Total phosphorus and its extractable form in plant drugs. Interrelation with selected micro- and macroelements

Determinations of total phosphorus, its extractable inorganic form and selected essential elements (Ca, Mg, Na, K, Fe, Zn, Mn, Cu) in 27 leaves of medicinal plants supplied from the Polish herbal enterprise – Herbapol, were carried out. After the microwave digestion of plant samples, the total phosphorus was determined spectrophotometrically, using the phosphomolybdenum blue method, whereas contents of metals were established by flame atomic absorption spectrometry (FAAS). Extraction with 2% (v/v) acetic acid solution was done in order to separate the extractable inorganic fraction of phosphorus, which was evaluated by the same method as used for the total elements. The macroelements (P, Ca, Mg, Na, K) were determined in a range of concentration from several hundreds of mg/kg to thousands of mg/kg of dry plant tissue. Microelements (Fe, Zn, Mn, Cu) were found in a range up to several hundreds of mg/kg of dry plant weight. The average level of the inorganic fraction of phosphorus represented 63.2% of the total concentration of that non-metal in leaves, which indicates that a large fraction of phosphorus may be bioavailable for people who often use herbal teas in their everyday diet. Statistically significant correlations between the total and extractable phosphorus and among metals (Ca–Mg, Ca–K, Ca–Fe, Mg–Fe, Cu–K, Cu–Zn, and Mn–Zn) were observed, confirming their indispensable role in activation of the same group of enzymes in medicinal plants. PCA revealed, that the levels of the total, extractable phosphorus and metals, may depend on the origin of the analyzed leaf sample from plants of the same plant species.