Determination of mineral element concentrations, heavy metal contents, and antioxidant amounts of some commercially sold medicinal-aromatic plant drugs

There are reliability- and efficacy-based quality issues regarding herbal drugs in our country. It is evident that there is a lack of sufficient scientific information addressing the quality concerns of commercially sold (bulk) herbal drugs. Consequently, there is a need for outputs targeting consumers and stakeholders in the medicinal and aromatic plant sector. This study focuses on determining the mineral element concentrations, heavy metal contents, and antioxidant compound levels of certain medicinal and aromatic plant drugs commercially sold in Antalya. In this context, the plant drugs studied include linden, green tea, fennel, thyme, echinacea, chamomile, and sage, obtained from two different suppliers. The study identifies the total nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), iron (Fe), zinc (Zn), manganese (Mn), copper (Cu), total nickel (Ni), chromium (Cr), lead (Pb), cadmium (Cd), aluminum (Al), total phenolic, and total flavonoid contents for linden (A1; B1), green tea (A2; B2), fennel (A3; B3), thyme (A4; B4), echinacea (A5; B5), chamomile (A6; B6), and sage (A7; B7). The results obtained in the study are as follows: The highest total nitrogen (A2), total Ca (B5), total Mg (B5), total Na (A1 and B6), total Fe (B7), total Zn (A1), total Mn (A2), and total Cu (A3) levels were found to be consistent with previous studies. However, total phosphorus levels (A1, A3, B3, B6) were determined to be higher compared to previous studies. On the other hand, it was observed that even the highest potassium content (A1) in this study was at a very low level. The highest total Ni (B6), Pb (B7), and Al (A1, A3) levels obtained in this study were found to be in agreement with previous studies. In contrast, considering the values obtained from previous studies, total Cr (A4) and total Cd (B6) levels were found to be significantly higher than those reported in previous research. The highest total phenolic (B2) and flavonoid (B7, A1, A2, A5) contents obtained in this study were determined to be consistent with previous studies. As a result, this study determined that among tea leaves with the potential to be used as herbal drugs sold by suppliers, the total phosphorus content was high, while the total potassium content was low in terms of mineral nutrients. Regarding heavy metals, chromium and cadmium levels were found to be significantly high. Additionally, the antioxidant compound levels were also determined to be high. For herbal drugs to be considered high quality and used safely, they should not pose issues concerning heavy metals while being rich in minerals and antioxidant compounds. From this perspective, the findings of this study indicate that these plant drugs present a risk of heavy metal toxicity in terms of consumption. Given that these drugs have undergone mechanical processing, they may have been contaminated with Cd and Cr due to the composition of the equipment used during processing or protocol-related factors. Considering this situation, it is deemed appropriate and beneficial for future studies to include heavy metal analyses of samples obtained directly from the field.