Table 1.
Chemical composition of stinging nettle (Urtica dioica L.) leaves (FW).
| April | May | June | July | August | September | |
|---|---|---|---|---|---|---|
| Dry matter, % | 21.24 ± 0.53 bc* | 21.57 ± 0.15 bc | 24.41 ± 0.15 a | 21.13 ± 0.18 bc | 22.61 ± 0.53 ab | 20.48 ± 0.43 c |
| Total soluble solids, % | 11.70 ± 0.49 a | 3.47 ± 0.26 d | 1.47 ± 0.09 f | 4.60 ± 0.15 c | 2.57 ± 0.03 e | 8.07 ± 0.26 b |
| Ascorbic acid. mg 100 g−1 | 8.17 ± 0.59 b | 6.45 ± 0.29 c | 1.31 ± 0.25 d | 9.02 ± 0.29 b | 25.66 ± 1.04 a | 0.58 ± 0.15 d |
| Total carotenoids, mg 100 g−1 | 12.68 ± 0.15 cd | 28.41 ± 0.45 a | 6.46 ± 0.82 e | 15.70 ± 0.79 c | 19.52 ± 0.89 b | 9.68 ± 0.86 d |
| Chlorophyll a, mg 100 g−1 | 40.47 ± 0.59 d | 161.02 ± 1.86 a | 18.05 ± 0.41 e | 64.31 ± 1.01 c | 80.46 ± 2.15 b | 39.43 ± 1.71 d |
| Chlorophyll b, mg 100 g−1 | 16.40 ± 0.95 c | 67.69 ± 1.96 a | 6.48 ± 0.15 d | 32.60 ± 0.74 b | 36.97 ± 1.74 b | 14.67 ± 1.46 cd |
| Titratable acidity, % | 1.27 ± 0.32 ab | 1.91 ± 0.28 a | 1.10 ± 0.01 b | 0.96 ± 0.16 b | 1.60 ± 0.16 ab | 1.43 ± 0.27 ab |
| Total phenolics, mg GAE g−1 | 7.96 ± 0.02 c | 3.28 ± 0.76 e | 3.62 ± 0.01 e | 5.32 ± 0.01 d | 19.07 ± 0.92 a | 13.96 ± 0.02 b |
| Antioxidant activity, % | 63.35 ± 0.06 d | 95.17 ± 0.01 a | 57.32 ± 0.01 e | 52.92 ± 0.30 f | 68.99 ± 0.23 c | 84.44 ± 0.01 b |
* Significant differences (p < 0.05) in lines are marked by different letters; for each measured parameter, the general mean ± SD is presented; FW—fresh weight; mg GAE g−1—results expressed as equivalents of gallic acid.