Effect of repeated harvesting on the content of caffeic acid and seven species of caffeoylquinic acids in sweet potato leaves

Figures & data

Fig. 1. Chemical structures of CA and CQAs in sweet potato leaves.

Note: All data for CQAs presented in this manuscript use the recommended IUPAC numbering system.²³⁾

Table 1. Average content of CA and CQA in the leaves of six cultivars (“Elegant Summer,” “Kogane Sengan,” “Kokei-14,” “Kyuikukan-1,” “Kyuikuyou-2,” and “Suioh”) and two breeding lines (06382-1 and 06385-2) of sweet potato, harvested once a month from 1st (May) to 4th (August) in 2011 and 2012.

Cultivar/line	Leaves color	Harvest times	CA and CQAs contents (μg g^−1)
			CA	3-CQA	4-CQA	5-CQA	3,4-diCQA	3,5-diCQA	4,5-diCQA	3,4,5-triCQA	Total
Elegant summer	Green	1st	133	1293	1411	6090	4968	8668	827	25	23,415
			(0.57%)	(5.52%)	(6.03%)	(26.0%)	(21.2%)	(37.0%)	(3.53%)	(0.11%)	(100%)
		2nd	46	1051	937	4753	5522	11,783	1476	50	25,618
			(0.18%)	(4.10%)	(3.66%)	(18.6%)	(21.6%)	(46.0%)	(5.76%)	(0.19%)	(100%)
		3rd	200	975	939	4572	4559	20,742	2786	53	34,826
			(0.57%)	(2.80%)	(2.70%)	(13.1%)	(13.1%)	(59.6%)	(8.00%)	(0.15%)	(100%)
		4th	33	891	1052	4955	5551	9754	1654	72	23,962
			(0.14%)	(3.72%)	(4.39%)	(20.7%)	(23.2%)	(40.7%)	(6.90%)	(0.30%)	(100%)
Kogane sengan	Green	1st	121	1359	1408	7191	9902	10,437	1162	17	31,597
			(0.38%)	(4.30%)	(4.46%)	(22.8%)	(31.3%)	(33.0%)	(3.68%)	(0.05%)	(100%)
		2nd	55	1068	522	3548	11,297	15,246	2103	21	33,860
			(0.16%)	(3.15%)	(1.54%)	(10.5%)	(33.4%)	(45.0%)	(6.21%)	(0.06%)	(100%)
		3rd	127	1250	574	3426	8583	16,380	2135	16	32,491
			(0.39%)	(3.85%)	(1.77%)	(10.5%)	(26.4%)	(50.4%)	(6.57%)	(0.05%)	(100%)
		4th	82	1123	623	4260	11,384	18,463	2889	37	38,861
			(0.21%)	(2.89%)	(1.60%)	(11.0%)	(29.3%)	(47.5%)	(7.43%)	(0.10%)	(100%)
Kokei-14	Green	1st	40	1684	2096	6051	5516	10,383	402	68	26,240
			(0.15%)	(6.41%)	(7.99%)	(23.1%)	(21.0%)	(39.6%)	(1.53%)	(0.26%)	(100%)
		2nd	45	1123	993	3987	4920	14,296	798	42	26,204
			(0.17%)	(4.29%)	(3.79%)	(15.2%)	(18.8%)	(54.6%)	(3.04%)	(0.16%)	(100%)
		3rd	20	968	913	3783	4920	11,232	639	34	22,509
			(0.08%)	(4.30%)	(4.05%)	(16.8%)	(21.9%)	(49.9%)	(2.84%)	(0.15%)	(100%)
		4th	37	871	1017	3729	5532	11,439	830	36	23,491
			(0.16%)	(3.71%)	(4.33%)	(15.9%)	(23.6%)	(48.7%)	(3.53%)	(0.15%)	(100%)
Kyuikukan-1	Purple	1st	73	743	920	3202	8446	6907	1283	N.D.	21,574
			(0.34%)	(3.45%)	(4.27%)	(14.8%)	(39.1%)	(32.0%)	(5.94%)	N/A	(100%)
		2nd	31	618	191	1257	6830	7449	741	N.D.	17,117
			(0.18%)	(3.61%)	(1.12%)	(7.34%)	(39.9%)	(43.5%)	(4.33%)	N/A	(100%)
		3rd	24	444	182	968	4794	6364	1322	N.D.	14,098
			(0.17%)	(3.15%)	(1.29%)	(6.87%)	(34.0%)	(45.1%)	(9.38%)	N/A	(100%)
		4th	33	575	230	1170	5748	5252	852	N.D.	13,860
			(0.23%)	(4.15%)	(1.66%)	(8.44%)	(41.5%)	(37.9%)	(6.14%)	N/A	(100%)
Kyuikuyou-2	Green	1st	55	1352	555	4217	4180	17,871	833	34	29,097
			(0.19%)	(4.65%)	(1.91%)	(14.5%)	(14.4%)	(61.4%)	(2.86%)	(0.12%)	(100%)
		2nd	231	674	360	2793	3701	23,095	1520	64	32,438
			(0.71%)	(2.08%)	(1.11%)	(8.61%)	(11.4%)	(71.2%)	(4.69%)	(0.20%)	(100%)
		3rd	156	936	317	2551	3137	15,413	832	61	23,403
			(0.66%)	(4.00%)	(1.36%)	(10.9%)	(13.4%)	(65.9%)	(3.56%)	(0.26%)	(100%)
		4th	88	1597	570	4909	6081	18,629	1173	55	33,102
			(0.26%)	(4.83%)	(1.72%)	(14.8%)	(18.4%)	(56.3%)	(3.54%)	(0.17%)	(100%)
Suioh	Green	1st	183	1232	915	6495	3838	24,131	1407	27	38,228
			(0.48%)	(3.22%)	(2.39%)	(17.0%)	(10.0%)	(63.1%)	(3.68%)	(0.07%)	(100%)
		2nd	31	457	247	2084	2322	21,975	1471	25	28,612
			(0.11%)	(1.60%)	(0.86%)	(7.28%)	(8.12%)	(76.8%)	(5.14%)	(0.09%)	(100%)
		3rd	43	759	309	2331	3457	16,388	881	26	24,194
			(0.18%)	(3.14%)	(1.28%)	(9.63%)	(14.3%)	(67.7%)	(3.64%)	(0.11%)	(100%)
		4th	44	1160	725	5096	5976	21,149	1356	25	35,531
			(0.13%)	(3.26%)	(2.04%)	(14.3%)	(16.8%)	(59.5%)	(3.82%)	(0.07%)	(100%)
06382-1	Purple	1st	128	555	812	5797	9686	13,465	558	N.D.	31,001
			(0.41%)	(1.79%)	(2.61%)	(18.7%)	(31.2%)	(43.4%)	(1.80%)	N/A	(100%)
		2nd	33	264	155	2066	3648	7609	320	N.D.	14,095
			(0.23%)	(1.87%)	(1.10%)	(14.7%)	(25.9%)	(54.0%)	(2.27%)	N/A	(100%)
		3rd	112	454	285	2875	3262	9532	1065	N.D.	17,585
			(0.64%)	(2.58%)	(1.62%)	(16.3%)	(18.6%)	(54.2%)	(6.06%)	N/A	(100%)
		4th	107	390	302	3076	5156	9014	1361	N.D.	19,406
			(0.55%)	(2.01%)	(1.56%)	(15.9%)	(26.6%)	(46.4%)	(7.01%)	N/A	(100%)
06385-21	Purple	1st	39	1127	637	3145	4930	8955	604	N.D.	19,437
			(0.20%)	(5.80%)	(3.28%)	(16.2%)	(25.4%)	(46.1%)	(3.11%)	N/A	(100%)
		2nd	18	717	173	1358	3189	7691	558	N.D.	13,704
			(0.13%)	(5.24%)	(1.26%)	(9.91%)	(23.3%)	(56.1%)	(4.07%)	N/A	(100%)
		3rd	22	947	224	1612	3994	8559	807	N.D.	16,165
			(0.14%)	(5.86%)	(1.39%)	(9.97%)	(24.7%)	(52.9%)	(4.99%)	N/A	(100%)
		4th	25	1054	310	1749	3954	6208	518	N.D.	13,818
			(0.18%)	(7.63%)	(2.24%)	(12.7%)	(28.6%)	(44.9%)	(3.75%)	N/A	(100%)

Notes: N.D: Not detected. N/A: Not available. CA: Caffeic acid, 3-CQA: 3-caffeoylquinic acid, 4-CQA: 4-caffeoylquinic acid, 5-CQA: 5-caffeoylquinic acid, 3,4-diCQA: 3,4-dicaffeoylquinic acid, 3,5-diCQA: 3,5-dicaffeoylquinic acid, 4,5-diCQA: 4,5-dicaffeoylquinic acid, 3,4,5-triCQA: 3,4,5-tricaffeoylquinic acid.

Table 2. Effect of cultivar/breeding line, harvest time, harvest year, and their interactions on CA and CQA in sweet potato leaves.

Compounds	Cultivar/breeding line		Harvest time		Harvest year		Cultivar/breeding line × Harvest time		Cultivar/breeding line × Harvest year		Harvest time × Harvest year
	F value	Pr > F	F value	Pr > F	F value	Pr > F	F value	Pr > F	F value	Pr > F	F value	Pr > F
CA	1.429	0.246	0.768	0.525	1.362	0.256	0.634	0.848	0.302	0.945	0.747	0.536
3-CQA	3.665	0.009^b	3.003	0.053	2.109	0.161	0.453	0.962	0.460	0.852	7.584	0.001^b
4-CQA	9.799	0.000^b	14.53	0.000^b	0.126	0.726	0.545	0.914	0.400	0.891	2.182	0.120
5-CQA	4.700	0.003^b	8.870	0.001^b	0.000	0.985	0.418	0.974	0.321	0.936	4.755	0.011^a
3,4-diCQA	11.40	0.000^b	2.990	0.054	0.570	0.459	1.127	0.393	0.672	0.694	3.844	0.024^a
3,5-diCQA	5.940	0.001^b	0.128	0.942	0.500	0.487	0.594	0.879	0.016	1.000	2.874	0.061
4,5-diCQA	3.142	0.019^a	1.146	0.354	4.083	0.056	0.616	0.863	0.787	0.606	0.885	0.465
3,4,5-triCQA	3.572	0.038^a	0.447	0.724	0.018	0.896	0.891	0.577	1.864	0.182	1.920	0.180
Total	4.128	0.005^b	0.578	0.636	0.489	0.492	0.451	0.962	0.072	0.999	3.348	0.039^a

CA: Caffeic acid, 3-CQA: 3-caffeoylquinic acid, 4-CQA: 4-caffeoylquinic acid, 5-CQA: 5-caffeoylquinic acid, 3,4-diCQA: 3,4-dicaffeoylquinic acid, 3,5-diCQA: 3,5-dicaffeoylquinic acid, 4,5-diCQA: 4,5-dicaffeoylquinic acid, 3,4,5-triCQA: 3,4,5-tricaffeoylquinic acid.

^a significant at p < 0.05.

^b significant at p < 0.01.

Fig. 2. Variation of the content of 3-caffeoylquinic acid, 4-caffeoylquinic acid, 5-caffeoylquinic acid, and 3,4-dicaffeoylquinic acid harvested at different harvest time.

Notes: *: significant at p < 0.05; **: significant at p < 0.01. CQA: Caffeoylquinic acid. ○: “Elegant Summer”, ●: “Kogane Sengan”, ◇: “Kokei-14”, ◆: “Kyuikukan-1”, △: “Kyuikuyou-2”, ▲: “Suioh”, □: 06382-1, ■: 06385-21. Sweet potato leaves were harvested at May, June, July, and August, corresponding to the harvest time of 1st, 2nd, 3rd, and 4th, respectively.

IUPAC, Nomenclature of cyclitols. Biochem. J. 1976; 153:23–31.

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