Introduction

As a member of Apiaceae family, Coriandrum sativum L. (coriander) is one of the most beneficial spices and medicinal herbs1. Hippocrates (460–377 BC) used the essential oil (EO) from coriander in time-honored Greek treatments, and it has a historic medicinal use2,3. It is an annual herb that indigenous to the Mediterranean and Western Asia regions. The main nations that produce coriander plants are Syria, Canada, China, India, Morocco, Bulgaria, Egypt, and Romania. More than 80% of the world’s coriander production is produced in India4. In Egypt, the average amount of coriander crop production was 9336.8 tons between 1990 and 1997, and 13,094 tons between 1998 and 20045,6 and 3496 ton in 20177. According to data from 2008–2009, coriander is grown on about 8079 feddan, with a production of about 7292 tons8, while throughout the years 2000–2016, the coriander crop was grown on an average of roughly 9.50 thousand feddan7. The total exported quantity of Egyptian coriander during the period 2009–2011 was 1539 tons8, while it was 1181.6 tons during the period 2000–20177.

Due to its widespread use from the Middle East across all of southern Asia and the majority of Latin America, green coriander leaves have been dubbed the most widely used herbal flavoring in the creation of salad and sauces worldwide9,10. Cilantro, also known as Chinese parsley, is frequently used in Chinese, South American, Mexican, and Indian cuisines11. Due to their high concentration of health-promoting metabolites such as antioxidants, chlorophylls, carotenoids, certain elements, fibers, vitamin C, vitamin A, as well as their low-fat content, green coriander leaves play a significant role in the diet1.

One of the constraints restricting modern agriculture is the use of chemical nitrogen, which must be reduced to reduce the negative economic and environmental effects of fertilization as well as the accumulation of nitrate12,13,14. According to studies by Alberici et al.15 and Cavaiuolo and Ferrante16, increased nitrate availability in leafy vegetables frequently leads to an accumulation in leaves with nitrate levels that are higher than those permitted by EU regulations. High N fertilizer rates can harm the environment by increasing greenhouse gas emissions of nitrous oxide and nitrate flows into streams14,17,18. Fruits and vegetables can accumulate high amounts of nitrates, which can have a negative effect on human health19,20. Utilizing a biostimulant made from plant extracts collected from various arboreal plant parts to increase nitrogen uptake while maintaining yields21,22.

Biostimulants are tools for sustainable agriculture since they are eco-friendly particularly in developing agricultural nations, where the usage of mineral fertilizers places a heavy financial burden on farmers23. By definition, biostimulants are “substances or mixtures of particles or microorganisms that, when used with plants, are capable of improving trophic efficiency, abiotic stress tolerance, and/or crop quality traits”24,25. As a result, biostimulants are employed as growth promotors and as supplements to mineral fertilizers since they help to increase growth, yield and crop quality26,27,28,29,30. By promoting root growth and increasing the antioxidant capacity of plants, biostimulants application in vegetables permitted a decrease in fertilizers and an increase in leaf pigments (chlorophyll and carotenoids) and plant growth31,32,33.

Low dosages of bio-based products, such as plants, seaweed, and agricultural wastes, might be a viable way to reduce fertilizer usage while simultaneously enhancing plant development34. In this context, plant extracts are a potential class of biostimulants of vegetal origin that improve vegetable quality in terms of phytochemical content and crop performance by enhancing nutrient availability, absorption, and metabolic utilization35,36,37. The effects of plant extracts are brought about by their interference with the phytohormone balance in plants, according to Paradikovi’c38. Additionally, plant extracts are designed to function as defense mechanisms against abiotic stress since they include bioactive molecules that control plant physiology and metabolism. This can help minimize yield losses brought on by unfavorable soil conditions39,40. Treatments with soybean leaf extract raised the Mg and Ca concentrations in lettuce, whereas Chinese chive treatments enhanced the Fe contents41. Furthermore, Chinese chive, soybean leaf, and soybean stem extracts raised the levels of total and free amino acids in test plants while also increasing the glucose and maltose contents in lettuce plants following treatments41.

Numerous treatments and biostimulants have a substantial impact on the vegetative characteristics, oil content, and biochemical components including ascorbic acid, total chlorophyll, and carotenoids of the C. sativum and other horticultural plants. The administration of biostimulants to chilled plants caused an increase in L-ascorbic acid, total phenolic content, and overall antioxidant activity42. The biostimulants can also alter certain metabolic pathways, speeding up the adaption of chilled coriander plants42. With 4% of moringa leaves extract (MLE), pea plants (Pisum sativum L.) accumulated the most nutrients, growth indices, and photosynthetic pigment43. By enhancing leaf pigments and photosynthetic activity as well as plant fresh weight after treatments with 10 mL/L dosages of borage extracts, lettuce's primary metabolism was improved44.

The matured leaves of coriander contain high levels of moisture, protein, and total ash (1.7%, 87.9%, and 3.3%, respectively), as well as carbohydrates (6.5% total sugar)45. The trans-tridecen in the EO from immature fruits and leaves of coriander is what gives off the unpleasant odor known as the “stink bug smell”46. (E)-2-decenal, is the most prevalent compound in the EOs extracted from the leaves of C. sativum, with a concentration of 52%, varied depending on the amount of treatment47. 44 chemicals were found in the EO of C. sativum leaves, the majority of which were aromatic acids such 2-decenoic acid, E-11-tetradecenoic acid, capric acid, undecyl alcohol, tridecanoic acid and undecanoic acid48. The seed extract was shown to include phenolic compounds such as gallic acid, caffeic acid, ellagic acid, quercetin, and kaempferol49.

Natural extracts from forestry trees have been proven to increase crop and product quality attributes (pre- and post-harvest) nutrient usage efficiency, seed germination, horticultural plant growth and yield and resistance to abiotic stresses50,51,52. Wattle or Acacia saligna (Labill.) Wendl, is a woody plant found in the warm climates of the world, including Australia, the Americas, Africa and Asia53. It is also described as a woody tree that grows quickly, is invasive, and has a sizable quantity of protein (18.25–35.5%)53. A. saligna extracts from the stem and leaves contain allelopathic compounds that are thought to be phytotoxic and inhibits plant development or germination54,55,56.

Therefore, the objective of this research was to evaluate the biostimulant effects of Acacia saligna fruit aqueous extract as a foliar application in combination with N fertilizer on the vegetative and biochemical parameters, and the essential oil composition of coriander plants.

Materials and methods

Experimental conditions and Calypso cultivar properties

At the experimental farm of the Faculty of Agriculture and Natural Resources, Aswan University, Aswan, Egypt, two field experiments on Coriandrum sativum L. were carried out in the winter of 2020 and 2021. The site is located at 23° 59′ 56″ N, 32° 51′ 36″ E, with an average elevation of 85 m above sea level. The average temperatures; High 25–30 °C, and Low 12–14 °C, the relative humidity (RH 40%), the wind speed in winter season blows at an average speed of 13.5 mph (21.8 kph) and average wind speed of 13.0 mph (20.9 kph).

The Calypso cultivar, which was obtained from Harraz Company vegetable seed (Cairo, Egypt), was used in this study. It may grow huge, uniform leaves of a consistent color, endure high temperatures, moderate bolting, and have around 110 seeds/g. This cultivar was recommended in some works57,58.

Soil analysis of the experimental site

Following the prescribed protocols, soil samples were taken from the experimental planting site in both seasons at depth of 30 cm and examined for physical and chemical characteristics59. Table 1 lists the major physical and chemical soil parameters for the two trial sites.

Table 1 Soil analysis of the experimental site during both seasons.
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Preparation of Acacia saligna (Labill.) H.L.Wendl. fruit aqueous extract

A. saligna (Labill.) H.L.Wendl. trees grown in Abies Station Farm, Alexandria, Egypt (31°12N 29°55E), were chosen and identified at the Department of Forestry and Wood Technology. A. saligna fruits (legumes with seeds) were taken after they were fully developed, air-dried in a lab conditions for 4 weeks, and then ground into a fine powder using a small laboratory mill. Approximately 100 g of the ground fruits were put in a conical flask containing 300 mL of distilled water (DW), then extracted for 3 h under heating using a water bath at 50 °C60. The extract was concentrated to a small volume after being run through cotton plugs, and filtered by Whatman No. 1 filter paper. The fruit aqueous extract (FAE) was prepared at the concentration of 2%, 4%, and 6%, by dissolving the respective amount in DW.

Experimental procedure and treatments

In both seasons, coriander seeds were sown from the beginning of November to the end of December. The prepared concentrations (2, 4 and 6%) of A. saligna FAE were evaluated in combination with nitrogen fertilizer rate (50% from recommended dose) to measure their effects on growth, productivity, and phytochemicals of coriander. At 20, 30, and 40 days following sowing, the plants were sprayed with foliar treatments (2, 4 and 6% of A. saligna FAE) three times. Each experiment included four treatments as shown in Table 2. In a randomized complete block design, the four tested treatments were set up with three replicates, totaling 12 experimental plots. Each replicate (experimental plot) had a surface area of 3 m2 (2 × 1.5 m2) and included 300 seeds/m2. After 20 and 40 days of sowing, the source of N fertilizer, (NH4)2 SO4 (20.5% N), was added twice to the soil.

Table 2 Combination treatments of A. saligna extract and N fertilizer used for coriander plants.
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Vegetative and biochemical parameters

Vegetative parameters

To assess the vegetative development, 10 plants were randomly selected from each experimental unit at harvest time in both seasons to measure plant height (cm), number of leaves/plant, plant fresh weight (g) and total yield (kg/m2).

Measuring of photosynthetic pigments

The extraction of chlorophylls (a, b and a + b) and carotenoids, which are photosynthetic pigments, were extracted from leaves using ethanol 96% (v/v) in a ratio of 1:10 (w/v). The absorbance was measured at 664 and 649 nm for chlorophylls a and b, respectively, and 470 nm for carotenoids61.

Measuring of total soluble solids, total carbohydrates and crude protein content

A portable digital refractometer (Atago Co. Ltd., modelPR-1, Tokyo, Japan) was used to measure the total soluble solids (TSS %) in the leaf juice. The percentage of total carbohydrates (%) in leaves' dry matter was calculated62. The approved Kjeldahl technique outlined in AOAC62, was used to calculate the crude protein content.

Total phenolic content and antioxidant activity

The total phenolic content (TPC) was determined by Folin–Ciocalteu reagent and the absorbance was measured by Optizin UV–Vis spectrophotometer model (Thermo Electron Corporation, Waltham, MA, USA) at 750 nm63. Using the gallic acid calibration curve, the absorbance was converted to gallic acid equivalent (GAE). The antioxidant activity was evaluated using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay64.

Extraction of essential oils and Gas chromatography–mass spectrometry (GC–MS) analysis

The essential oils (EOs) from leaves of coriander plants treated with the four treatments were extracted using a Clevenger-type apparatus through the hydrodistillation method65. To do this, 1 L of distilled water was added to a 2 L flask containing 100 g of leaves and then connected to Clevenger-type apparatus with the condenser and heated continuously for 3 h at a temperature of 120 °C. We proceeded with the extraction of the EOs using the method of Shahwar et al.66 approach because it has already been mentioned that the volatiles from coriander leaves was extremely low.

Analysis the essential oils by gas chromatography–mass spectrometry (GC–MS)

Thermo Scientific's Trace GC Ultra-ISQ mass spectrometer, which has a direct capillary column TG-5MS (30 m × 0.25 mm × 0.25 m film thickness), was used to analyze the chemical composition of the EOs. The temperature of the column oven was first maintained at 70 °C, then increased by 5 °C/min to 280 °C, kept for 5 min, and then increased to 300 °C at 5 °C/min. Temperatures were maintained at 250 °C for the MS transfer line and injector. As a carrier gas, helium was employed at a constant flow rate of 1 mL/min. Using an Autosampler AS1310 combined with GC in split mode, diluted samples of 1 L were automatically injected with a solvent delay of 2 min. Full scan EI mass spectra covering the m/z range of 40–600 were collected at 70 eV ionization voltages. The temperature of ion source was set at 200 °C67. By comparing the retention times and mass spectra of the components with those of the WILEY 09 and NIST 11 mass spectral databases and calculating the match factor, the components were identified68,69.

Chemosystematic significance via multivariate analysis

The chemosystematic significance of this plant was established via the multivariate assessing, comprising principal component analysis (PCA), of the EO principal components of the various C. sativum plants. The major compounds of the C. sativum EO (> 2.5%) and those of the other C. sativum plants around the world were used to construct the chemo-systematic significance of the species.

Leaf methanol extracts

For the extraction, leaf samples from the four treated C. sativum plants (Table 2) were obtained. Each of the treated leaves weighed about 50 g, and 150 mL of methanol was used to extract them over the course of a week at room temperature by the soaking method26. The extracts were then filtered using a cotton plug and Whatman no. 1 filter paper. Prior to usage, the extracts were concentrated and kept in the refrigerator in brown vials.

Analysis of flavonoid and phenolic compounds by HPLC

With the use of High Performance Liquid Chromatography (HPLC) system (Agilent 1100), which consists of two LC pumps, a UV/Vis detector, and a C18 column (250 mm × 4.6 mm, 5 µm), flavonoid components from the methanol extracts of the four treated C. sativum plants were identified. With an isocratic elution (70:30) program, the mobile phase consisted of acetonitrile (A) and 0.2% (v/v) aqueous formic acid (B). The detection wavelength was set at360 nm70.

Using HPLC, The phenolic and flavonoid components from Acacia saligna FAE were identified by HPLC analysis70. For instance, to analyze the phenolic compound, HPLC (Agilent 1100, Agilent ChemStation) had a UV/Vis detector, two LC pumps, and a C18 column (125 mm × 4.6 mm, 5 µm particle size) was used to gather and examine chromatograms. By using a gradient mobile phase of two solvents—Solvent A (Methanol) and Solvent B [Acetic acid in water (1:25)], phenolic compounds were isolated. For the first 3 min, the gradient program was maintained at a concentration of 100% B. The concentration of eluent A was then raised to 80% for the following 2 min, then decreased to 50% once again for the following 5 min detection wavelength at 250 nm. This was followed by 5 min of 50% eluent A. As a result, the order of phenolic compounds was established utilizing this mobile phase to verify standard compounds.

Statistical analysis

All the collected data were analyzed using the CoStat software version 6.30371 and the treatments means were compared using the LSD test at 0.05 level of probability72.

Ethics approval and consent to participate

This study is complied with relevant institutional, national, and international guidelines and legislation. This study does not contain any studies with human participants or animals performed by any of the authors.

Results

Measurement of vegetative growth and total yield parameters

The plants treated with the control treatment (Fig. 1a) had the maximum plant height values of 55.4 and 56.7 cm in both seasons, followed by the plants treated with 4% and 6% of A. saligna FAE + 50% N fertilizer. Plants treated with A. saligna FAE 2% + 50% N fertilizer treatment had the lowest plant height values..

Figure 1
figure 1

Plant height (cm) of C. sativum plants treated with A. saligna FAE + N fertilizer. Letters in Figure indicated that, means ± S.E of treatments with the same letter/s were not significantly different according to LSD at 0.05 level of probability. LSD 0.05 for Season 1 = 2.38 and Season 2 = 1.98.

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The maximum number of leaves were produced by the plants treated with A. saligna FAE 4% + 50% N fertilizer with values of 15.9 and 16.3 leaf/plant in both seasons, respectively (Fig. 2).

Figure 2
figure 2

The number of leaves/plant of C. sativum plants treated with A. saligna FAE + N fertilizer. Letters in Figure indicated that, means ± S.E of treatments with the same letter/s were not significantly different according to LSD at 0.05 level of probability. LSD 0.05 for Season 1 = 1.01 and Season 2 = 1.50.

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The control plants had the maximum plant weight in both seasons, measuring 35.30 and 35.44 g (Fig. 3), followed by the plants given A. saligna FAE 4% + 50% N fertilizer in each season. While plants treated with A. saligna FAE 2% + 50% N fertilizer had the lowest values. The highest total yield was observed in the control treatment with values of 8.82 and 8.88 kg/m2, in both seasons, respectively (Fig. 4).

Figure 3
figure 3

The plant weight (g) of C. sativum plants treated with A. saligna FAE + N fertilizer. Letters in Figure indicated that, means ± S.E of treatments with the same letter/s were not significantly different according to LSD at 0.05 level of probability. LSD 0.05 for Season 1 = 5.20 and Season 2 = 5.71.

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Figure 4
figure 4

Total yield (kg/m2) of C. sativum plants treated with A. saligna FAE + N fertilizer. Letters in Figure indicated that, means ± S.E of treatments with the same letter/s were not significantly different according to LSD at 0.05 level of probability. LSD 0.05 for Season 1 = 1.07 and Season 2 = 1.39.

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Photosynthetic pigments measurements and biochemical compounds

Chlorophyll a, chlorophyll b, and chlorophylls a + b contents in the leaves of coriander plants treated with A. saligna FAE (2, 4, and 6%) + 50% N fertilizer are shown in Fig. 5a–c, respectively, along with a comparison to the control plants (treated with 100% N) in both seasons. The highest content of Chlorophyll a was found with the treated plants with A. saligna FAE 4% + 50% N fertilizer (Fig. 5a) in both seasons with values of 0.443 and 0.449 mg/g fw, respectively. Chlorophyll b content (Fig. 5b) reached the highest content in both seasons as the plants treated with A. saligna FAE 4% + 50% N fertilizer with values of 0.256, and 0.267 mg/g fw, respectively. The highest values of chlorophyll a + b content was obtained in plants treated with 4% A. saligna FAE + 50% N fertilizer, in both seasons, which reached 0.699 and 0.716 mg/g fw, respectively (Fig. 5c).

Figure 5
figure 5

Characterization of photosynthetic pigments of C. sativum plants as affected by the treatments of A. saligna FAE + N fertilizer. (a) Chlorophyll a content (mg/g fw); (b) Chlorophyll b content (mg/g fw); (c) Chlorophylls a + b (mg/g fw), and (d) Carotenoids (mg/g fw). Letters in Figure indicated that, means ± S.E of treatments with the same letter/s were not significantly different according to LSD at 0.05 level of probability.

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The highest level of carotenoids (Fig. 5d) in the first season was observed in plants treated with A. saligna FAE 6% + 50% N fertilizer (0.134 mg/g fw), which was not statistically significant from those plants treated with A. saligna FAE 4% + 50% N fertilizer (0.128 mg/g fw) and in control plants (0.127 mg/g fw). In the second season, the highest values were found in control plants (0.141 mg/g fw), followed by the treated plants with A. saligna FAE 4% + 50% N fertilizer (0.133 mg/g fw).

LSD 0.05

Chlorophyll a content (mg/g fw)

Chlorophyll b content (mg/g fw)

Chlorophylls a + b (mg/g fw)

Carotenoids (mg/g fw)

Season 1

0.021

0.051

0.086

0.011

Season 2

0.027

0.072

0.092

0.012

Measurements of biochemical compounds, total phenolic and antioxidant activity

The total soluble solids (TSS), total carbohydrates, total protein, total phenolic compounds (TPCs), and the total antioxidant activity (TAA) of coriander leaf are shown in the Table 3. A. saligna FAE (4%) + 50% N fertilizer-treated plants had the highest TSS levels in both seasons, with values of 8.8 and 8.9%, respectively.

Table 3 Biochemical compounds, the total phenolic content and antioxidant activity of coriander leaf.
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The total carbohydrates was presented in the highest amount in plants treated with of A. saligna FAE 4% + 50% N fertilizer, with percentages of 24.36% and 25.21% in each season, respectively (Table 3).

The highest content of protein was found in leaves of plants treated with A. saligna FAE 4% + 50% N fertilizer with values of 16.32% and 16.16%, respectively, in both seasons (Table 3).

The plants treated with A. saligna FAE 4% + 50% N fertilizer had the highest total phenolic content with values of 266.54, and 269.22 mg GAE/100 g fw, respectively, in both seasons (Table 3).

The leaf methanol extract from plants treated with A. saligna FAE 4% + 50% N fertilizer had had the highest total antioxidant activity as determined by the DPPH method with values of 78.30, and 79.53%, in both seasons, respectively (Table 3).

Leaf essential oil compositions

The percentages of the obtained essential oils (EOs) were in the samples collected from untreated, and In the samples taken from treated plants with 2%, 4%, and 6% A. saligna FAE + 50% N fertilizer, respectively, and control plants, the percentages of the obtained EOs were 0.06, 0.13%, 0.09% and 0.08%. Table 4 displays the chemical composition of the EOs derived from C. sativum leaves as influenced by various treatments of A. saligna FAE + 50% N fertilizer compared the control plants that treated with 100% recommended dose of N (240 kg N/ha).

Table 4 Chemical compounds of the essential oils from C. sativum leaves as affected by various treatment.
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In the control treatment, 26 compounds were identified in the EO from leaves, where the highest percentage components were 2-octyn-1-ol (23.93%), 2-butyl-1-octanol (8.80%), 2-dodecenal (7.67%), 8-azabicyclo[5.1.0]octane (5.56%), dodecyl-oxirane (5.32%), 3,5,5-trimethyl-1-hexene (5.23%), methyl 10,12-pentacosadiynoate (3.74%), and 2,4,6,8-tetramethyl-1-undecene (3.11%), while the minor compounds were 1-decene (2.68%), 4-methyl-2-propylpentan-1-ol (2.66%), 1-(ethenyloxy)-octadecane (2.63%), (Z)-5-tridecene (2.34%), 1-nonanol (2.32%), and 1,2-epoxy-5,9-cyclododecadiene (2.17%).

The EO from leaves of C. sativum plants treated with 2% A. saligna FAE + 50% N fertilizer showed the 17 compounds, were (E)-2-decen-1-ol (32.00%), 1-methoxymethoxy-oct-2-yne (13.71%), trans-2-undecenoic acid (11.38%), 1,12-tridecadiene (11.21%), 1-nonanol (8.26%), 10-methyl-E-11-tridecen-1-ol propionate (5.14%), 1-(ethenyloxy)-octadecane (3.83%), 9,12-octadecadienal (3.74%), and 5,7-dodecadiyn-1,12-diol (2.72%) were presented as main compounds, while methyl 12,13-tetradecadienoate (1.98%), and 1-decene (1.13%) were found with minor percentages.

The treated plants with 4% A. saligna extract + 50% N fertilizer showed the presence of 23 compounds, where the highest percentage of compounds were E-2-undecen-1-ol (32.70%), 3,5,5-trimethyl-1-hexene (8.91%), 2-butyl-1-octanol (8.85%), dodecyl-oxirane (4.86%), 1,10-decane-1,1,10,10-D4-diol (4.61%), 9,12-octadecadienal (4.58%), 1-nonanol (4.12%), 1-decene (2.83%), methyl 10,12-pentacosadiynoate (2.81%), trans-2,3-epoxydecane (2.58%), (Z)-5-tridecene (2.44%), and 1-(ethenyloxy)-octadecane (2.00%).

Using the A. saligna extract at 6% + 50% N fertilizer, 7 compounds were identified in the EO from leaves of C. sativum, where phytol, the most abundant compound in the EO reached 80.44%, followed by other compounds (Z)6,(Z)9-pentadecadien-1-ol (13.75%), and 1,10-decane-1,1,10,10-D4-diol (6.07%).

The foundation of this work was the multivariate analysis of the principal component analysis (PCA). The PCA space observation of main constituents of coriander EOs from the 4 treatments showed that moderate correlation or association ((+ 28.8%) among the EOs identified from the plants extracted from the four treatments (T1 Control (100% N), T2 2% of A. saligna FAE + 50% N fertilizer, T3 4% of A. saligna FAE + 50% N fertilizer and T4 6% of A. saligna FAE + 50% N fertilizer) (Fig. 6).

Figure 6
figure 6

PCA space observation of main constituents of coriander EOs from the 4 treatments.

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The correlation circle PCA of main constituents of C. sativum EOs as affected by the four treatments was compared with the mains compounds of the EOs from coriander species including from worldwide of the various coriander plants as from Pakistan66 (Cor 1), Brazil73 (Cor 2) Iran74 (Cor 3), Kenya75 (Cor 4), Poland76 (Cor 5) and two EOs (Cil 1 and Cil 2) from C. sativum grown from dried fruits (Johnny’s Selected Seeds, Albion, ME)77 is shown in Fig. 7.

Figure 7
figure 7

The correlation circle PCA of main constituents of EO of C. sativum as affected by four treatments and the coriander species including from worldwide.

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The PCA analysis showed that C. sativum has a weak association (+ 17.1%) with the other coriander species. The findings demonstrated that the coriander EOs have a distinctive phenomenon of the existence of 2-Octyn-1-ol (T1), (E)-2-decen-1-ol (T2), E-2-undecen-1-ol (T3) and phytol (T4) as the primary components.

HPLC analysis of flavonoid components in C. sativum leaves

The identified flavonoid components from methanol extracts of C. sativum leaves are shown in Table 5 and Fig. S1. In the methanol extract from the control treatment, the two main flavonoid components were catechin (8.65 µg/mL) and luteolin (8.14 µg/mL). The primary flavonoid components present in the methanol extract of leaves from plants treated with 2% A. saligna FAE + 50% N fertilizer included luteolin (8.66 µg/mL), naringin (6.54 µg/mL), and kaempferol (5.44 µg/mL). The most prevalent flavonoid component found in the methanol extract of the plants treated with 4% A. saligna FAE + 50% N fertilizer was apigenin (9.56 µg/mL). The predominant flavonoid components in the methanol extract of leaves from plants treated with 6% A. saligna FAE + 50% N fertilizer were catechin (14.87 µg/mL), luteolin (12.66 µg/mL), and rutin (10.49 µg/mL).

Table 5 Flavonoid compounds identified in the leaf methanol extracts of C. sativum by HPLC.
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Analysis of phenolic and flavonoid compounds from A. saligna FAE by HPLC

The identified phenolic and flavonoid constituents in A. saligna FAE are shown in Table 6 and Fig. S2. Syringic acid (13.12 μg/g FAE), pyrogallol (9.42 μg/g FAE), and ferulic acid (8.89 μg/g FAE) were the abundant phenolic compounds (Fig. S2a), and apigenin (15.22 μg/g FAE), naringin (12.45 μg/g FAE) and rutin (9.02 μg/g FAE) were the abundant flavonoid compounds (Fig. S2b).

Table 6 Phenolic and flavonoid compounds identified fruit aqueous extract from Acacia saligna by HPLC.
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Discussion

Due to the recent growth in food demand, agricultural expansion, and increased crop productivity have resulted in a rise in the use of many synthetic products in the fields, which has created a number of issues for the environment, farmers, and consumers78. As a result, the use of plant biostimulants is a novel, ecologically friendly strategy for sustainable crop production, which is constrained by issues including water shortages, resource depletion, environmental stresses, and climate change33.

Coriander plants must be provided with nitrogen during the growing season in order to accomplish the necessary increase in vegetative growth and quality improvement and production79,80. Moreover, N fertilization affects the accumulation of phytochemicals in the plant, including phenolic compounds, and nitrogen deficiency, which may lead to an increase in their concentration in the plant81.

It is ideal to comprehend the balance between using the proper amount of nitrogen for plant growth and production, especially in leafy green vegetables like the coriander that was the subject of this study. With less of the suggested mineral N fertilizer for coriander growing, this study assessed the biostimulant effect of Acacia saligna aqueous fruit extract at various concentrations. The overuse of N fertilizers and their improper application are two major issues that restrict the yield of leafy crops. Leafy vegetables can have toxicity issues as a result of excessive fertilization9,82. As a result, it is advised to use natural plant biostimulants as a promising and creative strategy to ensure better and long-lasting yields while minimizing the usage of inorganic fertilizers83.

The spraying of various A. saligna extract concentrations had an impact on vegetative development and yield in this consistency. The findings usually showed that the application of a concentration of A. saligna FAE (4%) combined with 50% N fertilizer, improved coriander plant production and vegetative development. The abundance phytochemicals found in the extract, including phenolic and flavonoid components, may be responsible for these results. According to the findings of earlier research, the various botanical parts of A. saligna contain a variety of powerful compounds that promote the growth of many plants, including proteins, carbohydrates, phenolic, gallic acid, p-coumaric acid, palmitic, oleic, and linoleic acids60,84. By reducing the negative impacts of stress, phenolic compounds demonstrated a biostimulant action on many plant species. Most likely, phenolic chemicals help to combat various stressful situations by triggering the body's antioxidant defense mechanism. Terpenes and phytohormones also have a favorable impact through seed priming and foliar spraying37. Furthermore, certain extracts, such as those from the Moringa oleifera leaf, which is rich in proteins, lipids, carbohydrates, minerals, vitamins, and amino acids, have a simulative effect on plant growth and productivity on the okra and tomato plants85,86,87. Utilizing plant biostimulant increased the overall yield of the leaves produced by the spinach and lettuce plants88.

Chlorophyll a, chlorophyll b, and chlorophylls a + b contents were reached the highest amount in plants treated with A. saligna FAE 4% + 50% N fertilizer while carotenoids content showed the highest amount in plants treated with A. saligna FAE 4% + 50% N fertilizer and A. saligna FAE 4% + 50% N fertilizer. A significant number of secondary metabolites are phytotoxic and have an allelopathic effect in addition to their biostimulant activity on plant development and seed germination89,90. Fruit extract from A. saligna might be regarded as a biostimulant to enhance vegetative growth and production because of the chemicals found in it, which called allelochemicals55,91.

The methanolic extracts of A. saligna had a greater impact on the seedling length of the plant diversity along Egypt's Nile Delta Coast than the aqueous extracts, but only at low doses54. Two agricultural crops, wheat and canola, showed persistent declines in their vegetative growth parameters (shoot and root length, fresh and dry weight), as the allelopathic extract concentration from leaves and stems of A. saligna increased to 10%56. A. saligna leaf and root aqueous extract concentrations (0%, 5%, 10%, 15%, and 20%) significantly increased the inhibition of seed germination and the lengthening of shoot and root, which gradually reduced the seedling performance of three native Mediterranean shrubs (Astragalus armatus Willd., Retama raetam (Forssk.) Webb & Berthel., and Helianthemum kahiricum Del.)92. According to another study, stem and leaf extracts of A. saligna contain significant amounts of allelochemicals that hinder the growth and development of wheat, radish, barley, and arugula. This reduces crop biomass and has an negative impact on other related parameters at concentrations of 5–25%55.

Researchers and consumers are paying increasing attention these days to fruits and vegetables high in phytonutrients. Phytoalexins, antioxidants, and signaling molecules are the roles played by these substances, which are secondary metabolites produced by plants from primary metabolites40,93. They also aid in the defense mechanisms used by plants to respond to stress. By altering plant biochemical, molecular, and physiological processes, plant-derived biostimulants are able to enhance plant growth, water usage efficiency, nutrient uptake, tolerance to abiotic and biotic challenges, and photosynthesis26,40,94,95.

Coriander leaves are regarded as a significant source of biological substances. In the present investigation, different concentrations of A. saligna FAE had a significant impact on biochemical compounds (antioxidant, flavonoid, total phenolic, and carbohydrates) and total soluble content. In this sense, using biostimulants raised the biochemical components of a variety of leafy vegetables while improving their quality39,96,97.

Low essential oil (EO) percentages from the leaves, in the range of 00.06–0.13%, were observed. The least amount of EOs was observed in Coriandrum sativum (0.12%) among the EOs extracted by hydrodistillation from several medicinal plants98. Numerous chemicals, including (E)-2-decenal, 1-methoxymethoxy-oct-2-yne, (E)-2-decen-1-ol, 3,5,5-trimethyl-1-hexene and phytol were present in treated and untreated plants' EOs. The main constituent in the EO from the leaves was (E)-2-decenal, which followed by decanal, dodecanal, (E)-2-tridecenal and (E)-2-dodecenal47. Decanal, trans-2-decenal, 2-decen-1-ol, cyclodecane, cis-2-dodecenal, dodecan-1-ol and dodecanal were identified as the major components in the leaf EOs73. In the leaf EO, (E)-2-decenal made up the majority of aldehydes (52.2%), whereas 1-decanol made up the majority of monoterpene alcohols77,99.

The primary constituents decanal, cis-phytol, 1-tetradecanol, (E)-2-dodecenal, dode-canal, n-decanol, and trans-2-undecen were present in both fresh and dried coriander plants in the isolated coriander EOs74. The main chemicals found in coriander leaves EO were (E)-2-decenal, linalool, (E)-2-dodecenal, (E)-2-tetradecenal, 2-decen-1-ol, (E)-2-undecenal, dodecanal, (E)-2-tridecenal, (E)-2-hexadecenal, pentadecenal, and α-pinene66. Another study showed that the coriander plant EO contained the largest concentration of aliphatic aldehydes (decanal, E-2-dodecanol and E-2-decenol), as well as phytol, linalool, and oleic acid76. n-Decanal, 2E-dodecanal, 2E-decanal, 2E-tridecen-1-al, and n-nonane made up the majority of the leaf EO100. Additionally, the EO from coriander stems revealed that phytol (61.86%) was the primary component present101. EOs from coriander leaves that were extracted using two different procedures and had linalool as the primary component (51.32% and 61.78%, respectively) were analyzed by GC-MS102.

The presence of various phenolic compounds, including 7-hydroxyflavone, naringin, rutin, quercetin, kaempferol, luteolin, apigenin, and catechin, in varying amounts, was seen in coriander plants treated with the four treatments. These substances play a significant role in the antibacterial and antioxidant actions103,104,105,106.

Aqueous coriander extract was shown to include phenolic components such catechol, salicylic acid, glycitin, pyrogallol, gentisic acid, protocatechinic acid, quinic acid, and caffeic acid107. Aerial parts of C. sativum were found to contain the phenolic chemicals apigenin, catechin, and p-coumaric acid, as well as aliphatic alkenals and alkanals108,109.

Different plant parts, their various developmental stages, and environmental alterations all have an impact on the composition of phytochemicals110. These elements affect the biosynthetic pathways of the plant, which in turn affects the relative proportion of the primary constituents. Numerous studies have demonstrated that biostimulants affected the production and content of EOs111,112,113. Plants create phytochemicals for defense and communication through secondary metabolic pathways.

Conclusion

Under field conditions, coriander's phytochemicals and growth productivity responded to the application of Acacia saligna extract biostimulant (2, 4, and 6%) combined with 50% N fertilizer, were evaluated. The treatment of A. saligna plant extract at 4% + 50% N fertilizer was found to have positive impacts on coriander plants' vegetative development, green yield, and phytochemicals. The findings showed that coriander plants generally produced more leaves per plant, had heavier plants overall (g), and produced a greater overall yield (kg/m2). The use of plant extracts as a biostimulant may assist reduce environmental pollution caused by the use of mineral nitrogen fertilizers by reducing the amount used in agriculture, which may leak into the ecosystem.