The maximum values for heavy metals in herbal drugs and extracts have been discussed by several authors. In
1998, Kabelitz [33] published a detailed evaluation of a database on heavy metals, which included more than 12 000
samples originating from quality control analyses by several pharmaceutical companies. On this basis, maximum
levels of Pb of 10 mg/kg-1 and for Cd of 0.5 mg/kg-1 were proposed. In this context, the WHO again proposes a limit
of 10 mg/kg-1 for plumbum and 0.3 mg/kg-1 for cadmium dried herbs [34]. The concentrations of plumbum and
cadmium in leaves, stems and flowers of Stevia rebaudiana given in Table 2, assessed are in the range that classifies
them as a low source of plumbum and cadmium according to Kabelitz and WHO propose.
Arsenic can be hazardous for humans and animals when ingested as fine particles of dust or consumed in
contaminated water. The uptake of arsenic by plants is associated with a change in speciation (methylated or
complexes as phytochelatins) that also changes its toxicity, although some authors consider that plants rarely
accumulate Arsenic to toxic levels [35]. If viewed concentration of arsenic in leaves, stems and flowers of Stevia
rebaudiana as shown in Table 2, these were still lower than the total concentration normal range arsenic in plants,
see Table 1.
The maximum values for heavy metals in herbal drugs and extracts have been discussed by several authors. In
1998, Kabelitz [33] published a detailed evaluation of a database on heavy metals, which included more than 12 000
samples originating from quality control analyses by several pharmaceutical companies. On this basis, maximum
levels of Pb of 10 mg/kg-1 and for Cd of 0.5 mg/kg-1 were proposed. In this context, the WHO again proposes a limit
of 10 mg/kg-1 for plumbum and 0.3 mg/kg-1 for cadmium dried herbs [34]. The concentrations of plumbum and
cadmium in leaves, stems and flowers of Stevia rebaudiana given in Table 2, assessed are in the range that classifies
them as a low source of plumbum and cadmium according to Kabelitz and WHO propose.
Arsenic can be hazardous for humans and animals when ingested as fine particles of dust or consumed in
contaminated water. The uptake of arsenic by plants is associated with a change in speciation (methylated or
complexes as phytochelatins) that also changes its toxicity, although some authors consider that plants rarely
accumulate Arsenic to toxic levels [35]. If viewed concentration of arsenic in leaves, stems and flowers of Stevia
rebaudiana as shown in Table 2, these were still lower than the total concentration normal range arsenic in plants,
see Table 1.
Chromium is a non-essential and toxic metal to plant growth, and it may be possible that plants do not have any
specific mechanism of transport of Cr [36]. Chromium compounds are highly toxic to plants and are detrimental to
their growth and development. Although some crops are not affected by low Cr concentration (3.8x10-4 μM) [37, 38],
Cr is toxic to higher plants at 100 μM. kg-1 dry weight [39].
The uptake of the copper from the soil by plants depends on the ability of the plants to transfer the metal across
the soil–root interface and the total amount of copper present in the soil [40]. The normal heavy metal contents of
terrestrial plants growing in uncontaminated soils were found to be in the range 0.4 to 45.8 mg kg-1 for Cu [16].
Copper (Cu) is necessary for plant growth in low concentrations, a structural part of enzymes, and is taken up as the
divalent cation (Cu2+) or Cu chalet. Copper, however, is often present in high concentrations that are toxic enough to
biota. If viewed concentration of chromium and copper in leaves, stems and flowers of the Stevia rebaudiana plant
as shown in Table 2, these were still in normal range.
Iron is essential for plant growth and is generally considered to be a micronutrient. Iron is considered the key
metal in energy transformations needed for syntheses and other life processes of the cells [41]. Although iron itself is
not considered toxic, it is environmentally significant because of its interaction with metals that are toxic. Iron
oxides adsorb many elements and participate in the attenuation of most trace and heavy metals. Excess amounts of
heavy metals, and of manganese, nickel, and cobalt in particular, caused a reduction in absorption and translocation
of iron and resulted in a decrease of chlorophyll. On the other hand, high levels of iron compounds in the soil are
known to greatly decrease trace metal uptake. Reactions between iron and manganese are commonly observed and
the ratio of these two metals in both growth medium and plant tissue seems to be more important to plant
metabolism than their concentrations [42, 43]. The result shows in Table 2, that by using Elan 9000, iron in leaves
Stevia rebaudiana was 623 mg/kg-1. Meanwhile, the result of iron in stems was 472 mg/kg-1 and in flowers was 972
mg/kg-1. Then, the result shows in Table 2 that by using Agilent 7500a, iron in leaves of Stevia rebaudiana was 719
mg/kg-1. Meanwhile, the result of iron in stems was 125.11 mg/kg-1 and in flowers was 614 mg/kg-1.
The magnesium concentration of tissues considered as deficient, sufficient, or toxic depends on what growth
parameter is being measured in the crops. In many food crops, classification of nutrient sufficiency is based on