Multiple Element Isotopic Analysis as a Tool to Discriminate the Geographical Origin of Ipomoea violácea

Abstract

Aims: This study aimed at testing the possibility of differentiating the geographical origin of I. violacea wild specimens by its carbon, nitrogen and oxygen stable isotopic compositions. Study Design:  Completely randomized design with 3 replications. Place and Duration of Study: Sample: the laboratorial analyzes were carried out at the Institute of Biosciences in Botucatu, Brazil between January 2016 and December 2016. Methodology: We collected the shoots of ten I. violacea wild specimens at each of the two selected regions in Brazil (Botucatu – SP and Três Lagoas – MS). Samples were dried in a forced-ventilation oven at 60ºC for 48 hours, and they were placed individually in plastic capped recipients containing lead spheres for the milling process. After that, the samples were weighed within individual capsules in a high precision balance and stored until analysis. For carbon and nitrogen analyses, tin capsules were used, and the average weight was 60 μg and 1100 μg, respectively. For oxygen analysis, the amount weighted was 170 μg within silver capsules. Isotopic analyses were performed by isotopic ratio mass spectrometry (IRMS) in triplicate. The isotope values were expressed in the standard delta notation (δ[‰]) with analytical errors of 0.2‰, 0.3‰ and 1.0‰ for carbon, nitrogen and oxygen, respectively. Results are presented as mean ± standard deviation. Principal component analysis was performed to define which isotope presents the greater variability. Results: Results allowed to clearly differentiate I. violacea specimens collected from different regions. They provide the possibility of discriminating the geographical origin of I. violacea specimens by multiple element stable isotope analysis. Results also certified that multiple element isotope analysis can contribute to the building of a database containing the isotopic signature of I. violacea specimens with known origin. Conclusion: The isotopic composition varied between plants of different regions. Thus, the technique is effective in I. violacea’s geographical origin discrimination.