Free radical scavenging activity of conjugated linoleic acid as single or mixed isomers

Figures & data

Figure 1.  Kinetic curve of single CLA isomers against DPPH free radical (a) cis-9, trans-11 CLA (b) trans-10, cis-12 CLA. The final concentrations of CLA were 2.5, 5, 10, 20, 40 and 80 (mg/mL) in the reaction mixtures. DPPH^• concentration was 500 µM in all reaction mixtures. Values are mean ± SE (n = 3).

Figure 2.  Kinetic curve of mixed CLA isomers against DPPH free radical (a) at ratio 1:6 of trans-10, cis-12/cis-9, trans-11. (b) at ratio 1:13 of trans-10, cis-12/cis-9, trans-11. The final concentrations of CLA were 2.5, 5, 10, 20, 40 and 80 (mg/mL) in the reaction mixtures. DPPH^• concentration was 500 µM in all reaction mixtures. Values are mean ± SE (n = 3).

Table 1.  Inhibition % of DPPH^• radical at steady state among different concentrations of selected CLAs, and median inhibitory concentration (IC₅₀) value for each selected CLA.

Selected CLA	Concentration (mg/mL)
	2.5	5	10	20	40	80	IC50
cis-9, trans-11	13 ± 6^a	35 ± 4^a	51 ± 4^a	57 ± 2.5^a	64 ± 5^a	72 ± 4^a	11.1 ± 3.8^a
trans-10, cis-12	6 ± 4^a	8 ± 3^b	40 ± 3^b	64 ± 3^a	72 ± 3^b	86 ± 4^b	12.6 ± 3.4^a
1:6	7 ± 5^a	13 ± 4^b	40 ± 2^b	56 ± 1.5^a	63 ± 3.5^a	73 ± 3^a	16.3 ± 1.1^a
1:13	5 ± 2^a	9 ± 7^b	23 ± 3^c	44 ± 4^b	56 ± 1^c	72 ± 4^a	27.9 ± 8^b

Values were expressed as mean ± standard error (n = 3).

IC₅₀ value was defined as the CLA concentration that caused 50% inhibition of DPPH• radical formation at steady state of reaction.

Means in a column with different letters were significantly different at the level p < 0.05.

1:6 and 1:13 ratios represent the mixtures of trans-10, cis-12 and cis-9, trans-11CLA isomers.

Figure 3.  Disappearance of DPPH as a function of trans-10, cis-12 and cis-9, trans-11CLA isomers as single or mixed at two ratios, 1:6 and 1:13 (trans-10, cis-12/cis-9, trans-11) Concentration at steady state of reaction. Vertical bars represent the standard error of each data points (n = 3).

Figure 4.  Comparison of TAC of trans-10, cis-12 and cis-9, trans-11 CLA isomers as single or mixed at two ratios, 1:6 and 1:13 (trans-10, cis-12/cis-9, trans-11) with Selected antioxidants vitamin E (Vit E) and butylated hydroxytoluene (BHT). All antioxidants were compared at 50 mM final concentration against 500 µM DPPH radical. Vertical bars represent the standard error of experimental data (n =  3). Columns marked with the same letter are not significantly different (P < 0.05).