




































East


East Afr. J. Biophys. Comput. Sci. (2022), Vol. 3, Issue. 2, 48-60 
 

 

 

 

*Corresponding author: 

  Email: teferi.tademe@wsu.edu.et,  +251 10001811 https://dx.doi.org/10.4314/eajbcs.v3i2.5S 

 
 

 

 

 

Eyob Yishak and Teferi Tademe Dadebo* 

Department of Chemistry, College of Natural and Computational Sciences, Wolaita Sodo University, Ethiopia;  

 

 

 

KEYWORDS:  

Adverse effects; 

FAAS; 

Medicinal plants;  

Herbal remedies; 

Permissible limits 

 

 

 

 

 

 

ABSTRACT 

Medicinal plants have global applications in the treatment of diverse types of human 

animal diseases. Among the medicinal plants of Ethiopia, Ocimum lamiifolium Hochst. Ex 

Benth (Damakese, in Amharic) is one of the well celebrated and most widely used home 

remedy for the treatment of a disease locally known as “Mitch” which is characterized by 

headache, fever, inflammation, joint pain, sweat, loss of appetite, etc. The aim of the 

present study on this medicinal plant was to determine the levels of heavy and trace metals 

in the leaves using the flame atomic absorption spectrometer (FAAS), which is nov AA 

model. The sampling technique used to carry out the analysis was purposive for the 

community in the selected area use the plant widely to treat different diseases. In addition, 

for each of three kebeles, selected from Duguna Fango District, three sites were selected to 

homogenize the samples. The concentrations or levels of heavy and trace metals, Cd, Co, 

Pb, Cr, Cu and Zn, in the leaves of the selected medicinal plant were  found to be (in 

mg/L) 0.0489, 0.0579, 0.0936, 0.153, 0.214 and 0.847, respectively. The results revealed 

that the selected medicinal plant accumulated these metals at different concentration levels 

in different sites. The results also confirmed that the concentration levels of the metals in 

the leaves of the selected medicinal plant were not higher than the globally accepted 

permissible limits. Thus, the results indicated that the medicinal plant under the study is 

safe for medicinal uses. Furthermore, monitoring such medicinal plants for heavy and 

trace metals concentrations is of great importance in protecting the community from the 

adverse effects of the heavy metals.. 

  

 

INTRODUCTION 

Background of the study 

Medicinal plants play an important role since 

prehistoric time as they are used in traditional 

medicine and also as home remedies. 

Environment, pollution, atmosphere, soil are 

some of the issues, which play a major role in 

contamination of medicinal plants by metals and 

also by microbial growth. Traditional medicines 

include herbal medicines composed of herbs, 

herbal materials, and finished herbal products, 

that contain as active ingredient parts of plants, 

or other plant materials, or combinations of all 

mentioned (WHO, 2005).  

East African Journal of Biophysical and Computational Sciences 

Journal homepage : https://journals.hu.edu.et/hu-journals/index.php/eajbcs 
 

Hawassa University

College of Natural & Computational Sciences

Year 2021

Volume xx No xx

 

Determination  of  the  Levels  of  Some  Selected  Metals  in  Ocimum  lamiifolium  in  Wolaita 

Zone, Southern Ethiopia  

 
Research article

https://dx.doi.org/10.4314/eajbcs.v3i2.5S


East Afr. J. Biophys. Comput. Sci. (2022), Vol. 3, No. 2, 48-60 
 

49 
 

Herbal medicines usually refer to plant-derived 

substances that occur in nature and are utilized 

with little or no industrial processing for 

treatment of illnesses (Tilburt and Kaptchuk, 

2008). Herbal medicines are formulated using 

various parts of plants, including leaves, roots, 

barks, fruits, and seeds. Due to their natural 

origin, many people who use herbal remedies 

believe they are safer than conventional 

pharmaceutical products. The WHO reckons 

that over 80% of the population in Africa and 

other developing countries depend on herbal 

remedies for their healthcare needs (WHO, 

2005). For many people in Africa, the high costs 

of Western pharmaceuticals make modern health 

care services inaccessible. As a result, they 

heavily rely on herbal medicine and medicinal 

plants to fulfill their primary health care needs. 

In addition, western pharmaceuticals are most of 

the time inaccessible to most people in Africa 

and so herbal medicines have become one of the 

major options for treating various diseases 

(Debas et al., 2006).  

When consumed in excess, lead (Pb) can 

increase blood pressure and lead to serious 

damage to vital organs such as the kidney and 

the brain. Cadmium (Cd) poisoning is linked 

with a number of respiratory disorders, renal 

failures and cardiovascular issues. Although 

zinc (Zn) is an essential mineral, overdosing on 

it can result in symptoms such as fever, nausea, 

and general weakness. Though iron deficiency 

causes anemia, too much iron is predominantly 

dangerous in young children and could cause 

gastrointestinal and skin problems (Baker et al., 

2010).Therefore, it is necessary to measure and 

establish the levels of heavy and trace metals in 

the herbal plants as these elements when 

consumed at higher levels become toxic. Thus, 

the objective of the present study was to 

determine the levels of selected heavy and trace 

metals in the leaves of Ocimum lamiifolium 

plant using flame atomic absorption 

spectrophotometer 

Statement of the problem  

The use of herbal medicines is rapidly 

expanding around the world. Many individuals 

now turn to herbal medicines or associated 

products for their healthcare within various 

national healthcare systems. However, mass 

media coverage of adverse events is often 

exaggerated, leading to the negative perceptions 

of herbal medicines in general, rather than 

focusing on the specific causes behind these 

events. 

Currently, most adverse associated with the use 

of herbal medicines are attributable either to 

poor product quality or the improper usage. In 

order to expand knowledge about genuine 

adverse reactions to herbal medicines, and to 

avoid wasting scarce resources for identifying 

and analyzing adverse events, events resulting 

from such situations will need to be reduced or 

eliminated.  

Ocimum lamiifolium, among vital medicinal 

plants, is used to treat various ailments such as 

cough, headache, eye infections, abdominal 

colic, bloat, inflammation, joint pain, etc. Thus, 

it is used by most people in wolaita zone for the 

treatment of mentioned diseases. The level of 

heavy and trace metals in herbal medicines 

beyond the permissible limit is a matter of great 

concern to public safety all over the world 

(Khan et al., 2008). The problem is more 

pronounced in the case of Ethiopia because the 

herbal medicines used by the society without 

realizing the concentration of toxic heavy metals 

as well as the trace metals. World Health 



East Afr. J. Biophys. Comput. Sci. (2022), Vol. 3, No. 2, 48-60 
 

50 
 

Organization (WHO) basically recommends that 

medicinal plants which form the raw materials 

for the finished products may be checked for the 

presence of heavy metals, further it regulates 

maximum permissible limits of toxic metals like 

arsenic, cadmium, and lead which amounts to 

1.0 ppm, 0.3 ppm and 10 ppm, respectively 

(WHO, 2006). The common conception among 

the population is that “natural” means “safe” 

and that drugs of natural origin are harmless and 

have no risk associated with their use, does not 

match reality. Some medicinal plants have 

inherent toxicity and herbal medicines, like any 

medicine, have side effects that can cause many 

diseases (Lanini et al., 2009). Thus, the current 

study focuses on the determination of the levels 

of heavy and trace metals in the leaves of 

Ocimum Lamiifolium that is grown in Duguna 

Fango district in order to protect the individuals 

from their adverse effects when used beyond the 

permissible limits  

Objectives of the study 

The study was carried out with the objectives of 

determining the levels of selected heavy and 

trace metals (lead, cadmium, chromium, cobalt, 

copper, and zinc) in Ocimum lamiifolium using 

FAAS technique and comparing the levels of 

the mentioned metals present in the leaves of 

Ocimum lamiifolium with the permissible limits 

of WHO standard and other international 

standards. 

Significance of the study 

Society has increasing curiosity in the 

therapeutic use and benefits of herbal remedies. 

However, there is a wide spread misconception 

that natural herbs and plants are inherently safe. 

There is also insufficient information available 

on the safety of traditional herbs and their 

products. Therefore, this study helps provide 

important evidence on the levels of selected 

heavy and trace metals in Ocimum lamiifolium 

grown in the study area so that the society could 

be free of the potential health risks caused from 

the excessive uptake of the heavy and trace 

metals in the herbal medicines. On the other 

hand, the results of this study could be used as 

reference for other researchers who want 

conduct the similar studies on the same plant 

growing in different parts of the country. 

Scope of the study 

This study was restricted to the investigation of 

concentrations of the selected heavy and trace 

metals found in Ocimum lamiifolium grown in 

Duguna Fango District, Wolaita zone, Southern 

Ethiopia using the widely used analytical 

technique called spectroscopy specifically using 

the analytical instrument flame atomic 

absorption spectrophotometer. The metals Pb, 

Cd and Cr were selected for they are more toxic, 

and the metals Co, Cu and Zn were selected 

merely to represent trace elements. Furthermore, 

leaf part of the selected medicinal plant was 

taken to carry out the analysis for the society 

use this part of the plant to treat different 

diseases. 

MATERIALS AND METHODS 

Study Area 

Description of the Study Area 

The study was conducted in three selected 

kebeles (the smallest administrative unit) from 

Duguna Fango Woreda of Wolaita zone, which 

is found in Southern Nations, Nationalities, and 

Peoples Regional (SNNPR) state. The area is 

located at 431Km south of Addis Ababa and 82 



East Afr. J. Biophys. Comput. Sci. (2022), Vol. 3, No. 2, 48-60 
 

51 
 

Km from Hawassa, between 6o40' - 7o58'N 

latitude and 37o4' - 37o56'E longitude with a 

total land area of 46,660 hectares. Wolaita Zone 

has 16 woredas (districts) and 3 town 

administrations. The Wolaita people are one of 

the indigenous people of Ethiopia who have 

their own culture, tradition, political legacy and 

kingdom. The study area lies at an altitudinal 

range between 1000 – 2500 meter above sea 

level and have agro ecologies of dega (high 

land), woynadega (mid altitude) and kola (low 

land) with a average annual temperature of 

l9.5oc and annual rainfall that varies from 750-

1350mm according to the projected CSA final 

report of 2019. 

 

Figure 1: The map of Ethiopia, SNNPR and Wolaita zone (Adapted from Wikipedia) 

Instrument and apparatus 

Heavy and trace metals determination in the 

leaves of Ocimum Lamiifolium was done using 

atomic absorption spectroscopy (AAS). Flame 

atomic absorption spectrometer (FAAS) 

(Germany, novAA) is a suitable technique for 

determining metals at parts per million (ppm) 

concentration levels with good precision for 

many elements. FAAS offers air-acetylene 

and/or nitrous oxide flame atomizer. FAAS 

technique delivers fast analysis of 10-15s per 

sample, with very good precision (repeatability), 

moderate interferences that can be easily 

corrected, and relatively low cost. As indicated 

in Figure 3, a typical AAS consists of radiation 

(energy) source, atomization compartment, 

monochromator, detector and data readout 

system.  

Plant material was sectioned using a stainless 

steel axe and Teflon-coated (SSAT) knife, then 

dried in an air-circulating oven on porcelain 

supports. Samples were subsequently ground 

and homogenized using a blending device and 

ceramic pestle and mortar. A digital analytical 



East Afr. J. Biophys. Comput. Sci. (2022), Vol. 3, No. 2, 48-60 
 

52 
 

balance was used for accurate sample weighing. 

Microwave digestion was performed in 100 mL 

round-bottom flasks with ground-glass fittings 

and reflux condensers (Gallenhamp, England). 

Borosilicate volumetric flasks (50, 100, and 250 

mL) were employed for sample dilution and the 

preparation of metal standard solutions. 

 

 

Figure 2: Basic components of atomic absorption spectrophotometer 

Chemicals and reagents 

Analytical grade chemicals were purchased 

from Sigma-Aldrich Company found in 

Germany. 69% nitric acid (HNO3), 70% 

perchloric acid (HClO4) and 30% hydrogen 

peroxide (H2O2) were used for digestion in 

microwave digester, while multi-element 

standard solution was used as a reference 

material. Stock standard solution for each metal 

cadmium (Cd), lead (Pb), zinc (Zn), cobalt (Co), 

chromium (Cr) and copper (Cu) with a 

concentration of 1000mg/L was used to prepare 

intermediate or working standard solutions of 

10mg/L for the calibration standards of each 

metal. Throughout the study, deionized water 

was used. All glass wares were soaked in 5% 

(v/v) HNO3 overnight then rinsed with 

deionized water and dried using laboratory dryer 

prior to use. 

Experimental work procedures  

Sample collection and preparation 

The samples of fresh leaves of Ocimum 

Lamiifolium were collected from three different 

kebeles, which are Aruse weyde, Edo mazegaja 

and Dendo Koysha, in Duguna Fango district 

from uncultivated fields. From each kebele, 

three sites were selected to collect the plant 

leaves in order to homogenize the sample. 

Samples were placed in plastic bags and labeled, 

and brought to the laboratory. Samples were 

washed with distilled water, and first air-dried at 

room temperature and oven was used for further 

drying and placed in dust free environment; then 

ground in to fine powder manually using a 

porcelain mortar and pestle and allowed to pass 

through a sieve of 0.5mm mesh size. The 

powdered samples were put in plastic containers 

and kept in a dry, cool closet until they were 

analyzed. The plant species was collected from 

different localities based on its availability and 

knowledge of the societies regarding its 

medicinal values of the plant.  

Optimization of the digestion procedure of 

samples 



East Afr. J. Biophys. Comput. Sci. (2022), Vol. 3, No. 2, 48-60 
 

53 

Achieving optimal sample digestion is essential 

for accurate analysis. Key criteria for optimum 

digestion include minimal reagent volume and 

digestion time, a clear solution with minimal 

residue, low digestion temperature, and 

procedural simplicity. The digestion procedure 

was optimized by varying parameters such as 

reagent volume, digestion temperature, and 

digestion time. Based on visual assessment of 

the resulting solutions, the optimal and 

appropriate digestion conditions (Table 1), were 

selected for subsequent FAAS analysis. 

Sample digestion 

One gram (1 g) of each powdered sample was 

accurately weighed using a calibrated digital 

analytical balance and transferred into a 250 mL 

beaker. To each sample, an optimized mixture 

of 69% concentrated nitric acid (HNO3), 70% 

perchloric acid (HClO4), and 30% hydrogen 

peroxide (H2O2) was added, following the 

optimized digestion procedure. After cooling for 

30 minutes, distilled deionized water was added 

to dissolve any precipitate, followed by gentle 

swirling. The resulting solution was filtered into 

a 50 mL volumetric flask using Whatman filter 

paper number 41 to remove any suspended 

matter. The filter paper was subsequently rinsed 

with distilled deionized water until the volume 

reached the mark. Each bulk sample was 

processed in triplicate. The digested and diluted 

sample solutions were then stored in plastic 

sample bottles for FAAS analysis. 

Chemical analysis 

Instrument operating conditions 

Intermediate standard solutions (10 mg/L) were 

prepared from 1000 mg/L atomic absorption 

spectroscopy (AAS) stock solutions. These 

intermediate standards were further diluted 

using distilled deionized water to create five 

working standards for each target metal. Flame 

atomic absorption spectrophotometry (FAAS), 

equipped with a deuterium arc background 

corrector and an air-acetylene flame system, 

was used to analyze six metals. An external 

calibration curve was used for quantification, 

and all instrument parameters (burner and lamp 

alignment, slit width, and wavelength) were 

optimized for maximum signal intensity. AAS is 

a quantitative method that measures the 

concentration of the element by passing light in 

specific wave length emitted by a radiation 

source of a particular element through cloud of 

atoms from a sample. Atoms absorbed light 

from an energy source known as hollow cathode 

lamp (HCL). In FAAS, the reduction in light 

intensity reaching the detector is directly 

proportional to the concentration of the target 

element in the original sample. A typical FAAS 

instrument consists of a light source, a sample 

atomizer, a monochromator, a detector, and a 

data processing system. Three replicate 

measurements were performed for each sample. 

The hollow cathode lamp for each metal was 

operated at the manufacturer’s recommended 

conditions, using the respective primary source 

line for analysis. Acetylene and air flow rates 

were carefully controlled to ensure optimal 

flame conditions. The absorption mode of the 

instrument was used to analyze all six target 

metals (Pb, Zn, Cu, Co, Cr, and Cd). 

Instrument Calibration 

Calibration curves were cautiously prepared to 

determine the concentration of the metals in the 

sample solution. Before the commencement of 

the experiment, the instrument (i.e. flame 

atomic absorption spectrometer [FAAS]), was 



East Afr. J. Biophys. Comput. Sci. (2022), Vol. 3, No. 2, 48-60 
 

54 

standardized using five series of working 

standards. The working standard solution of 

each metal was prepared from the 10 mg/L 

intermediate standard solutions of their 

respective metals. Wavelengths, concentration 

of the intermediate standards, working standard 

solutions and the correlation coefficients of the 

calibration curve for each of the metals were 

identified and presented (Table 4). 

Method detection limits (MDL) 

The method detection limit (MDL), also known 

as the limit of detection (LOD), represents the 

minimum concentration of an analyte that can 

be reliably detected by an analytical method 

with a specified level of confidence. The limit is 

statistically determined as the lowest possible 

concentration distinguishable from a blank, 

typically with 95% confidence. The MDL/LOD 

is often defined as the point where the signal-to-

noise ratio exceeds 3, but is not necessarily a 

precisely quantified value. It can be calculated 

by multiplying the standard deviation of the 

reagent blank (Sblank) by three: MDL = 3 × 

Sblank (Chen, 2007). 

Method validation 

Method validation is essential to confirm that an 

analytical method is suitable for its intended 

purpose. Given the lack of certified reference 

materials for the leaf and seed samples, the 

efficiency of the optimized digestion procedure 

was assessed by spiking 1 g Ocimum 

lamiifolium leaf samples with known 

concentrations of each target metal. Percentage 

recovery, a crucial parameter for method 

validation, was calculated by comparing the 

measured concentrations in spiked and non-

spiked samples, which were digested and 

analyzed under identical conditions. Then the 

percentage recovery of the analyte was 

calculated by: 

Percentage recovery = 

 x 100% 

Where, Cm = Concentration of metal of interest       

(Adapted from: IJRPC (2014), 4(1), 202-216) 

Statistical Analysis 

All measurements were done in triplicates and 

expressed as mean ± standard deviations. Data 

was analyzed using analysis of variance 

(ANOVA) at level of 5% (p≤ 0.05) followed by 

least significant difference Post Hoctest in 

Microsoft Excel for the determination of 

statistical significance of a given metal across 

the samples, not within a given sample. Data 

was further manipulated with Origin Pro 2020b 

SrOH(1) for windows version software 

program. 

RESULTS AND DISCUSSION 

Optimization of working procedures 

As indicated in Table 1 below, eight 

optimization procedures were used to get the 

optimum digestion conditions. The procedures 

used in steps one through four were not chosen 

as optimum conditions for they used maximum 

reagent volumes and the highest digestion 

temperature as well as long time even if some of 

the procedures gave clear and colourless 

solutions. In steps six up to eight, the volumes 

of reagents were relatively low, but they took 

place at relatively long times. Therefore, 

procedure five was chosen as optimum 

condition for the digestion, because it took place 

at relatively minimum reagent volumes, low 

digestion time to give clear and colorless 



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55 

solution.   

 

Table- 1: Methods tested during optimization of the digestion procedure for the samples of the  

leaves of Ocimum Lamiifolium. 

No. Wt. (g) 

 

 

Volume of reagents (mL) Max. 

Temp. (oC) 

Time 

(min) 

Results 

HNO3 HClO4 Total 

1 1.0 4 3 7 200 60 Clear but turbid 

2 1.0 5 2 7 200 60 Clear but yellowish 

3 1.0 5 1 6 200 60 Clear but pale yellow 

4 1.0 3 2 5 200 10 Clear and colourless 

5 1.0* 3* 2* 5* 150* 20* Clear and colourless 

6 1.0 3 2 5 140 60 Clear and colourless 

7 1.0 4 1 5 130 40 Clear and light yellow 

8 1.0 3 2 5 140 30 Clear and light yellow 

*Optimum digestion conditions 
 

The results of the analytical recovery test 

The validation of the method was tested by 

spiking the samples with a standard of known 

concentration of the analyte metals. As 

depicted in Table 2 below, the results 

indicated that the concentrations of elements 

determined are in agreement within the 

acceptable range for all metals, that is 80-120%. 

Hence, the digestion method was efficient 

because the values of the percentage recoveries 

lied within the acceptable range.  

Table- 2: Analytical recvery results btained for the validation of the ptimized procedure of 

plant samples. 

 

Instrument operating conditions 

The operating conditions for the instrument 

were prepared for each metal at an appropriate 

wave length, slit width, current and IDL (Table 

3). Intermediate standard solutions of 10mg/L 

were prepared using 100 mL flask from stock 

standard solution that contained 1000 mg/L of 

soluble salts of Cd(NO3)2, Pb(NO3)2, Co(NO3)2, 

Zn(NO3)2, Cu(NO3)2 and oxide of chromium for 

each metal of interest. MDL was calculated by 

Metal Concentration in non-

spiked sample (mg/L) 

Amount added 

(mg/L) 

Concentration in spiked 

sample (mg/L) 

Percentage 

recovery (%) 

Cd 0.05 0.03 0.08±0.01 100±0.025 

Co 0.06 0.04 0.095±0.01 87.5±0.028 

Cr 0.15 0.14 0.28±0.007 92.9±0.078 

Cu 0.21 0.19 0.39±0.01 94.7±0.11 

Pb 0.09 0.08 0.17±0.007 100±0.049 

Zn 0.85 0.82 1.68±0.02 101±0.49 



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56 

multiplying the standard deviation of blank solution by three (MDL = 3Sblank). 

 

Table- 3: Instrument operating conditions for the analysis of metals in the samples of selected 

plant. 

Element    Wavelength 
(nm) 

Slit width 
(nm) 

Current 
(mA) 

IDL* 
(mg/Kg) 

Cd 228.80 0.70 2.00 0.0001 

Zn 213.90 0.70 2.00 0.0001 

Cu 324.80 0.70 2.50 0.0001 

Co 240.70 0.20 5.00 0.00075 

Cr 357.90 0.70 4.04 0.00005 

Pb 283.3 0.7 2 0.003 

*Instrument Detection Limit 
 

 

Concentrations of working standard 

solutions and correlation coefficients of 

calibration Curves 

Working standard solutions were prepared from 

intermediate standard solutions containing 

10mg/L, which was prepared from stock 

standard solutions, by diluting with deionized 

water to obtain five working standards for each 

metal of interest as indicated in Table 4. The 

table also showed that the correlation 

coefficients of calibration curves of all six 

metals were closer to one. Thus, these results 

confirmed that there are strong linear 

relationships between two variables, which are 

absorbance and the concentrations of working 

standard solutions. 

Table- 4: Cncentrations of working standard solutions and crrelation cefficients of the 

calibration curves for the analysis of plant samples. 

Metal Concentrations of working 

standard solution 

Correlation coefficient 

Cd 0.5, 1.0, 1.5, 2.0, 2.5 0.999 

Co 0.1, 0.5, 1.0, 1.5, 2.0 0.9989 

Cr 0.5, 1.0, 1.5, 2.0, 2.5 0.9988 

Cu 0.1, 0.5, 1.0, 1.5, 2.0 0.9977 

Pb 0.5, 1.0, 1.5, 2.0, 2.5 0.9959 

Zn 0.5, 1.0, 1.5, 2, 2.5 0.9974 

 

 

 

 

 



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57 

The determination of heavy and trace metals 

in Ocimum Lamiifolium 

As indicated in Table 5, all six metals (Cd, Pb, 

Co, Cr, Cu, Zn) were detected in all samples of 

the selected medicinal plant with variable 

concentrations in the sites. The results revealed 

that the concentration of zinc was the highest and 

that of cadmium was the least of all the metals. 

Furthermore, the results revealed that there were 

variable concentrations of each analyte metal in 

the selected sites. 

Concentration trends of metals in Dendo koysha 

As depicted in Table 5, zinc had the highest 

concentration among the metals and the metal 

with the next highest concentration was copper. 

The fact that zinc had the highest concentration 

among these metals was also true in other herbal 

medicinal plants based on different literatures 

(Baye and Haymete, 2010). But, cadmium and 

cobalt had the same concentration, which is 0.04 

mg/L; similarly chromium and lead had the same 

concentration, that is, 0.10 mg/L. 

Concentration trends of metals in Aruse weyde 

The concentration of the metals in this sample 

site varied from 0.05 to 0.78 mg/L. The metal 

with the highest concentration and the one with 

the least concentration were zinc and cadmium, 

respectively. The concentrations of Co, Cr, Cu 

and Pb were 0.06, 0.18, 0.25, and 0.08, 

respectively (Table 5). The concentrations of the 

selected metals varied in different sites may be 

due to the difference in soil types, ecological 

locations, etc. (Ambaye and Mussa S., 2015). 

 

Concentration trends of metals in Edo mazegaja 

Based on the results given on Table 5, the 

concentrations of the metals varied from 0.05 to 

0.54 mg/L. Though the concentrations differed 

from the other sample sites in this study, the 

metals with the highest and the least 

concentrations were zinc and cadmium, 

respectively. The concentration of Co, Cr, Cu 

and Pb were 0.07, 0.17, 0.19 and 0.10, 

respectively. Here, also the concentration 

differences of the selected metals from the other 

sites were observed due to the variation of 

different factors like ecological locations.   

Comparison of the concentration of each 

metal among the sample sites and with 

different permissible limits 

Cadmium 

As indicated in Table 5, the concentration of 

cadmium ranges from 0.04 mg/L to 0.05 mg/L. 

This result showed that there was no such much 

difference in the concentration of Cd in all the 

sites selected. Other literatures showed that the 

concentration of cadmium in other herbal 

medicines varied between 0.0045 mg/L and 

0.0091 mg/L; for instance, in champion leaf, its 

concentration was 0.0068 ppm (Baye and 

Haymete, 2010). However, the concentration of 

cadmium in the study area was well below the 

permissible limit set by WHO and other 

organizations. The permissible limit of cadmium 

in medicinal plants set by WHO, China and 

Thailand, was 0.3 mg/L, which is equivalent to 

0.3 mg/L (FAO/WHO, 2006). The literatures 

suggested that it is safe for consumption if its 

level is less or equals to this permissible limit. 

 



East Afr. J. Biophys. Comput. Sci. (2022), Vol. 3, No. 2, 48-60 
 

58 

Cobalt 

The concentration of cobalt in the studied 

medicinal plant ranges from 0.04 mg/L to 0.07 

mg/L. This result indicated that there was 

variation in the concentration of cobalt in the 

sample sites. However, the difference in the 

concentration is not such much great. For herbal 

plants, the WHO/FAO has not set any regulation 

limit for cobalt. But, according to Jabeen et al. 

(2010) the concentration of cobalt in different 

plant samples ranges from 0.18 to 0.4 mg/L 9. 

Thus, the obtained result of cobalt is not greater 

than these results.  

Chromium 

As depicted in Table 5, the concentration of 

chromium ranges from 0.10 mg/L to 0.18 mg/L. 

This range indicated that there was a 

concentration variation of chromium in different 

sites of the selected area. The research done on 

the heavy metal analysis of seven herbal 

medicines reported that the concentration of 

chromium ranges from 0.04 ppm to 0.20 ppm 

(Baye and Haymete, 2010). So, these values are 

comparable with the concentrations of chromium 

in the current study. The permissible limit for 

chromium in herbal medicinal plants has not 

been set by the WHO yet. However, 2.0 ppm was 

set by Canada as the permissible limit of 

chromium in raw medicinal plant. High intake of 

chromium is reported to have a toxic effect, 

causing skin rash, kidney and liver damage, 

cancer of the lungs and nose irritations (Khan et 

al., 2008). 

Copper  

As indicated in Table 5, the concentration of 

copper varied between 0.19 mg/L and 0.25mg/L. 

This result indicated that there is a concentration 

difference of the metal in different sites which 

may be related with different factors like soil 

type difference. Regulatory limits for copper in 

herbal medicines have not yet been established 

by the WHO/FAO However, China and 

Singapore in 2008 set the permissible limits of 

20 mg/Land 150 mg/L, respectively (Jabeen et 

al., 2010). Thus, the concentration of copper in 

the studied medicinal plant was well below than 

these limits. 

Lead 

The results in Table 5 showed that the 

concentration of lead in the study area varied 

between 0.08 mg/L and 0.1 mg/L. From this, it 

is obvious that there was almost uniform pattern 

in the distribution of lead. The concentrations of 

lead varied between 0.02 mg/L and 0.09 mg/L 

in other medicinal herbs as indicated in the 

report of the Journal of Scientific and 

Engineering Research, 2016, 3(2). So, the result 

of lead in the present study was approximately 

equals to the above values. The WHO (2006), 

Malaysia, China and Thailand (2008) set the 

permissible limit for lead in medicinal herbs as 

10 mg/L (Khan et al., 2008). So, the results of 

the study area showed that the concentration of 

lead was well below the permissible limit. 

Zinc 

Table 5 indicated that the concentration of zinc 

in the study area ranges from 0.54 mg/L to 1.21 

mg/L. When compared to the variation in the 

concentration of other metals, the difference is 

great in the case of zinc as well as its 

concentration was high. The permissible limit 

for zinc in herbal medicines set by WHO/FAO 

is 50 mg/L. Though there is little information 



East Afr. J. Biophys. Comput. Sci. (2022), Vol. 3, No. 2, 48-60 
 

59 

about its toxicity, consumption of zinc beyond 

the permissible limit may result in toxic effect 

on the immune system (Waheed and Fatima, 

2013). The concentration of zinc in the studied 

medicinal plant was very much below than this 

value. 

 

Table- 5: Mean cncentrations of metals (mg/L) in the studied medicinal plant in the samples 

cllected from different sites. 

 

Metals 

Concentrations of metals in three sites (mg/L) 

Mean±SD 

Dendo Koysha Aruse weyde Edo Mazegaja 

Cd 0.04 ± 0.01 0.05 ± 0.01 0.05 ± 0.01 

Co 0.04 ± 0.01 0.06 ± 0.00 0.07 ± 0.01 

Cr 0.10 ± 0.01 0.18 ± 0.03 0.17 ± 0.02 

Cu 0.20 ± 0.02 0.25 ± 0.01 0.19 ± 0.00 

Pb 0.10 ± 0.01 0.08 ± 0.02 0.10 ± 0.06 

Zn 1.21 ± 0.13 0.78 ± 0.06 0.54 ± 0.06 

 

CONCLUSION  

The contamination of herbal medicines is due to 

the accumulation of the metals in different parts 

of the medicinal plants. Hence, the 

concentrations of the metals should be measured 

in order to be free of their toxic effects. 

In the present study, the analysis of heavy and 

trace metals in the selected medicinal plant was 

made by using FAAS by following the 

optimized digestion method. The digestion 

method was optimized by changing the 

parameters until clear and colourless solution 

was obtained. The concentrations of all the 

selected metals in the medicinal plant, Ocimum 

Lamiifolium, were determined. The 

concentrations of Zn, Cu, Cr, Pb, Co and Cd are 

0.847, 0.214, 0.153, 0.0936, 0.0579 and 0.0489, 

respectively. 

In the studied area, the concentration of zinc 

was the highest of all the metals. However, its 

concentration was not above internationally 

accepted permissible limits. In the medicinal 

plant under study, the concentrations of some 

metals were below and that of others were 

nearly equal to internationally accepted 

permissible limits so that this showed the plant 

is safe for medicinal uses. 

Furthermore, the efficiency of the digestion 

method was confirmed by percentage recoveries 

which were within accepted ranges, that is, 80 – 

120%. 

Acknowledgement 

First and for most the author would like to 

glorify almighty God. The author also 

acknowledge Wolaita Sodo University, Ethiopia 

for financial support and cooperation in this 

research work. 



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60 

References 

Ambaye T.G. and Mussa S. 2015. In Vitro Antimicrobial 

Efficacy of fractions from Ocimum lamifollium 

leaves extrct. Nat Prod Chem Res 3:6 196. 

doi:10.4172/2329-6836.1000196  

Baker R.D., Greer F.R. and Committee on Nutrition. 

(2010). Diagnosis and prevention of iron deficiency 

and iron-deficiency anemia in infants and young 

children (0–3 years of age). Pediatrics, 126(5), 

1040-1050. 

Baye H. and Hymete A. 2010. Lead and cadmium 

accumulation in medicinal plants collected from 

environmentally different sites. Bull Environ 

Contam Toxicol. 84: 197-201. 

Chen K., Jiao J.J., Huang J. and Huang R. 2007. 

Multivariate statistical evaluation of trace elements 

in groundwater in a coastal area in Shenzhen, 

China. Environ. Pollut. 147(3): 771-780 

CSA (Central Statistics Agency) 2019. Final report THE 

FEDERAL DEMOCRATIC REPUBLIC OF 

ETHIOPIA CENTRAL STATISTICAL AGENCY, 

ETHIOPIA 

Debas H.T. 2006. The problem of heavy reliance on 

international medical graduates to supply the 

surgical workforce in the United States. Surgery 140 

(3): 359-361.  

Jabeen S., Shah M.T., Khan S. and Hayat M.Q. 2010. 

Determination of major and trace elements in ten 

important folk therapeutic plants of Haripur basin, 

Pakistan. J. Med. Plant. Res. 4(7): 559-566. 

Khan A., Khan L., Hussain I., Marwat K. and Akhtar N., 

2008. Profile of heavy metals in selected medicinal 

plants. Pak. J. Weed Sci. Res. 14(2): 101-110 

Khan S.A., Khan L., Hussain I., Marwat K.B. and 3 and 

Akhtar N. 2008. Profile of heavy metals in selected 

medicinal plants. Pak. J. Weed Sci. Res 14 (2): 101-

110. 
Lanini J., Duarte-Almeida J.M., Nappo S. and Carlini E. 

A. 2009. What comes from the earth does not hurt: 

reports of problems related to the use of medicinal 

plants by roots of Diadema/SP. Brazilian Journal of 

Pharmacognosy 19: 121-129. 

Tilburt J.C. and Kaptchuk T.J. 2008. Herbal medicine 

research and global health: an ethical analysis. Bull. 

World Health Organ. 86: 594-599. 

Waheed S. and Fatima I. 2013. Instrumental neutron 

activation analysis of Emblica officinalis, 

Terminalia belerica and Terminalia chebula for 

trace element efficacy and safety. Appl Radiat Isot. 

77: 139-144. 

WHO 2005. Quality Control Methods for Medicinal Plant 

Materials, Revised, Geneva.   

WHO 2006.The world health report 2006: working 

together for health. World Health Organization  

.  

  
 


