Phenolic Profiles of Different Apricot Varieties Grown in Spain: Discrimination Among Cultivars During the Harvest Season

Abstract

Apricot is one of the most important Mediterranean fruits with high diversity and fruit quality properties, being an excellent raw material for polyphenol compounds. This study aimed to determine the anthocyanin, quercetin glycoside and phenolic acid contents in new apricot genotypes from the breeding program at the Instituto Valenciano de Investigaciones Agrarias, confirming the potential of the ‘Goldrich’ cultivar to be a parental donor for increasing the antioxidant content, which would, in turn, enhance fruit quality. Phenolic composition of the apricot accessions is strongly genotype-dependent, with the concentrations of overall total phenolic compounds ranging from 770 to 260 mg 100 g⁻¹ DW, reflecting significant genetic diversity. ‘Goldrich’ contributed to the polyphenol content; however, its influence varied across derived varieties, with ‘GG9310’ and ‘GG979’ enhancing the shikimic acid pathway and accumulating high levels of total phenolics. In contrast, ‘Mitger’ and ‘HG9850’ stood out for high anthocyanin synthesis, despite their lower levels of flavonols and phenolic acids. The predominant anthocyanin was cyanidin-3-O-rutinoside, followed by cyanidin-3-O-glucoside and peonidin-3-O-rutinoside in smaller amounts. Other phenolics were rutin and quercetin-3-O-glucuronide, as well as neochlorogenic and chlorogenic acids. The PCA model was applied to all data to identify the most attractive cultivars, and chromatographic analysis was performed in a short time using Ultra-High-Performance Liquid Chromatography (UHPLC) with diode array and mass spectrometric detection. Apricot peel is an excellent source of nutraceutical compounds with a chemical composition strongly determined by the cultivar. Results can help establish authenticity markers for apricot cultivars.

1. Introduction

Apricot (Prunus armeniaca L.) belongs to the Rosaceae family and originates from China, although it has highly adapted to Mediterranean conditions. It is one of the most important Mediterranean fruits, offering a range of phytochemicals that contribute significantly to its significant health benefits, high nutritional value and good sensory appearance [1,2,3,4]. Apricot and other stone fruits, such as peach, nectarines or plumbs, are appreciated due to their unique aesthetic and organoleptic qualities. Traditionally fruit quality attributes are typically assessed based on appearance, sugars and acids [5]. Organic acids and sugars have an important role on apricot taste and flavor compound accumulation patterns, and concentrations differ between species and even cultivars [6,7,8]. Apricot fruit exhibits a wide range of variability in size, shape and color, depending on the cultivar [1], and despite its wide geographical spread, each region usually grows locally adapted apricot cultivars because this species has very specific ecological requirements [7]. Metabolomic profiling can provide valuable insights into the biochemical pathways underlying apricot quality traits, aiding in the selection of cultivars with desirable characteristics [9]. The literature reports appreciable amounts of phenolic compounds in apricot fruit, which enhance their value as functional foods [1]. These include flavonoids with diverse chemical structures, particularly flavonols and anthocyanins (notably in redder varieties), as well as non-flavonoid compounds such as neochlorogenic acid [1,2]. The levels of these compounds vary greatly depending on the cultivar and on fruit parts (peel and flesh), and as a general rule, the accumulation of phenolic compounds in fruits is far greater in the outer tissues than in the inner tissues [4,10].

All of them are interrelated through the shikimate pathway (Figure 1) [11,12]. The shikimate pathway is a crucial metabolic route in plants that provides the foundation for synthesizing various secondary metabolites, including phenolic acids and flavonoids. These compounds play vital roles in plant stress responses, pigmentation and health, while also serving as key antioxidants with significant applications in agriculture and human nutrition [11,12,13,14,15]. Phenolic acids are among the primary derivatives of the phenylpropanoid pathway, which is initiated by the deamination of phenylalanine (a product of the shikimate pathway) through the action of phenylalanine ammonia-lyase (PAL). This step leads to the production of cinnamic acid, 4-coumaric acid and, next, 4-coumaroyl-CoA, which is further modified to form phenolic acids such as chlorogenic acid and neochlorogenic acid. These compounds contribute to cell wall integrity, protect against UV radiation and enhance pathogen resistance, making them integral to plant survival under stress conditions [11,12,13,14,15]. Compound 4-coumaroyl-CoA plays a crucial role in the biosynthesis of flavonoids. The condensation reaction between 4-coumaroyl-CoA with three molecules of 3-malonyl-CoA, under the action of the enzyme chalcone-synthase (CHS), yields the production of the chalcone skeleton, initiating the flavonoid pathway that will produce the different classes of flavonoids, including flavanones, dihydroflavonols, flavonols and anthocyanins, depending on the degree of nucleous oxidation, saturation level and the place of substituent insertion [11,12]. Flavonols, in particular, like quercetin and rutin, are known for their role in scavenging reactive oxygen species (ROS), which protects plants from the oxidative damage caused by environmental stresses such as drought and UV exposure [12,13]. Anthocyanins, another class of flavonoids, are pigments responsible for red, purple, and blue hues in plants, aiding in pollinator attraction and providing strong antioxidant properties. These pathways are highly interconnected, with phenylalanine serving as a critical precursor. The allocation of metabolic flux among phenolic acids, flavonols and anthocyanins depends on environmental cues and plant developmental stages. Their production is often upregulated under stress, reflecting their protective role in mitigating damage from environmental challenges. These processes are tightly regulated by transcription factors such as MYB and WRKY, which fine-tune gene expression to optimize metabolic responses [11,12,13,14].

It has been have demonstrated that the phenolic compounds play essential roles in biological processes and responses to environmental factors in plants, exhibiting a wide range of health benefits, such as free-radical-scavenging properties, the protection and regeneration of other dietary antioxidants and the chelation of pro-oxidant metals [4,16,17,18,19]. Their antioxidant properties have been linked to additional health benefits, including anticancer activity, the prevention of cardiovascular diseases and antiviral effects [20]. These factors have driven growing interest in polyphenols concerning fruit quality and human diets, particularly due to their antioxidant effects. However, while flavonoid metabolites and related transcription factors in apricots have been studied, the molecular mechanisms of flavonoid accumulation and biosynthesis remain unclear [21,22,23].

Numerous studies have demonstrated the large variability in the bioactive compounds in apricots depending on the cultivar and geographical origin. For years, the Valencian Institute for Agricultural Research (IVIA) in Moncada (Valencia, Spain) has conducted a breeding program aimed at developing new apricot genotypes resistant to plum pox virus (PPV), the most important disease affecting Prunus species worldwide [24]. PPV is among the five most dangerous viral diseases of fruit, and its economic impact includes reduced yields and diminished fruit quality, which lower the commercial value of production [25]. Since its first detection in Spain in 1984, PPV has caused extensive fruit losses leading to the removal of over 1.5 million trees [26]. As a result of the IVIA’s apricot breeding program, numerous hybrids have been produced [24,26]. Among these, new cultivars have been selected for commercial production due to their great interest and good agronomic performance. Badenes et al. [24] reported that among the PPV-resistant cultivars, ‘Goldrich’ was the best adapted to Mediterranean conditions. This variety has been used as the main donor of resistance in the IVIA breeding program, showing that ‘Goldrich’ contributed significantly to the content of flavonols and phenolic acids in the studied accessions, suggesting its suitability for the breeding program [7,17,18]. However, these studies did not evaluate the anthocyanin content.

Polyphenols, especially anthocyanins, play a crucial role in various plant mechanisms and are increasingly valued in human nutrition; these compounds are key indicators of fruit quality. Nonetheless, introducing PPV resistance into apricots may affect the adaptability and fruit quality of the resulting cultivars [17]. Given this context, our study focuses on assessing the anthocyanin content in new apricot genotypes, confirming the potential of the ‘Goldrich’ cultivar as a parental donor for increasing the antioxidant content through breeding, which would, in turn, enhance fruit quality.

This study aimed to quantify the levels of anthocyanins, quercetin glycosides and phenolic acids in novel apricot genotypes developed through the breeding program at the Instituto Valenciano de Investigaciones Agrarias. The findings confirm the potential of the ‘Goldrich’ cultivar to be a valuable parental source for enhancing the antioxidant content, thereby contributing to improved fruit quality. A rapid laboratory-scale extraction of phenolics was conducted using ultrasound-assisted methods, and the chromatographic analysis was performed in a short time using Ultra-High-Performance Liquid Chromatography (UHPLC) coupled with diode-array and electrospray ionization mass detection. Twelve selected PPV-resistant apricot cultivars, mainly from the IVIA’s breeding program, were analyzed. From the results obtained in previous years [17], now the analysis was focused on the peel, since it is the main contributor to the polyphenols of the fruit. Taking into account that fresh and dried apricots are consumed with the peel, this is the part of the fruit most important for assessing the antioxidant capacity.

2. Materials and Methods

2.1. Plant Materials and Sampling

The plant material consisted in a set of cultivars and selections from the IVIA breeding program, which focuses on developing new varieties resistant to PPV (plum pox virus) [24,26]. The research included two Mediterranean cultivars (‘Canino’ and ‘Mitger’), one North American variety (‘Goldrich’), and nine hybrids (‘Dama rosa’, ‘Dama taronja’, ‘GG9310’, ‘GG979’, ‘GP9817’, ‘HG9821’, ‘HG9850’, ‘HM964’ and ‘SEOP934’) from the IVIA’s apricot breeding program (

Table 1. Plant material during 2023 season of apricot cultivars.

Genotype	Pedigree	Origin	Peel Color 1
Canino	Unknown	Spain	yellow green to orange
Dama rosa	Goldrich × Ginesta	IVIA	yellow green to orange
Dama taronja GG9310	Goldrich × Katy	IVIA	yellow green to orange
	Goldrich × Ginesta	IVIA	yellow green to orange
GG979	Goldrich × Ginesta	IVIA	yellowish to orange
Goldrich	Goldrich Sunglo × Perfection	USA	orange
GP9817	Goldrich × Palau	IVIA	yellow green
HG9821	Harcot × Ginesta	IVIA	yellow green to orange
HG9850	Harcot × Ginesta	IVIA	yellow green to orange
HM964	Harcot × Mitger	IVIA	yellow green to orange
Mitger	Unknown	Spain	yellowish
SEOP934	Seo × Palau	IVIA	yellowish to orange

¹ Gomez-Martínez et al. [7].

). ‘Goldrich’, used as the main donor of resistance to PPV at the breeding program, is one of the parents in most of the resistant hybrids obtained. ‘Canino’ and ‘Mitger’ are two autochthonous varieties used for introgression of the adaptability to Mediterranean conditions [17,18]. The trees are maintained at the experimental orchand from the IVIA germplasm collection located in Moncada (latitude 37°45′31.5″ N., longitude 1°01′35.1″ W.) (Spain).

Apricot fruits were harvested randomly at commercial maturity, specifically at the “ready-to-eat” ripening stage, in early June 2023 (Table 1). After each harvest time, fruits were transported to the IVIA where physico-chemical and biocomponent analyses were carried out. For each fruit, the peel was separated with a peeler. Samples were frozen with liquid nitrogen, freeze-drying and crushing and kept at −80 °C until processing. Tissue homogenization was carried out using a Polytrom 3100 (Kinematica AG, Luzern, Switzerland) and a vortex. Samples consisted of a mix of the peel from 5 fruits per genotype in a similar way, as was performed with the five successive harvest’s seasons, and for which results were previously reported by Gómez-Martínez et al. [7,17,18].

2.2. Extraction and UHPLC Analysis

Phenolics were extracted according to the procedure described by Orazem et al. [27] with slight modifications. Briefly, 100 mg of the sample, dried and powdered, was dissolved in 0.5 mL of an extraction solution consisting of methanol containing 3% formic acid and 0.5% of 2,6-di-tert-butyl-4-methylphenol (BHT), shaken and extracted under ultrasound treatment for 1 h, at 20 °C (ultrasound cleaner LBX ULTR, Labbox Labware S.L., Barcelona, Spain). Resulting mixtures were centrifuged at 4 °C for 30 min at 12.000 rpm (Eppendorf 5425, Eppendorf, Hamburg, Germany), the precipitate was discarded and the supernatants were filtered through a 0.45 μm nylon, passed to the chromatography vial and stored at −20 °C until UHPLC analysis.

Individual phenolic compounds were analyzed using an Ultra-High-Performance Liquid Chromatography (UHPLC) system equipped with Vanquish separation modules, a diode array detector, an autosampler and pump modules and a column compartment, coupled to a TSQ Fortis Triple-Quadrupole Mass Spectrometer (UHPLC-QqQ-MS, Thermo Fisher Scientific, Madrid, Spain), using an Acquity Premier HSS T3 C18 (100 × 2.1 mm, 1.8 μm, Waters) column. The column temperature was maintained at 35 °C, with autosampler at 10 °C, and the injection volume was 1 μL. The mobile phase consisted of acetonitrile (A) and water with 5% of formic acid (B) in a linear gradient of 10 min at 0.3 mL min⁻¹, starting with 10% A, ramped to 100% A at 4 min, retuned to 10% A at 5 min and then held at 10% A until 10 min. Chromatograms were recorded from 270 to 550 nm absorbance, and mass analysis was performed in a full scan from 100 to 850 m/z, with an electrospray ionization source in positive and negative modes. Chromeleon, 7.3 chromatography data system software was used for data treatment.

Compounds were identified by comparing their retention times, UV–Vis spectra and mass spectral data with authentic standards and quantified using an external calibration curve with them. Three replicates per sample were analyzed, and the results were expressed as mg 100 g⁻¹ DW. Anthocyanin concentrations were determined using an external calibration curve with cyanidin-3-O-glucoside (Cy-3-O-glu, RT: 2.90 min, [MH]⁺ 449 m/z) and cyanidin-3-O-rutinoside (Cy-3-O-rut, RT: 3.05 min, [MH]⁺ 595 m/z) standards. Due to the unavailability of a peonidin-3-O-rutinoside standard, this compound was tentatively identified based on its retention times, absorption spectrum characteristics and mass spectrum data (Pn-3-O-rut, RT: 3.50 min, [MH]⁺ 609 m/z), with data described in the literature [16]; a calibration curve was constructed using Cy-3-O-rut as an external standard, and Pn-3-O-rut was quantified as Cy-3-O-rut equivalents. Phenolic acid and flavonol contents were determined using an external calibration curve with neochlorogenic acid (RT: 2.02 min, [M-H]⁻ 353 m/z), chlorogenic acid (RT: 3.17 min, [M-H]⁻ 353 m/z), rutin (RT: 3.71 min, [MH]⁺ 611 m/z) and quercetin-3-O-glucuronide (Querc-3-O-glur, RT: 3.81 min, [MH]⁺ 479 m/z) standards.

The calibration range was adjusted based on the expected phenolic concentrations in the samples. Four concentrations were prepared to carry out the external calibration curve: 0.1; 0.05; 0.02; and 0.01 mg mL⁻¹. Stock solutions of each compound at a concentration of 0.5 mg mL⁻¹ were prepared using ethanol for anthocyanins, dimethyl sulfoxide-methanol (1:1) for rutin and Querc-3-O-glur and methanol for neochlorogenic and chlorogenic acids. Linearity was assessed via linear regression analysis, with correlation coefficients (R²) of 0.990 or higher, demonstrating good linearity. Furthermore, low relative deviation percentages indicated satisfactory precision in the analyses conducted. All standards and samples were filled into HPLC brown glass vials and sealed properly to protect the solutions from light and evaporation. Standards were run daily with samples for validation. Anthocyanin chlorides and phenolic acid standards were purchased from Cymit química S.L. (Barcelona, Spain). Rutin and Querc-3-O-glur were obtained from Extrasynthese (Genay, France). All the solvents used were of UHPLC-MS grade and purchased from Scharlab S.L. (Barcelona, Spain).

2.3. Statistical Analysis

All statistical analyses, including Principal Component Analysis (PCA), were performed using Statgraphics Centurion (version 18. Manugistics Inc., Rockville, MD, USA). Prior to PCA, the data were standardized (mean-centered and scaled to unit variance) to account for differences in the scale of phenolic compound concentrations. All the data were subjected to an analysis of variance, and means were compared by performing an LSD test at p ≤ 0.05. For Principal Component Analysis (PCA), the complete dataset of all replicates was considered.

3. Results and Discussion

3.1. The Profile of Phenolic Compounds

Apricot fruit, demanded for its high organoleptic quality, is also valued for its high content of phenolic compounds, which contribute to its nutritional properties and potential health benefits. Phenolic compounds are crucial secondary metabolites in plants for a wide range of vital responses and are considered one of the most important antioxidants in fresh fruit. In apricot, numerous phenolic metabolites have been described, with several studies reporting notably higher levels of phenolic acids and flavonols in the apricot peel compared to the pulp. Furthermore, significant differences in concentrations have been observed among cultivars; therefore, it can be suggested to the consumers that, regarding the health-promoting properties of fruit, unpeeled fruits should be eaten or used for processing [4,10,28].

The phenolic composition of apricots has been widely determined using different extraction methods, and several studies have evaluated how factors such as the pH and solvent type influence the extraction efficiency of polyphenols, particularly anthocyanins [29]. For example, Iglesias-Carres et al. [30] optimized an extraction protocol using methanol and formic acid to accurately characterize the phenolic profile of apricots. In previous research, we used a methanol: dimethysulfoxide mixture to extract phenolic compounds from hybrids developed in the IVIA breeding program; however, under those extraction conditions, anthocyanins in the apricot peels were not detected in sufficient quantities [17,18]. In the present study, we employed an acidic methanol solution for extraction. This method involved a rapid ultrasound-assisted extraction process on a laboratory scale, followed by chromatographic analysis using reversed-phase UHPLC in a short time frame to simultaneously determine three classes of phenolic metabolites: anthocyanins, flavonols and phenolic acids. These conditions enabled the detection and quantification of anthocyanins without altering the phenolic profile previously reported by Gómez-Martínez et al. [17,18], although some differences in phenolic concentrations were noted, likely due to variations in the harvest season dates of the samples.

Phenolic metabolite separation was conducted using reversed-phase UHPLC, and identification and classification of the compounds were based on the UV–Vis absorption spectra acquired with a diode array detector. These data, combined with mass spectra analysis and literature references or comparisons with standard compounds, provided the identification of peaks in the UHPLC chromatograms. Overall, nine phenolic compounds were detected in the apricot peels (see

Table 2. Anthocyanin, flavonol and phenolic acid contents (mg 100 g⁻¹ DW) in peels of apricot varieties *.

Genotype	Anthocyanins			Flavonols				Phenolic Acids
	Cy-3-O-glu 1	Cy-3-O-rut 1	Pn-3-O-glu 2	Rutin 1	Querc-3-O-g 1	Flavonol-1 3	Flavonol-2 3	Neochlorog 1	Chlorog 1
Canino	nd	0.46 ± 0.6	0.10 ± 0.0	267.48 ± 7.9	26.79 ± 1.3	7.05 ± 0.4	22.33 ± 1.3	104.36 ± 4.1	70.69 ± 4.5
Dama rosa	1.95 ± 1.1	6.60 ± 5.9	nd	146.96 ± 10.6	20.44 ± 1.6	5.21 ± 0.6	12.10 ± 0.9	88.44 ± 6.6	89.51 ± 3.8
Dama taronja	0.69 ± 1.0	2.46 ± 2.0	0.88 ± 1.0	210.75 ± 12.9	22.50 ± 0.7	6.03 ± 0.1	29.00 ± 2.1	139.23 ± 6.5	84.10 ± 1.7
GG9310	1.22 ± 2.5	5.50 ± 4.9	0.46 ± 0.6	275.75 ± 37.5	15.27 ± 7.8	0.89 ± 0.5	15.02 ± 2.3	328.24 ± 25.2	132.10 ± 11.3
GG979	5.68 ± 2.0	21.99 ± 11.9	nd	294.93 ± 22.4	21.10 ± 2.6	2.23 ± 0.6	22.39 ± 3.6	168.37 ± 8.9	152.41 ± 3.5
Goldrich	0.29 ± 0.0	2.16 ± 1.7	0.39 ± 0.0	230.14 ± 3.7	12.27 ± 0.6	3.02 ± 0.7	12.79 ± 0. 9	119.12 ± 1.8	113.32 ± 4.7
GP9817	1.36 ± 1.5	5.70 ± 5.7	nd	138.70 ± 10.3	17.18 ± 1.6	1.79 ± 0.3	8.89 ± 0.9	86.81 ± 7.1	97.18 ± 8.2
HG9821	1.03 ± 1.6	5.70 ± 2.6	nd	137.18 ± 6.5	16.75 ± 2.4	1.99 ± 0.8	6.17 ± 0.9	118.25 ± 6.8	109.34 ± 13.3
HG9850	4.00 ± 0.9	14.30 ± 4.1	0.95 ± 0.6	113.44 ± 3.8	23.22 ± 1.3	1.31 ± 0.1	8.01 ± 0.3	51.83 ± 1.7	63.61 ± 3.9
HM964	2.86 ± 0.1	12.63 ± 5.9	nd	159.76 ± 4.1	18.08 ± 0.9	2.83 ± 0.2	7.83 ± 0.1	116.14 ± 3.9	110.35 ± 6.3
Mitger	8.56 ± 1.9	18.75 ± 4.9	0.69 ± 0.1	101.97 ± 2.9	21.15 ± 0.6	1.38 ± 0.1	4.42 ± 0.3	58.06 ± 0.9	47.56 ± 5.3
SEOP934	7.53 ± 2.9	23.31 ± 5.9	4.81 ± 4.9	167.61 ± 14.6	23.31 ± 0.9	26.47 ± 0.8	9.95 ± 1.9	128.53 ± 3.8	130.81 ± 4.8
p-value	0.0000 **	0.0000 **	0.0000 **	0.0000 **	0.0000 **	0.0000 **	0.0000 **	0.0000 **	0.0000 **

* The results are expressed as the means (n = 3) ± standard deviation; nd: not detected. ** p-values of the compounds measured onto twelve different cultivars. ¹ Identified using authentic standards; ² quantified as Cy-3-O-rut equivalents; ³ quantified as rutin equivalents. Cy-3-O-glu, cyanidin-3-O-glucoside; Cy-3-O-rut, cyanidin-3-O-rutinoside; Pn-3-O-rut, peonidin-3-O-rutinoside; Querc-3-O-g, quercetin-3-O-glucuronide; Neochlorog, neochlorogenic acid; Chlorog, chlorogenic acid.

). The phenolic analysis showed a similar profile across all cultivars, but a wide range of variability was found, and significant differences were detected in their content. This variability can likely be attributed to genetic differences in the evaluated samples, as the apricot varieties were obtained through a breeding program that used apricot parents from diverse genetic origins. Figure 2 represents the overall total phenolic content found in the peels and shows a wide range of variability among the apricot varieties. Table 2 provides a detailed summary of the concentrations of different phenolic types found in the studied varieties.

3.1.1. Anthocyanin Content

The identification of anthocyanins is complicated due to the wide variety of these compounds found in nature, standards not being readily available for most of them and differences in experimental conditions, which can make comparisons of anthocyanins in different foods more difficult [31]. The identification and peak assignment of anthocyanins with UHPL is generally based on comparisons of their retention times and mass spectral data with those of available standards and published data [31]. The anthocyanins play an important role in peel color variation and are responsible for their distinctive coloration especially in the redder varieties. Although apricot fruits are rich in phenolic compounds including anthocyanins, studies on anthocyanins in apricot are rare, while they have received the most attention in fruits of other Prunus species [16,31,32,33]. In fruits such as sweet cherry, peach and nectarine, the major anthocyanins are typically Cy-3-O-glu or Cy-3-O-rut depending on the fruit considered, along with minor components like pelargonidin or peonidin glycosides [31]. Similarly, in some red-skinned apricots, Bureau et al. [15] reported Cy-3-O-rut and Cy-3-O-glu as the dominant anthocyanins, previously described in apricot [28,32], along with a minor compound, Pn-3-O-rut.

In this study, quantitative differences in anthocyanin concentrations were observed among the 12 apricot studied cultivars (Table 2). The UHPLC chromatogram of the methanol extracts from apricot peels recorded at 550 nm showed three anthocyanin molecules. Two peaks were identified as Cy-3-O-glu and Cy-3-O-rut based on the retention times, UV–Vis spectra and mass spectral data, compared with the authentic standards, while a third peak was identified tentatively as Pn-3-O-rut. All of these anthocyanins are characterized by their orange–red color, with a λ max in the visible spectrum at around 515–520 nm [16,28]. Consistent with other reports [16,33], out of three anthocyanins determined here, the major compound was Cy-3-O-rut, present in all varieties studied, and the concentration results revealed significant differences among accessions. Regarding Cy-3-O-rut, ‘SEOP934’ (‘Seo’ × ‘Palau’) was the cultivar with the highest content (23.31 mg 100 g⁻¹ DW), followed by ‘GG979’ (‘Goldrich’ × ‘Ginesta’) and ‘Mitger’ (Unknown) consecutively (Table 2), with significant differences among these three cultivars. Conversely, ‘Canino’ had the lowest content, close to 0.50 mg 100 g⁻¹ DW (Table 2). These results align with reported values for red apricot cultivars [16]. Similarly, Cy-3-O-glu, as precursor of Cy-3-O-rut, exhibited a similar tendency. In this case, ‘SEOP934’, ‘GG979’ and ‘Mitger’ were also the cultivars with the highest anthocyanin content with little variations, since ‘Migter’ was the cultivar with the highest levels. The contents in these cultivars ranged between and 5.68 and 8.56 mg 100 g⁻¹ DW. The lowest concentration was also exhibited by ‘Canino’, notably lacking detectable Cy-3-O-glu. These results confirm the high dependence between these two compounds also in apricot cultivars. Finally, Pn-3-O-rut was identified only in trace amounts and was not presented in all varieties. Notwithstanding, it was also the ‘SEOP934’ cultivar that had the highest amount.

Apricot species present large variability in peel color, ranging from white and orange to a strong red blush. The relationship between anthocyanin levels and both external and internal fruit coloration has been previously reported, with anthocyanin concentrations strongly influenced by genetic factors [16,32]. In this same sense, considering the total content of anthocyanins (Figure 2), it has been found that ‘SEOP94’ exhibited the highest total anthocyanin concentration (35.65 mg 100 g⁻¹), followed by ‘Mitger’ (around 28.00 mg 100 g⁻¹) and ‘GG979’ (around 27.67 mg 100 g⁻¹). Despite this, between these three cultivars, the parental was not coincident in any case, and all of these varieties displayed peel colors ranging from yellowish to orange according to Gómez-Martínez et al. [7] and also showed a dark to medium intensity over a color from pink to purple. Moreover, the inconsistent effect of the parental can also be appreciated in the cultivars where the parentals are the same: ‘GG9310’/‘GG979’/‘Dama rosa’ (‘Goldrich’ × ‘Ginesta’) and ‘HG9850’/’HG9821’ (‘Harcot’ × ‘Ginesta’). Between each group of cultivars, there were always significant differences between the anthocyanins determined. On the other hand, the relevance of combining the parental ‘Goldrich’ with ‘Ginesta’ (‘Dama rosa’, ‘GG9310’, ‘GG979’) can be pointed out, since all these combinations enhance the concentrations of anthocyanins in the peel of apricot. Conversely, the remaining varieties with lower anthocyanin levels were predominantly yellow–green in color, except for ‘Goldrich,’ which exhibited an orange skin (Table 1). Interestingly, even small anthocyanin amounts significantly influence the apricot peel coloration. This highlights the importance of these compounds not only in defining fruit quality but also in enhancing the aesthetic and nutritional appeal of apricots.

3.1.2. Flavonol and Phenolic Acid Content

All flavonols detected in this study were quercetin derivatives, with rutin (quercetin-3-O-rutinoside) consistently being the most abundant compound across all apricot varieties. ‘GG979’ and ‘GG9310’, both with the parental ‘Goldrich’ × ‘Ginesta’ and ‘Canino’, showed the highest levels of rutin, with values between 267.48 to 294.93 mg 100 g⁻¹ DW (Table 2). The lowest concentration of rutin was found in ‘Mitger’, close to 100 mg 100 g⁻¹ DW, without significant differences with ‘HG9850’. As described in the previous paragraph, ‘Mitger’ showed the opposite trend with respect to the anthocyanin concentration, as it stands out for its high concentration. The same trend, with a less marked degree, is repeated in the ‘HG9850’ variety.

Querc-3-O-glur was the second most abundant flavonol, with concentrations ranging from 12.27 to 26.79 mg 100 g⁻¹ DW. It was found at a much lower concentration than rutin, corroborating that Querc-3-O-glur is the metabolite synthesized prior to rutin synthesis. As it was observed in rutin, ‘Canino’ was the cultivar with the highest concentration of Querc-3-O-glur. Nevertheless, this correlation between these two flavonoids (rutin and Querc-3-O-glur) was not repeated in all cultivars studied. For instance, ‘GG9310’ exhibited, together with ‘Goldrich’, the lowest Querc-3-O-glur, while they exhibited high rutin concentrations in their peel. These flavonol concentration results are consistent with other reports on apricot. Additionally, two compounds (flavonol-1 at RT 3.90 min, and flavonol-2 at RT 4.05 min) with UV–Vis absorption bands characteristics of the flavonol type [20] were detected but not fully identified and were tentatively quantified as rutin equivalents. Flavonol-1 concentrations ranged from 0.89 to 26.47 mg 100 g⁻¹ DW, while flavonol-2 ranged between 4.42 to 29.00 mg 100 mg⁻¹ DW.

Among the phenolic acids, two major compounds were identified as neochlorogenic acid and chlorogenic acid. Neochlorogenic acid was the most abundant, with concentrations ranging from 51.83 to 328.24 mg 100 g⁻¹ DW, while chlorogenic acid ranged from 47.56 to 152.41 mg 100 g⁻¹ DW (Table 2). These results are consistent with previous studies, and the relation between this pair of compounds were repetitive in the main cultivars studied [4,17,18,28]. Similarly to that observed in the flavonol profile, the highest concentrations were shown in ‘GG9310’ and ‘GG979’, and the lowest amount was exhibited by the peel of ‘Mitger’ and ‘HG9850’.

The overall total phenolic compound content varied widely among cultivars, and results from this study showed that ‘Goldrich’ is a good contributor to increasing polyphenolic compounds compared to the other cultivars studied. The cultivars ‘GG9310’and ‘GG979’ exhibited the highest amounts of overall total phenolic compound contents, close to 700 mg 100 g⁻¹ DW of peel tissue (774.45 and 689.81 mg 100 g⁻¹ DW, respectively). This fact corroborates that a cross of the parentals ‘Goldrich’ with ‘Ginesta’ can enhance the shikimic acid pathway and increase the phenolic profile of apricot fruits, dominated by rutin, neochlorogenic and chlorogenic acids. But it is not repeated in all cases, as it can be observed with the ‘Dama rosa’ cultivar. On the other hand, Mitger’ and ‘HG9850’, two unrelated cultivars with ‘Goldrich’ as a donor, displayed the lowest levels, 280.67 and 262.54 mg 100 g⁻¹ DW, respectively (Figure 2). Interestingly, aside from ‘GG979,’ no strong correlation was observed between a high total phenolic content and high anthocyanin levels. This suggests that while both phenolic acids and flavonols contribute significantly to the total phenolic profile, their abundance does not necessarily predict the anthocyanin content.

3.2. Principal Component Analysis

Principal Component Analysis (PCA) was applied to evaluate the interrelationships among the 12 apricot cultivars and their phenolic compound profiles, including anthocyanins, flavonols and phenolic acids, as detailed in Table 2. The PCA explained 82.61% of the total variance through the first three principal components (Figure 3): PC1 (36.95%), PC2 (27.96%) and PC3 (17.70%). Figure 3 illustrates these groupings. In the PCA biplot (Figure 3), the loading vectors have been scaled to match the score space for visual clarity. This graphical scaling does not affect the interpretation of variable contributions, which are reported with their original values in Supplementary Table S1.

PC1 separated anthocyanins (Cy-3-O-rut, Cy-3-O-glu and Pn-3-O-rut) from other phenolic compounds, emphasizing their contribution to variability among the cultivars. However, it can be appreciated that these compounds were also related to Querc-3-O-glur and flavonol-1. This is because quercetin, as it can be observed in Figure 1, is involved both in flavonol and anthocyanin biosynthesis. Moreover, the approximation between rutin and flavonol-2 could indicate that this unknown flavonol is related to rutin, and it could be tentatively one of the final compounds synthesized through rutin metabolism. Otherwise, PC2 distinguished high-overall-total-phenolic-content varieties like ‘GG9310’ and ‘GG979’ from low-content varieties like ‘Mitger’ and ‘HG9850’ (see Figure 3a). As shown in Figure 1, anthocyanin synthesis represents the last step of the shikimic acid metabolic pathway, from which the main metabolic compounds predominant in apricot varieties are generated. Different patterns of behavior were identified in the varieties studied, corroborating the PCA distribution. In particular, the varieties ‘Mitger’ and ‘HG9850’ stand out for having, compared to the rest of the varieties analyzed, a higher concentration of anthocyanins and a lower concentration of other metabolic compounds compared with the other cultivars studied. This behavior suggests that these varieties have a higher capacity to synthesize anthocyanins. These results are in agreement with the previous study by Gómez-Martínez et al. 2021 [17], in which it was observed that these varieties showed a higher gene expression of ParPAL2 and ParDFR compared to the other nine varieties, and a higher expression of ParDFR and ParPAL2 was associated with accessions showing a reddish blush on the skin of the fruit.

Regarding varieties ‘GG9310’ and ‘GG979’, these do not stand out for having higher expression of the aforementioned genes [17]. These two varieties, both originating from the cross between ‘Goldrich’ × ‘Ginesta’ parents, are the ones that show a higher concentration of flavonols and phenolic acids and, in addition, a representative concentration of anthocyanins. In fact, ‘GG979’ is one of the varieties with the highest concentration of anthocyanins. These varieties are the ones with the most enhanced shikimic acid pathway, resulting in a variety with a high concentration of secondary metabolic compounds. ‘SEOP934’ apricot was the cultivar with a more different secondary metabolomic profile of the 12 cultivars studied since it stands out for being the variety with a high concentration of anthocyanins, Querc-3-O-glur and flavonol-1 but a low content of the rest of the secondary metabolites detected. In fact, aesthetically, it is the variety with the greatest differences with respect to the rest.

On the other hand, PC3 focused on flavonols and their distinction from other phenolic compounds. A high loading of flavonols (rutin, Querc-3-O-glur, flavonol-1 and flavonol-2) was observed on PC3 (see Figure 3b), providing additional separation based on the flavonol content against phenolic acids and anthocyanins, demonstrating their unique patterns of distribution among the apricot genotypes. The separation of anthocyanins in PC1 and flavonols in PC3 emphasizes their potential as biochemical markers for cultivar differentiation.

4. Conclusions

In summary, the phenolic composition among the set of apricot accessions analyzed is strongly genotype-dependent, confirming the genetic diversity among cultivars. The cultivar ‘Goldrich’ used as a donor of resistance to the PPV diseases at the IVIA’s breeding program, despite it exhibiting a high contribution to the polyphenol content, did not provide the same pattern of behavior in all the varieties of which it is the parental. The applied PCA highlighted the contribution of the analyzed compounds to the variability in the apricot cultivar composition, as well as the specific compounds that could be used as authenticity markers. According to our study, apricot peel was identified as an excellent source of nutraceutical compounds, emphasizing its potential for health-focused applications. The data provided can support the selection of specific cultivars with desirable phenolic profiles for use in breeding programs as plant material for future crosses. In addition, phenolic profiles and PCA results can help establish authenticity markers for apricot cultivars.