Valorization of biodiversity : phytochemistry, biological activities of two wild olive subspecies

Abstract

As part of the valorization of natural resources“wild and endemic plants”, two subspecies of the wild olive trees that have been inventoried in Algeria, one of which is commonly referred to Oleaster "Olea europaea L.var. sylvestris", spreads mainly in the northern region, and the other is known as ālew or āliwan among the Tuareg Berbers "Olea europaea subsp.laperrinei", spreads in the central Sahara. The first part deals with physio-anatomical mechanisms developed to adapt to their environmental conditions. The histological study and the physiological parameters measured revealed that the laperrine olive tree exhibited significant anatomical and physiological changes compared to the Oleastre tree. The second part focuses on studying of phenolic profiles of aqueous and methanolic leaf extracts from the two subspecies by high-performance liquid chromatography analysis which allowed the identification of several phenolic compounds with oleuropein as the main compound in all extracts, with Saharan subspecies extracts showing a higher level.All the extracts showed significant antiradical activity, but a high value was detected in the Saharan subspecies extracts with an IC50 value near to those exerted by the butylated hydroxytoluene, Methanol was found as a better extraction solvent than water. The third part relates to a phytochemical study and the antibacterial activity of the two essential oils, the gas Chromatography coupled with flame ionization detector analysis revealed the identification of 31 compounds where α-pinene main components in Olea europaea subsp. laperrinei volatile oil and 29 compounds with nonanal as major constituents in the Oleaster, both volatile oils showed an efficient antibacterial activity, with the endemic one has a higher range of inhibition, in which P. aeruginosa is the sensitive strain and K. pneumoniae is the resistant one. The last part is based on the valorization of the nutritional value of their extra virgin olive oils, through their chemical analysis, and their therapeutic value through their antibacterial activity. The results allowed the detection of 22 components in Olea europaea L.var. sylvestris oil, with squalene, oleic acid, palmitic acid, linoleic acid, as predominant components, while 14 components were identified in the endemic one, in which palmitic acid, linoleic acid, oleic acid, squalene were the main components. Unsaturated fatty acids represented the dominant class in the two oils, where the linoleic acid was apparent by high percentage and significant amount for the first time comparable with the previous study that was conducted on olive oil. In addition, the results indicate that the effect of the two extra virgin oils on gram positive bacteria is greater than on gram negative bacteria, with Olea europaea subsp. laperrinei oil exhibited the highest range of inhibition with all bacterial strains tested.