Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol

Endpoint summary

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

basic toxicokinetics in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: study summary from peer reviewed publication

Objective of study:

metabolism

Qualifier:

no guideline followed

Principles of method if other than guideline:

The test items, α -D-glucopyranosido-1,6-sorbitol (GPS) and α-D-glucopyranosido-1,6-mannitol (GPM) were incubated with disaccharidases from different sources and the kinetics of enzymatic cleavage analysed by an enzymatic-spectrophotometric assay. Disaccharidases were: α-glucosidase from yeast, β-fructosidase from yeast, human jejunal mucosa homogenate as well as acid maltase from rat liver lysosomes. Jejunal mucosa was scraped of from 10 healthy intestines of autoptic samples and mixed by homogenisation in incubation buffer. The low-speed supernatant was used as source of enzyme. Rat liver lysosomes were prepared and incubated for acid maltase. lncubations with yeast enzymes were done at 25 °C, with mammalian enzymes at 37 °C. Kinetic data were evaluated according to Cornish-Bowden.

GLP compliance:

no

Radiolabelling:

no

Statistics:

All statistical calculations were done with Student's t-test.

Preliminary studies:

not specified

Type:

metabolism

Results:

Enzymatic cleavage occured at slow rates by maltase of jejunal mucosa, liver lysosomes and yeast.

Metabolites identified:

not measured

Details on metabolites:

Enzymatic cleavage of the glycoside bond in the test item, α-D- glucopyranosido-1,6-sorbitol (GPS) and α-D-glucopyranosido-1,6-mannitol (GPM) is effected by maltase (α-glucosidase) from yeast. Since all disaccharide alcohols inhibit maltose hydrolysis competitively, α-glucosidase of yeast is unequivocally identified as the carbohydrase responsible for their cleavage. Whereas in crude homogenates of intestinal mucosa maltase and saccharase (sucrase) activities are present simultaneously, inhibition data demonstrate maltase as being active against the test item and its components. Lack of inhibition of intestinal saccharose, as well as the inability of yeast saccharase to split the test item at all or to bind it at the active site, exclude this enzyme from those being active against the test item (for details see Table 1). Amylo-1,6-glucosidase from Aspergillus niger is able to attack the test item, but only at high enzyme concentrations, and cannot compare with yeast α-glucosidase.

Table 1. Cleavage of disaccharide alcohols by carbohydrases

Enzyme/Substrate	Vmax (nmol/min x mg protein)	Km (nM)	Ki (nM)	Type of inhibition
α-glucosidase from yeast
maltose	7000	20	--
test item	30	14	7	competitive vs. maltose
GPS	11	9	10	competitive vs. maltose
GPM	8	23	21	competitive vs. maltose
β-fructosidase from yeast
saccharose	76000	25	--
test item	< 0.2	not determinable	60	non-competitive vs. saccharose
Human jejunal mucosa, homogenate
maltose	1540	2.7	--
saccharose	380	17.2	--	no inhibition by disaccharide alcohols
palatinose	170	3.0	not determined
test item	35	5.5	--	not definable vs. maltose
GPS	67	7.7	35	uncompetitive vs. maltose
GPM	32	11.4	29	competitive vs. maltose
Acid maltase from rat liver lysosomes
maltose	2.5	1.8
GPS	0.03	not determinable	not determined
GPM	0.01	not determinable	not determined

Reference 2

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Objective of study:

metabolism

Qualifier:

no guideline followed

Principles of method if other than guideline:

Female rats of 180 g were adapted to 34.5% test item in the diet during 24 days. On the day of the experiment, 5 g food containing 1.7 g test item were fed to the fasted animals, and 20 animals sacrified 0.5-1 h after start of feeding, 20 animals 2-3 h later, 5 animals after 4.5 h and 9 animals after 6 h. The contents of stomach, small intestine, caecum and large intestine were collected under methanol, and the combined samples of each time period and anatomical location analysed by gas chromatography.

GLP compliance:

no

Radiolabelling:

no

Species:

rat

Strain:

other: SIV-50

Sex:

female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Ivanovas, Kisslegg, Germany
- Weight at study initiation: 180 g
- Housing: individually in wire cages
- Diet: Altromin (Altrogge, Lage, Geramny), offered in limited amounts
- Water: tap water from bottles, ad libitum
- Acclimation period: not specified

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 1
- Humidity (%): 55

Route of administration:

oral: feed

Vehicle:

not specified

Details on exposure:

DIET PREPARATION
- Rate of preparation of diet (frequency): not specified
- Experimental diets were based on casein-starch as follows: 20% casein, 0.24% vitamin mixture, 4% salt mixture, 5% hydrogenated vegetable oil, 2% cellulose, 69% corn starch. Additions of test item, GPS or GPM respectivcly were made by exchanging 50% of starch or saccharose with the corresponding disaccharidc alcohols, giving 34.5% of each component. At the start of feeding experiments, however, the initial diet contained only 10% of the disaccharide alcohols, which was raised to 20%, 30% and finally 34.5% within a few days each, in order to avoid diarrhoea.

Duration and frequency of treatment / exposure:

Following 24 days of adaption to increasing amounts of test item in the diet, animals were fasted and subsequently dosed once with 1.7 g/animal in 5 g of diet

Dose / conc.:

1.7 other: g/animal

Remarks:

in 5 g synthetic diet

No. of animals per sex per dose / concentration:

5 to 20 animals per sampling time point

Control animals:

no

Details on dosing and sampling:

METABOLITE CHARACTERISATION STUDIES
- Tissues and body fluids sampled: intestinal contents (stomach, small intestine, caecum, large intestine)
- Time and frequency of sampling: 0.5-1 h after start of feeding (20 animals), 2-3 h after feeding (20 animals), 4.5 h after feeding (5 animals), 6 h after feeding (9 animals)
- From how many animals: see above, pooled samples were analysed
- Method type for identification: gas chromatography
- Limits of detection and quantification: not specified

Statistics:

All statistical calculations were done with Student's t-test.

Preliminary studies:

not specified

Type:

metabolism

Results:

Ingested test item partially arrived unsplit in the caecum and underwent fermentation there; excretions in faeces and urine are neglegible in the rat.

Metabolites identified:

yes

Remarks:

α -D-glucopyranosido-1,6-sorbitol , α-D-glucopyranosido-1,6-mannitol, sorbitol and mannitol

Details on metabolites:

The time course of the fate of test item in the digestive tract is depicted in Table 1. While the stomach is being emptied after a standard dose of 1.7 g in 5 g synthetic diet, progressively more disaccharide alcohols and hexitols are found in small intestine, caecum, and to some extent also in large intestine, as time proceeds. lt follows from these data, that uncleaved disaccharide alcohols appear beyond the small intestine and must have escaped digestion by carbohydrases in the upper part of the digestive tract. α -D-glucopyranosido-1,6-sorbitol (GPS) and α-D-glucopyranosido-1,6-mannitol (GPM) are found in small intestine at 5-14% of the amount in the stomach. Three to six hours after the test meal, per animal 80-105 mg of disaccharide alcohols plus hexitols are found beyond the small intestine. Whereas these compounds may exist in even Iarger amounts in the caecum than in small intestine at intermediate times, a sharp decrease is observed between caecum and large intestine: after, e.g., 4.5 h, 4.8 to 8.3 times higher amounts of all four compounds are recovered from the caecum than from the Iarge intestine. Obviously, the caecum is functioning like a sink for disaccharide alcohols as well as hexitols which points to this part of the gut as the site where substances which have escaped digestion and/or absorption in small intestine, are cleaved and eventually fermented.
Actually, caeca were enlarged, both in tissue and in total. weights, and their content is always a grayish mass with many small gas bubbles, indicating fermentation. From the data of Table 2 it can be concluded that disaccharide alcohols as well as hexitols disappear while passing through the caecum, thus cleavage of glycoside bonds as well as bacterial fermentation obviously proceeds in this organ.

A small portion of disaccharide alcohols is excreted in stool and feces respectively. Data for rat faeces demonstrate that after a few days the test item is excreted just at the level of analytical detectability. In experiments with healthy human volunteers, only neglegible amounts of test item are found in the stool. Accordingly, the test item undergoes practically complete degradation in man and rat during passage through the digestive tract. Whatever amount may have escaped caecal fermentation (see data for large intestine in Table 1) becomes obviously finally degraded in the colon or rectum.

Table 1. Disaccharide alcohols and hexitols in the intestinal tract of rats (mg/animal)

Time period after feeding (h)			GPS	GPM	Sorbitol	Mannitol
0.5 -1		stomach	205	260	6	5
		small intestine	20	35	22	15
		caecum	5	5	8	9
		large intestine	0	0	0	0
2 - 3		stomach	155	170	7	6
		small intestine	23	45	25	1.5
		caecum	5	35	42	40
		large intestine	0	5	6	3
4.5		stomach	80	100	6	3
		small intestine	25	50	22	12
		caecum	24	65	27	25
		large intestine	5	10	5	3
6		stomach	25	30	3	2
		small intestine	20	30	12	10
		caecum	18	70	21	15
		large intestine	5	12	3	2

Reference 3

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Objective of study:

absorption

distribution

excretion

Qualifier:

no guideline followed

Principles of method if other than guideline:

- Principle of test:
- Short description of test conditions: single doses of 250, 1000, and 2500 mg/kg bw of C14 radiolabelled 6-alpha-D-glucopyranosido-sorbitol and 6-alpha-D-glucopyranosido-mannitol were orally administered to rats
- Parameters analysed / observed: radioactivity in blood, tissue and excrements (urine, faeces, expired air and voided intestinal gas)

GLP compliance:

no

Radiolabelling:

yes

Species:

rat

Strain:

Sprague-Dawley

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Mus Rattus AG, Munich, Germany
- Weight at study initiation: approximately 200 g
- Diet: Altromin-R, 15 g/animal/day
- Water: ad libitum

Route of administration:

oral: gavage

Vehicle:

water

Duration and frequency of treatment / exposure:

single treatment

Dose / conc.:

250 mg/kg bw/day (actual dose received)

Dose / conc.:

1 000 mg/kg bw/day (actual dose received)

Dose / conc.:

2 500 mg/kg bw/day (actual dose received)

No. of animals per sex per dose / concentration:

4 males/dose

Control animals:

no

Details on dosing and sampling:

TOXICOKINETIC / PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled: urine, faeces, blood, exhaled air, voided intestinal gases , whole body (with and without gastrointestinal tract)
- Time and frequency of sampling: Elimination of radioactivity through urine, faeces, exhaled air and intestinal gas was determined for 0 - 48 h after dosing. Tissue distribution was determined by whole body autoradiography 48 h after dosing.

Preliminary studies:

no data

Type:

absorption

Results:

Absorption in rats depends heavily on the administered dose. Relative absorption declines with increasing doses. Absorption after oral administration amounts to approximately 80% (250 mg/kg bw), 70% (1000 mg/kg bw), and 45% (2500 mg/kg bw).

Type:

distribution

Results:

48 h after an oral dose of 250 mg/kg bw, a mean equivalent concentration of approximately 30 µg/g is found in the body. Higher concentrations are found in fat, the adrenal cortex, the thymus and the liver.

Type:

excretion

Results:

48 h after dosing of 250, 1000 and 2500 mg/kg bw 62, 53, and 33% radioactivity had been eliminated via exhaled air; 18, 32, and 54% in the faeces and 6.4, 5.4, and 5.0% in the urine. The body still contained 13, 9 and 7% of the administered radioactivity.

Details on absorption:

The percentage of absorbed test item is dependent on the administered dose; it varies between approximately 80% (250 mg/kg bw), 70% (1000 mg/kg bw), and 45% (2500 mg/kg bw). The absorption rate also differs according to the administered doses. As the curves representing the concentration of radioactivity in the blood versus time illustrate, the absorption of test item is clearly slower for the high dose than for the low dose.

It was assumed for this evaluation of the absorption rate that there was no biliary or extrabiliary secretions (saliva, gastric juices, intestinal mucosa, etc.) of radioactivity absorbed. This assumption is obviously true for the vast majority of cases concerning the absorption phenomena of sugars or sugar analogous substances. Otherwise, the absorption rates indicated would still be even higher.

The values on the test item absorption confirm the opinion that the glucosidic bond is cleaved more slowly for the test item components than for cane sugar. However, the test item cleavage rate is fast enough to cleave small amounts (corresponding to a dose of less than 250 mg/kg bw) into basically reabsorbable fragments. But if the adminstered test item amount is considerably greater, enzymatic cleavage achieved during intestinal transit time of the substance limits the formation of glucose, sorbitol, and mannitol. The relative absorption and, as a result, relative elimination of CO2 are slower and lower.

Details on distribution in tissues:

48 h after dosing, depending on the dose, between 6 and 11% of the administered radioactivity was found in the animal's body (stomach and intestines not included) and only approximately 1% in the digestive tract (stomach and intestinal walls plus contents).
48 hours after oral dosing, radioactivity is practically distributed to all tissues. The mean equivalent concentration is approximately 30 µg/g in the animal's body. Besides the intestines, the highest concentrations are primarily found in adipose tissues, adrenal cortex, thymus, liver, bone marrow and tonsils. The concentration of radioactivity is much lower in the blood than in most other tissues. Quantitative radioactivity measurements indicate that the dark area observed at the liver corresponds to an equivalent concentration of approximately 80 µg/g. Blood concentrations were approximately 5 times lower (determined by quantitative measures versus time for the 3 doses).

Details on excretion:

The elimination of radioactivity through urine, faeces, exhaled air, and intestinal gases was measured versus time for 48 hours after single oral doses 250, 1000, and 2500 mg/kg bw. For each experiment, the radioactivity found in the excreta and the average radioactivity recorded at the end of the experiment in the animals' bodies were located between 80 and 95%. To be able to compare results, the value 100% was assigned to the sum of the radioactivity found in the animals' bodies and in their excreta.

Elimination via respiratory air and intestinal gases
14CO2 elimination by exhaled air was relatively high. Depending on the administered dose, the radioactivity eliminated roughly ranged from 35 to 60% after 48 hours.
A relationship between radioactivity elimination and dose was noted. After 250 and 1000 mg/kg bw 14CO2 was eliminated relatively rapidly, while after 2500 mg/kg bw, it was eliminated more slowly; for the highest dose, the value obtained at the end of an experiment was much lower (approx. 30%). For the lower doses, the values obtained at the end of an experiment ranged from 50 and 65%.
The percentage of 14CO2 eliminated by intestinal gases was very low and independent of the dose; it ranged between 1 and 2%. Accordingly, this way of elimination is negligible.

Urinary elimination
48 hours after dosing of 250, 1000, and 2500 mg/kg, 6.4 ± 1.8, 5.4 ± 0.1, and 5.0 ± 1.2% of the administered radioactivity had been eliminated in urine. For the high dose, elimination was achieved more slowly. However, 48 hours post dose values were almost identical for the 3 doses.

Faecal elimination
Radioactive elimination in faeces also depended on the dose. The higher the dose, the higher the amount of radioactivity measured in the faeces (250 mg/kg bw: 18%; 1000 mg/kg bw: 32%; 2500 mg/kg bw: 54%).

Metabolites identified:

not measured

Table 1. Elimination of radioactivity and concentration of radioactivity in the body 48 hours after dosing

Dose (mg/kg bw)	No. of animals (n)	% radioactivity in
		Exhaled air	Urine	Body (without digestive tract)	Digestive tract	Faeces	Intestinal gas
250	4	60 ± 6	6.4 ± 1.8	11 ± 2.0	1.4 ± 0.2	18 ± 7	1
1000	4	53 ± 7	5.4 ± 0.1	7.4 ± 1.4	1.2 ± 0.1	32 ± 7	2
2500	4	33 ± 5	5.0 ± 1.2	6.4 ± 1.1	0.8 ± 0.1	54 ± 7	1

Values are given in % with respect to the administered radioactivity.

Description of key information

Several in vivo and in vitro studies on the toxicokinetic behaviour of Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol have been performed in experimental animals and humans including vitro studies on enzymatic cleavage. The substance is a mixture of two constituents, 6-O-alpha-D-glucopyranosyl-D-sorbitol (GPS) and 1-O-alpha-D-glucopyranosyl-D-mannitol dihydrate (GPM) with molecular weights of 344.32 and 380.32 g/mol, respectively. Complete hydrolysis of Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol yields glucose, sorbitol and mannitol (2:1:1)(JECFA, 1985). The measured water solubility and log Pow values are 308-488 g/L at 20 °C (Gehrich, 2017) and -4.2 - -3.7 (Gehrich, 2018a), respectively. The vapour pressure is 3.1E-11 to 1.6E-07 hPa at 20 °C (Dreisch, 2018) and the particles sizes range from 1 µm to 3.5 mm (Gehrich, 2018b).

Further information on the toxicokinetic properties (absorption, distribution, metabolism and excretion) of Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol is given in the JECFA/WHO Food Additive Series 20 on the substance. Information from this document is cited in the relevant sections hereafter.

Absorption

Oral

A reliable study on the absorption, distribution and excretion of 14C-radiolabeled Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol after oral dosing is available (Patzschke, 1975). In this study the test item was administered orally to rats (4 males/dose) at single doses of 250, 1000 or 2500 mg/kg bw.

Absorption of 14C activity was dose-dependent, varying from 80% in the low dose group to 45% in the high dose group. 14CO2 in expired air, 2 days after administration, ranged from 62% of the administered dose in the low dose group to 33% in the high dose group. The authors pointed out that the 14CO2 they measured could have originated in two ways: from the expired air due to metabolism of glucose, sorbitol, and mannitol after their absorption from the gut, or from intestinal gases due to microbial fermentation in the caecum. Consequently, 14CO2 excretion could not be used as a direct indication of bioavailability. 48 h after dosing, depending on the dose, between 6 and 11% of the administered radioactivity was found in the animal's body (stomach and intestines not included) and only approximately 1% in the digestive tract (stomach and intestinal walls plus contents). 48 hours after oral dosing, radioactivity was distributed to all tissues. The mean equivalent concentration in the body was approximately 30 µg/g wet weight. The highest concentrations were found in adipose tissues, adrenal cortex, thymus, liver, bone marrow and tonsils. The concentration of radioactivity was much lower in the blood than in most other tissues. Quantitative radioactivity measurements in the liver corresponded to an equivalent concentration of approximately 80 µg/g wet weight. Blood concentrations were approximately 5 times lower (determined by quantitative measures versus time for the 3 doses). 14C elimination in the faeces ranged from 18-54% of the administered dose over a period of 48 hours. Approximately 5% of the administered 14C activity appeared in urine.

Reliable in vivo data on the intestinal metabolism of Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol has been published (Grupp, 1978). The fate of the test item in the gastrointestinal tract of female rats that had before been adapted to the compound was investigated. After administration of 1.7 g test item to fastened animals, the contents of the stomach, small intestine, caecum, and large intestine were examined at intervals up to 6 hours. From the content of GPS, GPM, sorbitol, mannitol, and sucrose found in these organs, the authors concluded that GPS and GPM were only partially hydrolysed by the carbohydrases (mainly maltase, also known as α-glucosidase) in the small intestine, while a substantial proportion of these compounds reached the caecum, where further hydrolysis of glycosidic bonds occurred. Fermentation of the liberated hexitols occurred in the caecum, which was enlarged, and only small amounts of GPS, GPM, and hexitols reached the large intestine.

Reliable in vitro data on the enzymatic cleavage of Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol, GPS and GPM has been published in the same publication as the above mentioned data (Grupp, 1978). In the study the test item as well as GPS and GPM were incubated with disaccharidases from different sources and the kinetics of enzymatic cleavage analysed. Used disaccharidases were: α-glucosidase from yeast, β-fructosidase from yeast, human jejunal mucosa homogenate as well as acid maltase from rat liver lysosomes. Kinetic data were evaluated according to Cornish-Bowden. Enzymatic cleavage of the glycoside bond in the test item, GPS and GPM is effected by maltase (α-glucosidase) from yeast I, but the rates of hydrolysis were slow.

In the rat, Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol appears in small amounts in the urine after oral ingestion (Musch, 1973). The same holds true for man (Grupp, 1978), thus indicating that a small portion of test item is absorbed as such without cleavage from the intestinal tract and excreted by the kidneys as the intact disaccharide alcohol. Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol was fed to groups of rats (10 males and 10 females) at levels up to and including 10.0% of the diet; a group fed 10% sucrose was used as an additional control (Sinkeldam, 1983). From the results, it seems clear that the test item is largely digested or degraded in the gastrointestinal tract of the rat, since neither D-arabino-hexitol, the test item nor its degradation products, such as sorbitol or mannitol, could be detected in the faeces. If it is assumed that degradation takes place mainly by bacterial flora in the large bowel, one may expect an increased production of short-chain fatty acids, which generally result from bacterial fermentation. The fact that in the present study faecal excretion of short-chain fatty acids was not increased and the pH of the faeces was not decreased indicates that any short-chain fatty acids formed were absorbed through the gut wall. (Sinkeldam, 1983).

The hypothesis that degradation of Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol takes place mainly by bacterial flora in the large bowel is supported by toxicity studies in rats during which increased weights of filled and empty caecum were noted especially in high dose animals. This caecal enlargement has been ascribed to incomplete absorption of the test item and subsequent microbial fermentation in the large intestine, giving rise to an increased osmotic load attracting water and thus leading to caecal enlargement (Jonker and Lina, 2001).

In a rat study,the apparent digestibility and metabolisability of the energy of Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol were 91.3% and 90.1%, respectively. Faecal excretion of nitrogen after feeding Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol was elevated because of increased microbial activity. In contrast to the control and sucrose groups, there was no prostprandial increase in the activity of serum insulin; the authors concluded that this is due to reduced and delayed hydrolysis and absorption of Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol in the gastrointestinal tract (Kirchgessner et al., 1983).

GPM and GPS, were assayed for glucose bioavailability using ketotic rats. With conversion rates into glucose of 6 and 20%, respectively, for free mannitol and sorbitol, 39% for GPM, and 42% for GPS, the metabolic glucose pool of the rat does not receive the full carbohydrate complement of these compounds. Under these conditions, 36% of the GPM and 32% of the GPS provided bioavailable glucose; 50% is the theoretical maximum. Less-than-theoretical bioavailability of glucose from Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol was ascribed by the authors to microbial attack in the hind gut. The authors concluded that the data on rats were valid for other species demonstrating carbohydrate fermentation in the caecum and/or colon (Ziesenitz, 1983).

Groups of 12 ileum re-entrant fistulated pigs and 12 normal pigs were fed 80% basal ration plus a combination of 10% Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol and 10% sucrose, 20% Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol (van Weerden et al., 1984a). After exposure to the test item, no test item could be detected in the faeces. 67% of the intact test item, plus mannitol and sorbitol, reached the terminal ileum in the group fed 20% test item; 54% reached the terminal ileum in the group fed 10% test item. This means that 33% to 46% of the ingested amount of test item, respectively, was hydrolysed and absorbed in the small intestine.

In pigs fed 10%, and especially 20%, Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol, the flow of the chyme along the small intestine was considerably accelerated during the first 3-4 hours after feeding, and the amount of chyme appearing at the terminal ileum was greatly increased. This accelerated and increased flow of the chime along the small intestine was ascribed by the authors as most likely due to the osmotic properties of the non-absorbed test item and its constituents. (van Weerden et al., 1984a).

Fistulated and normal pigs were fed 5 or 10% Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol between meals, or 10% Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol with meals. The passage and absorption rate of these substances were determined at the terminal ileum (10 pigs per treatment) or over the whole distance of the digestive tract (4 pigs per treatment). 61-64% of the ingested compound passed the terminal ileum in the form of intact test item plus free sorbitol, free mannitol, and free glucose. None of these sugars was excreted in the faeces, indicating that the test item and its constituents passing the terminal ileum are completely broken down in the large intestine. (van Weerden et al., 1984b).

In conclusion, the systemic bioavailability of Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol following oral ingestion cannot be excluded, but is limited by the fact that degradation into absorbable monosaccharides does only partially occur in the small intestine but mainly by microbial fermentation in the large intestine.

Dermal

There are no data available on dermal absorption or on acute dermal toxicity of Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol. Based on the following considerations, the dermal absorption of the substance is considered to be low.

The smaller the molecule, the more easily it may be taken up. In general, a molecular weight below 100 g/mol favors dermal absorption, above 500 g/mol the molecule may be too large (ECHA, 2017). As the molecular weights of GPS and GPM are 344.32 and 380.32 g/mol, respectively, dermal absorption of the molecules may be impeded due to their size. For substances with a log Pow below 0, the rate of dermal penetration is limited by the rate of penetration into the stratum corneum (ECHA, 2017). As the water solubility of Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol is high (308 - 488 g/L) and the log Pow is well below 0 (-4.2 - -3.7), dermal uptake is likely to be very low.

If the substance is a skin irritant or corrosive, damage to the skin surface may enhance penetration (ECHA, 2017). However, the surrogate substance 6-O-alpha_D-glucopyranosyl-D-fructose (CAS 13718-94-0) did not reveal any skin irritating properties (Lehmeier, 2012) and applying a read-across approach, similar properties are expected for Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol.

Furthermore, QSAR based dermal permeability prediction (Dermwin v 2.02, Epi Suite 4.1) using molecular weight, log Pow and water solubility for the two constituents GPS and GPM was performed resulting in a calculated dermal permeability coefficient (Kp) of 4.02 x 10E-8 cm/h and 2.66 x 10E-8 cm/h for GPS and GPM, respectively, indication low dermal permeability of the compounds.

This is further supported by dermal flux rates of 0.000335 and 0.000273 mg/cm2 per h calculated for GPS and GPM, respectively, indicating a very low dermal absorption potential for both constituents (please refer to Table 1). These values are considered indicators for a very low dermal absorption rate.

Table 1: Dermal absorption value for GPS and GPM (calculated with Dermwin v 2.02, Epi Suite 4.1)

Component	Structural formula	Flux (mg/cm2/h)
GPS	C12H24O11	0.000335
GPM	C12H24O13	0.000273

 

Overall, the high water solubility, the relatively high molecular weight (>340 g/mol), the low log Pow value and the fact that the substance is not considered to be irritating to skin leads to the expectation that dermal uptake of Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol will be low.

Inhalation

No studies with Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol via the inhalation route are available.

In humans, particles with aerodynamic diameters below 100 μm have the potential to be inhaled. Particles with aerodynamic diameters below 50 μm may reach the thoracic region and those below 15 μm the alveolar region of the respiratory tract (ECHA, 2017). Based on the commercially available particle size of 1 µm to 3.5 mm (Gehrich 2018b), the inhalation of Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol is possible, although the vapour pressure of the compound was determined to be 3.1E-11 to 1.6E-07 hPa at 20°C (Dreisch, 2018) thus being of low volatility (ECHA, 2017).

As the components of Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol represent hydrophilic compounds, which are very well soluble in water, passive transfer through cell membranes in the respiratory tract without transport systems is impeded. Passive diffusion was shown possible in the gastrointestinal tract for monosaccharides (Rugg-Gunn, 1991), and therefore, absorption across the respiratory epithelium cannot be excluded for monosaccharides but for disaccharides, which in general require digestion to monosaccharides prior to absorption. Due to the fact that spontaneous hydrolysis of GPS and GPM under aqueous conditions is limited, it is expected that they will mainly be present in their disaccharide from and therefore may not be subject to uptake by passive diffusion.

The substance is neither irritating to skin or the eye nor sensitizing. It is therefore expected that even after potential inhalation no adverse local effects to the mucous membranes will occur that might facilitate absorption.

Overall, an inhalative exposure to Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol cannot be excluded, e.g. after inhalation of dusts with aerodynamic diameters as low as 1 µm. However, due to the expected low absorption of the dissacharides, systemic exposure to Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol is expected to be low and not higher than following oral exposure.

Distribution and accumulation

A reliable study on the absorption, distribution and excretion of 14C-radiolabeled Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol after oral dosing is available (Patzschke, 1975). In this study the test item was administered orally to rats (4 males/dose) at single doses of 250, 1000 or 2500 mg/kg bw. 48 h after dosing, depending on the dose, between 6 and 11% of the administered radioactivity was found in the animal's body (stomach and intestines not included) and only approximately 1% in the digestive tract (stomach and intestinal walls plus contents). 48 hours after oral dosing, radioactivity was distributed to all tissues. The mean equivalent concentration in the body was approximately 30 µg/g wet weight. The highest concentrations were found in adipose tissues, adrenal cortex, thymus, liver, bone marrow and tonsils. The concentration of radioactivity was much lower in the blood than in most other tissues. Quantitative radioactivity measurements in the liver corresponded to an equivalent concentration of approximately 80 µg/g wet weight. Blood concentrations were approximately 5 times lower (determined by quantitative measures versus time for the 3 doses).

When Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol was fed to rats for several weeks it was observed that faecal excretion declined steadily, while the caecum enlarged. The authors concluded that this resulted from adaptation and metabolism by the gut microflora. Similarly, during a 17-day feeding period in which 6 female rats received daily doses of 3.5 g Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol the faecal content fell from 25% of the dose at the beginning to 1% at the end (Musch et al., 1973; Grupp & Siebert, 1978).

Highly lipophilic substances in general tend to concentrate in adipose tissue, and depending on the conditions of exposure may accumulate. Although there is no direct correlation between the lipophilicity of a substance and its biological half-life, it is generally the case that substances with high log Pow values have long biological half-lives. The low log Pow < 0 and the high water solubility (≥ 308 g/L) imply that Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol may not accumulate in adipose tissue (ECHA, 2017). This is supported by experimental data (Patzschke, 1975), demonstrating that 48 h after oral dosing of 250, 1000 and 2500 mg/kg bw of 14C radiolabelled Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol the body only contained 13, 9 and 7% of the administered radioactivity.

These data in combination with the excretion data given below indicate that no significant bioaccumulation in adipose tissue has to be considered for Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol.

Excretion

Patzschke (1975) demonstrated that 48 h after oral dosing of 250, 1000 and 2500 mg/kg bw of 14C radiolabelled Reaction mass of 1-O-α-D-glucopyranosyl-D-mannitol and 6-O-α-D-glucopyranosyl-D-glucitol 62, 53, and 33% of administered radioactivity had been eliminated via air (exhaled or from intestinal gases due to microbial caecal fermentation); 18, 32, and 54% in the feces and 6.4, 5.4, and 5.0% in the urine.

 

References

ECHA 2017: Guidance on information requirements and chemical safety assessment, Chapter R.7c: Endpoint specific guidance. Version 3.0, June, 2017.

 

Grupp, U. & Siebert, G. 1978: Metabolism of hydrogenated palatinose, an equimolecular mixture of alpha-D-glucopyranosido-1,6-sorbitol and alpha-D-glucopyranosido-1,6-mannitol. Res. Exp. Med.

(Berl.), 173, 261-278.

 

JECFA 1985: Isomalt. International Programme on Chemical Safety, World Health Organization. Toxicological Evaluation of Certain Food Additives and Contaminants. Who Food Additives Series 20. WHO, Geneva

 

Kirchgessner, M., Zinner, P.M., & Roth, H.-P. 1983:. Energy metabolism and insulin activity in rats fed Palatinit(R). Internat. J. Vit. Nutr. Res., 53, 86-93Ziesenitz 1983

 

Musch, V.K., Siebert, G., Schiweck, H., & Steinle, G. 1973: Physiological-nutritional studies on the utilization of isomaltitol in rats. Zeitschrift fur Ernährungswissenschaft Suppl., 15, 3-16.

 

Rugg-Gunn: 1991: Sugarless - The Way Forward: Proceedings of an International Symposium Held at the University of Newcastle at Tyne, U. K., September 1990. ISBN-10 / 13 :1851665986 / 9781851665983. Publisher: Elsevier Applied Science

 

Sinkeldam, E.J. 1983: Effects of Palatinit(R) ingestion on the gut flora and the gut contents of rats. Unpublished report No. V 83.007/212651 from Centraal Instituut voor Voedingsonderzoek (CIVO/TNO), Zeist, The Netherlands. Submitted to WHO by Bayer A.G.

 

van Weerden, E.J., Huisman, J., & van Leeuwen, P. 1984a: The digestion process of Palatinit(R) in the intestinal tract of the pig. Unpublished report No. 528 from Institut voor Landbouwkundig Onderzoek van Biochemische Producten (ILOB), Wageningen, The Netherlands. Submitted to WHO by Bayer A.G.

 

van Weerden, E.J., Huisman, J., & van Leeuwen, P. 1984b: Further studies on the digestive process of Palatinit(R) in the pig. Unpublished report No. 530 from Institut voor Landbouwkundig Onderzoek van Biochemische Producten (ILOB), Wageningen, The Netherlands. Submitted to WHO by Bayer A.G.

 

Ziesenitz, S.C. (1983). Bioavailability of Glucose from Palatinit(R). Z. Ernährungswiss., 22, 185-194.

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential