2-[7-(diethylamino)-2-oxo-2H-1-benzopyran-3-yl]-1,3-dimethyl-1H-benzimidazolium chloride

Toxicity to aquatic algae and cyanobacteria

Administrative data

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

Experimental test result performed according to the guideline.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Report date:

2016

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Principles of method if other than guideline:

This study was conducted to assess the effect of the test item 2-[7-(diethylamino)-2-oxo-2H-1-benzopyran-3-yl]-1,3-dimethyl-1H-benzimidazolium chloride; CAS No. 29556-33-0 on the growth of green alga Chlorella vulgaris

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

2-[7-(diethylamino)-2-oxo-2H-1-benzopyran-3-yl]-1,3-dimethyl-1H-benzimidazolium chloride

EC Number:

249-694-9

EC Name:

2-[7-(diethylamino)-2-oxo-2H-1-benzopyran-3-yl]-1,3-dimethyl-1H-benzimidazolium chloride

Cas Number:

29556-33-0

Molecular formula:

C22H24N3O2.Cl

IUPAC Name:

2-[7-(diethylamino)-2-oxo-2H-chromen-3-yl]-1,3-dimethyl-2,3-dihydro-1H-3,1-benzimidazol-1-ium chloride

Test material form:

solid: particulate/powder

Details on test material:

- Name of test material: 2-[7-(diethylamino)-2-oxo-2H-1-benzopyran-3-yl]-1,3-dimethyl-1H-benzimidazolium chloride
- Molecular formula: C22H24N3O2.Cl
- Molecular weight: 347.4159 g/mol
- Smiles notation (if other than submission substance): c1(c2c(oc3c(c2)ccc(N(CC)CC)c3)=O)nc2ccccc2n1C
- InChl (if other than submission substance): 1S/C21H21N3O2/c1-4-24(5-2)15-11-10-14-12-16(21(25)26-19(14)13-15)20-22-17-8-6-7-9-18(17)23(20)3/h6-13H,4-5H2,1-3H3
- Substance type: Organic
- Physical state: Bright Yellow to Greenish Yellow Powder

Specific details on test material used for the study:

- Name of test material: 2-[7-(diethylamino)-2-oxo-2H-1-benzopyran-3-yl]-1,3-dimethyl-1H-benzimidazolium chloride
- Molecular formula: C22H24N3O2.Cl
- Molecular weight: 347.4159 g/mol
- Smiles notation (if other than submission substance): c1(c2c(oc3c(c2)ccc(N(CC)CC)c3)=O)nc2ccccc2n1C
- InChl (if other than submission substance): 1S/C21H21N3O2/c1-4-24(5-2)15-11-10-14-12-16(21(25)26-19(14)13-15)20-22-17-8-6-7-9-18(17)23(20)3/h6-13H,4-5H2,1-3H3
- Substance type: Organic
- Physical state: Bright Yellow to Greenish Yellow Powder
-Batch No.:FG/15-16/2453

Sampling and analysis

Analytical monitoring:

no

Test solutions

Vehicle:

no

Details on test solutions:

The test solution was prepared in aseptic condition. The test item 2-[7-(diethylamino)-2-oxo-2H-1-benzopyran-3-yl]-1,3-dimethyl-1H-benzimidazolium chloride was prepared by adding 50 mg of test item in 250 ml of BBM to get the final concentration of 200mg/L. This stock solution was kept for stirring for 30 minutes to obtain a homogenous solution for the experiment.

Test organisms

Test organisms (species):

Chlorella vulgaris

Details on test organisms:

TEST ORGANISM
- Common name: green alga
- Source (laboratory, culture collection): National Environmental Engineering Research Institute (NEERI), Nagpur (Laboratory)
- Method of cultivation: Bold’s Basal Medium(BBM)


ACCLIMATION
- Culturing media and conditions (same as test or not): The medium to be used for the growth of algae was Bold’s Basal Medium (BBM). It is a medium composed of macronutrients, micronutrients, alkaline EDTA solution and Iron solution. Stock solution of each of these was prepared separately and then a complete medium was prepared and sterilized. De-ionized water was used to prepare the BBM
- Any deformed or abnormal cells observed: no

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Post exposure observation period:

24, 48, 72 hrs

Test conditions

Test temperature:

22 °C±2°C

Nominal and measured concentrations:

6.25mg/l, 12.5mg/l, 25mg/l, 50mg/l, 100mg/l and 200mg/l All the six concentration were in geometric series spaced by a factor of 2.

Details on test conditions:

TEST SYSTEM
- Test vessel: Conical flasks
- Material, size, headspace, fill volume: 100 ml conical flasks filled with 60 ml was used for the study.
- Initial cells density: 10000cells/ml
- No. of organisms per vessel: 10000cells/ml
- No. of vessels per concentration (replicates): Two replicates for each test concentration
- No. of vessels per control (replicates): Three replicates for Control

GROWTH MEDIUM
- Standard medium used: yes
- Detailed composition if non-standard medium was used: The medium to be used for the growth of algae was Bold’s Basal Medium (BBM). It is a medium composed of macronutrients, micronutrients, alkaline EDTA solution and Iron solution. Stock solution of each of these was prepared separately and then a complete medium was prepared and sterilized. De-ionized water was used to prepare the BBM.


OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH: Yes
- Photoperiod: 16 Hour Light Period : 8 Hour Dark Period
- Light intensity and quality: continuous, uniform fluorescent illumination(1500Lux)

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: Spectrophotometer - The absorbance values of each test vessel and control vessel was noted at 680nm.The BBM was taken as blank for both control and test vessels. The absorbance value of each vessel was in line with the average specific growth rate.
- Chlorophyll measurement: No data
- Other: The cultures were observed daily with the help of a microscope to verify a normal and healthy appearance of the algal culture and also to
observe any abnormal appearance of the algae (as may be caused by the exposure of the test item). Apart from this, the cell count of each test vessel was also noted with the help of a microscope and haemocytometer.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: All the six concentrations were in geometric series spaced by a factor of 2.
- Test concentrations: Six test concentration were: 6.25mg/l, 12.5mg/l, 25mg/l, 50mg/l,100mg/l and 200mg/l (Nominal concentrations)
- Results used to determine the conditions for the definitive study: Mortality of test organisms

Incubation :
1. The temperature of the orbital shaking incubator was kept constant throughout the period of exposure of the experiment. The temperature was maintained at 22 ° C±2°C.
2. The test vessels were incubated with a continuous, uniform fluorescent illumination (1500Lux).
3. The pH of the control cultures needs to be noted during the study and the pH of the control medium should not increase by more than 1.5 units during the test.
4. The orbital shaking incubator was set at a speed of 120 revolutions per minute throughout the study period. This is to provide constant shaking to the algal cells to keep them in suspension and to ensure that they do not settle down on the bottom of the test vessel.
5. Study duration : The experimental phase of the study was lasted for a period of 72 hours.

Reference substance (positive control):

not specified

Results and discussion

Effect concentrations

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

85.831 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: calculated from equation through probit analysis

Details on results:

The microscopic observations were also noted in each of the experimental flasks. All the cells appeared healthy, round and green throughout the test duration in the control and in the experimental flask also no significant changes were observed.

Reported statistics and error estimates:

To obtain a quantitative concentration-response relationship by regression analysis, a linearizing transformation of the response data into probit was performed. Using the same, effective concentration (EC) was determined.

Any other information on results incl. tables

Table 1: Showing the average cell count using Haemocytometer of the test vessels at an equal interval of 24hrs, 48hrs and 72hrs

Test vessels and test concentration	24 Hours	48 Hours	72 Hours
Control
Replicate 1	3.6 x10^4	5.08 x10^4	6.96 x10^4
Replicate 2	2.44 x10^4	5.16 x10^4	6.64 x10^4
Replicate 3	2.84 x10^4	4.11 x10^4	6.4 x10^4
CAS No. 29556-33-0
6.25mg/l
Replicate 1	2.4 x10^4	3.52 x10^4	4.48 x10^4
Replicate 2	2.68 x10^4	3.96 x10^4	3.88 x10^4
12.5mg/l
Replicate 1	4 x10^4	2.4 x10^4	4.12 x10^4
Replicate 2	2.6 x10^4	2.36 x10^4	3.4 x10^4
25mg/l
Replicate 1	3.28 x10^4	2.64 x10^4	2.76 x10^4
Replicate 2	2.56 x10^4	2.52 x10^4	2.48 x10^4
50mg/l
Replicate 1	2.64 x10^4	2.88 x10^4	2.56 x10^4
Replicate 2	2.28 x10^4	2.4 x10^4	2.12 x10^4
100mg/l
Replicate 1	3.32 x10^4	2.36 x10^4	2.76 x10^4
Replicate 2	2.52 x10^4	1.8 x10^4	2.28 x10^4
200mg/l
Replicate 1	2.08 x10^4	2.4 x10^4	2.8 x10^4
Replicate 2	2.16 x10^4	1.48 x10^4	2.52 x10^4

Table 2: Showing the values of average specific growth rate and percentage inhibition after an interval of 72 hours

	CONTROL		6.25mg/l		12.5mg/l		25mg/l		50mg/l		100mg/l		200mg/l
Average Specific Growth rate (µ )	R1	0.647	R1	0.500	R1	0.472	R1	0.338	R1	0.313	R1	0.338	R1	0.343
	R2	0.631	R2	0.452	R2	0.408	R2	0.303	R2	0.250	R2	0.275	R2	0.308
	R3	0.619
Mean of Avg. Specific growth rate	0.632		0.476		0.440		0.321		0.282		0.307		0.326
Percentage Inhibition (%I)	_		24.719		30.409		49.289		55.407		51.506		48.488

Table 3: Depicting pH values at 0 Hours and after 72 Hours of test item exposure to algae

Test vessels and test concentration	0 Hours	72 Hours
CONTROL
Replicate 1	7.05	7.52
Replicate 2	7.08	7.59
Replicate 3	7.05	7.9
Average	7.06	7.67
CAS No. 29556-33-0
6.25mg/l
Replicate 1	9.53	8.07
Replicate 2	9.43	7.96
12.5mg/l
Replicate 1	9.40	7.61
Replicate 2	9.40	7.74
25mg/l
Replicate 1	9.19	7.83
Replicate 2	9.05	7.85
50mg/l
Replicate 1	8.75	7.60
Replicate 2	8.76	7.62
100mg/l
Replicate 1	7.95	7.48
Replicate 2	7.95	7.47
200mg/l
Replicate 1	7.90	7.12
Replicate 2	7.90	7.30

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

Based on the growth inhibition of green alga Chlorella vulgaris by the test chemical 2-[7-(diethylamino)-2-oxo-2H-1-benzopyran-3-yl]-1,3-dimethyl-1H-benzimidazolium chloride , the EC50 was determine to be 85.831 mg/l .

Executive summary:

The study was designed to assess the toxic effects of the test compound 2-[7-(diethylamino)-2-oxo-2H-1-benzopyran-3-yl]- 1,3-dimethyl-1H-benzimidazolium chloride on the green alga Chlorella vulgaris. Test was conducted in compliance with the OECD guideline 201 (Alga, Growth Inhibition Test).

All the tests were carried out in 100mL conical flasks which were carefully autoclaved and sterilized. The test solution in each of these test vessels was kept constant which is 60 ml so that a sufficient amount of head space was left. The test item ( ) was prepared by adding 50 mg of test item in 250 ml of BBM to get the final concentration of 200mg/L. This stock solution was kept for stirring/ sonication for 0 minutes to obtain a homogenous solution for the experiment. The test concentrations 6.25mg/l, 12.5mg/l, 25mg/l, 50mg/l, 100mg/l and 200mg/l were chosen according to the available data of the test item. The concentrations chosen were set up to the water solubility limit. The remaining test solutions were prepared by dilution from the above stock solution.

For the assessment of algal growth, the test was conducted in replicates. The control flask was maintained in triplicates as recommended in the OECD guideline and the test concentration were selected in geometric series which were maintained in duplicates. To obtain a quantitative concentration-response relationship by regression analysis, a linearizing transformation of the response data into probit was performed. Using the same, effective concentration (EC) were determined.

Algal growth was calculated daily by counting the cells microscopically with the help of haemocytometer. For microscopic observations the cultures were observed daily with the help of a microscope to verify a normal and healthy appearance of the algal culture and also to observe any abnormal appearance of the algae (as may be caused by the exposure of the test item). Apart from this, the cell count of each test vessel was also noted with the help of a microscope and haemocytometer. By spectrophotometer the absorbance values of each test vessel and control vessel was noted at 680nm.The BBM was taken as blank for both control and test vessels. The absorbance value of each vessel was in line with the average specific growth rate.

As per OECD 201, the biomass in the control cultures should have increased exponentially by a factor of at least 16 within the 72 hr test period. This corresponds to a specific growth rate of 0.92 per day. Thus, the observed specific growth rate in the control cultures during the experiment was 0.358 per day. Secondalyt The mean coefficient of variation for section by section specific growth rates (days 0-1, 1-2 & 2-3, for 72 hr tests) in the control cultures must not exceed 35%. Thus, the observed mean coefficient of variation in the control cultures during the experiment was 33.42%. Thirdly the coefficient of variation of average specific growth rates during the whole test period in replicate control cultures must not exceed 10%. Thus, the observed coefficient of variation of average specific growth rates during the experiment in control cultures was 8.26%. Hence, the test is considered valid as per OECD guideline, 201

After 72 hours of exposure to test item 2-[7-(diethylamino)-2-oxo-2H-1-benzopyran-3-yl]-1,3-dimethyl-1H-benzimidazolium chloride to various nominal test concentrations, EC50 was determine to be 85.831 mg/l graphically and through probit analysis. Based on the EC50, it can be consider that the chemical was toxic to aquatic algae and cyanobacteria and can be consider to be classified aq aquatic chronic 3 as per the CLP classification criteria.