Chemical Composition and Antioxidant Activity of Aloe vera from the Pica Oasis (Tarapacá, Chile) by UHPLC-Q/Orbitrap/MS/MS

The chemical composition of Aloe vera growing in the small town of San Andrés de Pica, an oasis of warm waters and typical fruits, located in Tamarugal province in the Northern Chilean region of Tarapacá is reported. The chemical characterization was performed using liquid chromatography (UHPLC) coupled to PDA and high-resolution mass spectrometry (HESI-Q-Orbitrap®-MS) in four different plant parts of Aloe (peel, flowers, gel, and roots). Twenty-five phenolic compounds were identified, including cinnamic acids and other derivatives (e.g., caffeic and chlorogenic acids), chromones (e.g., aloesin and isoaloeresin D), anthracene compounds and derivatives (e.g., aloin A/B and emodin), and several C-flavonoids (e.g., orientin and isovitexin), among others. Total antioxidant activity of the ethanolic extracts of the peels, flowers, gel, and roots was measured as the capturing of the DPPH• and ABTS•+ radicals, while the iron-reducing antioxidant power (FRAP) was measured by spectroscopic methods. The peel had the highest antioxidant activity with values of 2.43 mM ET/g MF (DPPH•), 34.32 mM ET/g MF (ABTS•+), and 3.82 mM ET/g MF (FRAP). According to our results, the peel is the best part of the plant for the production of nutraceuticals or cosmetics products for its greatest number of bioactive compounds. This is a new and innovative finding since the only part used in traditional medicine is the gel of Aloe, and the peel is generally considered waste and discarded.


Introduction
In Tarapacá Region (I region, Northern Chile), a remote part of the Atacama Desert, there is a small town and oasis called San José de Pica.Pica has a lush greenery and thriving agriculture due to underground water sources surfacing in the middle of the desert [1]. is desert is one of the driest places on Earth resulting in extreme environmental conditions.ese varying abiotic conditions, as seasonal fluctuations of chemical and physical water composition (e.g., nutrients, temperature, and salinity), are challenging for the biota and affect the species assemblages and ecosystem stability [2].e different secondary metabolites produced by the plants are influenced by environmental conditions such as extreme light, water, soils, salts, chemicals, temperature, and geographical variations [3].
Environmental factors such as light intensity, temperature, water availability, type, and soil composition among others, have a substantial influence on the quality and productivity of medicinal plants.Plants of the same species occurring in different condition environments may differ significantly in their content of secondary metabolites [4].
Furthermore, the chemical composition of any plant depends upon the local geographical condition, type of soil, and its composition.For example, it has been reported that the chemical composition and yield of the essential oil of Mentha piperita var., grown under different agroecological locations in Egypt, vary significantly according to the climate conditions.Plants growing in high temperatures showed high menthone/menthol contents and high antioxidant activity that could be attributed to their high number of phenolic compounds and flavonoids compared to other locations [5].
Aloe vera (Aloe barbadensis Miller) is a native species to South Africa, which has been widely distributed in the continent of Europe from where they have spread to almost the entire world [6]. is plant is also extensively distributed in South America [6,7], where it is known for its therapeutic effects.A. vera has been studied for its clinical effectiveness against a great variety of affections and disorders of the skin [8], for example, wounds and burns [6,[9][10][11], for its effect as anti-inflammatory, antioxidant, healing, and antibacterial; these actions are biologically attributed to its chemical components [8].e part of the plant that has been usually used for therapeutic purposes is the gel [6,9].Traditionally, A. vera gel has been used both externally for the treatment of wounds, minor burns, and irritations of the skin, and internally in different formats to treat constipation, cough, ulcers, diabetes, and headaches among others [12].Regarding its chemical composition, A. vera gel consists mainly of water (>98%) and polysaccharides, including pectins, cellulose, hemicellulose, glucomannan, and acemannan, the latter being considered as the main functional component of A. vera gel, formed from a long chain of acetylated mannose [12].Aloe latex, also known as Aloe juice, is a bitter yellow exudate of the pericyclic tubules in the outer skin of the leaf.
e main active component of Aloe juice are hydroxyanthracenic derivatives, which represent between 15 and 40% of the total components, and among them are anthraquinone glycosides aloin A and B (also called barbaloin) along with Aloe emodin [12].A. vera flowers have received little attention, although there are some studies that suggest the use of these flowers for phytotherapeutic purposes, due to the presence of several phenolic compounds such as caffeic acid, chlorogenic acid, and ferulic acid among others.e compound mannose-6 phosphate, which is a constituent of the sugar of A. vera gel, has been shown to have woundhealing properties as well.In addition, some glycoproteins present in the A. vera gel have antitumor and antiulcer effects and may increase the proliferation of normal human skin cells [12].In the case of the root, some phenolic compounds, especially naphthoquinones and anthraquinones, have also been identified [13][14][15].
It is well known that the types and levels of the chemical components present in the plants can vary according to the geographical origin or variety; although there are some chemical characterization studies of A. vera from other countries, we were not able to find reports on the chemical composition of A. vera from the Chilean region of Tarapaca.In Chile, the studies carried out in A. vera have been scarce, focusing mainly on the farming conditions, the effect of high hydrostatic pressures (HHPs) on rheological properties [16], the effect of HHPs on functional properties and characteristics of the quality of Aloe gel [17], and the microbiological stabilization of A. vera gel using the treatment of HHP [18].
Moreover, other studies about the influence of temperature on drying kinetics, physicochemical properties, and antioxidant capacity of Aloe gel [19], plus the effect of temperature in the structural properties were also published [20]; however, studies covering the chemical composition of A. vera growing in extreme climatic conditions like the one growing in the region of Tarapacá have never been reported.
Several studies have shown that climatic conditions cause plants to develop metabolites that help in their survival; thus, species growing in extreme conditions, such as the Atacama Desert, can develop interesting metabolites to be studied.In this scenario, the use of state-of-the-art tools such as metabolomic mass fingerprinting can help to study the metabolomic processes in extreme systems like the one occurring among the "biodiversity of the Atacama Desert."For a complete chemical characterization of A. vera from Tarapaca Region, we used high-resolution hyphenated LC-MS (UHPLC-MS) techniques whose advantage is the rapid separation of compounds and the most accurate determination of the masses [21]. is technique is considered gold standard for the analysis of phenolic compounds, due to its versatility, precision, and relatively low cost [22].e UHPLC machine can be coupled to several mass spectrometers, such as time-of-flight (TOF or Q-TOF), quadrupole-Orbitrap (Q-OT), or triple quadrupole (TQ) mass spectrometers.e Orbitrap is an ion trap mass analyzer that consists of a high-resolution hybrid mass spectrometer, which has recently been published as an innovative technology that offers high-resolution MS/MS fragments, for metabolomic analysis of a variety of metabolites, including toxins, pesticides, antibiotics, peptides, and several small organic molecules up to 2000 Daltons [21].
Based on this background, we have studied the chemical composition of A. vera from Tarapacá Region, given the geographic conditions and the possible influence on the secondary metabolites present in the species.e phenolic compounds of each part of A. vera were characterized using UHPLC-Q/Orbitrap/MS/MS, and the chemical composition was related with the antioxidant activity.ermo Fisher Scientific, Bremen, Germany) system with a modern PDA detector and quadrupole hybrid high-resolution mass spectrometer-Orbitrap Q Exactive ® Focus were employed, using a quaternary Series RS pump and TCC-3000RS column compartments with a WPS-3000RS autosampler plus a rapid separations PDA detector controlled by Chromeleon 7.2 and Xcalibur 2.3.

Materials and Methods
e chromatographic system was coupled to the MS with a heated electrospray ionization source II (HESI II).Nitrogen (purity >99.999%) obtained from a Genius NM32LA nitrogen generator (Peak Scientific, Billerica, MA, USA) was employed as both the collision and damping gas.Mass calibration for the Orbitrap was performed in both negative and positive modes, to ensure a working mass accuracy lower than or equal to 5 ppm.e calibration was done once a week.For calibration of the mass spectrometer, caffeine, N-butylamine, buspirone hydrochloride, sodium dodecyl sulfate and taurocholic acid (Sigma-Aldrich, St Louis, Missouri, USA) besides Ultramark 1621 (Alfa Aesar, Heysam, UK), were used as standards.e softwares Q Exactive 2.0 SP 2, XCalibur 2.3, and Trace Finder 3.2 ( ermo Fisher Scientific and Dionex Softron GmbH) were used to control the mass spectrometer and for data processing.For UHPLC-mass spectrometer control and data processing, Q Exactive 2.0 SP 2, XCalibur 2.3, and Trace Finder 3.2 software ( ermo Fisher Scientific and Dionex Softron GmbH Part of ermo Fisher Scientific) were used, respectively [21].

LC Parameters.
A portion of each extract (2.5 mg) obtained as explained above was dissolved in 1 mL of 1% formic acid in MeOH, filtered through a 0.45 µm micropore membrane (PTFE, Waters Milford, MA, USA) before use.Later, it was injected into the UHPLC-PDA and ESI-Orbitrap-MS equipment.
e parameters of liquid chromatography were those previously published by our research group [21].

MS Parameters.
e HESI parameters were optimized as reported previously [21].Detection was based on calculated exact mass and on retention time of target compounds, presented in Table 1.

Sample Preparation.
e Aloe leaves were carefully cut and washed, leaving the leaf upright to drain the exudate and  4 Journal of Chemistry soaking it in distilled water overnight.Later, the peeled leaf and the gel inside was cut into pieces, soaked in water for half an hour, then passed through a strainer, and then liquefied.
A. vera peel was also cut into small pieces and washed with distilled water.e roots were carefully cut into small pieces and washed with distilled water.Flowers were provided by the company "Mundo Aloe vera" from Pica, Tarapaca Region, and dried at room temperature (25-30 °C).

Phenolic Compounds Extraction.
Each part of Aloe obtained (peels, gel, roots, and flowers; previously weighed) were macerated with methanol for 48 hours (sample: methanol; 1 : 2 (w : w)) then sonicated for 30 minutes in a Branson 3510 ultrasonic apparatus.e extracts from each sample were combined, filtered, and evaporated in vacuo in the dark (40 °C) in a rotavapor (Laborota 4001-efficient).e methanolic extracts were maintained at −86 °C in an ultralow freezer for 24 hours and then freeze-dried in a Labconco-Freezone 6-Plus equipment.e extracts were suspended in 20 mL ultrapure water and loaded onto an XAD-7 (100 g) column.e column was rinsed with water (100 mL), and phenolic compounds were eluted with 100 mL of MeOH acidified with 0.1% HCl. e solutions were combined and evaporated to dryness under reduced pressure (40 °C) to give dark-brown extracts from peels, gel, roots, and flowers.Samples were then analyzed by HPLC using the Agilent 1260 Infinity and by UHPLC using the ermo machine coupled to the PDA detector ermo Q Exactive Focus mass spectrometer.

DPPH Assay.
e DPPH • radical decoloration activity of the A. vera extracts was determined using the DPPH solution methanol, following the modification method of Sogi et al. [23].A portion of the DPPH stock solution (0.24 g/100 mL methanol) was diluted into 10 parts methanol at 80% (4 : 1 ratio of methanol and water, respectively) so that the working solution obtained an absorbance of 1.10 ± 0.02 at 515 nm. 3 mL of the working solution of DPPH was mixed with 0.6 mL of blank, standard, or sample, kept in the dark for 20 minutes, and the absorbance was recorded at 515 nm.Methanol at 80% (control) was used to calculate the radical decoloration activity of a standard curve, which was prepared with trolox solution (50-250 μM, R 2 : 0.9905).Samples were analyzed in triplicate, and the results are expressed in units equivalent to trolox (ET), mM ET/g fresh weight (FW).

ABTS Assay.
e ABTS •+ antioxidant activity of the extracts was carried out using the ABTS •+ radical cation discoloration test as described in Reference [23], with some modifications.e solution of 7 mM ABTS and 2.45 mM potassium persulfate was mixed in a 1 : 1 ratio, and the solution was allowed to stand in the dark for 12-16 hours to produce the ABTS •+ cation radical solution.e stock solution was then diluted ten times, with an 80% methanol solution, to reach the absorbance of 0.700 ± 0.020 at 734 nm. 3 mL of the ABTS •+ stock solution was mixed with 30 μL of blank, standard, or sample, and after 6 min, the absorbance at 734 nm was measured using a spectrophotometer.As a blank, 80% methanol was used, and the quantification was performed using a standard calibration curve of trolox antioxidant (0.30-1.5 mM, R 2 : 0.9886).
e samples were analyzed in triplicate, and the results were expressed in mM ET/grams of fresh mass (FM).

Ferric Reducing Antioxidant Power (FRAP) Assay.
e determination of ferric reducing antioxidant power or ferric reducing ability (FRAP assay) of the extracts was performed as described by Sogi et al. [23], with some modifications.
e stock solutions prepared were 10 mM TPTZ (2,4,6-tri (2-pyridyl)-s-triazine) solution in 40 mM HCl, 300 mM acetate buffer (pH 3.6), and 20 mM FeCl 3 •6H 2 O solution.e solution using in this assay was prepared with mixed buffer acetate, TPTZ solution, and ferric chloride solution at a proportion of 10 : 1 : 1 (v : v : v), respectively.Plant extracts, standards, or methanolic trolox solutions (300 µL) were incubated at 37 °C with 3 mL of the FRAP solution (prepared by mixing 25 mL acetate buffer, 5 mL TPTZ solution, and 10 mL FeCl 3 •6H 2 O solution) for 30 min in the dark.Absorbance of the blue ferrous tripyridyltriazine complex formed was then read at 595 nm.Quantification was performed using a standard calibration curve of antioxidant trolox (from 50 to 250 µM, R 2 : 0.995).Samples were analyzed in triplicate and results are expressed in mM ET/g fresh weight (FW).

Analysis of Data.
e statistical analysis was carried out using the SPSS program version 20. e determination was repeated at least three times for each sample solution.Analysis of variance was performed using ANOVA.Significant differences between means were determined by Tukey's comparison test (p values < 0.005 were regarded as significant).

Yield Percentage.
e peels, flowers, gel, and roots were extracted three times (n � 3) with MeOH, and phenolics were retained on Amberlite XAD-7 to obtain the phenolicenriched extract (PEE).e highest PEE was obtained from the peels (16.2%), while the extraction yields for flowers, gel, and roots were 12.6, 12.3, and 8.5%, respectively.2 shows antioxidant activity of the four methanolic extracts from several parts of A. vera using different methods for the antioxidant capacity.ree antioxidant assays were used to evaluate the antioxidant capacity of the samples, based on chemical aspects for the measurements of radical scavenging activity (DPPH • and ABTS •+ ) assays and a method based on metals reduction (FRAP).

Antioxidant Activity Quantification. Table
In the DPPH • radical trapping capacity assay (Table 2), the extract of the peels showed the greatest antioxidant capacity (2.43 ± 0.14 mM ET/g FM), followed by the extract of the roots (1.43 ± 0.08 mM ET/g MF), then flowers (1.25 ± 0.03 mM ET/g FM), and finally with less antioxidant capacity, the gel extract (0.34 ± 0.01 mM ET/g FM), with a statistically significant difference between them (p < 0.05), except between the flower extract and the Aloe roots.
e ABTS •+ assay (Table 2, column (b)) showed that the peel has the highest antioxidant activity with average values of 34.32 ± 2.60 mM ET/g FM, followed by the roots (17.54 ± 0.77 mM ET/g FM), then the flowers with 16.55 ± 2.30 mM ET/g FM, and finally the Aloe gel with 2.06 ± 0.06 mM ET/g FM. ere is a statistically significant difference between peel and gel extract (p < 0.05). is study allowed the measuring of the antioxidant capacity of polyphenols through the capture of free radicals.
e antioxidant activity values obtained by the DPPH method were carried out using the trolox reagent as a standard.In the column (c), the same sample presented the highest activity in the FRAP assay, with values of 3.82 ± 0.23 mM ET/g FM for peel, followed by the root (2.67 ± 0.16), flowers (2.01 ± 0.10), and in the last place, the gel (0.38 ± 0.01 ET/g FM).ere was a statistical correlation between the three antioxidant assays (p < 0.05).
Although the total phenolic content was not determined, when comparing the chromatographic profiles of the different parts of Aloe, under the same chromatographic conditions and sample concentration, we noticed that the greater variety, quantity, and abundance of the chemical compounds were in the peel, and these results correlate to the greater antioxidant activity.

Identification of Phenolic Compound to A. vera from Pica,
Tarapaca Region

Fingerprinting from Phenolic
Compounds.e phenolic profiles of PEE were assessed by UHPLC-PDA-QOT/ MS (ultrahigh-performance liquid chromatography photo diode array quadrupole Orbitrap mass spectrometry); using the negative heated HESI mass detection mode, phenolic compounds were tentatively identified in the different extracts of A. vera.Comparative UHPLC-TIC (total ion current) chromatograms of A. vera parts are showed in Figure 2. e retention time (Rt), UV spectral maxima, MS fragmentation, and tentative identification of the compounds are summarized in Table 1.
e methanolic extracts of the peel, flower, gel, and root of A. vera retained in XAD-7 was analyzed by HPLC-PDA, to obtain the fingerprint chromatograms for each of the parts.Figure 2 indicates that the peel and the flowers had the greatest abundance of compounds, followed by the roots.
e composition of the gel is scarce in phenolic compounds; thus, we could state differences in the composition of the organic compounds in each of the parts of the plant.
Twenty-five compounds (Table 1) were tentatively identified in different parts of A. vera.
e highlighted compounds determined include various cinnamic acids and their derivatives, chromones, anthracene compounds, and flavonoids, some of which have been reported previously in Aloe species.e identification was performed based on its total mass compared to the theoretical mass (<5 ppm) and the characteristic fragments for each compound, finding differences and similarities between the samples analyzed.Peaks 1-6, 8, 10-21, and 24-25 were detected in the peel, peaks 1-6, 8-12, 14, 15, 19, and 22-24 in the flower, peaks 1, 14, 15, 17, 18, 20, 21, 23, and 24 in the gel, and peaks 1-4, 6, 7, 10-15, 23, and 24 in the root of A. vera, shown in Figure 2. A detailed explanation of the characterization of these compounds, grouped based on their chemical characteristics, is given below.), compound identified by its difference in mass of 1.99954 ppm respect to the theoretical mass ion [26].e presence of chlorogenic acid has been reported in A. brevifolia leaves [26] and caffeic acid was reported in leaves of A. barbadensis Miller and A. arborescens Miller [27].In the case of 3,4-di-O-caffeoylquinic acid, its presence was reported in A. saponaria [26], and the feruloylquinic acid had not been reported in any Aloe species until this study.− ) [26]. e aloesin was reported in A. grandidentata, A. perfoliata [26], A. ferox Miller [28], and A. barbadensis Miller [29].Peaks 13, 15, and 21 showed [M-H] − ions at m/z 569.16626 amu (Rt 11.74 min), 555.18677 amu (Rt 11.85 min), and 583.18146 amu (Rt 13.40 min) and were tentatively identified as a caffeoyl ester of aloesin [30], isoaloeresin D, and 7-methylether of 2′feruloylaloesin [26], respectively.For these peaks, a great accuracy was observed demonstrated by their small differences in ppm (0.33382, 0.75650, and 1.09743, respectively) with respect to the theoretical mass ion [26].Isoaloeresin D has been reported in A. eru, A. grandidentata, A. perfoliata, A. brevifolia [26], and A. barbadensis Miller [29].e compound 7-methylether of 2′-feruloylaloesin was described in A. eru, A. grandidentata, and A. saponaria [26], and caffeoyl ester of aloesin was described in A. broomii [30].), which showed an [M-H] − ion at m/z 593.15063 amu (Rt 9.98 min). is compound was tentatively identified by its difference in mass of 0.94411 ppm with respect to the theoretical mass ion. is compound was reported in A. arborences, A. grandidentata, and A. ferox [26].e compound emodin (C 15 H 9 O 5

−
) was assigned to peak 7 with an [M-H] − ion at m/z 269.04538 amu (Rt 10.40 min), identified by its difference in mass of 0.63186 ppm with respect to the theoretical mass ion and by the identification of the typical fragments MS ) [29]. Figure 3 shows TIC (total ion current, negative mode) and full high-resolution mass spectra showing the UHPLC chromatograms of [M-H] − ion and proposed structure of aloin A.
In the same manner, Peak 18 with an [M-H] − ion at m/z 417.11893 amu was identified as aloin B (C 21 H 21 O 9
is peak was identified by the difference in mass of 0.43153 ppm with respect to the theoretical mass ion and by the identification of two typical ions MS n ; at  ) [24]; both isomers were confirmed by their characteristic UV max at retention time of 12.18 min for aloin A and 12.36 min for aloin B [32].
Aloin A has been reported in A. barbadensis Miller, A. arborences, and A. grandidentata, while aloin B was reported in A. barbadensis Miller and A. grandidentata [26]; both aloins (A and B) have also been reported in A. ferox Miller [28] and in A. barbadensis Miller [29].Aloin is a mixture of aloin A (also called barbaloin) and aloin B (or isobarbaloin), corresponding to an anthraquinone glycoside to which attributed a characteristic of purgative effects, present in the Aloe leaf [26].According to the International Aloe Science Council, the maximum concentration for human consumption of barbaloin present in derived products of Aloe is 10 mg/L [33].
Peaks ), which showed an [M-H] − ions at m/z 553.17041 amu and 297.07669 amu, respectively.ese peaks were identified by their difference in mass of 2.04277 ppm and 0.53858 ppm with respect to the theoretical mass ion.e 2′-p-methoxy coumaroyl aloeresin B was reported in A. eru, A. perfoliata, and A. saponaria [26].Mass spectra of peak 19 (Rt 1.69 min) showed [M-H] − ion at m/z 503.11911 amu, and it was identified as 6′-malonylnataloin (nataloin). is compound was identified by the difference in mass of 0.77516 ppm with respect to the theoretical mass   ) product of the loss of a CO 2 molecule [34]. is peak was detected in A. barbadensis Miller, A. arborences, A. eru, A. grandidentata, A. brevifolia, A. ferox [26], and A. ellenbeckii [34].
Aloe emodin- ) with Rt 9.98 min and their difference in mass of 1.46840 ppm with respect to the theoretical mass ion and its characteristic MS n ion at m/ z 301.55185 amu [24,35]. is compound was reported in A. arborences and A. eru [26].Peak 6 was recognized as kaempferol- ), respectively, due to its great accuracy demonstrated by their small differences in mass −0.75775, 0.02247, and 0.05830 with respect to the theoretical mass ion, respectively.Chrysoeriol-7-Oglucuronide was reported in A. grandidentata and 5,3′dihydroxy-6,7,4′-trimethoxy-flavone in A. arborences, A. eru, A. grandidentata, and A. brevifolia [26], while naringenin-4′-methoxy-7-O-glucuronide had not been reported in any Aloe species until this study.

3.3.6.
Oxylipins.An oxylipin corresponding to peak 24, was identified as trihydroxy octadecenoic acid (C 18 H 33 O 5 − ) with a m/z 329.23328 amu (Rt 18.28 min), determined by its small difference in ppm (0.21262) with the theoretical mass ion; this compound has been previously reported in A. saponaria [26].
e distribution of phenolic compounds identified in this study can be observed in Table 3, allowing a more graphical demonstration of the differences or similarities in the different plant parts.UHPLC-Q/Orbitrap/MS/MS analysis of the methanol extract of the peel, flower, gel, and root showed that the highest number of phenolic compounds is found in peel, flowers, and roots of Aloe.Peaks 1, 14, 15, and 24 were detected in the peel, flowers, gel, and roots of the methanolic extract.Among the twenty-five compounds detected, only nine compounds were detected in the gel of Aloe.

Conclusions
Twenty-five compounds were tentatively identified for the first time in the native A. vera from Pica, Tarapacá Region, in Chile using UHPLC-Orbitrap-ESI-MS.e UHPLC fingerprints obtained indicate that the methodology developed in this study was appropriate for the analysis of A. vera from the Atacama Desert. is is the first study reporting a tentative identification of several phenolic compounds in this species.ese findings could be used as quality control for the plant and for the chemical comparison with other Aloe species, as well as with cosmetics or dietary products made from the raw material.e highest antioxidant activity was observed in the peel in the three assays used (measurement of DPPH • , ABTS •+ , and FRAP resulting in 2.43 ± 0.14 mM ET/g MF, 34.32 ± 2.60 mM ET/g MF, and 3.82 ± 0.23 mM ET/g MF, respectively).e antioxidant capacity could be related to the presence of several phenolic compounds that were identified in the peel, being higher than in the other parts of A. vera.Based on these results, we could say that the waste material of the Aloe husk could be used more sustainably, which until now had not been used, given that the highest antioxidant activity was found in this part of the plant.

Figure 1 :
Figure 1: Map of Chile showing the location of Tarapaca Region: commune of Pica (a), La Concova sector (b), and the A. vera crops (c).
Derivatives.Four cinnamic acids and their derivatives were tentatively identified in the negative mode.Peaks 2 and 9 were identified as chlorogenic acid (5-caffeoylquinic acid, C 16 H 17 O 9 − ) and feruloylquinic acid (C 17 H 19 O 9 − ), respectively.Peak 2 shows an [M-H] − ion at m/z of 353.08752 amu with retention times of 9.54 min, and peak 5 shows an ion [M-H] − at m/z around 6 Journal of Chemistry

Table 1 :
Tentative identification of phenolic compounds in peel, flower, gel, and root of A. vera from Tarapaca Region detected by UHPLC-Q-OT-MS.

Table 3 :
Distribution of the phenolic compounds identified tentatively in methanolic extract of peel, flower, gel, and root from Chilean A. vera.