CARBON ISOTOPE COMPOSITION AS A TOOL FOR QUALITY CONTROL OF HERBS, SPICES AND MEDICINAL PLANTS

Isotope screening is a simple and cheap test for determining the photosynthetic pathway used by plants. The scope of this work was to classify the photosynthetic type of Melissa officinalis L. and Cymbopogon citratus [DC.] Stapf. through studies of the carbon isotope composition (¹³C), and we are proposing the use of carbon isotope composition results as a tool to control the quality of medicinal plants. For studies of ¹³C (¹³C% = [R (sample)/R (standard) – 1] x 10^-3), dried, powdered leaves were analyzed in a mass spectrometer coupled with an elemental analyzer for determining the ratio R (R = ¹³CO₂/¹²CO₂). As results, M. officinalis presented a C₃ photosynthetic type, and C. citratus presented a C₄ photosynthetic type. The carbon isotope composition from this study can be used as quality control of M. officinalis adulterants.