Antioxidant activity and DNA protection against oxidative damage of bambara groundnut seeds (Vigna subterranea (L.) Verdc.) as affected by processing methods

Figures & data

Table 1. Total phenolic, tannin, and flavonoid content of raw and processed bambara groundnut seeds.

Samples	Total phenolic content (µg GAE/g extract)	Total tannin content (µg GAE/g extract)	Total flavonoid content (µg RE/g extract)
Raw	118^a ± 2	92^a ± 2	841^a ± 18
Dry heating	104^b ± 5	81^b ± 5	785^a ± 17
Boiling	108^b ± 1	83^b ± 1	805^a ± 21
Steaming	104^b ± 3	81^b ± 2	666^b ± 49

Data are expressed as mean ± SD of three independent samples analyzed in triplicate. Values in the same row sharing different letters are significantly different (p < 0.05).

Table 2. FRAP, metal chelating, DPPH, and ABTS activity of raw and processed bambara groundnut seeds.

Samples	FRAP (µmol Fe(II)/ g extract)	Metal chelating (EC50 µg/mL)	DPPH^• (EC50 µg/mL)	ABTS^•+ (EC50 µg/mL)
Positive controls BHA BHT Gallic acid Rutin Trolox EDTA Samples	28 ± 2 43 ± 4 98 ± 4 40 ± 4 ND ND	ND ND ND ND ND 0.06 ± 0.0002	1.4 ± 0.5 ND 0.52 ± 0.02 3.7 ± 0.2 5.3 ± 0.3 ND	1.69 ± 0.01 2.80 ± 0.06 0.51 ± 0.01 7.9 ± 0.5 2.69 ± 0.02 ND
Raw	0.91^a ± 0.02	854^a ± 48	141^a ± 6	61^a ± 2
Dry heating	0.75^b ± 0.01	3543^b ± 665	153^b ± 4	76^c ± 2
Boiling	0.84^ab ± 0.06	898^a ± 5	149^b ± 4	70^b ± 1
Steaming	0.75^b ± 0.05	1689^a ± 276	173^c ± 2	74.6^c ± 0.8

Values are means ± SD (n = 3). Mean values followed by different letters in a column are significantly different (P < 0.05). BHA, Butylated hydroxyanisole; BHT, butylated hydroxytoluene; EDTA, ethylenediamine tetra acetic acid; ND, not detected.

Table 3. The correlation between total phenolic, tannin, and flavonoid content and antioxidant activity (FRAP and 1/EC₅₀ of metal chelating, DPPH, and ABTS) of bambara groundnut seeds.

Parameters	Phenolic	Tannin	Flavonoid
FRAP	0.959^b	0.932	0.754
Metal chelating	0.799	0.744	0.531
DPPH^•	0.791	0.790	0.992^a
ABTS^•+	0.999^a	0.992^a	0.675

^a Correlation is significant at the 0.01 level (2-tailed).

^b Correlation is significant at the 0.05 level (2-tailed).

Figure 1. DNA protection of raw and processed bambara groundnut seeds. Lane 1 is pBR 322 plasmid DNA. Lane 2 is pBR 322 plasmid DNA + AAPH. Lanes 3–16 are pBR 322 plasmid DNA + AAPH + bambara groundnut seed extract. The bambara groundnut seed extract concentrations of lanes 3–16 are 10,000, 5,000, 2,000, 1,000, 500, 300, 100, 50, 10, 5, 1, 0.5, 0.1, and 0.05 µg/mL, respectively. The arrows indicate the minimum concentration of extract that can protect DNA against oxidative damage.