ÉTUDE ETHNOBOTANIQUE, PHYTOCHIMIQUE ET ACTIVITÉS BIOLOGIQUES DE TROIS PLANTES MEDICINALES RECOLTÉES EN ALGÉRIE

Abstract

The Algerian flora appears as a rich and interesting source for complementary ethnomedical and phytochemical studies. Our study focused, on one hand, on an ethnobotanical survey conducted with 42 individuals (08 phytotherapists, herbalists, and 32 local residents) from the Mostaganem province to document local knowledge on the traditional use of three medicinal plants namely L. guyonianum, R. raetem, and R. chalepensis, using a predefined questionnaire. On the other hand, aqueous extracts of the aerial parts and roots of L. guyonianum collected from El-Bayadh, the aerial parts of R. raetem from Mostaganem and Ghardaïa, and the aerial parts of R. chalepensis from Mostaganem and Aïn Sefra, were selected to quantitatively estimate phenolic compounds, identify their different classes of phytochemical metabolites, and evaluate their antioxidant and antimicrobial effects. The ethnobotanical survey allowed us to ascertain the frequent use of the studied plant for treating various diseases, the parts used, and the preparation methods by the surveyed population. Phytochemical screening to highlight the main secondary metabolites of the studied plants was established, as well as colorimetric quantification of total polyphenols (using the Folin-Ciocalteu method) and total flavonoids (using the aluminum trichloride method). The antioxidant activity of the aqueous extracts was tested in vitro through three different tests: the ABTS and DPPH radical scavenging assays and the ferric reducing antioxidant power (FRAP) assay. Tests were also conducted for their potential antibacterial activity against five pathogenic strains using the disc diffusion method. Analysis of the results shows that the studied species are among the most commonly used plants as sedatives and for treating diabetes, rheumatism, and digestive disorders. The aerial parts are the most commonly used parts, mainly in the form of infusions and poultices. Phytochemical screening revealed the richness of the aerial parts of the three species in coumarins, flavonoids, cardiotonic glycosides, free quinones, tannins, and essential oils, with a significant presence of these compounds, in addition to alkaloids in R. chalepensis from Aïn Sefra. The different extracts exhibited variable contents of polyphenols and flavonoids, with higher levels in the R. raetam and R. chalepensis extracts from desert areas, with values of 32.82 ± 0.9 and 17.44 ± 0.3 mg GAE/g DW, respectively. Conversely, the aerial parts of L. guyonianum exhibited the highest values compared to the roots, with contents of 2.92 ± 0.004 and 2.33 ± 0.02 GAE/g DW, respectively. The results showed that the same extracts exhibited the highest antioxidant activities compared to others for all tests. Moreover, these same extracts demonstrated considerable antibacterial properties against human pathogenic strains, notably against E. coli and C. albicans. The results highlight the importance of traditional knowledge and confirm the therapeutic potential of these plants.