146 

Journal of Tropical Forest Products 4(2): 146-152 (1998) 

INORGANIC ELEMENTS IN COMMON TROPICAL CHEWING STICKS 
J.A. Akande 
University of Ibadan, PO Box 21715, Ibadan, Nigeria 
& 
K Yamamoto 
Japanese International Research Centre for Agricultural Sciences, Ohioashi, Tsukuba, Ibaraki 305, Japan 
Received April 1997 
AKANDE,j.A. & YAMAMOTO, K 1998. Inorganic elements in common tropical chewing 
sticks. Chewing species from tropical West Africa were analysed for 11 inorganic elements 
using inductively coupled plasma and ion chromatography. Inorganic contents in the whole 
wood, xylem and bark meals were analysed. The elements accounted for 26 to 74% of the 
ash content. Calcium and potassium concentrations were highest while phosphorus, 
aluminum, sodium, magnesium and fluorine were found in appreciable amounts. Notable 
differences in elemental concentrations occurred between the bark and xylem and between 
species. 
Key words: Chewing sticks - inorganic concentrations - oral hygiene 
AKANDE, j.A. & YAMAMOTO, K 1998. Unsur bukan organik dalam kayu kunyahan 
tropika yang biasa. Kayu kunyahan dari kawasan tropika Afrika Barat dianalisis untuk 11 
unsur bukan organik dengan menggunakan plasma digandingkaii teraruh dan 
kromatografi ion. Kandungan unsur bukan organik dalam kayu kisar tulen, xilem kisar 
dan kulit kisar dianalisis. Un sur tersebut membentuk 26 hingga 74% daripada kandungan 
abu. Kepekatan kalsium dan kalium paling tinggi manakala kepekatan fosforus, aluminium, 
natrium, magnesium dan fluorin boleh dikesan. Perbezaan dalam kepekatan unsur dapat 
dikesan di antara kulit dan xilem dan juga di antara spesies kayu. 
Introduction 
Knowledge of mineral inclusions in woody tissues is important for their diagnostic 
and pharmaceutical values. Chewing sticks are non-timber forest products commonly 
used for oral hygiene, especially for cleaning dental units. The product has prominent 
market values in many parts of tropical West Africa where they are generally obtained 
in the wild. The chewing sticks are normally cut to 15 or 20 em long and 0.5 to l.25 em 
diameter for sale. 
The elemental content of woody tissues has long been a subject of investigation 
(Young & Guinn 1966, Wardel & Hart 1973, Safford et al. 1974, Guyette et al. 1992). 
The instrumentation for performing such tasks has since undergone progressive 
modifications and improvements to meet the current needs. In the early 1970s, Meyer 
and Langwig (1973) used neutron activation analysis (NAA) to monitor inorganic 
elements in a wide range of species. NAA was also used by Slocum et al. (1978) to 
analyse oak and hickory charcoal for inorganic elements at different charring 

Journal of Tropical Forest Products 4(2): 146 - 152 (1998) 

147 

temperatures. In 1992, Guyette et al. utilised inductively coupled plasma (ICP), a newer 
technology, to compare data on inorganic concentrations of eastern red cedar wood 
from different sites with values obtained using NAA. They recorded very close data 
sets with the two analytical methods, indicating that the ICP was as effective as the 
NAA and could generate reproducible accurate results of inorganic contents in wood. 
The difference is that while NAA can be performed on solid samples, sawdust or ash, 
ICP requires chemical digestion protocols and the use of standard solutions as controls. 
ICP was used in this study to analyse for Ca, P, At, Na, Mg, K, Mn, Fe, Ni and Zn. 
The ion chromatograph was, however, used to evaluate for F as it was felt that the 
volatility problems with halide (Meyer & Langwig 1973) could be a problem with ICP. 
Materials and methods 
Materials and sample preparation 
Seven species of chewing sticks (Figure 1) were investigated. They were obtained in 
the form they were marketed and utilised and were identified at the Forest Research 
Institute, Ibadan, Nigeria. All the species are widely distributed over tropical West 
Africa. At least 30 samples were collected per species, air-dried, cellophane-wrapped 
and shipped to the Forestry and Forest Products Research Institute, Tsukuba, Japan 
for testing. 
The samples were ground with the bark on them (described as whole wood meal) 
or with the stripped bark only (bark meal) or with the bark removed (xylem meal). 
The species and the parts used were Garcinia mannii (branch without bark), Massularia 
accuminata (branch with bark), Azadirachta indica (branch with-bark), Terminalia 
glaucescens (root with bark), Zanthoxylum gilletii (root with bark), Anogeissus leiocarpa 
(branch with bark) and Pseudocedrela kotschyi (branch with bark). The ground samples 
were then sifted with a l.O-mesh screen of aJanke & Kunkel Ika werk mill model 7813 
staufen. 

	

Z. 
gillefii 

p. 
kot. .• chyi 

A. 
indh~(f 

	G. 	M. 
numnii accuminata 

	I; 	A. 
glaucesccns ~ Ieiocarpo 

Figure 1. The chewing sticks 

148 

Journal of Tropical Forest Products 4(2): 146 - 152 (1998) 
Ash determination 

This was done on a Yamato muffle furnace at 580 DC as per procedure in the 
ASTM D 11 02-84 (Anonymous 1985). Approximately 2 g of each sample in the crucibles 
were ignited in the furnace for 3 h. The samples were normally ashed after this period. 
The samples were reignited if there were traces of carbon in the ash residue. Each 
sample was replicated three times. 
Inductively coupled plasma analysis 
Inorganic concentrations in the species were analysed using ICP optical emission 
spectroscopy. The decision on which inorganic elements to analyse was based on our 
preliminary survey of elemental contents in several tooth pastes (Aquafresh, Dent ° 
Clean, Colgate, Close-up, McLean and Maxam dental cream). 
Ground meal (0.5 g) from the different samples was prepared using HNO/H202 
digestion procedure. A colourless solution was obtained by carefully adding aliquot 
(2 ml) volumes of H202 as the heating progressed and as nitrogen oxide gas was fully 
expelled. The solution was filtered of any residue and made up to 100 ml with distilled 
water. ICP analyses were conducted on the prepared solutions using a SII Seiko 
Instruments Inc SPS-7700 (vers. l.04). The instrument was standardised with two 
different solutions containing 10 elements. The elements sampled were Ca, Mg, P, AI, 
Na, Zn, Ni, Fe, Mn and K. 
Ion chromatography 
Fluoride concentration in the chewing sticks was determined using the same solution 
prepared for the ICP experiment. The ion chromatograph analyser IP 500 (Yokogawa 
Electric Corporation) was used. The operating temperature was 40 DC, separator 
column SAX-205 and a dilution factor of 100. 
Results and discussion 
Quantitative data on chemical elements are useful for providing information needed 
to improve the phytochemical database (Beckstrom-Sternberg 1993). Such data 
facilitate ready connections between wood biomass constituents, phytochemistry and 
pharmacology. Many investigations have analysed minerals in wood collectively by 
measuring the ash contents. In this study, the measured ash content was generally 
high (Table 1) ranging from 0.3% in the xylem of C. mannii to 5.6% in the xylem 
of P kotschyi. The values for the bark were even higher, ranging from 5.5% in 
A. leiocarpa to 10.4% in P kotschyi. Pseudocedrela kotschyi seemed to be rich in 
inorganic contents. 
Meyer and Langwig (1973) reported that the inorganic contents in temperate wood 
could range from 0.2 to 0.9% while tropical wood could be as much as 4.0 to 5.0% of 
the dry weight. As this study was not designed to identify all elements in the chewing 
sticks, only elements felt to be important to oral hygiene and elements which could be 

Journal of Tropical Forest Products 4(2): 146 - 152 (1998) 
Table 1. Proportion of analysed elements to total ash content 
Ash content Detected elements (%) 

Terminalia glaucescens 			
Wood meal 	3.21 b 	62 	
Bark 	9.13a 	45 	
Xylem 	1.11 b 	26 	
Azadirachta indica 			
Wood meal 	4.81 b 	43 	
Bark 	8.59a 	42 	
Xylem 	2.55 c 	35 	
Pseudocedrela kotschyi 			
Wood meal 	7.45b 	37 	
Bark 	10.35 a 	74 	
Xylem 	5.55b 	39 	
Massulana accuminata 			
Wood meal 	3.28b 	28 	
Bark 	6.53a 	39 	
Xylem 	0.52c 	51 	
A nogeissus leiocarpa 			
Wood meal 	3.74b 	34 	
Bark 	5.50a 	30 	
Xylem 	2.01 b 	41 	
Garcinia mannii 			
Xylem 	0.30 	66 	
Zanthoxylum gilletii 			
Wood meal 	3.28b 	31 	
Bark 	7.54a 	26 	
Xylem 	1.50b 	44 	
Means of each species followed by the same letter are not signifi~antly 
different at p < 0.05. 

149 

added based on the ease of obtaining standard solution for the ICP analyses were 
considered. Calcium and potassium concentrations were highest while phosphorus, 
aluminum, sodium, magnesium and fluorine were found in appreciable amounts 
(Table 2). Appreciable levels of calcium may improve the abrasive properties of the 
chewing sticks while the other elements contribute to their cleansing properties. The 
ash content values showed that the elements identified constituted only fractions of 
the total ash. These elements may, however, be major since Slocum et al. (1978)had 
indicated that radicals such as oxide, carbonate, phosphate, sulphate and oxalate of 
these elements might account for much of the rest. It is noteworthy to mention that 
the absence of an element in our analyses does not mean that it is not present in the 
samples. 
We do not have previous data sets on the elemental concentration of tropical species 
for comparison. Even for temperate species, the data were very limited. The closest 
available data were from NAA analyses (Young & Guinn 1966) carried out on small 
tree branches and roots of red spruce, balsam fir, hemlock, white pine, white birch, 
red maple and aspen. We recognise the difficulty in comparing results obtained using 
different analytical techniques, as highlighted by Osterhaus et al. (1975). However, 
since the results obtained using ICP and NAA had been proven to be very close (Guyette 
et al. 1992), the Young and Guinn (1966) data appear to be fairly reliable. 

150 					Journal of Tropical Forest Products 4(2): 146 - 152 (1998) 	
	Table 2. 	Inorganic concentrations in tropical chewing sticks 				
					Element (ppm) 					
	Ca 	P 	AI 	Na 	Mg 	F 	K 	Mn 	Fe 	Ni 	Zn 	
Terminalia glaucescens 												
Wood meal 	16582 	433 	110 	297 	486 	51.6 	1886 	10 	56 	0.2 	3 	
Bark 	36448 	567 	233 	338 	652 	70.6 	2758 	23 	179 	2 	15 	
Xylem 	708 	516 	13 	173 	382 	4.7 	1054 	6 	27 	I 	7 	
Azadirachta indica 												
Wood meal 	11496 	2060 	78 	226 	1779 	21.3 	4848 	II 	48 	0 	14 	
Bark 	16662 	3394 	ll8 	341 	2890 	ll8.1 	11992 	22 	74 	I 	20 	
Xylem 	4428 	784 	33 	242 	590 	16.7 	2660 	3 	13 	4 	20 	
Pseudocedrela kotschyi 												
Wood meal 	20448 	1198 	122 	233 	636 	48.4 	4724 	5 	23 	0 	16 	
Bark 	67900 	506 	347 	347 	712 	78.0 	6002 	25 	156 	2 	12 	
Xylem 	14354 	1428 	105 	207 	681 	4.0 	4770 	3 	18 	5 	8 	
Massulana acruminata 												
Wood meal 	4762 	706 	92 	320 	2407 	68.6 	706 	ll2 	91 	0 	8 	
Bark 	17788 	420 	123 	296 	5468 	149.4 	1030 	209 	71 	4 	16 	
Xylem 	962 	158 	12 	219 	720 	11.6 	454 	106 	8 	0 	11 	
A nogeissus leiorarpa 												
Wood meal 	7088 	874 	76 	229 	544 	32.6 	3590 	28 	40 	0 	7 	
Bark 	9768 	508 	13 	272 	1072 	29.4 	4246 	82 	505 	4 	13 	
Xylem 	4074 	590 	35 	202 	421 	4.0 	2862 	19 	19 	5 	12 	
Carania mannii 												
Xylem 	894 	112 	20 	152 	212 	76.2 	472 	38 	13 		6 	
Zanthoxylum gilletii 												
Wood meal 	6758 	428 	83 	216 	630 	34.0 	1786 	14 	79 	0 	15 	
Bark 	15050 	346 	143 	432 	795 	77.5 	2744 	34 	res 	3 	10 	
Xylem 	4496 	342 	37 	261 	387 	11.0 	1056 	7 	11 	1 	8 	
The calcium contents in the branchbark of P kotschyi and the rootbark of 
T.	glaucescens outweighed those in the root bark of white pine, hemlock, balsam fir 
and aspen (Figure 2). The calcium concentration in the branch bark of P kotschyi far 
outweighed those of A. indica and M. accuminata. Calcium in the branchwood of 
P kotschyiwas fairly within the range of those of the temperate softwood and hardwood 
(Figure 2). 
The branchbark of A. indica and P kotschyi had significant levels of potassium 
(Figure 2). Potassium concentrations in the branchbark and branchwood of A. indica, 
P kotschyi and A. leiocarpa were higher than those in the branchbark of white birch, 
red spruce, hemlock, aspen, red maple and white pine. The phosphorus content in 
the branchwood of P kotschyi was in the same range as that of the temperate species, 
hemlock. As for the magnesium content, the branchbark and branchwood of 
M. accuminata and A. indica stood out among the rest. Phosphorus content was also 
appreciable in the branchwood and branchbark of A. indica. 
The aluminum content in the branchbark of P kotschyi outweighed those in the 
branchbark of white pine and balsam fir (Figure 2). When rootbark was evaluated, 
T. glaucescens had fairly high aluminum content (233 ppm) compared to Z. gilletii 
(143 ppm) [Table 2]. The rootbark of T. glaucescens was richer in aluminum than 
those of white birch, red maple, balsam fir and hemlock. The branchbark of P kotschyi, 

Journal of Tropical Forest Products 4(2): 146 - 152 (1998) 					151 	
	80000 		12000 	Al(BB) 			600 				
		PK(BB) 							AL(BB) 		
S 			10000 				500 				
0- 	60000 										
8- 											
~ 			8000 				400 				
0 											
·c 								PK(BB) 			
o:l 											
b 	40000 		6000 	PK(BB) 			300 				
~ 											
V 		TG(RB) 									
u 											
~ 								TG(RB) 			
0 				"\.I(BW~ 							
U 			4000 	AL(BB 			200 	H,(RB) 			
				PK(BW 					BF(BB) 		
		':..'\~~~' "A(BB) 		AL(B\\) 	AI (BB) 			BF(BB) 	~(<::? 		
	20000 			WP(BB) 		MA(BB) 		WP(BB) 			
		~iB:Ji H,(BB) 		R.\f(BB) 							
						AI(BB), MA(B\\') 		BF(KB) 			
		"'(~~' WB(BB) 		ti~(r:J) 				R.\f(RB) 	WP(BB) 		
			2000 		AI (BW) 		100 				
		"'( ) 				AI (BW) 		II"B(RB) 	:\5(88) 		
		m~:l 			PK(B\\?, B,(BB) 						
		He(RB) 		RS(BB) 	~~:) Zi&~:) 			R.\f(BB) 		
				II"B(BB) 	W8~B~) H,(B ), BF(BB) 			\\1\\(8) 		
	0 	WP(RB) 			"'( B) RM(BB) 					
		Ca 		K 	P 	Mg 		AI 	Fe 		
				Element 						
Figure 2. Available data on some inorganic elements in the wood of temperate species 
and chewing sticks. PK = P kotschyi, TG = T. glaucescens, MA = M. accuminata, 
AI = A. indica, AL = A. leiocarpa, RS = red spruce, RM = red maple, 
BF = balsam fir, He = hemlock, WP = white pine, WB = white birch, As = Aspen; 
BB = branch bark, BW = branchwood, RB = rootbark 
however, had aluminum content of 347 ppm which was higher than the concentration 
found in T glaucescens rootbark. Only the branch bark of A. leiocarpa was appreciably 
rich in iron content compared to the other temperate species (Figure 2). 
Industrial interest in wood silicon was highlighted by Meyer and Langwig (1973). 
Silicon is found in some of the toothpastes while calcium in others. We did not analyse 
for silicon using ICP because preliminary studies on these species using energy 
dispersive X-ray analysis showed non-detectible level of silicon. It is noteworthy to 
mention that different brands of toothpastes have different elemental composition 
and concen trations. 
Some toothpastes have fluoride while others don't. Fluorine is acclaimed to be 
capable of stopping tooth decay. Nevertheless, a large majority of toothpastes in the 
Japanese market have no fluoride. Since the toothpaste manufacturers have the liberty 
to play around with the inorganic concentration of elements in their products and 
the chewing sticks contain appreciable quantities of these elements, then the hygienic 
properties and potentials of the chewing sticks deserve pharmaceutical attention. 
Conclusion 
Calcium and potassium concentrations were found to be highest in the chewing sticks 
while phosphorus, aluminum, sodium, magnesium and fluorine were found in 
appreciable quantity. The elements accounted for 26 to 74% of the ash content. 
Variations within and between samples were noted. Pronounced differences in 
elemental concentrations occurred between the bark and xylem with the branchbark 
often rated best. 

152 

Journal of Tropical Forest Products 4(2): 146 - 152 (1998) 
Aclrnowledgements 

The authors thank T. Shinmura of the Kagoshima Institute of Industrial Technology 
for his assistance in the fluoride test. The financial assistance of the Science and 
Technology Agency of Japan is gratefully appreciated. 
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