Elimination of Exogenous Pollution Influence on the Microelement Composition of Medicinal Plants

INTRODUCTION. The compendial analytical procedure for determining the content of heavy metals and arsenic impurities in herbal drugs does not differentiate between endogenous and exogenous elemental impurities. Higher-precision data on the microelement composition of plants, particularly data on endogenous and exogenous impurities, could be instrumental in chemosystematics and in the identification of raw materials.

AIM. This study aimed to modify the analytical procedure for quantifying macro- and microelements in herbal drugs with the intention to eliminate the influence of exogenous pollutants on test results.

MATERIALS AND METHODS. The study focused on herbal drugs from the Boraginaceae family, including reproductive shoots of lungwort (Pulmonaria mollis Wulf. ex Hornem) and leaves of common borage (Borago officinalis L.). A portion was spiked with elemental pollutants. All herbal drugs were ground and fractionated by sieving. Quantitative determination was performed by inductively coupled plasma mass spectrometry. Statistical analysis of the results used Microsoft Excel and Statistica 8 software.

RESULTS. A total of 30 elements were quantified in 9 fractions of herbal drugs with different particle sizes. Cluster analysis showed that unfractionated herbal drugs and the fraction comprising particles smaller than 0.2 mm formed sepa rate clusters, indicating significant differences in elemental compositions. Grubbs’ test confirmed that these two samples were significantly different from the others. The fraction of particles smaller than 0.2 mm had the maximum content of the spiked elements; more than 90% of the spiked amounts were recovered from this fraction. The high content of elements observed in unfractionated herbal drugs was due to the plant parts that would have passed the 0.2 mm sieve had they been ground and fractionated.

CONCLUSIONS. The use of unfractionated herbal drugs leads to a systematic error in the results of elemental content determination, which significantly hinders the applicability of such results for the identification of herbal drugs. To ensure reliable results in the determination of the microelement status of plants, the authors suggest performing additional fractionation of herbal drugs and discarding the fraction under 0.2 mm.

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