Primary DNA damage test in E. coli PQ37 (SOS-chromotest):
The SOS-chromotest in E. coli PQ37 was used to determine the potential for noni seed extract to induce primary DNA damage.
This test was carried out according to a previously developed method .
E. coli PQ37 was incubated at 37ºC in the presence of the extract at a concentration of 1000 ug/mL in a 96-well plate.
Samples, both with and without S9 mix, were evaluated in triplicate. Following incubation, 5-bromo-4-chloro-3-indolyl-$-D-galactopyranoside was added to the wells to detect $-galactosidase enzyme activity, which is induced during SOS repair of damaged DNA.
Nitrophenyl phosphate is also added to the wells to measure alkaline phosphatase activity, an indicator of cell viability.
The samples were again incubated and the absorbances of the samples, blanks and controls were measured at 410 and 620 nm with a microplate reader.
Vehicle blanks and positive controls, 5 :g/mL 4- nitroquinoline 1-oxide (4NQO) and 100 :g/mL 2- aminoanthracene (2AA), were included in this test.
The induction factor of each material was calculated by dividing the absorbance of the sample at 620 nm by that of the blank, while also correcting for cell viability.
Induction factors less than two indicate an absence of genotoxic activity.