NATURAL RESOURCE LETTER

Study on selected trace elements and heavy metals in somepopular medicinal plants from Sudan

Ammar Mubark Ebrahim • Mohamed Hassan Eltayeb •

Hassan Khalid • Haidar Mohamed •

Wail Abdalla • Peter Grill • Bernhard Michalke

Received: 15 September 2010 / Accepted: 17 January 2012 / Published online: 12 February 2012

� The Japanese Society of Pharmacognosy and Springer 2012

Abstract This study reports on the determination of 11

elements in 33 medicinal plants from Sudan and discusses

a possible correlation between their curative effects and

their trace elements content. Further, a possible accumu-

lation of adverse heavy metals could be excluded. A total

of 11 elements (cadmium, lead, mercury, tin, copper, iron,

manganese, zinc, chromium, selenium and magnesium)

were determined using inductively coupled plasma (ICP)-

optical emission spectrometry (ICP-OES), ICP-sector field-

mass spectrometry (ICP-sf-MS) and hydride generation

(HG)-ICP-OES techniques. The results of the present study

showed no heavy metal accumulation in any of the plants.

Cd, Pb, Hg and Sn were found only in trace concentrations

significantly below the global limits. This indicates the

possibility of a safe use of these medicinal plants. Elevated

chromium concentrations were found in those phytophar-

maca which are employed for the treatment of diabetes

mellitus in Sudanese traditional medicine. Cr was detected

in the same range as in other plants reported to be applied

for diabetes mellitus treatment. Aside from these medicinal

plants, some others were identified which could be poten-

tial sources for providing reasonable amounts of Cr, Zn,

Mn, Se and Mg for the treatment of diabetes mellitus,

smooth muscle relaxation and/or against gastro-intestinal

cramps.

Keywords Trace elements � Heavy metals �Medicinal plants

Introduction

Importance of trace elements and minerals

In recent years, research on the role of trace elements and

minerals in various metabolic processes and their impact

on human health has become an area of particular concern

and high priority in environmental research and protection.

The functional role of trace elements is described in terms

of their nutritionally essential role or their potential toxicity

[1, 2].

Minerals are of critical importance in the diet.

Throughout the world, there is increasing interest in the

importance of dietary minerals in the prevention of several

diseases. An essential element is that required for the

maintenance of life when a deficient intake consistently

results in an impairment of a function from optimal to

suboptimal and, in turn, supplementation with this element

(but not of others) prevents or cures this impairment [3].

Trace elements play an important role as catalysts or parts

of prosthetic groups for enzymes, and, consequently,

insufficient supply leads to element-specific deficiency

symptoms. However, when present in enormous excess, all

of them can exert toxicity. In tissues and fluids, metals are

mostly present as complexes with organic compounds like

amino acids, proteins and peptides, organic acids or

glutathione [4, 5].

A. M. Ebrahim (&) � M. H. Eltayeb

Sudan Atomic Energy Commission, Khartoum, Sudan

e-mail: ammar_mubark@yahoo.com

H. Khalid � H. Mohamed � W. Abdalla

Medicinal and Aromatic Plants Research Institute,

National Center for Research, Khartoum, Sudan

P. Grill � B. Michalke

Research Unit Analytical BioGeoChemistry, Helmholtz Center

Munich, German Research Center for Environmental Health,

Neuherberg, Germany

123

J Nat Med (2012) 66:671–679

DOI 10.1007/s11418-012-0630-6

Medicinal plants

According to the World Health Organization (WHO), the

use of traditional herbal medicine has spread not only in the

developing countries, but also in the industrialised regions,

as a complementary way to treat and to prevent diseases.

The pharmacological properties of the medicinal plants

have been attributed to the presence of active constituents

which are responsible for important physiological functions

in living organisms [3, 6]. Consequently, medical practi-

tioners are also prescribing herbal medicine teas and herbal

extracts as a supplementary type of treatment in everyday

problems caused by our modern civilisation [7].

Sudan has an immense diversity and variation in vege-

tation and is one of the richest countries with regard to

phytopharmaca. Although herbal remedies are often per-

ceived as being natural and, therefore, safe, they are not

principally free from adverse effects. While many inves-

tigations of the quality values of medicinal plants are being

reported in the current literature, less emphasis has been

made on the metal content of herbal products [7].

Sudanese phytopharmaca and trace elements

The WHO estimates that 80% of the developing world’s

people rely on herbs for their primary health care needs [8].

This is also the case in Sudan (personal communications).

Sudanese medicinal plants in dried form have been

exported to different African, Asian, European, North and

South American countries since 1952. Variation in mar-

keted species and the quantity of plant material exported is

subjected to international demands. It was recently

observed that the demand for Hibiscus sabdariffa, Cassia

acutifolia and Boswellia papyrifera has increased, with an

annual revenue of about 42.2 billion USD. Sudan imports a

variety of plant species for use in traditional medicine in

their crude form or as herbal teas. Plant materials are

mainly imported from Egypt, Syria, India, China, Niger,

Guatemala, Saudi Arabia and Tanzania, as well as other

nearby African countries. This cost the country about

900,000 USD annually [9].

It is generally accepted that trace elements play an

important role in the maintenance of human health. How-

ever, a correlation between the elemental composition of

the Sudanese medicinal plants investigated here and their

probably curative properties have not been established yet.

Besides, element concentrations present in medicinal plants

are, aside from other organic plant compounds, of great

importance in order to understand their pharmacological

actions [3, 6, 10]. And, on the contrary, in some cases,

plants may be contaminated with toxic concentrations of

metals which may cause serious health hazard sequences,

such as renal failure, symptoms of chronic toxicity and

liver damage [7].

One very important feature when considering the health

effects of trace elements is their slow accumulation in

tissues, even at low doses. Hence, acute effects are reported

very rarely, whereas chronic exposure can lead to the

build-up of higher concentrations and onset of disease.

Trace element toxicity can manifest with non-specific

symptoms and, often, epidemiology is the only possible

approach to ascertain their role [5].

The present study was conducted to establish baseline

information for trace elements and the levels of heavy

metals in various Sudanese plants, which may help

upcoming research to focus on the site of nutrition, phar-

macology and toxicology. The results are compared to the

trace element concentrations of other medicinal plants from

the literature and discussed with respect to the known

actions of some trace elements. For our investigations, we

have selected the most popular items used in traditional

medicine in Sudan.

Materials and methods

Sample collection

Thirty-three different medicinal plants were collected from

a local market in Sudan. Botanical identification and

authentication of the collected species with depositions of

herbarium specimens have been done by the Medicinal and

Aromatic Plants Research Institute (MAPRI)—National

Center for Research, Sudan. A brief review on the use of

these plants in alternative phytopharmaca-based (tradi-

tional) medicine with their common and scientific names is

given in Table 1.

Chemicals and reagents

Chemicals and reagents used throughout this work were

of suprapure grade. Certified stock standards (1000 mg/L,

each) for Cd, Hg, Pb and Se were purchased from CPI

(Santa Rosa, CA, USA), whilst the customised certified

multi-element standard containing Cr, Zn, Cu, Mg and

Mn was bought from Horiba Jobin Yvon, Pullach, Ger-

many. Dilutions of standards and samples were done

using deionised water (18.2 MX cm) prepared by a

Milli-Q system (Millipore, Bedford, MA, USA). HNO3

was purchased from Merck (Darmstadt, Germany) and

sub-boiling distilled before use. Arliq and oxygen

(99.999% purity) were purchased from Air Liquide,

Grobenzell, Germany.

672 J Nat Med (2012) 66:671–679

123

Ta

ble

1A

bri

efre

vie

wo

fth

est

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ied

pla

nts

and

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ru

sein

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itio

nal

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icin

e

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tan

ical

nam

eL

oca

ln

ame

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ily

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rm,

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icin

alu

ses

and

do

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e/d

ayC

oll

ecti

on

area

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cia

nil

oti

ca(L

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el.

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atio

no

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uit

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mo

nia

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mal

aria

,

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asa

gar

gle

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ton

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ow

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of

fru

its

isu

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eat

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rrh

oea

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sen

tery

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cold

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dfe

ver

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ank

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ulc

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ive,

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nce

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esti

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wia

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etr

eatm

ent

of

gen

eral

fati

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ean

dir

on

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cien

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mia

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eid

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sen

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len

sis

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mel

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eish

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mb

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ceae

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no

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of

the

leav

esis

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rth

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ent

of

bro

nch

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,fe

ver

,co

ug

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dst

om

ach

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pla

ints

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rov

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eh

ealt

ho

fh

yp

er-t

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on

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ph

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mtu

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tum

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uta

ceae

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no

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go

fth

ele

aves

isu

sed

asan

anti

-sp

asm

od

ic,

anti

-dia

rrh

oea

and

also

use

dfo

rth

etr

eatm

ent

of

the

pro

stat

e

Ab

uH

amed

J Nat Med (2012) 66:671–679 673

123

Ta

ble

1co

nti

nu

ed

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tan

ical

nam

eL

oca

ln

ame

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ily

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rm,

med

icin

alu

ses

and

do

sag

e/d

ayC

oll

ecti

on

area

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iscu

ssa

bd

ari

ffa

L.

Kar

kad

ehM

alv

acea

eM

acer

atio

no

rin

fusi

on

of

5g

of

the

fru

its

epic

aly

ces

isu

sed

anan

ti-h

yp

erte

nsi

ve,

diu

reti

c,an

ti-m

icro

bia

l,an

ti-s

pas

mo

dic

and

for

rela

xat

ion

Kh

arto

um

Sta

te

Hyp

ha

ene

theb

aic

aD

om

Are

cace

aeT

eng

ram

so

fa

po

wd

ero

ffr

uit

epic

arp

sis

use

dfo

rth

e

trea

tmen

to

fg

astr

oin

test

inal

ailm

ents

,w

ou

nd

s

anti

-in

flam

mat

ory

and

anti

-hy

per

ten

siv

e

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azin

La

wso

nia

iner

mis

L.

Hen

na

Ly

thra

ceae

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erat

ion

of

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esis

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das

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acte

rial

and

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-fu

ng

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har

tou

mlo

cal

mar

ket

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msa

tivu

mL

.H

abel

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ssic

acea

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so

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ep

ou

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fse

eds

for

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trea

tmen

to

fM

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ot

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arto

um

loca

lm

ark

et

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pin

us

term

isL

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urm

us

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acea

e–P

apil

ion

oid

eae

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eb

oil

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eds

are

eate

nfo

rth

eh

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ng

of

bo

ne

frac

ture

s,b

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ved

tore

du

ceb

loo

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gar

Do

ng

ola

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ella

sati

vaL

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lkam

oo

nA

laso

dR

anu

ncu

lace

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wo

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ms

of

the

seed

sar

eu

sed

totr

eat

man

yd

isea

ses,

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asd

iab

etes

,h

yp

erte

nsi

on

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do

min

alu

lcer

s,p

rost

ate

gla

nd

infl

amm

atio

ns

and

asan

thel

min

tics

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arto

um

loca

lm

ark

et

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an

um

ha

rma

laH

arm

alZ

yg

op

hy

llac

eae

1.5

gra

ms

of

ap

ow

der

of

the

seed

sis

use

das

anan

thel

min

tic

and

wit

ho

ther

her

bs

for

dem

enti

a

Kh

arto

um

loca

lm

ark

et

Pen

nis

etu

mg

lau

cum

(L.)

R.

Br.

Du

kh

nP

oac

eae

Th

ep

ow

der

of

fru

its

isu

sed

asan

anti

-rh

eum

atic

Ny

alla

Sa

lva

do

rap

ersi

caL

.A

rak

Sal

vad

ora

ceae

Th

eb

ran

ches

and

roo

tsar

eu

sed

for

bru

shin

gte

eth

Kas

sala

Sen

na

ale

xan

dri

na

Mil

l.S

enn

aM

ekk

aF

abac

eae-

Cae

salp

inio

idea

eM

acer

atio

no

f5

go

fth

efr

uit

sis

use

das

ala

xat

ive

Wes

tO

md

urm

an

Ses

am

um

ind

icu

mL

.S

imsi

mP

edal

iace

aeO

ilfr

om

seed

sis

use

dto

pic

ally

asa

bo

dy

mas

sag

ean

dfa

tig

ue

trea

tmen

t,fo

rco

ug

han

dco

ld.

20

go

fth

ese

eds

isal

so

use

das

nu

trit

ive,

lax

ativ

e,d

emu

lcen

tan

dem

oll

ien

tp

rop

erti

es

Ged

arif

So

len

ost

emm

aa

rgel

(Del

.)H

ayn

eH

arg

hel

Asc

lep

iad

acea

eM

acer

atio

no

f2

go

fth

ed

ried

aeri

alp

arts

isu

sed

for

cou

gh

,

gas

tro

-in

test

inal

cram

ps

and

uri

nar

ytr

act

pro

ble

ms

Riv

erN

ile

Sta

te

So

rgh

um

bic

olo

ur

Mo

ench

Zu

raP

oac

eae

Po

wd

ero

ffr

uit

sis

use

das

po

rrid

ge,

then

use

das

an

anti

-ab

ort

ive,

cyan

og

enet

ic,

dem

ulc

ent,

diu

reti

c,em

oll

ien

t,

into

xic

ant

also

use

das

ah

aem

atin

icag

ent

(an

ti-a

nae

mic

)

Ged

arif

-Rah

ad

Ta

ma

rin

du

sin

dic

aL

.A

red

eib

Fab

acea

e–C

aesa

lpin

ioid

eae

Mac

erat

ion

of

10

go

fth

efr

uit

sis

use

das

anti

-mal

aria

trea

tmen

tan

da

lax

ativ

e

Al

Ob

eid

Tri

ticu

ma

esti

vum

L.

sub

sp.

aes

tivu

mG

amih

Po

acea

eT

he

fru

its

are

use

das

pil

lsto

trea

tco

nst

ipat

ion

,as

an

erv

es

rela

xan

t.T

he

fru

its

wit

hm

ilk

and

gh

eear

eu

sed

tofe

ed

pu

erp

eral

wo

man

Gez

ira

Ziz

iph

us

spin

a-c

hri

sti

(L.)

Des

f.A

lsid

rR

ham

nac

eae

Th

ree

gra

ms

of

the

leav

esar

ecr

ush

edan

du

sed

asa

po

ult

ice

for

hai

rto

nic

(sh

amp

oo

san

do

ther

cosm

etic

pre

par

atio

ns)

Al

Ob

eid

674 J Nat Med (2012) 66:671–679

123

Sample preparation

Drying and homogenisation

Samples had already been dried at room temperature before

transportation to the laboratory. There, freeze-drying was

applied at 10�C sample temperature (Christ-Heraeus Beta

freeze dryer, Osterode, Germany) for 4 days until weight

constancy was reached. Aliquots of the plant material were

cut into small pieces using a ceramic knife and subse-

quently grinded and homogenised using an agate ball mill.

The resulting fine powder was used for digestion.

Pressure digestion

The dried and homogenised samples were properly

weighed into quartz vessels. Subsequently, 1 mL HNO3,

suprapure, sub-boiling distilled (Merck, Darmstadt), was

added. The vessels were closed and introduced into a

pressure digestion system (Seif, Unterschleissheim) for

10 h at 170�C. The resulting clear solutions were filled up

exactly to the mark at 10 mL with Milli-Q H2O and were

then ready for element determination.

Sample analysis

Cd, Hg and Pb were analysed with inductively coupled

plasma (ICP)-sector field-mass spectrometry (ICP-sf-MS),

Cr, Zn, Cu, Mg and Mn were measured using ICP atomic

emission spectrometry (ICP-AES), whilst Se was deter-

mined with hydride generation ICP-AES (HG-ICP-AES).

These methods were each best suited for measurement of

the respective elements at the given concentrations in these

samples.

ICP-optical emission spectrometry (OES) measurement

An ICP-AES ‘‘Spectro Ciros Vision’’ system (SPECTRO

Analytical Instruments GmbH & Co. KG, Kleve, Germany)

was used for the Cr, Zn, Cu, Mg and Mn determination in

digested samples. Sample introduction was carried out using

a peristaltic pump equipped with an ‘‘anti-pulse-head’’

(SPETEC, Erding, Germany), connected to a Meinhard

nebuliser with a cyclone spray chamber. The measured

spectral element lines were Cr 267.716 nm, Zn 213.956 nm,

Cu 324.754 nm, Mg 279.079 nm and Mn 257.611 nm. The

RF power was set to 1400 W, the plasma gas was 13 L Ar/min

and the nebuliser gas was 0.6 L Ar/min.

ICP-sf-MS measurement

An ELEMENT 1, Thermo-Finnigan (Bremen, Germany)

ICP-sf-MS instrument was employed for the 114Cd, 202Hg

and 208Pb determination in low-resolution mode. 103Rh was

administered to each sample at a concentration of 1 lg/L as

the internal standard. Sample introduction was carried out

using a peristaltic pump equipped with an ‘‘anti-pulse-

head’’ (SPETEC, Erding, Germany), connected to a

Meinhard nebuliser with a cyclone spray chamber. The RF

power was set to 1200 W, the plasma gas was 15 L Ar/min

and the nebuliser gas was 0.9 L Ar/min.

HG-ICP-OES

An ICP-AES ‘‘Optima 7300’’ system (Perkin Elmer,

Rodgau-Jugesheim, Germany) was used for the Se deter-

mination in digested samples. Sample introduction was

carried out using on-line hydride generation by mixing the

sample with NaBH4 (prepared in 100 mM NaOH) and 5%

HCl at a ratio of 1:2:1. A glass gas–liquid separator was

employed as the sample introduction part to the ICP torch.

The measured spectral element line was Se 196.090 nm.

The RF power was set to 1200 W, the plasma gas was

15 L Ar/min and the nebuliser gas was 0.6 L Ar/min.

Quality control for element determinations

Each of the determination methods had been validated

previously by regular laboratory inter-comparison studies

and by regular analysis of adequate certified reference

materials, the latest directly before this study.

Routinely, ten measurements, three blank determina-

tions and a control determination of a certified standard for

all the mentioned elements were performed. Calculation of

the results was carried out on a computerised laboratory

data management system, relating the sample measure-

ments to calibration curves, blank determinations, control

standards and the weight of the digested sample.

Results and discussion

In the present work, trace element analysis was carried out

among some popular Sudanese medicinal plants in order to

determine their trace elements content or to monitor a

possible accumulation of adverse heavy metals. A total of

11 elements were analysed: cadmium, lead, mercury, tin,

copper, iron, manganese, zinc, chromium, selenium and

magnesium were determined in all the plants listed in

Table 1.

Table 2 gives the concentrations of Cd, Pb, Hg and Sn.

The concentration of heavy metals in collected, non-culti-

vated medicinal plants (non-controlled growth) beyond

permissible limits is a matter of great concern to public

safety all over the world. The problem is rather more

serious in Sudan, because medicinal plants are neither

J Nat Med (2012) 66:671–679 675

123

controlled nor properly regulated by quality assurance

parameters; however, medicinal herbs are easily contami-

nated during growth, development and processing. The

WHO recommends that medicinal plants may be checked

for the presence of heavy metals; further, it regulates the

maximum permissible limits of toxic metals like arsenic,

cadmium and lead, which amount to 1.0, 0.3 and 10 mg/kg,

respectively [11]. The analysis of the present data reveals

that heavy metals such as Cd, Pb, Hg and Sn are found only

in trace concentrations. Lead and cadmium were signifi-

cantly below the WHO limits. Mercury was found to be

much lower than the limit of 0.5 lg Hg/g recommended in

drugs derived from plants in Singapore [12]. This indicates

the possibility of the safe use of these medicinal plants, as

shown in Table 2.

Cadmium was found in the range 0.8–187 lg/kg, where

the highest concentration was detected in Guiera senegal-

ensis, while the lowest value was found in Acacia Senegal.

Lead was observed in the range between 2.6 and 481 lg/kg,

the highest value being associated with Senna alex-

andrina and the lowest with Acacia senegal. Mercury was

observed in very trace amounts in all the studied plants,

varying between 0.2 lg/kg (Grewia tenax) and 40 lg/kg

(Guiera senegalensis). Tin showed a range between 0.2 and

845 lg/kg in Lupinus termis and Cymbopogon nervatus,

respectively. The heavy metal concentrations in these

Table 2 Concentration of Cd,

Pb, Hg and Sn in the studied

Sudanese medicinal plants

Plant Cd

(mean ± SD,

lg/kg)

Pb

(mean ± SD,

lg/kg)

Hg

(mean ± SD,

lg/kg)

Sn

(mean ± SD,

lg/kg)

Acacia nilotica (L.) Willd. Ex Del. 16 ± 1.6 85 ± 3.4 0.23 ± 0.002 49.8 ± 4.3

Acacia senegal (L.) Willd. 0.8 ± 0.01 3 ± 0.1 0.21 ± 0.001 13.8 ± 0.1

Adansonia digitata L. 6.0 ± 0.3 16 ± 0.9 0.25 ± 0.002 13.6 ± 3.9

Allium sativum L. 13 ± 0.5 8 ± 1.0 0.33 ± 0.002 6.70 ± 1.0

Ammi visnaga L. 51 ± 1.4 334 ± 7.1 0.24 ± 0.001 23.1 ± 2.9

Balanites aegyptiaca (L.) Del. 7.0 ± 0.5 11 0.21 ± 0.001 17.1 ± 2.2

Cajanus cajan (L.) Millsp. 114 ± 0.7 7 ± 0.9 0.23 ± 0.004 53.0 ± 2.5

Capsicum frutescens L. 29 ± 0.8 63 ± 1.2 0.46 ± 0.001 92.6 ± 4.6

Citrullus colocynthis (L.) Schrad. 9 ± 0.2 326 ± 26 0.22 ± 0.002 9.4 ± 1.2

Coriandrum sativum L. 29 ± 0.7 23 ± 2.8 3 ± 0.001 9.6 ± 1.3

Cucurbita maxima L. 36 ± 3.7 95 ± 9.4 4 ± 0.001 14.9 ± 0.9

Cymbopogon nervatus (Hochst.) Chiov. 67 ± 3.5 206 ± 10 6 ± 0.01 845 ± 41

Cymbopogon proximus Stapf. 29 ± 1.2 61 ± 4.6 0.27 ± 0.001 10.2 ± 0.1

Foeniculum vulgare P. Mill. 63 ± 1.9 351 ± 4.9 8 ± 0.002 35.5 ± 2.9

Grewia tenax (Forssk.) Fiori 16 ± 0.3 15 ± 1.9 0.2 ± 0.001 18.2 ± 0.1

Guiera senegalensis J.F. Gmel. 187 ± 10.6 454 ± 74 40 ± 0.1 54.8 ± 3.9

Haplophyllum tuberculatum 91 ± 0.8 32 ± 7.5 0.22 ± 0.002 3.1 ± 0.3

Hibiscus sabdariffa L. 59 ± 0.4 167 ± 36 0.25 ± 0.001 81.0 ± 6.6

Hyphaene thebaica 5.0 ± 0.03 8 ± 1.4 0.21 ± 0.002 24.3 ± 2.8

Lawsonia inermis L. 15 ± 0.01 293 ± 68 25 ± 0.01 53.2 ± 4.9

Lepidium sativum L. 60 ± 2.5 16 ± 0.9 0.25 ± 0.001 4.9 ± 1.1

Lupinus termis L. 131 ± 7.7 8 ± 0.1 7 ± 0.02 0.2 ± 0.001

Nigella sativa L. 6.0 ± 0.4 106 ± 6.3 0.29 ± 0.001 83.0 ± 2.6

Peganum harmala 104 ± 1.4 252 ± 16 3. 0 ± 0.01 38.7 ± 3.8

Pennisetum glaucum (L.) R. Br. 25 ± 1.7 41 ± 3.6 0.21 ± 0.001 22.0 ± 2.9

Salvadora persica L. 13 ± 0.2 31 ± 1.9 0.23 ± 0.001 22.6 ± 2.6

Senna alexandrina Mill. 30 ± 0.9 481 ± 43 0.24 ± 0.001 17.4 ± 0.6

Sesamum indicum L. 10 ± 1.3 41 ± 5.4 0.26 ± 0.002 12.5 ± 1.0

Solenostemma argel (Del.) Hayne 16 ± 1.1 120 ± 0.1 20 ± 0.01 5.3 ± 0.8

Sorghum bicolour Moench 7.0 ± 0.2 18 ± 5.3 0.22 ± 0.001 41.4 ± 4.2

Tamarindus indica L. 4.0 ± 0.7 197 ± 43 0.24 ± 0.002 34.5 ± 2.6

Triticum aestivum L. subsp. aestivum 17 ± 0.1 23 ± 0.7 0.21 ± 0.002 11.9 ± 2.8

Ziziphus spina-christi (L.) Desf. 3.0 ± 0.1 22 ± 2.4 0.42 ± 0.01 27.1 ± 3.8

676 J Nat Med (2012) 66:671–679

123

Sudanese phytopharmaca were considerably lower than the

global recommendations (see above) for these metals and

may be as comparably low as the herbal preparations from

Europe. No heavy metal-based health risk emanates from

the use of these phytopharmaca [11].

Another important aspect is the possible content of

(probably) curative trace elements. Plant-based drugs have

been in use in the amelioration of various ailments, ranging

from common cold up to the support of even cancer

therapies [13, 14], and various trace elements were previ-

ously shown to have a positive impact on some diseases.

As an example, Cr, Mn, Cu and Zn were reported to be

involved in the secretion of insulin from beta cells of the

islets of Langerhans and to enhance insulin action [15].

Further, abnormal zinc metabolism has been suggested to

play a role in the pathogenesis of diabetes [16].

The element concentrations of Cu, Fe, Mn, Zn, Cr, Se

and Mg are listed in Table 3. The variation in the elemental

Table 3 Concentration of some essential trace elements in the studied medicinal plants

Plant Cu

(mean ± SD,

mg/kg)

Fe

(mean ± SD,

mg/kg)

Mn

(mean ± SD,

mg/kg)

Zn

(mean ± SD,

mg/kg)

Cr

(mean ± SD,

mg/kg)

Se

(mean ± SD,

mg/kg)

Mg

(mean ± SD,

mg/kg)

Acacia nilotica (L.) Willd. Ex

Del.

3.4 ± 0.2 250 ± 9.0 9.8 ± 0.6 11.1 ± 2.0 0.58 ± 0.05 0.11 ± 0.01 459 ± 29

Acacia senegal (L.) Willd. 1.0 ± 0.1 10 ± 1.0 2.4 ± 0.01 0.2 ± 0.1 0.57 ± 0.01 0.02 ± 0.01 1235 ± 36

Adansonia digitata L. 4.3 ± 0.4 32 ± 3.0 10.5 ± 0.9 12.8 ± 1.0 0.58 ± 0.05 0.06 ± 0.01 2610 ± 24

Allium sativum L. 0.8 ± 0.1 5 ± 0.3 2.3 ± 0.1 5.6 ± 0.3 0.45 ± 0.06 0.05 ± 0.01 176 ± 7.8

Ammi visnaga L. 9.6 ± 0.1 1715 ± 8.0 64.3 ± 1.3 44.3 ± 0.9 2.6 ± 0.20 0.04 ± 0.01 4450 ± 49

Balanites aegyptiaca (L.) Del. 1.1 ± 0.1 12 ± 0.9 1.3 ± 0.1 3.0 ± 0.1 0.53 ± 0.05 0.04 ± 0.01 519 ± 9.2

Cajanus cajan (L.) Millsp. 11.8 ± 0.4 35 ± 1.0 13.6 ± 0.1 33.1 ± 0.4 0.56 ± 0.04 55 ± 0.01 1040 ± 0.01

Capsicum frutescens L. 9.5 ± 0.1 174 ± 2.0 12.2 ± 0.2 16.6 ± 0.2 0.53 ± 0.05 124 ± 0.02 1485 ± 35

Citrullus colocynthis (L.)

Schrad.

6.6 ± 0.5 46 ± 5.0 14.9 ± 0.8 27.6 ± 4.6 0.58 ± 0.05 1.13 ± 0.06 2070 ± 28

Coriandrum sativum L. 11.3 ± 0.2 107 ± 10 22.8 ± 1.6 39.3 ± 0.4 0.52 ± 0.04 0.08 ± 0.01 3455 ± 7.3

Cucurbita maxima L. 11.6 ± 0.1 173 ± 13 31.8 ± 0.1 74.3 ± 1.3 0.56 ± 0.02 0.2 ± 0.06 3750 ± 42

Cymbopogon nervatus(Hochst.) Chiov.

3.7 ± 0.1 224 ± 5.0 30.2 ± 0.6 81.4 ± 5.9 0.66 ± 0.03 526 ± 0.04 2240 ± 11

Cymbopogon proximus Stapf. 1.3 ± 0.1 189 ± 10 208 ± 10.3 22 ± 5.0 0.58 ± 0.01 0.31 ± 0.01 880 ± 12

Foeniculum vulgare P. Mill. 10.7 ± 0.5 2105 ± 34 65.7 ± 3.4 25.0 ± 1.0 3.6 ± 0.03 40 ± 0.02 3750 ± 84

Grewia tenax (Forssk.) Fiori 3.6 ± 0.03 19 ± 2.0 7.3 ± 0.04 7.1 ± 0.2 0.56 ± 0.01 0.05 ± 0.01 1410 ± 14

Guiera senegalensis J.F. Gmel. 5.8 ± 0.5 534 ± 5.0 517.5 ± 32 26.5 ± 2.0 1.2 ± 0.09 0.08 ± 0.01 1995 ± 46

Haplophyllum tuberculatum 2.6 ± 0.1 82 ± 3.0 13.4 ± 0.4 11.1 ± 1.0 0.66 ± 0.01 0.08 ± 0.01 763 ± 33

Hibiscus sabdariffa L. 2.6 ± 0.1 260 ± 6.0 454 ± 4.3 18.0 ± 0.4 0.7 ± 0.02 0.02 ± 0.01 2695 ± 21

Hyphaene thebaica 2.2 ± 0.04 37 ± 0.6 4.0 ± 0.23 6.5 ± 0.1 0.61 ± 0.01 0.07 ± 0.01 984 ± 7

Lawsonia inermis L. 4.2 ± 0.2 259 ± 15 52.2 ± 2.0 12.5 ± 0.5 0.57 ± 0.01 0.19 ± 0.01 4070 ± 19

Lepidium sativum L. 4.4 ± 0.1 98 ± 3.0 23.1 ± 1.5 45.3 ± 3.5 0.53 ± 0.08 0.32 ± 0.01 3655 ± 16.2

Lupinus termis L. 8.9 ± 0.01 28 ± 0.1 23.1 ± 1.5 47.1 ± 1.7 0.63 ± 0.02 0.32 ± 0.01 1620 ± 57

Nigella sativa L. 7.8 ± 0.2 695 ± 41 33.9 ± 0.6 45.7 ± 1.8 1.8 ± 0.01 36 ± 0.04 3130 ± 56

Peganum harmala 5.6 ± 0.1 449 ± 11 44.1 ± 0.2 23.9 ± 0.07 0.8 ± 0.02 0.43 ± 0.01 2955 ± 35

Pennisetum glaucum (L.) R. Br. 6.4 ± 0.1 138 ± 14 13 ± 0.6 33.9 ± 0.35 0.55 ± 0.01 119 ± 0.03 1680 ± 28

Salvadora persica L. 3.9 ± 0.2 25 ± 0.6 3.8 ± 0.2 8.0 ± 0.62 0.61 ± 0.02 0.05 ± 0.01 614 ± 23

Senna alexandrina Mill. 4.6 ± 0.4 261 ± 13 13.2 ± 0.9 21.1 ± 1.2 0.67 ± 0.03 0.21 ± 0.01 2950 ± 45

Sesamum indicum L. 15.8 ± 0.9 663 ± 4.0 22.6 ± 2.4 51.9 ± 1.7 1.23 ± 0.20 0.03 ± 0.01 3780 ± 35

Solenostemma argel (Del.)

Hayne

10.8 ± 0.01 501 ± 6.0 156.5 ± 9.2 24.7 ± 0.6 1.5 ± 0.05 0.46 ± 0.01 5825 ± 50

Sorghum bicolour Moench 3.8 ± 0.1 45 ± 3.0 16.3 ± 0.6 30.2 ± 1.3 0.58 ± 0.02 40 ± 0.07 1370 ± 42

Tamarindus indica L. 7.3 ± 0.2 96 ± 2.0 8.1 ± 1.2 8.8 ± 0.8 0.52 ± 0.03 0.02 ± 0.01 1035 ± 21

Triticum aestivum L. subsp.

aestivum5.2 ± 0.1 77 ± 0.3 20.0 ± 0.2 30.5 ± 0.6 0.58 ± 0.02 33 ± 0.05 1590 ± 28

Ziziphus spina-christi (L.) Desf. 2.8 ± 0.2 20 ± 3.0 13.3 ± 1.3 5.7 ± 0.2 0.53 ± 0.02 114 ± 0.06 722 ± 57

J Nat Med (2012) 66:671–679 677

123

concentrations of the analysed plants is mainly attributed to

the differences in botanical structure, as well as in the

mineral composition of the soil in which the plants are

cultivated. Other factors responsible for the variation in

the elemental content are preferential absorbability of the

plant, use of fertilisers, irrigation water and climatological

conditions [17].

The high concentrations of K, Ca, Cr, Mn, Cu and Zn in

several medicinal plants which are applied as anti-diabetic

agents in traditional Sudanese medicine fit well with the

attribution of these elements to stimulate insulin action

[15, 16, 18]. Chromium concentrations ranged from 0.45 mg/kg

(Allium sativum) to 3.6 mg/kg (Foeniculum vulgare).

Further medicinal plants with elevated Cr amounts

were Sesamum indicum (1.23 mg/kg), Solenostemma argel

(1.5 mg/kg), Ammi visnaga (2.6 mg/kg), Foeniculum vulgare

(3.6 mg/kg), Nigella sativa (1.8 mg/kg) and Guiera senegal-

ensis (1.2 mg/kg), the latter being used as anti-diabetic

medicinal plants in Sudan traditional medicine. These con-

centrations found in medicinal plants were up to 100-fold

higher compared to most food stuffs (\0.015 lg/kg) [19].

Nigella sativa also showed higher Zn values; this plant may also

be a candidate for future investigations about supplements.

Overall, zinc was found in all the analysed plants,

showing concentrations ranging from 0.2 to 81 mg/kg.

Elevated concentrations were monitored for Sesamum

indicum (51.9 mg/kg), Lepidium sativum (45.3 mg/kg),

Ammi visnaga (44.3 mg/kg), Lupinus termis (47.1 mg/kg),

Coriandrum sativum (39.3 mg/kg), Cucurbita maxima

(74.3 mg/kg), Cymbopogon nervatus (81.4 mg/kg) and

Nigella sativa (45.7 mg/kg). When examining Zn and the

biological roles of its forms, being an integral part of more

than 300 enzymes [20], it is not surprising that these plants

are frequently used in traditional Sudanese medicine.

As an example, Cucurbita maxima is used for treating

skin diseases. This agrees well with its high zinc content.

Zn is known to play an important role in wound healing or

prevention and the reduction of skin irritation [20, 21],

although there might be other, organic curative factors, too.

In the current literature, much attention is paid to Se due

to its protective health effects. In this study, a high quantity

of selenium was observed in Citrullus colocynthis

(1.13 mg/kg), a plant which is used for supporting cancer

treatment and against inflammation (e.g. after snake bites).

These uses could be referred to the anti-oxidant properties

of this plant, which may be—aside others—a result of its

high selenium content. Selenium is known for its protective

action against oxidative stress [22] and is discussed in the

prevention of cancer [13, 23]. The Se values determined for

Citrullus colocynthis agree with Ip and Lisk [24], who

studied the anti-cancer effect of Brazil nuts on mammary

cancer in rats. A dose-dependent inhibitory response was

observed at dietary selenium concentrations of 1–3 mg/kg.

Finally, a high content of magnesium was observed

in Ammi visnaga (4450 mg/kg), Solenostemma argel

(5825 mg/kg) and Sesamum indicum (3780 mg/kg). These

plants are traditionally used as smooth muscle relaxant and

against gastro-intestinal cramps, which is in accordance

with the accepted rectification of Mg deficiency. The latter

is known to cause muscle cramps, gastro-intestinal cramps

and tremor up to heart spasm. The results also agree with

the findings of Ohira et al. and Tong et al., who have

proved that magnesium has affected smooth muscle vaso-

constriction [25, 26].

In conclusion, medicinal herbs appear to demonstrate

significant success in the traditional treatment of many

diseases. Their pharmacological modes of action may be

multifactorial. This paper sheds light on their trace ele-

ments content. The data presented in this study showed that

many Sudanese medicinal plants can be considered as

potential sources for providing a reasonable amount of the

required elements to patients of different health disorders.

The values of some Sudanese medicinal plants support

their integration in modern therapy and may also be of

importance for the development of new medical supple-

ments. Adequate and necessary precautions should be

taken while supplementing the trace elements through such

medicinal plants in order to avoid other complications of

metal toxicity.

Acknowledgements The practical work was done with the help and

understanding of the staff of the Institute of Ecological Chemistry and

the financial support of Helmholtz Center Munich—German Research

Center for Environmental Health, Neuherberg, Germany, and Deut-

scher Akademischer Austausch Dienst (DAAD; German Academic

Exchange Service).

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