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Article

Impact of Picking Time on Leaf Quality Parameters of Three Varieties of Honeysuckle (Lonicera caerulea L.)

by
Erika Jakienė
*,
Edita Kaušė
and
Nijolė Vaitkevičienė
Department of Plant Biology and Food Sciences, Agriculture Academy, Vytautas Magnus University, Donelaicio Str. 58, 44248 Kaunas, Lithuania
*
Author to whom correspondence should be addressed.
Agriculture 2025, 15(3), 257; https://doi.org/10.3390/agriculture15030257
Submission received: 19 December 2024 / Revised: 21 January 2025 / Accepted: 23 January 2025 / Published: 24 January 2025
(This article belongs to the Section Agricultural Product Quality and Safety)
Browse Figure
Versions Notes

Abstract

:
Lonicera caerulea is a nutrient-rich plant of significant importance. Its chemical composition is influenced by various intrinsic properties and external factors, which change with the seasons. This study aimed to evaluate the effects of different picking times on the proximate composition and the contents of pigments, macroelements, bioactive compounds and antioxidant activity in honeysuckle leaves. Seasonal changes in the contents of fiber, ash, proteins, nitrogen (N), potassium (K), magnesium (Mg), phosphorus (P), calcium (Ca), chlorophylls, total carotenoids, total flavonoids and total phenolics were analyzed. The results revealed that picking time and plant variety significantly affected the chemical composition of honeysuckle leaves. The first picking yielded the highest levels of protein, N, P, K, chlorophyll a and b, total chlorophyll and total carotenoids. Conversely, the third picking showed the highest levels of Ca and Mg. Specifically, the third picking of ‘Indigo Yum’ leaves had the highest Ca and Mg contents, while the second picking of ‘Zojka’ leaves (116.67 mg 100 g−1 DM) and the third picking of ‘Wojtek’ leaves (115 mg 100 g−1 DM) contained the most total flavonoids. The first picking of ‘Wojtek’ leaves recorded the highest levels of protein, N, P and total carotenoids, whereas the third picking showed the highest fiber and ash contents. These findings provide valuable insights for farmers, enabling them to select appropriate cultivars and optimal picking times to produce high-quality honeysuckle leaves for use as food or medicinal supplements.

1. Introduction

Honeysuckle (Lonicera caerulea L.), a woody perennial plant belonging to the Caprifoliaceae family, produces berries rich in biologically active compounds. These include anthocyanins, polyphenols and various essential vitamins that play a critical role in human nutrition and must be sourced from different foods [1]. In addition, these berries are rich in ascorbic acid. Their antioxidant content makes honeysuckle berries beneficial as a potential treatment for oncological and cardiovascular diseases, while also supporting liver function, stabilizing blood pressure and offering value for individuals with diabetes due to their low sugar content [2]. In some countries, such as Japan, honeysuckle has long been cultivated and used in traditional folk medicine as an anti-aging, heart-healthy and digestive-stimulating berry [3]. Honeysuckle, called a nutritionally and biologically superior superfood, has been shown to have three to five times the antioxidant activity of strawberries or currants [4].
In recent years, interest in edible honeysuckle has increased and studies have been conducted to assess the nutritional value of the berries, but information about other parts of the edible honeysuckle, in this case, the leaves, is still scarce [5]. After the berries are picked, the honeysuckle leaves are usually left under the bushes and are considered agricultural waste [6]. However, studies have shown that honeysuckle leaves are a rich source of many biologically active compounds, such as flavonoids, chlorogenic acid, phenolic compounds, carotenoids and other compounds [7]. The polyphenols in honeysuckle leaves have contributed to their antioxidant and anti-inflammatory properties, which are beneficial for overall health and are associated with health-promoting properties [8]. Researchers suggest that extracts of these leaves can inhibit the growth of various pathogens, such as Streptococcus pyogenes. They are also used in traditional medicine for treating respiratory infections and reducing pro-inflammatory mediators [9,10]. Studies suggest that Lonicera caerulea leaves can be used as infusions for treating type 2 diabetes due to their pleiotropic effects, which include inhibiting sugar absorption enzymes, lowering cholesterol levels, reducing diabetes-related complications, and suppressing pro-inflammatory processes [11]. White mulberry leaves are currently the most widely used raw material for infusions; however, honeysuckle leaves have emerged as a promising alternative, offering unique therapeutic potential. Comprehensive research is still required to elucidate the mechanisms of action and explore the clinical applications of the bioactive compounds present in these leaves. Although leaves are often regarded as by-products, they contain valuable bioactive compounds. Utilizing these leaves as raw materials for their beneficial properties could contribute to environmental sustainability growth [10,12].
Despite the growing interest in the nutritional and functional properties of honeysuckle leaves, research in this area is still in its infancy and data are currently scarce. Honeysuckle leaves are used only as a waste product in agriculture. In particular, there is a lack of comprehensive studies examining the distribution of key biochemical constituents, such as proximate composition, pigments, macroelements and phenolic compounds in leaves at different picking times [13]. The effects of different picking times on these components are particularly understudied, leaving a significant knowledge gap on how temporal variations affect the nutritional profile and bioactive potential of honeysuckle leaves. Recommendations for the use of honeysuckle leaves are also lacking [14].
This study aims to systematically investigate the effects of picking time on honeysuckle leaves and explore their potential as a sustainable resource. The analysis encompasses proximate composition, pigment concentration, macroelements and selected bioactive compounds known for their health-promoting properties. Additionally, this study evaluates the antioxidant activity of the leaves, providing insights into how picking time can optimize their functional and nutritional qualities. By analyzing honeysuckle leaves as a novel raw material for nutrients, this research seeks to highlight their potential applications in nutrition and medicine. It is hoped that the findings will provide valuable knowledge to growers and processors and open up new opportunities in food science and the development of plant-based health products.

2. Materials and Methods

2.1. Field Experiment

A two-factor field experiment was conducted with three varieties of edible honeysuckle—‘Indigo Yum’, ‘Wojtek’ and ‘Zojka’ (A factor)—and three different picking times of leaves (B factor)—1st picking (27 April), 2nd picking (40 days after 1st picking), 3rd picking (80 days after 1st picking) (Table 1). The field experiment plots were arranged randomly with four replicates, and each experimental plot contained five bushes. The planting distances for edible honeysuckle were 4.0 m between the rows and 0.7 m between the bushes. The field experiment was carried out in 2024 on the edible honeysuckle farm in Alytus district, Lithuania (54°29′44.7″ N 24°00′14.5″ E).

2.2. Honeysuckle Leaf Sample Preparation

The leaves from each honeysuckle variety were manually collected from all four sides of the bush under uniform conditions to represent the entire bush. For the analyses, approximately 200 g of leaves was gathered for each variety and growth stage. The leaf samples were frozen at −35 °C and freeze-dried (ZIRBUS Technology GmbH, Bad Grund, Germany). Following lyophilization, the leaves were pulverized for 1 min at 8000 rpm using a laboratory mill (Grindomix GM 200, Retsch GmbH, Haan, Germany) and subsequently stored at −34 °C in a freezer until analysis.

2.3. Chemicals and Reagents

Analytical-grade ethanol from MV Group (MV Group, Kaunas, Lithuania) was used for extractions and derived from agricultural origin. Demineralized water was sourced from a Milli-Q system (Millipore, Burlington, MA, USA). Gallic acid (97%), Folin–Ciocalteu reagent, 2,2-diphenyl-1-picrylhydrazyl hydrate free radical (DPPH, 95%), aluminum chloride solution (2%) and sodium acetate (≥99.5% pure) were obtained from Enola (Enola, Riga, Latvia). Sulfuric acid (98%) was procured from Merck Company (Merck, Poznan, Poland). Acetone, nitric acid, hydrogen peroxide and sea sand were supplied by Sigma-Aldrich (Steinheim, Germany).

2.4. Fiber, Ash and Protein Analysis

The fiber content was determined following the official methods of the Association of Official Agricultural Chemists (AOAC) [15]. Ash content was quantified through combustion at 550 °C [16]. Protein content was analyzed using the Kjeldahl method, employing a KJELDATHERM apparatus (Gerhardt, Königswinter, Germany) [17].

2.5. Macroelements Analysis

Powdered samples of honeysuckle leaves were prepared and analyzed using standardized methodologies. Nitrogen (N) content was quantified through the Kjeldahl method using a KJELDATHERM apparatus (Gerhardt, Königswinter, Germany). Potassium (K), magnesium (Mg), phosphorus (P) and calcium (Ca) were measured photometrically following wet digestion in sulfuric acid. Additionally, the elements were analyzed using inductively coupled plasma atomic emission spectrometry (ICP-AES) after acid digestion with a nitric acid and hydrogen peroxide mixture (HNO3:H2O2, 5:3, v/v) in a microwave system. The digestion process was carried out by gradually increasing the temperature to 200 °C over 20 min and maintaining it at this level for 2 h. All procedures were carried out according to the standard method (LST EN 15510:2017) [18].

2.6. Pigments Analysis

The concentrations of chlorophyll a and b, total chlorophyll, and total carotenoids were quantified using UV-VIS spectroscopy [19]. Pigments concentrations were determined by calibration curves derived from known standard concentrations. For each analysis, 0.1 g of leaf tissue was homogenized with a small amount of sea sand and 50 mL of acetone. The resulting mixture was then filtered to obtain a clear solution. Absorbance measurements were recorded at wavelengths of 644.00 nm, 662.00 nm and 440.50 nm to evaluate the pigment levels.

2.7. Total Phenolics Analysis (TPC)

The total phenolic content of the leaves was determined by the Folin–Ciocalteu method and using gallic acid as a standard [20]. The sample was prepared using 0.5 g of freeze-dried honeysuckle leaf powder and 10 mL of 75% aqueous ethanol. The sample was homogenized for 60 s using a homogenizer (model VDI 25 s40, Retsch GmbH, Haan, Germany), left in the dark for 30 min and then filtered using Whatman paper (retention 8–12 µm). The reagent was prepared by diluting a stock solution with pure distilled water (1/10, v/v). To the test cuvette, 100 µL of the sample was added, followed by 300 µL of 0.2 M Folin–Ciocalteu’s reagent and 1.0 mL of Na2CO3. The mixture was subsequently incubated at room temperature for 60 min. After that, the absorbance of all samples was measured at a wavelength of 765 nm using a Spectro UVD-3200 (Spectro UV-VIS Double Beam PC, Labomed, Los Angeles, CA, USA) spectrophotometer. The total concentration of phenolic compounds was determined from the gallic acid calibration curve and expressed in mg 100 g−1 of dry sample [21].

2.8. Total Flavonoid Analysis (TFC)

The total flavonoid content was determined by the aluminum chloride colorimetric method [22]. The sample was prepared by incubating 0.5 g of lyophilized leaf powder with 10 mL of 75% EtOH for 60 min in an automatic shaker (Heidolph Vibramax 100, 31 W, Retsch GmbH, Haan, Germany) at 1200 rpm. Then, the sample was filtered through Whatman paper (retention 8–12 µm). To prepare the sample mixtures, 10 mL of 2% aluminum chloride solution, 2 mL of 96% ethanol, and 1.0 mL of 1M sodium acetate were added to 1.0 mL of the honeysuckle leaf extract. The mixture was then incubated for 30 min in the dark. After that, the absorbance was measured at a wavelength of 415 nm using the Varian Cary 50 UV spectrophotometer (Labomed Inc., Los Angeles, CA, USA)and a Spectro UV-VIS Dual beam (Labomed Inc., Los Angeles, CA, USA).

2.9. Antioxidant Activity

The antioxidant activity of the leaves was evaluated using the DPPH assay [23]. To the test tube, 0.5 g of lyophilized honeysuckle leaf powder was combined with 10 mL of 50% ethanol and 5 mL of a diluted DPPH solution. The mixture was thoroughly shaken and incubated in the dark for 30 min to prevent light-induced degradation. After incubation, the absorbance was measured at 517 nm using a Spectro UV-VIS Dual Beam Spectrophotometer (Varian Co., Palo Alto, Santa Clara, CA, USA).

2.10. Statistical Analysis

The data were statistically analyzed using analysis of variance (ANOVA) with STATISTICA 10 software. Arithmetic means of the experimental data were calculated, and the statistical significance of differences between group means was assessed using the Tukey test (p < 0.05). Samples of honeysuckle leaves from the three varieties, picked at different times, were classified using principal component analysis (PCA) with XLSTAT 2018 software (New York, NY, USA), based on their proximate compositions, pigments, macroelements, total flavonoids and total phenolics.

3. Results

3.1. Proximate Composition

This study revealed that the timing of leafs picking and the specific properties of honeysuckle varieties significantly influenced the proximate composition of honeysuckle leaves (Table 2). Among the findings, the highest protein content (15.99% DM) was observed in the leaves of the ‘Wojtek’ variety during the first picking, while the highest ash content (15.84% DM) was noted in the same variety’s leaves during the third picking. The highest fiber content was detected in ‘Wojtek’ leaves at the third picking (20.93% DM) and ‘Zojka’ leaves at the second picking (20.02% DM). Conversely, the lowest protein content (7.36% DM) was found in ‘Wojtek’ leaves during the second picking. During the first picking, all analyzed honeysuckle varieties exhibited the lowest fiber content (‘Zojka’: 9.51% DM, ‘Wojtek’: 10.08% DM and ‘Indigo Yum’: 9.04% DM) compared to subsequent pickings. Additionally, the lowest ash content (4.49% DM) was recorded in ‘Indigo Yum’ leaves during the third picking. Recent investigations by Rupasinghe et al. [1] indicate that honeysuckle leaves contain proteins at approximately 1.84 mg 100 g−1 (FM), suggesting their potential as a source of protein for human consumption. Although no data are available in the literature regarding the protein, fiber and ash content in honeysuckle leaves at different picking times, studies on other plants have confirmed our findings. The decrease in leaf protein content with plant age was also reported for white currant leaves [24]. According to the literature, as leaves age, proteins degrade and the resulting peptides and amino acids are transferred to other organs for storage and later reutilized for roots or flower growth during the next growing season [25,26]. A reduction in protein content as leaves age normally leads to an increase in the plant’s structural components, such as lignin, hemicellulose and cellulose [27]. Ortíz-Ocampo et al. [28] also found that fiber was significantly higher in the Gymnopodium floribundum Rolfe leaves in September as opposed to samples picked in March and June. An earlier study conducted by Ziobroń et al. [24] also demonstrated that the ash content in all studied currant leaves increased with maturity.

3.2. The Content of Pigments

The pigments content of honeysuckle leaf samples is summarized in Table 3. The highest chlorophyll a levels were observed during the first picking for the cultivars ‘Zojka’ (215.02 mg 100 g−1 DM), ‘Wojtek’ (230.77 mg 100 g−1 DM) and ‘Indigo Yum’ (217.57 mg 100 g−1 DM). In contrast, the lowest chlorophyll a levels were recorded during the third picking, ranging from 77.43 mg to 106.18 mg 100 g−1 DM across all tested varieties. Chlorophyll b levels in the leaves varied from 51.38 to 137.05 mg 100 g−1 DM, with the highest amounts found in the first picking of ‘Zojka’ (137.05 mg 100 g−1 DM) and ‘Indigo Yum’ (126.34 mg 100 g−1 DM). The total chlorophyll content was also highest during the first picking, with values of 352.08 mg 100 g−1 DM in ‘Zojka’, 338.14 mg 100 g−1 DM in ‘Wojtek’ and 343.91 mg 100 g−1 DM in ‘Indigo Yum’. A significant decline in pigment levels was observed as the leaves matured. Similarly, the highest carotenoid content was recorded in ‘Wojtek’ leaves from the first picking (59.93 mg 100 g−1 DM), while the lowest carotenoid levels were found in the third picking: ‘Zojka’ (25.59 mg 100 g−1 DM), ‘Wojtek’ (21.05 mg 100 g−1 DM) and ‘Indigo Yum’ (19.57 mg 100 g−1 DM). These results are consistent with previous studies. Sip et al. [11] reported chlorophyll a levels of 10.29–13.38 mg g−1 DM, chlorophyll b levels of 4.31–5.63 mg g−1 DM and carotenoid levels of 1.81–2.22 mg g−1 DM in honeysuckle leaves, emphasizing the role of light intensity and environmental factors in pigment concentration. Liu et al. [29] highlighted the relationship between chlorophyll, carotenoids and other phytochemicals, noting their importance for bioactive and medicinal properties. Yan et al. [30] also reported pigment concentrations in honeysuckle leaves: chlorophyll a (0.126 mg g−1), chlorophyll b (0.062 mg g−1), total chlorophyll (2.00 mg g−1) and carotenoids (0.23 mg g−1), underlining their critical roles in photosynthesis and overall plant function.

3.3. The Macroelements

The results indicated that picking timing and honeysuckle variety properties had a significant impact on macroelements in honeysuckle leaves (Table 4). All leaf samples examined had higher contents of N, followed by Ca, K, Mg and P. Significantly, the highest contents of N (2990 mg 100 g−1, DM) and P (430 mg 100 g−1, DM) were in ‘Wojtek’ leaves at the first picking. The significantly lowest content of N (1440 mg 100 g−1, DM) was found in ‘Indigo Yum’ leaves, whereas the lowest content of P (120 mg 100 g−1, DM) was in ‘Zojka’ leaves in the third picking. The results showed that in all varieties of honeysuckle leaves, the highest contents of N, P and K were in the first picking and the lowest contents were observed in the third picking.
The content of K in leaves also significantly differed among honeysuckle varieties. The ‘Zojka’ leaves contained the highest K content (930–1630 mg 100 g−1, DM), and the ‘Indigo Yum’ variety leaves had the lowest K content (790–1350 mg 100 g−1, DM). The contents of Ca and Mg in the young honeysuckle leaves were significantly lower, from 1.83 to 2.51 times and from 1.46 to 1.68, respectively, when in third picking leaves. The effect of age was confirmed by observations showing a significant increase in leaf Ca and Mg concentrations as leaves age [31]. This increase is associated with limited Ca mobility in the phloem [32]. Similar poor mobility within plants has been reported for Mg as well [33]. ‘Indigo Yum’ variety leaves showed significantly higher contents of Ca (2840 mg 100 g−1, DM) and Mg (510 mg 100 g−1, DM) in the third picking. As reported by some authors, plant species; variety; growth conditions, such as cultivation methods; biotic or abiotic stress; and nutritional status have a significant impact on the mineral content of plants [34]. The literature, however, lacks information on the mineral content of honeysuckle leaves at different picking times. Levickienė et al. [35] studied the effect of picking time on the accumulation of mineral elements in the leaves of white mulberry (Morus alba L.) and found that these substances vary depending on the cultivar and picking time. They found that the contents of Ca, Mg, P and S in the leaves increased with maturity, while K content decreased. Nour et al. [34] established that the black currant leaves had higher contents of K, Ca, Mg, Fe, Mg, Al, Cr and B in June, compared with those in July. According to Fernandez-Escobar et al. [36], the N, P, K, Zn and B contents were higher in younger olive (Olea europaea L.) leaves, whereas the contents of Ca, Mg, Mn, Cu and Fe were higher in older leaves.

3.4. Total Phenolics, Flavonoids and Antioxidant Activity

The results revealed significant variations in total phenolics content (TPC) among the studied honeysuckle varieties and across different picking times. The TPC ranged from 131.07 mg 100 g−1 DM in ‘Wojtek’ leaves at the first picking to 158.77 mg 100 g−1 DM in ‘Zojka’ leaves at the third picking (Table 5). Young leaves of ‘Zojka’ and ‘Wojtek’ (first picking) exhibited significantly lower TPC compared to leaves from the third picking. Kucharska et al. [37] previously reported that the TPC in honeysuckle leaves can reach levels between 300 and 600 mg of gallic acid equivalents (GAE) per 100 g FW. Similarly, Česonienė et al. [38] observed that TPC varies across honeysuckle varieties, suggesting that cultivar selection can influence potential health benefits. The total flavonoids content (TFC) in honeysuckle leaves was also significantly influenced by variety and picking time, ranging from 28.33 to 116.67 mg 100 g−1 DM. The highest TFC values were recorded in ‘Zojka’ leaves at the second picking (116.67 mg 100 g−1 DM) and ‘Wojtek’ leaves at the third picking (115.00 mg 100 g−1 DM), while the lowest TFC content was observed in ‘Zojka’ leaves from the first picking (28.33 mg 100 g−1 DM). Environmental factors and cultivar differences appear to play a substantial role in influencing TFC levels in honeysuckle leaves. The antioxidant activity of the leaves was highest in the first picking of ‘Indigo Yum’ (81.45% DM) and lowest in the second picking of ‘Wojtek’ (75.48% DM), although differences were not statistically significant. A study by Rop et al. [39] documented antioxidant activity in honeysuckle leaves ranging from 6.59 to 10.17 g ascorbic acid equivalents per kg (FW). In a comparative study of various Lonicera species, Feng et al. [40] examined the antioxidant activity of honeysuckle leaves and reported that their antioxidant content ranged from 160 to 250 μM Trolox g−1 DW. Nie et al. [41] emphasized that the nutritional composition of honeysuckle leaves, including phenolics and flavonoids, contributes to their antioxidant properties, which have significant potential for preventing chronic diseases. Studies on other plants have shown similar findings.

3.5. Principal Component Analysis (PCA)

PCA was used to categorize honeysuckle leaf samples from three varieties, picked at different times, based on chemical composition parameters such as proximate composition, pigments, macroelements, total flavonoids and total phenolics (Figure 1). The first two principal components (PC1—77.84%, PC2—9.90%) accounted for 87.74% of the total variance. PC1 was strongly correlated (r2 > 0.85) to N (+), P (+), K (+), chlorophyll a (+), chlorophyll b (+), total chlorophyll (+), total carotenoids (+), protein (+), Ca (−), Mg (−), total flavonoids (−) and fiber (−), whereas none of the variables were strongly correlated to PC2.
At the first picking, the data for honeysuckle leaves from all studied varieties were located on the opposite side compared to the data from the second and third pickings. This indicates that young leaves (first picking) of all tested varieties contained the highest contents of N, P, K, chlorophyll a, chlorophyll b, total chlorophyll and total carotenoids, and the lowest contents of Ca, Mg, total flavonoids and fiber.

4. Conclusions

To determine the optimal picking time, this study examined the proximate compositions, pigment content, macronutrients, total phenolics, flavonoids and antioxidant activity of three honeysuckle leaf varieties. The results indicated that different picking times significantly affected the chemical composition of the leaves, a finding that was supported by principal component analysis (PCA). Clear clustering based on the effects of different picking times was observed.
The highest levels of protein, nitrogen (N), phosphorus (P), potassium (K), chlorophyll a, chlorophyll b, total chlorophyll and total carotenoids were found in young leaves (first picking). In contrast, the content of calcium (Ca) and magnesium (Mg) was significantly higher in leaves from the third picking compared to the first and second pickings. Therefore, it is recommended to pick honeysuckle leaves at the appropriate time to maximize the content of these components.
The content of the tested compounds also varied significantly between honeysuckle varieties. The first picking leaves of the ‘Wojtek’ variety had the highest protein, N, P and total carotenoids contents, while the third picking leaves had the highest fiber and ash content. The third picking leaves of the ‘Indigo Yum’ variety contained the highest Ca and Mg levels. The highest content of total flavonoids was found in the second picking leaves of ‘Zojka’ and the third picking leaves of ‘Wojtek’.
These findings emphasize the complex interaction between picking time and variety in shaping the nutritional and bioactive properties of honeysuckle leaves. This study provides valuable insights into optimizing picking times to enhance the nutritional and functional qualities of honeysuckle leaves. For instance, the first picking leaves are richest in protein, nitrogen and chlorophyll, making them beneficial for nutritional and functional purposes. In contrast, the third picking leaves, with higher levels of calcium and magnesium, may be more suitable for applications requiring these specific minerals. These results suggest that selecting particular honeysuckle cultivars can help adapt the timing of leaf picking to meet the needs of various industries, such as nutrition, herbal medicine and natural products. By following these recommendations, researchers can maximize the commercial and medicinal potential of honeysuckle leaves, ensuring they are picked, processed and utilized in the most effective and beneficial way.

Author Contributions

Conceptualization, N.V.; methodology, E.J. and N.V.; software, E.J. and N.V.; formal analysis, E.J.; investigation, E.J. and N.V.; data curation, E.J. and E.K.; writing—original draft preparation, E.J. and N.V.; writing—review and editing, E.J. and N.V.; visualization, E.J. and E.K.; supervision, N.V. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Data Availability Statement

The original contributions presented in the study are included in the article; further inquiries can be directed to the corresponding author.

Conflicts of Interest

The authors declare no conflicts of interest.

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Agriculture 15 00257 g001
Figure 1. PCA was performed with the chemical parameters of leaves picked at different times with the first (1st) picking, second (2nd) picking and third (3rd) picking. Abbreviations: N—nitrogen, K—potassium, Mg—magnesium, P—phosphorus, Ca—calcium, Chl a—chlorophyll a, Chl b—chlorophyll b, TChl—total chlorophyll, TCar—total carotenoids, Tflav—total flavanoids, TPhen—total phenolic.
Figure 1. PCA was performed with the chemical parameters of leaves picked at different times with the first (1st) picking, second (2nd) picking and third (3rd) picking. Abbreviations: N—nitrogen, K—potassium, Mg—magnesium, P—phosphorus, Ca—calcium, Chl a—chlorophyll a, Chl b—chlorophyll b, TChl—total chlorophyll, TCar—total carotenoids, Tflav—total flavanoids, TPhen—total phenolic.
Agriculture 15 00257 g001
Table 1. Experiment variants.
Table 1. Experiment variants.
Varieties of honeysuckle (Lonicera caeruela L.) (A factor)Picking times of leaves (B factor)
1st picking (27 April 2024)2nd picking (6 June 2024) 40 days after 1st picking3rd picking (16 July 2024) 80 days after 1st picking
‘Indigo Yum’
‘Wojtek’
‘Zojka’
Table 2. Proximate composition of honeysuckle leaves at different picking times (%, DM).
Table 2. Proximate composition of honeysuckle leaves at different picking times (%, DM).
VarietiesPicking TimeProteinFiberAsh
‘Zojka’1st picking13.90 ± 0.15 b *9.51 ± 0.03 d6.46 ± 0.01 e
2nd picking11.43 ± 0.16 c20.02 ± 0.12 a9.44 ± 0.06 d
3rd picking8.05 ± 0.19 e16.67 ± 0.88 b9.48 ± 0.01 d
‘Wojtek’1st picking15.99 ± 0.06 a10.08 ± 0.22 d6.00 ± 0.52 e
2nd picking7.36 ± 0.14 f18.07 ± 0.59 b10.52 ± 0.35 c
3rd picking9.76 ± 0.51 d20.93 ± 1.51 a15.84 ± 0.05 a
‘Indigo Yum’1st picking13.67 ± 0.05 b9.04 ± 0.03 d6.45 ± 0.01 e
2nd picking7.41 ± 0.09 f18.22 ± 0.23 b11.83 ± 0.08 b
3rd picking9.30 ± 0.07 d14.82 ± 0.24 c4.49 ± 0.05 f
p-Value:
Variety<0.0001<0.0001<0.0001
Picking time<0.0001<0.0001<0.0001
Interactions of honeysuckle
variety × picking time		<0.0001<0.0001<0.0001
Note: * Different lowercase letters (a, b, c, d, e and f) in the columns represent significant differences between variety and picking time (p < 0.05).
Table 3. The content of pigments in honeysuckle leaves at different picking times (mg 100 g−1, DM).
Table 3. The content of pigments in honeysuckle leaves at different picking times (mg 100 g−1, DM).
VarietiesPicking TimeChlorophyll aChlorophyll bTotal
Chlorophyll		Total Carotenoids
‘Zojka’1st picking215.02 ± 19.10 a *137.05 ± 14.59 a352.08 ± 33.69 a51.63 ± 1.12 b
2nd picking149.58 ± 8.34 b82.94 ± 3.79 cd232.52 ±12.13 b41.43 ± 1.03 c
3rd picking106.18 ± 6.50 cd70.99 ± 5.16 de177.18 ± 11.66 bc25.59 ± 0.91d
‘Wojtek’1st picking230.77 ± 26.87 a107.37 ± 6.72 bc338.14 ± 33.58 a59.93 ± 0.51 a
2nd picking131.89 ± 10.70 bc82.95 ± 7.15 cd214.84 ± 17.85 b35.85 ± 0.35 c
3rd picking77.43 ± 9.11 d54.11 ± 6.00 e131.53 ± 15.11 c21.05 ± 1.05 d
‘Indigo Yum’1st picking217.57 ± 8.56 a126.34 ± 18.37 ab343.91 ± 24.21 a53.54 ± 4.51 b
2nd picking110.66 ± 10.75 bc62.63 ± 3.22 de173.29 ± 13.97 bc39.52 ± 2.37 c
3rd picking70.75 ± 18.73 d51.38 ± 13.07 e122.13 ± 31.80 c19.57 ± 3.68 d
p-Value:
Variety0.00990.00350.0054n.s.
Picking time<0.0001<0.0001<0.0001<0.0001
Interactions of honeysuckle variety × picking timen.s.<0.0001n.s.0.0002
Note: * Different lowercase letters (a, b, c, d and e) in the columns represent significant differences between variety and picking time (p < 0.05). n.s.—no significant differences.
Table 4. The content of macroelements in honeysuckle leaves at different picking times (mg 100 g−1, DM).
Table 4. The content of macroelements in honeysuckle leaves at different picking times (mg 100 g−1, DM).
Macroelements (mg 100 g−1, DM)
VarietiesPicking TimeNPKCaMg
‘Zojka’1st picking2800 ± 0.80 b *350 ± 0.20 c1630 ± 0.20 a950 ± 0.20 i250 ± 0.20 i
2nd picking1850 ± 0.50 d140 ± 0.05 g1000 ± 0.20 e1600 ± 0.20 e360 ± 0.20 e
3rd picking1550 ± 1.00 h120 ± 1.00 i930 ± 0.30 f1960 ± 0.30 c420 ± 0.30 d
‘Wojtek’1st picking2990 ± 0.80 a430 ± 0.20 a1490 ± 0.20 b990 ± 0.20 h280 ± 0.20 h
2nd picking1780 ± 0.50 f170 ± 0.10 f1030 ± 0.50 d1450 ± 0.50 f340 ± 0.50 f
3rd picking1560 ± 0.30 g130 ± 0.10 h760 ± 0.30 i1810 ± 0.30 d410 ± 0.30 c
‘Indigo Yum’1st picking2690 ± 0.60 c400 ± 0.20 b1350 ± 0.60c1130 ± 0.60 g310 ± 0.60 g
2nd picking1830 ± 0.40 e210 ± 0.10 d850 ± 0.30 g2010 ± 0.30 b460 ± 0.30 b
3rd picking1440 ± 0.80 i200 ± 0.05 e790± 0.20 h2840 ± 0.20 a510 ± 0.20 a
p-Value:
Variety<0.0001<0.0001<0.0001<0.0001<0.0001
Picking time<0.0001<0.0001<0.0001<0.0001<0.0001
Interactions of honeysuckle variety × picking time<0.0001<0.0001<0.0001<0.0001<0.0001
Note: * Different lowercase letters (a, b, c, d, e, f, g, h and i) in the columns represent significant differences between variety and picking time (p < 0.05).
Table 5. The content of total phenolics, flavonoids and antioxidant activity of honeysuckle leaves at different picking times.
Table 5. The content of total phenolics, flavonoids and antioxidant activity of honeysuckle leaves at different picking times.
VarietiesPicking TimeTotal Phenolic (mg 100 g−1, DM)Total Flavanoids
(mg 100 g−1, DM)		Antioxidant Activity (%)
‘Zojka’1st picking148.92 ± 11.05 de *28.33 ± 2.52 d78.28 ± 5.16 a
2nd picking155.35 ± 6.65 ab116.67 ± 8.50 a80.97 ± 0.91 a
3rd picking158.77 ± 2.20 a103.00 ± 1.00 b76.51 ± 0.83 a
‘Wojtek’1st picking131.07 ± 3.91 e54.33 ± 1.53 c78.02 ± 0.70 a
2nd picking131.71 ± 3.54 e102.33 ± 1.53 b79.78 ± 1.06 a
3rd picking151.69 ± 3.18 abc115.00 ± 0.00 a75.48 ± 0.83 a
‘Indigo Yum’1st picking143.56 ± 1.24 cd53.33 ± 0.58 c81.45 ± 3.13 a
2nd picking147.08 ± 0.63 bc101.00 ± 4.00 b80.76 ± 0.49 a
3rd picking149.79 ± 2.68 abc93.67 ± 0.58 b81.11 ± 0.01 a
p-Value:
Variety<0.0001<0.00010.0096
Picking time0.00020.0000000.0380
Interactions of honeysuckle variety × picking time0.0342<0.0001n.s.
Note: * Different lowercase letters (a, b, c, d and e) in the columns represent significant differences between variety and picking time (p < 0.05). n.s.—no significant differences.
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Jakienė, E.; Kaušė, E.; Vaitkevičienė, N. Impact of Picking Time on Leaf Quality Parameters of Three Varieties of Honeysuckle (Lonicera caerulea L.). Agriculture 2025, 15, 257. https://doi.org/10.3390/agriculture15030257

AMA Style

Jakienė E, Kaušė E, Vaitkevičienė N. Impact of Picking Time on Leaf Quality Parameters of Three Varieties of Honeysuckle (Lonicera caerulea L.). Agriculture. 2025; 15(3):257. https://doi.org/10.3390/agriculture15030257

Chicago/Turabian Style

Jakienė, Erika, Edita Kaušė, and Nijolė Vaitkevičienė. 2025. "Impact of Picking Time on Leaf Quality Parameters of Three Varieties of Honeysuckle (Lonicera caerulea L.)" Agriculture 15, no. 3: 257. https://doi.org/10.3390/agriculture15030257

APA Style

Jakienė, E., Kaušė, E., & Vaitkevičienė, N. (2025). Impact of Picking Time on Leaf Quality Parameters of Three Varieties of Honeysuckle (Lonicera caerulea L.). Agriculture, 15(3), 257. https://doi.org/10.3390/agriculture15030257

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