Effect of pH, heat, and light treatments on the antioxidant activity of sweet potato leaf polyphenols

Figures & data

Table 1. Content of individual phenolic compounds in purified sweet potato leaf polyphenols from Jishu No. 04150 and Shangshu No. 19 (g/100 g DW).

Peak no.	Retention time (min)	Identification	Standard curve	R^2	Jishu No. 04150		Shangshu No. 19
					Peak area	Content	Peak area	Content
1	1.47	5-O-caffeoylquinic acid	y = 11.372x – 0.428	0.9962	43.62 ± 0.76	1.94 ± 0.05	113.52 ± 5.95	5.01 ± 0.33
2	1.91	3-O-caffeoylquinic acid	y = 9.909x + 0.286	1.0000	15.28 ± 0.11	0.76 ± 0.01	30.23 ± 0.43	1.51 ± 0.04
3	2.10	4-O-caffeoylquinic acid	y = 25.894x – 17.128	0.9988	32.43 ± 0.47	0.96 ± 0.02	241.56 ± 0.99	5.00 ± 0.15
4	2.92	Caffeic acid	y = 28.183x – 1.211	1.0000	3.12 ± 0.09	0.08 ± 0.00	351.78 ± 0.82	6.26 ± 0.08
5	4.16	4,5-di-O-caffeoylquinic acid	y = 9.208x – 7.244	0.9987	341.56 ± 11.13	18.94 ± 0.19	619.65 ± 4.22	34.04 ± 0.58
6	4.54	3,5-di-O-caffeoylquinic acid	y = 18.056x – 18.405	0.9981	987.95 ± 10.59	27.87 ± 0.34	115.47 ± 0.58	3.71 ± 0.04
7	4.88	3,4-di-O-caffeoylquinic acid	y = 15.353x – 12.021	0.9987	351.26 ± 5.17	11.83 ± 0.36	27.46 ± 0.36	1.29 ± 0.01
8	6.87	3,4,5-tri-O-caffeoylquinic acid	y = 6.218x – 5.158	0.9949	24.33 ± 0.81	2.37 ± 0.07	1.63 ± 0.05	0.55 ± 0.00

Table 2. DPPH and hydroxyl radical scavenging ratio (%) of sweet potato leaf polyphenols from Jishu No. 04150 and Shangshu No. 19, tea polyphenols, and grape seed polyphenols.

	Samples	Concentration of sample solutions (μg/mL)					IC50 (μg/mL)
		5	7	10	15	20
DPPH radical scavenging ratio	Jishu No. 04150	28.42 ± 2.47a	54.61 ± 1.12a	72.75 ± 3.01a	85.66 ± 2.47a	86.12 ± 2.58a	6.99
	Shangshu No. 19	28.58 ± 2.39a	53.74 ± 3.02a	71.02 ± 2.98a	84.52 ± 2.89a	87.63 ± 2.96a	7.22
	Tea polyphenols	21.69 ± 3.11b	39.59 ± 3.86c	63.86 ± 2.88b	73.76 ± 2.32b	85.22 ± 2.62a	9.69
	Grape seed polyphenols	28.49 ± 2.41a	48.17 ± 1.23b	63.73 ± 3.21b	85.63 ± 2.54a	87.95 ± 1.74a	8.12
	Samples	Concentration of sample solutions (mg/mL)				IC50 (mg/mL)
		0.05	0.10	0.20	0.50
Hydroxyl radical scavenging ratio	Jishu No. 04150	36.72 ± 2.86a	43.96 ± 2.91a	65.99 ± 2.07a	79.83 ± 2.51a	0.14
	Shangshu No. 19	39.43 ± 4.62a	44.82 ± 2.03a	59.87 ± 1.68b	76.45 ± 1.99a	0.15
	Tea polyphenols	36.02 ± 2.41a	41.08 ± 3.35a	44.67 ± 3.88d	56.74 ± 2.89c	0.34
	Grape seed polyphenols	37.49 ± 3.15a	44.65 ± 3.11a	53.02 ± 2.86c	64.19 ± 2.76b	0.22

Values were means ± SD of three determinations.

DPPH or hydroxyl radical scavenging ratios in the same column that were not significantly different were represented by same letter (p > 0.05).

IC₅₀stand for DPPH or hydroxyl radical half maximal scavenging concentration.

Table 3. Ferric reducing antioxidant power (μg TE/mL), O₂⁻ scavenging activity, and oxygen radical absorbance capacity of sweet potato leaf polyphenols from Jishu No. 04150 and Shangshu No. 19, tea polyphenols, and grape seed polyphenols.

Samples	Concentration of sample solutions (μg/mL)
	10	50	100	5	10	20	5	10	20
	Ferric reducing antioxidant power (μg TE/mL)			O2^−• scavenging activity (μg ACE/mL)			Oxygen radical absorbance capacity (μg TE/mL)
Jishu No. 04150	8.26 ± 1.10a	46.89 ± 1.74a	91.55 ± 1.49a	13.56 ± 0.26a	29.65 ± 3.57a	61.86 ± 3.85a	21.79 ± 4.55a	32.91 ± 3.59a	54.86 ± 0.08a
Shangshu No. 19	8.11 ± 2.06a	40.56 ± 2.42b	82.75 ± 1.86b	9.87 ± 0.78b	21.12 ± 3.45b	46.51 ± 8.22b	10.98 ± 2.01b	26.03 ± 7.99a	43.12 ± 2.13b
Tea polyphenols	6.98 ± 1.83a	36.72 ± 2.13b	64.63 ± 2.12d	3.59 ± 0.02c	7.63 ± 0.46c	10.59 ± 0.78c	15.88 ± 3.12ab	31.87 ± 0.73a	42.89 ± 0.11b
Grape seed polyphenols	7.08 ± 1.66a	37.88 ± 2.01b	72.77 ± 1.85c	2.99 ± 0.03d	3.17 ± 0.53d	9.98 ± 0.11c	13.12 ± 0.58b	28.86 ± 3.68a	43.03 ± 0.25b

Values were means ± SD of three determinations.

Data in the same column that were not significantly different were represented by same letter (p > 0.05).

Figure 1. Effect of different pH value on A: the total polyphenol content and B: antioxidant activity of sweet potato leaf polyphenols from Jishu No.04150 and Shangshu No. 19. Values were means ± SD of three determinations. Data on the same broken line that were not significantly different were represented by same letter (p > 0.05).

Figure 2. Effect of different heat treatment on the retention rates (%) of total polyphenol content and antioxidant activity of sweet potato leaf polyphenols from Jishu No.04150 at A: 50°C, B: 65°C, C: 80°C, and D: 100°C, and that of Shangshu No.19 at E: 50°C, F: 65°C, G: 80°C, and H: 100°C. Values were means ± SD of three determinations. Data on the same broken line that were not significantly different were represented by same letter (p > 0.05).

Figure 3. Effect of different light treatment on the retention rates (%) of total polyphenol content of sweet potato leaf polyphenols from A: Jishu No. 04150 and B: Shangshu No. 19, and effect of different light treatment on the retention rates (%) of antioxidant activity of sweet potato leaf polyphenols from C: Jishu No. 04150 and D: Shangshu No. 19. Values were means ± SD of three determinations. Data on the same broken line that were not significantly different were represented by same letter (p > 0.05).

Islam, S. Sweet Potato (Ipomoea Batatas L.) Leaf: Its Potential Effect on Human Health and Nutrition. Journal of Food Science 2006, 71(2), R13–R121.

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