and Bi) were determined by inductively coupled plasma mass spectrometry (ICP-MS), while the isotope ratios (δ¹³C, δ¹⁵N, δ¹⁸O and δ²H) were determined using isotope ratio mass spectrometry (IRMS). According to the ICP-MS results, Fe, Zn and Mn comprised around 77% of the elemental composition. North Anatolia samples had higher concentrations of Cr and Ni, while samples from Southeast and East Anatolia regions were enriched in Cs. Isotopic ratios varied significantly between samples and minimum and maximum ratios were determined as − 29.76 and − 26.63‰, 0 and 6.66‰, 28.09 and 37.31‰, − 144.86 and − 84.20‰ for the δ¹³C, δ¹⁵N, δ¹⁸O and δ²H, respectively. Collected isotopic data was also evaluated by multivariate statistical analyses to discriminate according to their geographical origins of salep tubers. According to the findings, the samples had a characteristic isotopic fingerprint and the isotope ratios can be important predictors for the discrimination of geographical origins. Results indicate the significant compositional variation between salep of different origins, which may be attributable to differences in environmental conditions such as climate and soil composition and intrinsic factors such as fungal associations of orchids.