Volume 10, Issue 4: 167-171; July 27, 2020  
STUDY OF THE FLAVONOIDS AND SECONDARY METABOLITES  
OF THE ARGAN TREE (Argania spinosa L.)  
Miloudi HILALI, Hanae El MONFALOUTI and Badr Eddine KARTAH  
Laboratory of Plant Chemistry and Organic and Bioorganic Synthesis, Faculty of Science, University Mohamed-V, Av. Ibn Battouta, BP 1014 Agdal-  
Rabat, Morocco  
Supporting Information  
ABSTRACT: The separation and identification of the main phenolic compounds present in the co-product of the  
Argan tree (Argania spinosa) were carried out using high performance liquid chromatography techniques  
coupled with mass spectrometry (LC-ESI-MS/MS).The study was based on the retention times of the peaks of the  
phenolic compounds in samples and was compared to those of the controls (reference compounds) and  
supplemented by an analysis of the fragmentations of the molecules by mass spectrometry. Phenolic  
compounds in the pulp of the Argan namely such as catechin (2.8%), epicatechin (14.7%), procyanidin (2.7%),  
quercetin (1.6%), luteolin (0.2%) and naringenin (0.07%) were found. Phenolic acid is consisted of gallic acid  
(5%) and protocatechuic acid (21.1%). These compounds are more dominant than flavonoids. The flavonoids-O-  
rhamnoglucosides the most dominant compounds is isorhoifoline (7.2%) and hesperidin (4.5%) against rutin  
(0.1%) and rhamnetin-O-rutinoside (0.5%) are less dominant. The main compounds are the hyperoside (13.4%)  
and isoquercetin (10%). On the other hand, naringenin-7-O-glucoside constituted the most minority compound of  
this type of flavonoid in the pulp of the fruit of the Argan tree (the percentage of naringenin-7-O-glucoside and  
quercetin-3-O-arabinose is 15.3%). There are other phenolic compounds in the pulp of the Argan namely such as  
catechin (2.8%), epicatechin (14.7%), procyanidin (2.7%), quercetin (1.6%), luteolin (0.2%) and naringenin  
(0.07%). The main flavonoids found in the leaves of the Argan tree are Quercetin (21.73%), Myricetin (54.34%),  
Hyperoside (8.69%), and also Myricetin-3-Ogalactoside (9.78%). Argan cake is rich in flavonoids. Among these,  
epicatechin (110 mg/kg), catechin (11 mg/kg), protocatechic acid (15.2 mg/kg), vanillic acid (16.3 mg/kg) and  
4-hydroxybenzyl alcohol (8.6 mg/kg) are higher in Argan cake. Argan oil is richer in tocopherol (597 to 775  
mg/kg), Argan oil is rich in gamma tocopherol (631 mg/kg), and that make Argan valuable nutraceutical. The  
study of the secondary metabolites and especially the flavonoids of the Argan tree was undertaken with the aim  
of identifying new metabolites making it possible to increase the industrial than commercial value of the Argan  
tree.  
Keywords: Argan tree, Biological activity, Flavonoids, Metabolism, Phenolic acids.  
INTRODUCTION  
The Argan tree (Argania spinose L. Skeels) is used by the local populations : the wood and the woody shell of the fruit for  
heating. The almond of the fruit is used in the production of Argan oil. The foliage and the pulp of the fruit and also the  
oil cake (residue from the production of Argan oil) are designed for animal nutrition (Pumareda et al., 2006). The study of  
the chemical composition of Argan derivatives was undertaken with the aim of identifying new metabolites allowing  
increasing the industrial than commercial value of the Argan tree. Secondary metabolites are compounds naturally  
biosynthesized by plants but which do not directly participate in plant metabolism. Many secondary metabolites have  
therapeutic properties and are (or have been) used in human medicine (Gitton-Ripoll, 2009; Khallouki et al., 2017). A  
systematic study of the secondary metabolites of the Argan tree has been developed since the 1990s in order to see to  
what extent it is possible to increase the economic value of the Argan grove and hence promote its extension in the long  
term. The results of this study have revealed a wide variety of secondary metabolites within the different parts of the  
Argan tree. Besides molecules frequently encountered in higher plants (triterpenes, sterols, flavonoids, etc.), molecules of  
original structure and belonging to the group of flavonoids have been isolated. Multiple flavonoids, also extracted from  
plant species other than Argan (El Kabouss et al., 2001; Zhar et al., 2016; Falode et al., 2019), have therapeutic  
properties which are sufficiently encouraging to warrant further investigation (Guillaume et al., 2005). Some other  
flavonoids seem to be involved in phytoprotective phenomena (Jiang et al., 2020). Applications in the food or cosmetology  
fields are also being studied. All this clearly indicates that this chemical family of secondary metabolites has interesting  
potential in many fields. As a result, the analysis of several parts of the Argan tree (wood, oil cake, shell and fruit pulp)  
was carried out and many flavonoids of different and often original structures could be isolated and then identified, and  
the properties of certain d 'have been evaluated (Safer, 2018; Hilali et al., 2020). This study briefly describes the  
flavonoids of the Argan tree.  
167  
Citation: Hilali M, El MonfaloutiH and Kartah BE (2020). Study of the flavonoids and secondary metabolites of the Argan tree (Argania spinose L.). Online J. Anim. Feed  
Res., 10(4): 167-171.  
MATERIALS AND METHODS  
Plant material  
The fruits of the Argan tree and their leaves are harvested in the village of Tidzi province of Essaouira, The collected  
samples are dried in the open air then pulped, crushed and finally reduced, separately, in fine powder (Bellefontaine et al.,  
2011).  
Figure 1 - Different parts of the Argan fruit  
Identification of phenolic compounds  
The separation and characterization of the main phenolic compounds present in the Argan fruit pulp were carried  
out using high performance liquid chromatography techniques coupled with mass spectrometry (LC-ESI-MS/MS). This  
method already applied on other plants (cocoa, lepechinia graveolens) (SánchezRabaneda et al., 2003) is important for  
the study of polyphenols. It makes it possible to determine the molecular weight and to give certain structural information  
of the molecules (Adlouni, 2010). In our study, we based ourselves on the retention time of the peaks of the phenolic  
compounds in our sample and compared to those of the control peaks of the reference compounds.  
RESULTS AND DISCUSSION  
Phenolic compounds of the pulp of the Argan fruit  
The study of the phenolic composition of the pulp of Argan fruit has identified 16 phenolic compounds (Table 1). This  
study was approached as a biochemical approach to establish a polyphenolic identity card and allows highlighting a fairly  
significant structural diversity encompassing four main groups of phenolic compounds (El Kabouss et al., 2001; Charrouf  
et al., 2007). Phenolic acids consisting of gallic acid (5%) and protocatechuic acid (21.1%). These compounds are more  
dominant than flavonoids. In our study we did not find p-hydroxybenzoic acid among the phenolic acids in Argan pulp. The  
flavonoids-O-rhamnoglucosides the most dominant compounds is isorhoifoline (7.2%) and hesperidin (4.5%) against rutin  
(0.1%) and rhamnetin-O-rutinoside (0.5%) are less dominant. Flavonoids-O-glycosides: The main compounds are the  
hyperoside (13.4%) and isoquercetin (10%). On the other hand, naringenin-7-O-glucoside constituted the most minority  
compound of this type of flavonoid in the pulp of the fruit of the Argan tree (the percentage of naringenin-7-O-glucoside  
and quercetin-3-O-arabinose is 15.3%), (compounds 11 and 12). There are other phenolic compounds in the pulp of the  
Argan namely such as catechin (2.8%), epicatechin (14.7%), procyanidin (2.7%), quercetin (1.6%), luteolin (0.2%) and  
naringenin (0.07%). It is noted that epicatechin was the most affordable compound in the pulp of the Argan fruit after  
Protocatechuic acid (21.1%). The pulp of Argan fruit has been found to be rich in epicatechin and other catechic  
derivatives whose natural antioxidant power is important according to numerous studies (Ba et al., 2010). However, such  
combinations of natural phenolic compounds could be used for better preservation of Argan oil.  
Phenolic compounds of Argan leaves  
The study of the extracts of the leaves of the Argan tree by chromatography shows a higher content of flavonoids in  
the leaves of the Argan tree (Table 2) which are flavonic molecules including (Myricetin 3-O-galactoside, the hyperoside,  
quercitrine and myricitrine). The main flavonoids found in the leaves of the Argan are Quercetin, Myricetin and their  
glycosides (Quercetin, Myricetrine, Hyperoside, and Myricetin 3-O-galactoside) (Tahrouch et al., 1998). The derivatives of  
these aglycones represent 16.5% of the total flavonoids. The flavonoid extract of the leaves has a very interesting anti-  
radical and antioxidant activity. It is currently marketed as a protective cosmetic active ingredient for extracellular  
macromolecules in the skin such as collagen, glycoproteins, etc. (Charrouf et al., 2009).  
Phenolic compounds in Argan oil  
The proportion of phenols in Argan oil is low but their impact on its biological properties is very important. These are  
caffeic acids, 4-hydroxybenzoic, vanillic, syringic, ferrulic 4-o-glycosylated, oleuropein, 3-hydroxypyridine (3-Pyridinol), 6-  
168  
Citation: Hilali M, El MonfaloutiH and Kartah BE (2020). Study of the flavonoids and secondary metabolites of the Argan tree (Argania spinose L.). Online J. Anim. Feed  
Res., 10(4): 167-171.  
methyl-3-hydroxypyridine and catechol, resorcinol, vanillyl alcohol, tyrosol, 4 hydroxy-3-methoxyphenethyl, epicatechin and  
Table 1 - Phenolic compounds of the pulp of the Argan fruit  
MS/MS  
(Experimental  
method) Neutral  
loss scan  
MS/MS  
(Experimental  
method)  
Production  
-
MS/MS (Experimental  
method) Precursor  
scan  
Retention  
time (min)  
N°  
Compounds (%)  
[M-H]  
Fragments  
1
2
3
4
5
6
7
8
Gallic acid (5.0)  
Protocatechuic acid (21.8)  
Catechine (2.8)  
Isorhoifoline (7.2)  
Epicatechin (14.7)  
Procyanidin (2.7)  
Rutin (0.1)  
0.82  
1.44  
4.06  
7.13  
7.65  
169  
153  
289  
577  
289  
579  
609  
609  
463  
463  
433  
433  
623  
301  
285  
271  
125  
109  
-
-
-
-
-
-
-
-
-
-
-
-
-
-
289  
-
245  
-
245  
289,245  
301  
301  
301  
301  
301  
271  
289  
579  
609  
609  
463  
463  
433  
433  
623  
301  
-
7.67  
10.87  
11.19  
11.46  
11.70  
12.33  
12.69  
13.37  
17.83  
17.94  
18.51  
308  
308  
162  
162  
132  
162  
308  
-
Hesperidin (4.5)  
Hyperosid (13.4)  
463.301  
9
-
-
-
-
-
-
-
-
10  
11  
12  
13  
14  
15  
16  
Isoquercitrine (10)  
Quercetine-o-pentose  
Naringenine-7-o-glucoside  
Rhamnetine-o-rutinoside (0.5)  
Quercetin (1.6)  
315  
151, 121, 107  
-
119,109  
Luteolin (0.2)  
Naringenin (0.07)  
-
-
271  
Table 2 - Phenolic compounds of the Argan leaves  
N°  
1
Compounds (%)  
Retention time (min)  
Myricetine 3-Ogalactoside (9,78%)  
Myricitrine (54,34%)  
Hyperoside (8,69%)  
3.4  
3.9  
5
2
3
4
Quercitrine (21,73%)  
6
Compounds of tocopherols from Argan oil  
The tocopherols were analyzed by HPLC on a column in the normal phase, directly from vegetable oil without  
saponification. They were identified by comparison of their chromatogram with controls injected under the same  
conditions. Their dosage was possible by the use of α-tocopherol. The results obtained are grouped in Table 3. Tocopherols  
are natural antioxidants, they are molecules with carbon chains linked to a quinone function (Bouhadjra, 2011). In  
vegetable oils there are four groups of tocopherols (a, b, g and d). Tocopherols have both a vitamin power (vitamin E, in  
particular a tocopherol) and antioxidant properties (Landrier, 2011). In addition, these compounds can constitute an  
analytical criterion for controlling the purity of oil. Argan oil is richer in tocopherol (597 to 775 mg/kg) than olive oil (50 to  
150 mg/kg) and also than hazelnut oil (300 to 550 mg/kg) (Hilali et al., 2005, 2020). Tocopherols are natural  
antioxidants, gamma tocopherol has the highest antioxidant power (Bourre and Clement, 1996). Rich in gamma  
tocopherol, Argan oil is a valuable nutraceutical. Tocopherols (vitamin E) and polyphenols are natural antioxidants. These  
play an essential role in the prevention of several diseases, because they are anti-free radicals (Carrouf, 2002).  
Table 3 - Composition of tocopherols in Argan oil (mg / kg).  
Tocopherols  
Argan oil  
γ-tocopherol  
δ-tocopherol  
α-tocopherol  
β-tocopherol  
Total  
631,3 mg/kg  
59,5mg/kg  
26,6 mg/kg  
-
717.4 mg/ kg  
R1  
HO  
R2  
O
CH3  
CH3  
Figure 2 - Structure of tocopherols in Argan oil (R1 = R2 = CH3: α- tocopherol; R1 = CH3, R2 = H: β- tocopherol; R1 = H; R2  
= CH3: γ- tocopherol; R1 = R2 = H: δ- tocopherol)  
169  
Citation: Hilali M, El MonfaloutiH and Kartah BE (2020). Study of the flavonoids and secondary metabolites of the Argan tree (Argania spinose L.). Online J. Anim. Feed  
Res., 10(4): 167-171.  
Phenolic compounds of Argan cake  
The cake from the extraction or meal is currently used as feed for fattening cattle. It is rich in carbohydrates and  
proteins (46.6% to 49%) and contains an important pharmacodynamic group consisting of saponins (Guillaume et al,  
2005) and also contains an important group of flavonoids (Table 4). The Argan cake is rich in flavonoids, sixteen  
flavonoids were found. Among these, epicatechin, catechin, protocatechic acid, vanillic acid and 4-hydroxybenzylic alcohol  
are higher in Argan cake. On the other hand, epicatechin is a powerful antioxidant from the flavonoid family. A recent  
American study shows that epicatechin has positive health effects and shows that it can significantly reduce the risks of  
coronary heart disease and stroke during regular consumption (Rees et al., 2018).  
Table 4 - Polyphenols from Argan cake  
N°  
1
2
Phenolic compound  
Catechol  
Resorcinol  
Concentration (mg / kg)  
1.4  
1.3  
3
4
4-hydroxybenzyl alcohol  
Vanillin  
8.6  
1.1  
5
Tyrosol  
6.2  
6
7
8
P-hydroxybenzoic acid  
(4-hydroxyphenylacetic) acid Alcohol  
vanillic alcohol  
14.1  
1.0  
3.6  
9
3.4-dihydroxybenzyl alcohol  
Methyl 3.4-dihydroxybenzoate  
vanillic acid  
Hydroxytyrosol  
Protocatéchic acid  
Syringic acid  
0.9  
1.6  
16.3  
0.9  
15.2  
6.6  
10  
11  
12  
13  
14  
15  
16  
Epicatechine  
Catechin  
110.1  
11  
CONCLUSION  
Argan cake is rich in flavonoids. Among these, epicatechin (110 mg/kg), catechin (11 mg/kg), protocatechic acid (15.2  
mg/kg), vanillic acid (16.3 mg/kg) and 4-hydroxybenzyl alcohol (8.6 mg/kg) are higher in Argan cake. Argan oil is richer in  
tocopherol (597 to 775 mg/kg), Argan oil is rich in gamma tocopherol (631 mg/kg), and this metabolite making Argan oil  
is a valuable nutraceutical. The flavonoid extract of the co-products of the Argan tree has a very interesting anti-radical  
and antioxidant activity. It is currently marketed as a cosmetic active protector of the skin's extracellular macromolecules  
such as collagen, glycoproteins for this reason the co-product of Argan has become very important in the cosmetic field  
and its most widespread marketed.  
DECLARATIONS  
Corresponding author: hilali400@yahoo.com  
Authors' contribution  
The author reviewed the document and contributed to the development of the content.  
Availability of data  
The data can be availed to the journal upon request.  
A conflict of Interest  
The author declare that there is no conflict of interests regarding the publication of this paper  
Acknowledgments  
The author would like to thank my fellow plant chemistry lab colleagues for their invaluable help and especially Mr.  
Mohamed Greih. To all the people who contributed directly or indirectly to the realization of this work, I send them my  
warmest thanks. The author has stated that he is not taking any funding to do this work or to publish this article.  
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