Bergamot, ext.

Endpoint summary

Description of key information

There are no toxicokinetic studies available for Bergamot oil. Therefore, the toxicokinetic assessment of Bergamot oil will be primarily based on physicochemical parameters and available open literature on its constituents. In terms of constituents the focus will be on the major constituents: d-Limonene (CAS nr 5989-27-5), Linalyl acetate (CAS nr. 115-95-7) and Linalool (CAS nr. 78-70-6). Using these data results in a coverage of >80% of the composition of Bergamot oil, which ensures that the same data requirements are covered as for mono-constituent substances.

Additional information

Background

Bergamot oil is a Natural Complex Substance (NCS) which is a subgroup of Substances of Unknown, of Variable Composition, or of Biological Origin (UVCB substances). As such, Bergamot oil is part of the particular category of essential oils, extracts, fractions and distillation products of the Rutaceae family. With over 95% of the constituents of Bergamot oil known, this NCS can be considered a well-defined NCS Type 1.

There is only limited information available on toxicokinetics, metabolism and distribution of Bergamot oil itself. For this reason, the toxicokinetic assessment will be primarily based on physicochemical information and some accessible open literature on the constituents of Bergamot oil. The focus will be on the major constituents: d-Limonene (CAS nr 5989-27-5), Linalyl acetate (CAS nr. 115-95-7) and Linalool (CAS nr. 78-70-6). Using this data results in a coverage of >80% of the composition of Bergamot oil, which ensures that the same data requirements are covered as for mono-constituent substances.

 

Available studies for Bergamot oil

There are no toxicokinetic studies available for the Bergamot oil quality as registered. A study examining the enzyme induction of essential oils revealed that Bergamot terpenes quality elicited glutathione S-transferase (GST) enzyme activity >2.5 times of the control level in cytosols of liver, forestomach and small intestinal mucosa of A/J mice. Induction of GST has an impact on detoxification of other substances and an increased GST-activity suggests anticarcinogenic potential.

The observed effects in the acute oral toxicity study with Bergamot oil indicate that oral absorption of Bergamot oil occurs. In the acute dermal toxicity study, only mild erythema but no signs of edema, systemic toxicity or effects on hematology or clinical chemistry were observed. This suggests a low dermal absorption.

 

Available data for constituents of Bergamot oil

Physicochemical parameters including molecular weight, log Kow, water solubility and vapour pressure are parameters indicating whether absorption via the oral, inhalation and dermal route is expected. An overview of the relevant physicochemical parameters for Bergamot oil and its constituents is provided below.

 

Table 1. Physicochemical parameters of Bergamot oil and its constituents. *Main constituent:>10% of composition of Bergamot oil, minor constituent: ≤ 10% of composition Bergamot oil.

Constituent	CAS	Type of constituent*	Molecular weight	log Kow	Water solubility (mg/L at 25ºC)	Vapour pressure (Pa at 25ºC)
Bergamot oil	89957-91-5	-	UVCB	2.14-6.3	0.028 - 1767.3	123.1
D-Limonene	5989-27-5	main	136.24	4.38	44.388	193
Linalyl acetate	115-95-7	main	196.29	4.39	40.617	17.5
Linalool	78-70-6	main	198	3.38	709.26	11.1
Beta-Pinene	127-91-3	minor	136.24	4.35	2.6192	334
Gamma-Terpinene	99-85-4	minor	136.24	4.75	59.034	153
Bergamottin	7380-40-7	minor	338.41	6.24	0.028139	2.64E-07
Sabinene	3387-41-5	minor	141.81	4.69	2.6192	981
Myrcene	123-35-3	minor	167	4.88	17.814	320
Alpha-Pinene	80-56-8	minor	136.24	4.27	3.4834	536
Citral	5392-40-5	minor	152.24	3.45	1101	12.2
Neryl acetate	141-12-8	minor	196.29	4.48	57.985	6.17
Geranyl acetate	105-87-3	minor	196.29	4.48	57.985	6.17
Beta-Caryophyllene	87-44-5	minor	204.36	6.3	0.54268	4.16
Decanal	112-31-2	minor	156.27	3.76	85.498	31.4
Bergapten	484-20-8	minor	216.19	2.14	92.623	0.000101
Alpha-Thujene	2867-05-2	minor	136.24	4.61	3.4834	655
Terpinolene	586-62-9	minor	136.24	4.48	93.066	133
Alpha-Terpineol	98-55-5	minor	136.24	3.33	1767.3	2.62

 

As shown in Table 1, Bergamot oil has a log Kow in the range of 2.14-6.3, a water solubility in the range of 0.028 - 1767.3 mg/l and a calculated vapour pressure of 123.1 Pa. Given the criteria as outlined in the ECHA guidance (see Guidance on Information Requirements and Chemical Safety Assessment, Chapter R.7c: Endpoint specific guidance), oral and dermal absorption are anticipated for Bergamot oil given the fact that most constituents have a molecular weight <500 and a log Kow between 1-4. The low volatility (<500 Pa) of Bergamot oil suggests that Bergamot oil is not likely to be readily available for inhalation as a vapour. However, based on the use of Bergamot oil as a fragrance, absorption via inhalation should be taken into consideration.

 

Information on the major constituents

d-Limonene

d-Limonene has a log Kow of 4.38 and a water solubility of 44.388 mg/l. The vapour pressure is 193 Pa and the molecular weight is 136. The moderate log Kow and the relatively low molecular weight (<200) would favour oral, respiratory and dermal absorption of d-Limonene, but the relatively poor water solubility and the poor volatility suggest an opposite behaviour.

In a review done by the National Institute of Occupational Health the following information is mentioned for d-Limonene (Karlberg and Lundell, 1993):

1) Distribution: after absorption, d-Limonene disappears rapidly from blood. This is mainly due to distribution to different tissues and due to the biotransformation. The blood clearance in human after exposure has been determined to 1.1 L/kg x hour. A high solubility of d-Limonene in olive oil (calculated partition coefficient oil/blood = 140) as well as a long half-life in blood, in the slow elimination phase, indicate affinity to adipose tissues. Species differences in renal disposition and protein binding of d-Limonene were observed.

2) Biotransformation: studies in various species revealed that there are different pathways in the metabolism of d-Limonene, including oxidation at the 8,9-double bond or the 1,2-double bond, oxidation of the methyl groups to hydroxyl and further to carboxylic acid derivatives, ring hydroxylation at the C-1 and C-6 position, and glycine or glucuronide conjugation. Species differences in plasma and urinary metabolites were observed.

3) Excretion: three different phases of elimination of d-Limonene were observed in human blood. The half-lifes in blood after exposure by inhalation for 2 hours to 450 mg/m3 d-limonene were ca. 3 minutes, 33 minutes and 750 minutes.

In conclusion, based on this information d-limonene is expected to be readily absorbed by the oral route. This is confirmed by the findings in the repeated dose toxicity studies in mice, rats and dogs indicating the presence of systemic effects (clinical signs, reduced bodyweight and kidney effects) upon administration of d-Limonene via oral gavage.

Dermal absorption is assumed to be lower. However, as no information is available on the extent of dermal absorption, it is assumed to be similar to oral absorption as a worst case.

 

Linalyl acetate

As presented in the OECD SIDS toxicokinetics assessment of Linalyl acetate (OECD SIDS, 2002), the substance will be hydrolysed to Linalool and Acetic acid in the gastro-intestinal tract. As a consequence, the data for Linalool also covers Linalyl acetate, as this substance is quickly metabolized to Linalool.

 

Linalool

As shown in Table 1, Linalool has a log Kow of 3.38 and a water solubility of 709.26 mg/l. The vapour pressure is 11.1 Pa and the molecular weight is 198. The moderate log Kow and good water solubility, as well as the relatively low molecular weight would favour oral, respiratory and dermal absorption of Linalool. This is confirmed by the findings in the 28-day repeated dose toxicity study in rats, indicating the presence of systemic effects (stomach and kidney) upon administration of Linalool via oral gavage.

As presented in the OECD SIDS toxicokinetics assessment of Linalool (OECD SIDS, 2002), the substance is rapidly absorbed from the intestinal tract following oral administration. This is supported by the study performed by Parke et al. (1974), indicating that the orally (gavage) administered (radiolabelled) linalool is fully absorbed. Absorption was rapid and within 2 days after treatment and radioactivity was excreted via urine (approx. 60%), expired air (approx. 23%) and faeces after assumed enterohepatic circulation (approx. 15%). The remaining linalool (approx. 3%) is found in tissues of the animals. Bioavailability from an oral dose would therefore be approximately 100%.

Subsequent to absorption, Linalool is metabolised. Parke et al. (1974) found that no free linalool, but only polar conjugates were detectable in bile (partially hydrolysed by beta-glucuronidase and to a greater extent by a mixture of beta-glucuronidase and sulphatase) after an intraperitoneal dose. Non-polar ether-extractable metabolites (5% of dose) were detected in faeces. No indications for tissue accumulation of Linalool were found. The conclusion of the OECD SIDS assessment is that the relatively rapid overall excretion of Linalool and its metabolites suggests no long-term hazard from chronic concentrations.

In conclusion, Linalool is rapidly absorbed via the oral route and rapidly excreted mainly via urine, expired air and faeces. Overall, the data indicate a low potential for bioaccumulation. The data indicate further, that Linalool is metabolized extensively to harmless metabolites. Oral absorption is assumed to be 100%.

 

Other constituents

For the other (minor) constituents, physicochemical parameters (see table 1) are used to determine whether absorption via the oral, inhalation and dermal route is expected. Oral absorption and absorption via inhalation is expected to be moderate to high for most constituents, based on molecular weights <500, moderate to high water solubility and a log Kow between 2 and 4. However, the vapour pressure of almost all constituents is low (<1000 Pa), which suggests that Bergamot oil constituents are not likely to be readily available for inhalation as a vapour. Oral absorption for bergamottin, α-pinene, sabinene, β-pinene, β-caryophyllene, α-thujene and myrcene B may be less due to their log Kow >4 in combination with their relatively low water solubility.

Dermal absorption is not favoured based on the molecular weights of the substances, neither can it be ruled out. For the constituents with a log Kow <4 combined with a relatively high water solubility (e.g. citral, decanal, bergapten, alpha-terpineol) dermal absorption is expected. For bergamottin, α-pinene, sabinene, β-pinene, β-caryophyllene, α-thujene and myrcine B, which have a log Kow >4 and relatively low water solubility, dermal absorption is expected to be low to moderate. The vapour pressure of bergamottin, sabinene, α-pinene and α-thujene is >500 Pa, which would favour absorption via inhalation.

In conclusion, for most of the other constituents of Bergamot oil, the absorption via the oral, inhalation and dermal route is expected to be moderate to high.

 

Overall conclusions

Based on available information on Bergamot oil and its constituents, Bergamot oil is expected to be readily and fully absorbed by the oral route (approximately 100%). Dermal absorption is expected to be lower. However, as no specific information is available on the extent of dermal and inhalation absorption, this is assumed to be comparable to oral absorption as a worst case. For risk assessment purposes, the absorption after oral, dermal and inhalation exposure are therefore assumed to be identical and route-to-route extrapolation from the oral to inhalation and dermal route is not required.

 

References

- Karlberg A.T. and Lundell B (1993). Limonene, Beije B., Lundberg P. (eds). Criteria documents from the Nordic Expert group.Arbete och Habsa, 35, 1 -254.

- Lam, L.K.T, Zheng, BL, (1991), Effects of Essential oils on Glutathione S-transferase Activity in Mice. J. Agric. Food Chem. 39, 660-662.

- OECD SIDS (2002). Linalool. UNEP Publications, see http://www.inchem.org/documents/sids/sids/78706.pdf.

- OECD SIDS (2002). Linalyl acetate. UNEP Publications. http://www.inchem.org/documents/sids/sids/115957.pdf

- Parke, D.V., Quddusur Rahman, K.H.M., Walker, R. (1974a). The absorption, distribution and excretion of linalool in the rat. Biochemical Society Transactions 2: 612-615.