Analysis of Seeds and Rhizomes of Spices for Metals, Amino Acids, Polyphenols, Flavonoids, and Antioxidant Capacity for Evaluation of the Nutritional Quality*

Eleven plant extracts from the seeds and rhizomes of spices cultivated in Transylvania were investigated. To evaluate seeds and rhizomes nutritional profiles, several parameters were analyzed including metals, amino acids, polyphenols, flavonoids, and antioxidant capacity. The antioxidant activity, polyphenols, and flavonoids were determined using UV-Vis analytical methods. From investigated seeds and rhizomes, the most pronounced antioxidant character and the highest concentration of polyphenols were achieved in nutmeg seeds, allspice seeds, and ginger rhizomes. The highest flavonoid content was identified in turmeric rhizome and dill seeds. For the free amino acids quantification, a GC-MS analytical method using the 15N-glycine as internal standard was used. 16 amino acids were determined in the analyzed samples, and ginger rhizome and oregano seeds proved to have the highest content of essential amino acids. The trace metals were detected using inductively coupled plasma – optical emission spectrometry (ICP-OES). Essential trace elements (Cr, Mn, Co, Ni, Cu, and Zn) and toxic trace elements (As, Cd, and Pb) were determined in the samples. From essential trace elements, Mn and Zn were quantified in higher concentrations; for toxic elements As and Cd were found in the studied herbs. The findings indicate that the studied herbs parts may be valuable sources of compounds with bioactive properties.