Hop, Humulus lupulus, ext., isomerized, potassium salt

Genetic toxicity: in vivo

Administrative data

Endpoint:

in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

1 (reliable without restriction)

Justification for type of information:

This study is taken from a recently-published scientific article by S. Suzuki et al. on "Genetic, acute and subchronic toxicity studies of matured hop extract produced by extraction from heat-treated hops", published in the Journal of Toxicological Sciences (2018) vol. 43, no. 7, pp. 473-484, available freely as full text in the public domain. Matured hop extract contains oxidised alpha and beta acids. This substance is therefore of direct relevance to hop extract, and to alpha acids, iso-alpha acids, and beta acids, as the oxidised alpha and beta acids are common degradation products of hop alpha and beta acids. This article is useful in that it reports a number of toxicological studies, and the in vivo tests on chromosome aberration are reported in this end-point to add as weight of evidence for the lack of genotoxicity expected for hop extract and its constituents.

Data source

Reference

Reference Type:

publication

Title:

Genetic, acute and subchronic toxicity studies of matured hop extract produced by extraction from heat-treated hops

Author:

Shigeo Suzuki, Yumie Morimoto-Kobayashi, Chika Takahashi, Yoshimasa Taniguchi, Mikio Katayama

Year:

2018

Bibliographic source:

https://www.jstage.jst.go.jp/article/jts/43/7/43_473/_html/-char/en

Report date:

2018

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: In accordance with a previous protocol, viz. Hayashi, M., Sofuni, T. and Ishidate, M. Jr. (1983): An application of Acridine Orange fluorescent staining to the micronucleus test. Mutat. Res., 120, 241-247.

GLP compliance:

not specified

Type of assay:

mammalian germ cell cytogenetic assay

Test material

Test material information

Constituent 1

Reference substance name:

Hop, Humulus lupulus, ext.

EC Number:

232-504-3

EC Name:

Hop, Humulus lupulus, ext.

Cas Number:

8060-28-4

IUPAC Name:

Hop, Humulus lupulus, ext.

Test material form:

liquid: viscous

Remarks:

Depending on the extraction conditions and on the hop variety, the colour of the extract can vary from yellow to dark green. It is a semi-fluid paste at room temperature. The product becomes more fluid when heated.

Specific details on test material used for the study:

An aqueous extract of a heat-treated hop extract, designed for production and extraction of oxidised alpha and beta acids.

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male

Details on test animals or test system and environmental conditions:

Eight-week-old male rats. Body weight was between 289 - 310 g.

Administration / exposure

Route of administration:

oral: unspecified

Vehicle:

Sterlized water

Details on exposure:

High dose group: 2,000 mg/kg bw/day; middle dose group: 1,000 mg/kg bw/day; low dose group: 500 mg/kg bw/day. Once daily for 2 days.

Duration of treatment / exposure:

2 days

Frequency of treatment:

Once daily

Post exposure period:

24 h

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

2 000 mg/kg bw/day

Remarks:

High dose group

Doses / concentrations 2

Dose / conc.:

1 000 mg/kg bw/day

Remarks:

Middle dose group

Doses / concentrations 3

Dose / conc.:

500 mg/kg bw/day

Remarks:

Low dose group

No. of animals per sex per dose:

5

Control animals:

yes, concurrent vehicle

Positive control(s):

MMC. This was dissolved in sterilized water and it was injected intraperitoneally at 2 mg/kg bw. One dose only.

Examinations

Tissues and cell types examined:

Bone marrow cell smears for erythrocytes.

Details of tissue and slide preparation:

Notes from journal: "Bone marrow cell smears were prepared and stained with acridine orange. Numbers of polychromatic erythrocytes (PCEs) per 200 erythrocytes, and micronucleated polychromatic erythrocytes (MNPCEs) per 2,000 PCEs were counted."

Evaluation criteria:

Notes from journal: "Numbers of polychromatic erythrocytes (PCEs) per 200 erythrocytes, and micronucleated polychromatic erythrocytes (MNPCEs) per 2,000 PCEs were counted."

Results and discussion

Test results

Key result

Sex:

male

Genotoxicity:

negative

Vehicle controls validity:

valid

Positive controls validity:

valid

Additional information on results:

These results are part of a larger study reported in the article. Results in brief:

• Ames test – negative, up to 5,000 ug per plate, with and without metabolic activation
• In vitro chromosomal aberration test – positive at 3,330 and 5,000 ug per plate without metabolic activation (i.e. elevated structural aberration above negative control) but no increase in polyploid cells
• In vivo micronucleus test in rat bone marrow – no clastogenic potential at max dose of 2,000 mg/kg bw/day, i.e. negative
• Acute toxicity – No noticeable toxic signs at 2,000 mg/kg bw
• 90 days study – NOAEL considered to be over 3,484 mg/kg bw/day for male and 4,022 mg/kg bw/day for female rats.

Authors’ conclusion is that although the structural chromosomal aberration was positive in high dose group for the in vitro test, Ames test and in vivo micronucleus test suggests that the matured hop extract has no potential for mutagenicity and genotoxicity under in vivo conditions.

Further consideration of results noted that cytotoxicity was observed in the in vitro test.If the toxicity mechanism was to slow cell division or similar, it could look like a chromosome aberration. The in vivo test indicates lack of genotoxicity at appropriate doses. The authors' comment was as follows: "From the results mentioned above, it is judged that MHE does not have clastogenic potential in rats at the maximum dose, which is recommended by OECD guidelines (OECD, 1997)."

Applicant's summary and conclusion

Conclusions:

The studies reported in this journal article add weight of evidence to the lack of toxicity of hop extract, in particular for substances derived from hop alpha and beta acids.