Table 2 Types of lettuce cultivars and contents of individual phenolic acids and flavonoids at mature and bolting stages

3.99 ± 0.05f

2.51 ± 0.04b

0.87 ± 0.04a

9.85 ± 0.06abc

9.85 ± 0.06abc

1.79 ± 0.04cde

4.4 ± 0.7fg

1.72 ± 0.02a

2.6 ± 0.3def

10.6 ± 1.6bcde

10.6 ± 1.6bcde

1.62 ± 0.02bcd

3.22 ± 0.04e

3.9 ± 0.2h

3.17 ± 0.04gh

17.6 ± 0.2ij

17.6 ± 0.2ij

4.4 ± 0.3j

4.8 ± 0.1ghi

4.4 ± 0.1i

1.84 ± 0.06bc

15.9 ± 0.5hi

15.9 ± 0.5hi

4.5 ± 0.3j

5.1 ± 0.2i

5.6 ± 0.4k

0.70 ± 0.03a

9.4 ± 0.3abc

9.4 ± 0.3abc

0.59 ± 0.04a

4.57 ± 0.02gh

3.37 ± 0.06ef

0.84 ± 0.00a

13.61 ± 0.04g

13.61 ± 0.04g

1.03 ± 0.03ab

4.80 ± 0.07ghi

6.2 ± 0.3l

1.60 ± 0.02b

18.9 ± 0.2j

18.9 ± 0.2j

1.2 ± 0.1bc

5.00 ± 0.04hi

5.57 ± 0.03k

2.30 ± 0.02cde

16.6 ± 0.1i

16.6 ± 0.1i

2.87 ± 0.03h

1.90 ± 0.05b

3.6 ± 0.1fg

3.68 ± 0.09ij

10.4 ± 0.3bcd

10.4 ± 0.3bcd

2.8 ± 0.1fgh

2.04 ± 0.02bc

3.05 ± 0.06cd

3.49 ± 0.05hi

12.8 ± 0.2efg

12.8 ± 0.2efg

2.73 ± 0.06fgh

2.55 ± 0.04cd

3.41 ± 0.08ef

2.2 ± 0.2cd

14.4 ± 1.7gh

14.4 ± 1.7gh

2.18 ± 0.06def

1.34 ± 0.07a

2.51 ± 0.06b

5.2 ± 0.6l

8.3 ± 0.8ab

8.3 ± 0.8ab

2.65 ± 0.06fgh

1.88 ± 0.01b

5.03 ± 0.07j

3.11 ± 0.06fgh

11.1 ± 0.2cdef

11.1 ± 0.2cdef

2.32 ± 0.03efgh

2.21 ± 0.03bcd

4.56 ± 0.05i

2.76 ± 0.06efg

13.3 ± 0.2fg

13.3 ± 0.2fg

3.98 ± 0.01ij

3.22 ± 0.02e

5.55 ± 0.09k

1.38 ± 0.01b

14.0 ± 0.1gh

14.0 ± 0.1gh

1.45 ± 0.02bc

2.50 ± 0.05cd

5.04 ± 0.04j

4.04 ± 0.07j

12.6 ± 0.2defg

12.6 ± 0.2defg

2.81 ± 0.02gh

2.30 ± 0.02bcd

2.28 ± 0.00b

2.51 ± 0.01de

9.4 ± 0.3abc

9.4 ± 0.3abc

1.75 ± 0.00cde

1.91 ± 0.02b

2.96 ± 0.04c

2.46 ± 0.06de

9.4 ± 0.3abc

9.4 ± 0.3abc

1.45 ± 0.04bc

2.7 ± 0.2d

3.9 ± 0.2gh

2.7 ± 0.2efg

11.0 ± 0.6cde

11.0 ± 0.6cde

3.8 ± 0.2i

2.5 ± 0.5cd

3.3 ± 0.3de

4.6 ± 0.1k

12.8 ± 0.7efg

12.8 ± 0.7efg

5.2 ± 0.8k

1.3 ± 0.3a

2.4 ± 0.4b

4.0 ± 0.5ij

7.7 ± 0.8a

7.7 ± 0.8a

2.2 ± 0.4efg

2.7 ± 0.4d

4.6 ± 0.6i

1.9 ± 0.2bc

7.8 ± 1.1a

7.8 ± 1.1a

1.4 ± 0.2bc

9.85 ± 0.06abc

5.9 ± 0.2a

5.4 ± 0.8ab

3.0 ± 0.2a

1.6 ± 0.2a

16.1 ± 0.4d

0.56 ± 0.08ab

1.73 ± 0.04f

1.7 ± 0.9a

5.3 ± 0.9ef

10.6 ± 1.6bcde

5.51 ± 0.08a

6.5 ± 1.0bc

3.2 ± 0.1a

3.6 ± 0.6b

20.7 ± 0.3e

0.68 ± 0.08b

1.45 ± 0.01de

2.6 ± 2.08bc

4.0 ± 0.2cdef

17.6 ± 0.2ij

13.5 ± 0.7gh

12.1 ± 0.2f

8.1 ± 0.4gh

ND

28.2 ± 1.8gh

1.30 ± 0.01ef

1.88 ± 0.08f

7.5 ± 0.4m

11.5 ± 3.2i

15.9 ± 0.5hi

10.2 ± 0.3e

11.8 ± 0.4f

5.4 ± 0.1cd

ND

24.5 ± 0.8f

1.16 ± 0.03def

2.4 ± 0.1g

3.7 ± 0.6efg

10.4 ± 1.9hi

9.4 ± 0.3abc

13.9 ± 0.8ghi

4.3 ± 0.2a

8.7 ± 0.5h

6.2 ± 0.3d

3.1 ± 0.2a

1.63 ± 0.06g

0.65 ± 0.03a

1.4 ± 0.4a

2.8 ± 1.0abcd

13.61 ± 0.04g

8.2 ± 0.1c

8.58 ± 0.02de

5.30 ± 0.08cd

4.65 ± 0.02bc

18.4 ± 2.0de

1.15 ± 0.01def

1.31 ± 0.02bcd

2.4 ± 0.07b

2.1 ± 0.2abc

18.9 ± 0.2j

14.4 ± 0.6hij

12.8 ± 0.3f

7.6 ± 0.4fgh

ND

17.5 ± 1.6d

0.94 ± 0.01cd

1.21 ± 0.05b

5.8 ± 0.4l

5.9 ± 1.3f

16.6 ± 0.1i

11.8 ± 0.2f

12.3 ± 0.9f

7.5 ± 0.1fg

ND

18.2 ± 0.2d

1.24 ± 0.02ef

2.35 ± 0.02g

3.00 ± 0.05bcde

8.0 ± 0.5g

10.4 ± 0.3bcd

15.2 ± 0.6jk

6.6 ± 0.2bc

8.7 ± 0.4h

5.6 ± 0.2cd

35.2 ± 1.1i

1.20 ± 0.03ef

1.45 ± 0.05de

4.9 ± 0.7jk

9.2 ± 1.7gh

12.8 ± 0.2efg

11.6 ± 0.2f

8.3 ± 0.1de

5.9 ± 0.1cde

9.8 ± 0.1fgh

42.5 ± 0.7k

1.70 ± 0.02g

1.82 ± 0.02f

5.5 ± 0.4kl

4.1 ± 1.2cdef

14.4 ± 1.7gh

11.3 ± 0.5f

8.9 ± 0.9de

5.8 ± 0.3cd

5.9 ± 0.9cd

46.5 ± 1.4l

1.4 ± 0.1f

1.87 ± 0.02f

4.9 ± 1.2jk

4.8 ± 0.8def

8.3 ± 0.8ab

11.8 ± 0.3f

5.8 ± 0.7bc

6.0 ± 0.2cde

9.6 ± 1.4fg

28.7 ± 0.7h

1.67 ± 0.13g

1.87 ± 0.04f

4.5 ± 2.5hij

3.4 ± 0.4abcde

11.1 ± 0.2cdef

18.6 ± 0.2l

7.4 ± 0.2cde

8.3 ± 0.1gh

10.2 ± 0.3gh

26.0 ± 0.4fg

1.69 ± 0.01g

2.24 ± 0.02g

4.8 ± 0.4ijk

4.4 ± 0.2def

13.3 ± 0.2fg

13.1 ± 0.2g

9.0 ± 0.1e

8.5 ± 0.1gh

7.9 ± 0.1e

40.6 ± 0.4k

1.26 ± 0.01ef

1.38 ± 0.02cde

4.7 ± 0.4ij

10.7 ± 0.3hi

14.0 ± 0.1gh

13.6 ± 0.1gh

8.17 ± 0.09de

6.42 ± 0.07de

8.52 ± 0.08ef

12.4 ± 0.2c

0.91 ± 0.01c

0.65 ± 0.01a

2.90 ± 0.09bcd

1.7 ± 0.1ab

12.6 ± 0.2defg

15.4 ± 0.1k

8.6 ± 0.2de

8.15 ± 0.08gh

5.3 ± 0.1cd

38.1 ± 0.2j

1.14 ± 0.02def

1.28 ± 0.02bc

4.1 ± 0.4ghi

10.1 ± 0.5hi

9.4 ± 0.3abc

7.79 ± 0.02bc

6.5 ± 0.2bc

4.85 ± 0.02bc

2.38 ± 0.03a

29.8 ± 0.2h

0.65 ± 0.01b

0.56 ± 0.00a

3.7 ± 0.2efg

3.6 ± 2.0abcde

9.4 ± 0.3abc

11.5 ± 0.2f

6.5 ± 0.3bc

5.62 ± 0.07cd

4.5 ± 0.2bc

16.3 ± 0.3d

1.07 ± 0.01cde

1.48 ± 0.01e

3.2 ± 0.3cdef

3.7 ± 0.4bcde

11 ± 0.6cde

14.7 ± 0.8ijk

7.3 ± 0.5cd

7.0 ± 1.3ef

5.0 ± 0.3cd

45.0 ± 3.0l

0.89 ± 0.03c

1.37 ± 0.07cde

4.5 ± 1.4hij

13.9 ± 5.7k

12.8 ± 0.7efg

7.0 ± 1.0b

9.0 ± 0.2e

3.00 ± 0.08a

9.7 ± 0.2fgh

28.9 ± 1.6h

1.6 ± 0.2g

2.720.3h

5.5 ± 1.2kl

11.2 ± 6.6hi

7.7 ± 0.8a

10.9 ± 1.5ef

5.9 ± 0.5bc

3.9 ± 0.3ab

11.0 ± 1.2h

67.2 ± 4.1m

1.82 ± 0.04g

2.3 ± 0.1g

3.9 ± 0.7fgh

9.6 ± 1.6ghi

7.8 ± 1.1a

9.2 ± 1.1d

5.3 ± 0.4ab

5.0 ± 0.6c

1.67 ± 0.01a

7.8 ± 1.2b

0.39 ± 0.06a

0.51 ± 0.05a

3.4 ± 0.9def

1.6 ± 1.1a