Quantification of secondary metabolites and the evaluation of the in vitro antioxidant activity of the Argan tree of eastern Morocco

Abstract

Argania Spinosa (L.) Skeels is an endemic species of Morocco that belongs to the Sapotaceae family and which recommends a warm climate, and most of its trees are grown in tropical regions. This population is highly concentrated in the southwest of Morocco but is also found as a relic in the eastern region of the country. This work aims to valorize the different parts of the Argan plant (Leaves, branches, and for the first-time flower-buds) grown in two sites of eastern Morocco, Oujda (820885,945; 455262,165 Meters) and Chouihiya (755725,636; 477 008,053 Meters) coordinate system: nord Maroc, and this by the quantification of different secondary metabolites such as polyphenols, flavonoids, and tannins. The investigation of their antioxidant activity was assessed using two different technics, the free radical scavenging activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) and the ferric reducing power (FRAP). The crude extracts were obtained by soaking the different parts of Argania Spinosa L. in a hydroalcoholic solution (70%) for 48 h.The quantitative evaluation of the various secondary metabolites of the different studied parts of the plant showed that flower-buds and leaves from Oujda are the highly rich with polyphenols, and flavonoids respectively, Fb-O :498,9 ± 20,08 µg Eq AG/mg DW; Le-O :71,2 ± 0,8 µg Eq QE/mg DW. On the other hand, the results obtained reveals that the tannins are very concentrated in flower-buds from Chouihya 212,4 ± 5,8 µg Eq CA/mg DW. It was also found that the different secondary metabolites vary between the two regions studied and different organs. All the extracts for the two regions showed interesting antioxidant activities compared to the Ascorbic acid used as a standard for the DPPH and the FRAP. The antiradical activity of the crude extract of the flower-buds from Oujda showed the best IC50 with a value of 64,68 ± 3,5 µg/ml, while the leaves from Oujda showed the smallest IC50 value 208,33 ± 5,08 µg/ml in the ferric reducing power test comparing to the other parts of the plant. The antioxidant activities varied significantly according to both regions and organs.