Phenolic Constituents, Photoprotective Effect, and Antioxidant Capacities of Achillea ligustica All

The present investigation was performed to figure out the chemical constituents and biological potential of polar extracts (AcOEt and BuOH) from Achillea ligustica, a medicinal species of the Asteraceae family. Liquid chromatography quadrupole time-of-flight mass spectrometry (LC-Q-TOF-MS) was utilized to conduct a preliminary analysis of the phytochemical profiles of the AcOEt and BuOH extracts. The analysis revealed the existence of twenty compounds in the AcOEt extract and twenty-two in the BuOH extract, classified into various types of secondary metabolites. Subsequently, the exudate from the plant yielded five flavonoids, including two 6-methoxyflavonols identified for the first time in this genus. The isolation of compounds from AcOEt and BuOH extracts was achieved through the combined use of column chromatography (silica gel and Sephadex LH-20) and preparative TLC chromatography. The structures have been elucidated using 1D and 2D NMR spectroscopy, alongside comparisons with research data. Our study measured the total phenolic and flavonoid contents and carried out a comprehensive range of antioxidant tests using DPPH, GOR, CUPRAC, reducing power, and O-phenanthroline assays. Both extracts exhibited considerable antioxidant potential and contained high levels of phenolic and flavonoid compounds. The photoprotective effect of the AcOEt and BuOH extracts was evaluated in vitro by measuring the sun protection factor. Both extracts exhibited a high capacity for UV radiation absorption. Consequently, this plant presents an intriguing prospect for future research focused on incorporating it into photoprotective cosmetic products and pharmaceutical formulations.


Introduction
The Achillea genus, belonging to the Asteraceae family, includes around 120 species predominantly found in Central Southwestern Asia and Southeastern Europe, with a distribution that extends across North America and Eurasia [1,2].Five species have been identified within the Algerian flora, including Achillea ligustica All.[3]. A. ligustica is a plant with an aromatic scent and bitter taste; it can reach 100 cm in height.The species grows spontaneously in the Mediterranean region; in Algeria, it is called Benkisson [1,3].
Sunlight exposure is crucial for human health in various ways, such as contributing to melanin production and aiding in the treatment of skin diseases such as psoriasis and vitiligo [22].Nevertheless, extended exposure to solar ultraviolet (UV) radiation can lead to increased oxidative stress in skin cells, potentially initiating and promoting cancer [23].Using sunscreen helps mitigate the risk of skin cancer associated with solar radiation [22].Additionally, natural substances have been explored as potential sunscreen alternatives due to their ability to absorb UV radiation and their antioxidant properties [23], offering new approaches for preventing and treating UV-induced conditions [24].
Based on its diversity of secondary metabolites and its significant biological and pharmacological potential, the current study intended to define the chemical constituents of polar extracts of A. ligustica aerial parts collected in Algeria.Moreover, the study assessed the antioxidant and photoprotective properties through in vitro assays, along with quantifying the total phenolic and flavonoid contents.

HPLC-Q-TOF-MS
The LC-Q-TOF-MS analysis of A. ligustica unveiled the existence of twenty compounds in the AcOEt extract and twenty-two in the BuOH extract, with retention times ranging from 3.22 to 26.31 min.The molecular formula, m/z, and the retention time (Rt) for each compound are listed in Table 1.

Structure of the Isolated Compounds
The phytochemical investigation of the AcOEt and BuOH extracts obtained from the aerial parts of A. ligustica yielded five flavonoids, in which compounds (3) and (4) were isolated from the Achillea genus for the first time.The compounds' structures were established through 1 H-NMR, 13 C-NMR, COSY, HSQC, and HMBC techniques alongside comparisons with research data.The structures of the isolated compounds are displayed in Figure 1, and the NMR spectrum data are provided in the Supplementary Materials.

Total Phenolic and Flavonoid Contents
The total phenolic and flavonoid contents of the AcOEt and BuOH extracts were measured using the Folin-Ciocalteu and AlCl 3 methods, respectively (Table 2).

Antioxidant and Photoprotective Activities
Five different in vitro methods were utilized to assess the antioxidant potential of the AcOEt and BuOH extracts of A. ligustica, including GOR, DPPH, CUPRAC, reducing power, and O-phenanthroline assays.The findings, presented as IC 50 and A 0.50 values measured through linear regression analysis, are given in Table 3.Furthermore, the photoprotective efficacy of both extracts was examined through the determination of their sun protection factor (SPF) within the UV-B spectrum.The recommendations of the CEC (Commission of European Communities 2006) were used to evaluate the SPF values and their classification (Table 4).

Discussion
A comprehensive examination of the LC-Q-TOF-MS findings reveals that the compounds identified in the AcOEt and BuOH extracts are categorized into five classes: flavonoids, phenolic acids, phenolic aldehydes, dicarboxylic acid, and dihydroxybenzenes.
In this analysis, twelve flavonoids from different subclasses were identified.These included five flavonols, namely rutin, quercetin, hyperoside, rhamnetin, and fisetin; three flavones, namely apigenin, apigenin-7-O-glucoside, and luteolin-7-O-glucoside; and four flavanones, namely naringenin, naringin, hesperidin, and hesperetin.Notably, naringin and hesperidin were only detected in the BuOH extract, while naringenin was only found in the AcOEt extract.Through a comparison with the literature, it was revealed that naringin and hesperetin were previously identified in A. abrotanoides and A. lingulata, respectively [30].Hyperoside and hesperidin were earlier detected in A. kotschyi and A. lycaonica [31], while fisetin and naringenin were found in A. distans [32] and A. vermicularis [33], respectively.These compounds have been found for the first time in A. ligustica.Moreover, this study is the first to our knowledge that reveals the presence of rhamnetin in the Achillea genus.
Additionally, eight phenolic acids, including caffeic acid, quinic acid, chlorogenic acid, protocatechuic acid, rosmarinic acid, syringic acid, p-coumaric acid, and 4-hydroxybenzoic acid, were identified in both extracts, with syringic acid found only in the BuOH extract.All these compounds were previously identified in the Achillea genus.However, the present study reports the first occurrence of syringic acid, protocatechuic acid, p-coumaric acid, and 4-hydroxybenzoic acid in A. ligustica.
Furthermore, phenolic aldehyde (vanillin) and dicarboxylic acid (malic acid), along with dihydroxybenzenes (catechol) were identified for the first time in the A. ligustica species.Previously, vanillin and malic acid had been found in A. coarctata and A. monocephala [34], while catechol was identified in A. millefolium [35].
From the AcOEt and BuOH extracts obtained from A. ligustica aerial parts, five compounds were isolated.NMR spectra analysis disclosed the presence of flavone structures, identifying compound 1 as apigenin and compound 2 as luteolin.Notably, these compounds were previously isolated from A. ligustica [1,10,17].Additionally, three other flavonoids were isolated from the BuOH extract, which were identified as 6-methoxykaempferol-3-Orutinoside 3, 6-methoxykaempferol 4, and luteoline-7-O-β-glucoside 5.The two compounds 3 and 4 are identified for the first time from the Achillea genus, whereas compound 5 is a common compound in A. ligustica [10].
The TPC and TFC analysis revealed that both extracts exhibited significant levels of phenolic and flavonoid compounds with 465.47 ± 1.02 µg GAE/mg and 225.63 ± 0.59 µg EQ/mg for the AcOEt extract and 258.12 ± 1.02 µg GAE/mg and 147.50 ± 2.21 µg EQ/mg for the BuOH extract, respectively.In a previous study conducted on the same plant, the measured TPC of the hydroalcoholic extract was lower than our result [2].Furthermore, our findings were considerably higher than those reported for the species A. fragrantissima [36].
To provide a comprehensive knowledge of the antioxidant activity of the AcOEt and BuOH extracts, five different methods were employed.The results from all assays indicated that both extracts demonstrated potent antioxidant activity, with the AcOEt extract showing greater activity than the BuOH extract (Table 3).Additionally, the AcOEt extract exhibited superior activity compared to the standard BHA, BHT, and α-tocopherol in the GOR, CUPRAC, and reducing power assays, respectively.These results affirm the correlation between the phenolic and flavonoid contents and antioxidant activities [37].The AcOEt and BuOH extracts revealed strong antioxidant capacities when compared to the hydroalcoholic extract of the same plant, as evaluated by the DPPH and reducing power assays [2].Meanwhile, the antioxidant potential measured by the phenanthroline method in the same study yielded results similar to our findings.
Skin damage caused by UV radiation ranks among the most prevalent concerns throughout the world.Research has demonstrated that photoprotective agents, particularly sunscreens, are vital in decreasing the occurrence of skin disorders, such as pigmentation issues and premature aging caused by UV exposure [38].Numerous recent studies have explored natural substances as potential resources for sunscreen due to their capacity to absorb UV radiation and their antioxidant properties [24].In the present study, both examined extracts demonstrated a potent ability to absorb UV light (Table 4), with values higher than those of CSS 1 but lower than those of CSS 2, the standards used for this test.The significant UV absorption of both extracts is due to their richness in phenolic and flavonoid compounds.This conclusion is supported by research which recognized that phenolic compounds are potent sun filters, offering substantial photoprotective benefits [39].As a consequence, the AcOEt and BuOH extracts of A. ligustica can be utilized as sun protection agents in sunscreen products within the cosmetic industry or pharmaceutical formulations.The photoprotective properties of A. ligustica have not been studied before.Therefore, the findings of this research provide a novel contribution to existing research.

Plant Material
A. ligustica aerial parts were harvested during the flowering period (May 2018) at Mila in Northeast Algeria (36 • 34 N, 5 • 57 E).The plant was authenticated by Pr.Hocine Laouar (University of Sétif 1, Sétif, Algeria).The collected species was dried at room temperature far from light.A voucher specimen was kept in the PHYSYNOR laboratory (Chemistry department, University of Mentouri Constantine 1) under N • AL012.

Extraction and Isolation
The powdered aerial parts (500 g) of A. ligustica were defatted with cyclohexane solvent for 48 h.After filtration, the residue was macerated with Ethanol-H 2 O (7:3) solution for 48 h three times.The obtained extracts were combined and concentrated under reduced pressure until dry to produce a hydroalcoholic crude extract, which was then dissolved in distilled water.After filtration, the resulting aqueous phase was extracted sequentially with chloroform, ethyl acetate, and 1-butanol.These organic layers were evaporated until dry, yielding the corresponding extracts: 6.03 g of CHCl 3 , 3.99 g of AcOEt, and 11.68 g of BuOH.

HPLC-Q-TOF-MS Analysis
The MS analyses of AcOEt and BuOH extracts were performed by a 1290 infinity II liquid chromatography system (Agilent Technologies) equipped with a binary pump (model G7120A), an autosampler, a source ionization by electrospray (ESI, Dual Agilent Jet Stream model), a diode array detector (DAD), and a quadrupole time-of-flight mass spectrometry analyzer (Q-TOF, model 6546).A column (2.1 × 100 mm, 1.8 µm) (Agilent Technologies, Palo Alto, CA, USA) was used.Water with 0.1% formic acid (solvent A) and acetonitrile (solvent B) were used as gradient elution.The flow rate was 0.5 mL/min, the column temperature was maintained at 25 • C, and the injection volume was 4 µL.The solvent gradient involved in the B mobile phase was as follows: 0-1 min, 2% B; 1-30 min, 95% B; and 30-41 min, 2% B. The separated compounds were sequentially analyzed, initially using a DAD and subsequently using a mass spectrometry detector.Mass spectra were acquired over a mass range from m/z 100 to 2500, utilizing a negative ionization mode.The structural identification of the compounds was determined by comparing their retention times and mass spectra with standard compounds [39].

Isolation and Purification of Compounds
To further explore the constituents of A. ligustica, the two extracts were separated using chromatographic techniques.Consequently, 3.5 g of the AcOEt extract was fractioned by silica gel column chromatography (type 60, 0.063-0.200mm, Merck, Darmstadt, Germany) using cyclohexane-ethyl acetate-methanol as system solvents.Similar fractions were combined after TLC analysis over silica gel GF 254 plates to give 10 fractions (F 1 to F 10 ).Two compounds, 1 (2.8 mg) and 2 (6.6 mg), were isolated from fractions F 4 (89.4 mg) and F 6 (69.9 mg), respectively, after the treatment of the yellow precipitate with chloroform and subsequently with acetone.
On the other hand, a 6 g portion of the BuOH extract was subjected to polyamide SC6 column chromatography eluting with a gradient of H 2 O-MeOH (0% to 100%).After combining similar fractions based on TLC analysis over cellulose (CEL 400 plates, Merck) visualized under UV light at 365 nm, 15 fractions were obtained.Fraction F 4 (283.7 mg) was subjected to chromatographic separation using the Sephadex LH-20 column with methanol as the eluent, yielding five subfractions.Subsequently, the subfraction F 4 (2) was separated by preparative silica gel GF 254 TLC using AcOEt-MeOH-H 2 O (6:1:1) as an elution system to obtain compound 3 (6.1 mg), which was purified over a Sephadex LH20 column with MeOH as the eluent.Additionally, Fraction F 6 (155.1 mg) was also purified using a Sephadex LH-20 column with MeOH as the eluent, resulting in the isolation of compound 4 (3.8 mg).Meanwhile, compound 5 (5.8 mg) was isolated as a precipitate from fraction F 8 (190.7 mg), further purified by precipitation in methanol.The TPC was estimated spectrophotometrically using the Folin-Ciocalteu (FCR) reagent [40,41].A concentration of 1 mg/mL of the AcOEt and BuOH extracts was used in the analysis.A total of 20 µL of each extract solution was mixed with 100 µL of FCR (1:10) and 75 µL of sodium carbonate (7.5%).The resulting solution was left in the dark at room temperature for 2 h.After incubation, the absorbance was measured against a blank at 765 nm.The total polyphenol content was calculated from the calibration curve of a gallic acid standard solution, and the results were expressed as micrograms of gallic acid equivalents per milligrams of extract (µg GAE/mg).

Total Flavonoid Content (TFC)
The TFC was assessed spectrophotometrically according to the method described by Topçu et al. [42].Each extract solution (50 µL) was diluted with 130 µL of MeOH and then mixed with 10 µL of potassium acetate (1M) and 10 µL of aluminum nitrate solution (10%).The resulting solution was left in the dark at room temperature, and after 40 min of incubation, the absorbance was measured against a blank at 415 nm.The total flavonoid content was calculated from the calibration curve of a quercetin standard solution.The results were expressed as micrograms of quercetin equivalents per milligrams of extract (µg QE/mg).

DPPH Free Radical Scavenging Activity
The DPPH scavenging ability of the AcOEt and BuOH extracts was performed spectrophotometrically [43].To 40 µL of sample solutions (AcOEt, BuOH extracts, and the standard BHA) at different concentrations, 160 µL of DPPH solution (0.1 mM) in methanol was added, and the mixture was left in the dark at room temperature.After 30 min of incubation, the absorbance of the mixture was measured at 517 nm.The results were provided as IC 50 (µg/mL) values.The inhibition percentage of DPPH radical was calculated using the following formula: A control : Absorbance of control (contained in all reagents except the test extract or standard).
A sample : Absorbance of the test extract or standard.

Galvinoxyl (GOR) Scavenging Activity
The galvinoxyl free radical (GOR) antioxidant test of the AcOEt and BuOH extracts was evaluated spectrophotometrically using the Shi et al. [44] method.A volume of 40 µL of sample solutions (AcOEt, BuOH extracts, and the standards BHA, BHT) at various concentrations was mixed with 160 µL of galvinoxyl methanolic solution (0.1 mM).After incubation in the dark at room temperature for 2 h, the absorbance was measured at 428 nm.The results were expressed as IC 50 (µg/mL) values, and the above formula was used to calculate the inhibition percentage of GOR radicals.

Cupric Reducing Antioxidant Capacity (CUPRAC) Activity
The CUPRAC activity of the AcOEt and BuOH extracts was assessed spectrophotometrically using the method described by Apak et al. [45].Briefly, 60 µL of CH 3 COONH 4 buffer (1 M, pH 7), 50 µL of neocuproine solution (7.5 mM) in methanol, and 50 µL of CuCl 2 (10 mM) were added to 40 µL of sample solutions (extract and standard) at different concentrations.After incubation at room temperature for 60 min, the absorbance was measured at 450 nm using the microplate reader.BHA and BHT were used as standards, and the results were given as A 0.50 value.

Reducing Power Activity
The reducing power activity was investigated spectrophotometrically according to the procedure outlined by Oyaizu [46].For this assay, a volume of 10 µL of sample solutions (AcOEt, BuOH extracts, and standards) at different concentrations was mixed with 40 µL of phosphate buffer solution (0.2 M, pH 6.6) and 50 µL of potassium ferricyanide (1%).Later, after incubation for 20 min at 50 • C, 50 µL of trichloroacetic acid (10%), 40 µL of distilled water, and 10 µL of FeCl 3 solution (0.1%) were added.The absorbance was then measured at 700 nm using a microplate reader.Ascorbic acid, tannic acid, and α-tocopherol were used as standards, and the results were expressed as A 0.50 values.

O-Phenanthroline Activity
The phenanthroline chelating activity of AcOEt and BuOH extracts was performed spectrophotometrically according to Szydlowska-Czerniak et al. [47].The procedure consisted of adding 50 µL of FeCl 3 solution (0.2%), 30 µL of O-phenanthroline (0.5%), and 110 µL of methanol to 10 µL of sample solutions (extracts and standards) at different concentrations.The microplate was incubated for 20 min at 30 • C, and the absorbance was read at 510 nm.BHA and BHT were used as standards, and the results were provided as A 0.50 value.

Photoprotective Activity
The in vitro photoprotective activity of the AcOEt and BuOH extracts against UV damage was evaluated according to the method established by Mansur et al. [48], with results expressed as the sun protection factor (SPF).In this assay, 2 mg of each extract was dissolved in 1 mL of methanol.Afterward, a volume of 200 µL of sample solutions was placed into a microplate.The absorbance was measured in the range 290-320 nm (UV-B wavelength), with increments of 5 nm.The SPF value was calculated using the following formula: FPS = CF × ∑ 320 290 EE(λ) × I(λ) × Abs(λ) CF: correction factor (=10); EE(λ): erythemal effect spectrum; I(λ): solar intensity spectrum; Abs(λ): absorbance of sunscreen product.The values of EE(λ) × I(λ) are constants determined by Sayre et al. [49].

Statistical Data Analysis
All results are expressed as mean values ± standard deviation (SD) of three measurements.The IC 50 (inhibition concentration at 50%) and A 0.50 values (the concentration indicating 0.50 absorption) were calculated by the linear regression analysis from the curve [% Inhibition = f(concentration)] for IC 50 and [Absorbance = f(concentration)] for A 0.50 .Differences between means were assessed using Student's t-test, and p-values < 0.05 were found to be statistically significant.

Conclusions
This study delved into the metabolite composition of the AcOEt and BuOH extracts of A. ligustica aerial parts harvested from Algeria.The phytochemical examination using HPLC-Q-TOF-MS reveals a diverse array of bioactive compounds, such as flavonoids, phenolic acids, phenolic aldehydes, dicarboxylic acids, and dihydroxybenzenes.Furthermore, in addition to three flavones previously identified in this species, two flavonols known as 6-methoxykaempferol-3-O-rutinoside (3) and 6-methoxykaempferol (4) were separated for the first time from the Achillea genus.The study also highlighted the significant antioxidant and photoprotective properties of the plant, underscoring its potential as a promising natural resource for the development of pharmaceutical and cosmetic products.

Figure 1 .
Figure 1.Compounds isolated from the AcOEt and BuOH extracts of A. ligustica.

Figure 1 .
Figure 1.Compounds isolated from the AcOEt and BuOH extracts of A. ligustica.

Table 1 .
HPLC-MS data of compounds identified in AcOEt and BuOH extracts of A. ligustica.
Rt: Retention time; a : not detected in ethyl acetate extract; b : not detected in 1-butanol extract.

Table 2 .
TPC and TFC of AcOEt and BuOH extracts of A. ligustica.

Table 3 .
Antioxidant activity of AcOEt and BuOH extracts of A. ligustica.