Extract obtained from powder of Theobroma cacao (Malvaceae) by co-extraction with ethanol and propylene glycol

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

toxicity to microorganisms

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Non-GLP compliant guideline study, available as unpublished report, minor restrictions in design and/or reporting but adequate for assessment.

Principles of method if other than guideline:

Test according to the German guideline published in: "Bewertung wassergefahrdender Stoffe"

GLP compliance:

no

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

A stock solution containing 25,000 mg/l was prepared in distilled water and sterilized in an autoclave (30 min at 120 °C). Dilutions of the stock solution were prepared

Test organisms (species):

Pseudomonas putida

Details on inoculum:

A culture of the test organism, the gram negative bacterium Pseudomonas putida was obtained from prof. R. Kuhn. (Institut fur Wasser-, Bodem,- und Lufthygiene des Bundesgesundheitsamtes, Berlin). The bacterium was cultivated according to the method described in "III bestimmung der akuten bakterientoxizitat".
A preculture was prepared, and the test culture was prepared from this preculture by dilution with sterile NaCl- solution (0.5 g/l) until the bacterial suspension had an optical density of 0.43 measured in a 10 mm glass cuvette with a Pye Unicam SP 500 spectrofotometer at 436 nm.

Test type:

not specified

Water media type:

freshwater

Limit test:

no

Total exposure duration:

18 h

Post exposure observation period:

None

Hardness:

No data

Test temperature:

25 °C

pH:

No data

Dissolved oxygen:

No data

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal concentrations: 0; 9.75; 19.5; 39; 78; 156; 312.5; 625; 1250; 2500; 5000; 10000; 20000 mg/l

Details on test conditions:

In principle dilutions of the stock solution were prepared, and after addition of bacterial suspension and nutrients, the cultures (in 300 ml conical flasks) were incubated for 18 hours at 25°C

Reference substance (positive control):

not specified

Duration:

18 h

Dose descriptor:

NOEC

Effect conc.:

> 20 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth inhibition

Details on results:

The results show that above 312 mg/l propylene glycol added to the culture there are a slight stimulation of growth, which decreases again above 5000 mg/l. At the highest concentration tested there is a slight inhibition of growth of less than 10%. The toxicity treshold is therefore > 20.000 mg/l.

Executive summary:

The test was performed according to the German guideline published in: "Bewertung wassergefahrdender Stoffe".

The NOEC of propylene glycol is >20000 mg/L.

Key value for chemical safety assessment

EC50 for microorganisms:

20 000 mg/L