Genotoxic and Cytotoxic Safety Evaluation of Papain (Carica papaya L.) Using In Vitro Assays

Table 3

Mutoxitest—Number of Trp⁺ revertants/plate (mean ± SD). Aliquots (100 𝜇L) of exponentially growing cultures were mixed with 100 𝜇L of different concentrations of the papain or 0.9% NaCl, as negative control, and mixed with 2.5 mL molten top agar at 45∘C and plated on minimal glucose agar plates supplemented with 0.5 mg tryptophan/litre. The mutagenic responses were expressed as the absolute number of Trp⁺ revertants/plate, after incubation at 37∘C, for 48 hours. Values are the mean of 3 independent experiments with standard deviations not exceeding 15%.

	Number of Trp^+ revertants/plate (mean ± SD)
Agent (𝜇g/plate)	E. coli IC203 uvrA oxyR	E. coli IC204 uvrA umuDC
Papain 5	158 ± 26.0	15 ± 3.0
Papain 25	162 ± 16.0	17 ± 3.0
Papain 50	154 ± 26.0	12 ± 3.0
Papain 100	129 ± 24.0	14 ± 3.0
Papain 125	178 ± 10.0	16 ± 3.0
Papain 250	162 ± 25.0	17 ± 3.0
Papain 500	149 ± 24.0	18 ± 3.0
Positive control H2O2 (300)	853* ± 70.2	15^a ± 1.9
Negative control 0.9% NaCl (50 𝜇L/plate)	141 ± 28.0	16 ± 4.0

aNumber of H₂O₂-induced revertants equivalent to that found with other genotoxic agents used by Blanco et al. in 1998.
^∗𝑝<0.001 when compared to negative control (0.9% NaCl).