Chemical diversity of Moroccan medicinal and aromatic plants and their potential for agricultural bioproducts

Abstract

Terry, Leon A. - Associate Supervisor Beale, Mike H. - Associate Supervisor Sobeh, Mansour - Associate SupervisorBiostimulants and bioprotectants (bioproducts) have been recognised as potential alternatives to synthetic agrochemicals, or as substances that could enhance their use efficiency. Extracts from medicinal and aromatic plants, and their constituent secondary metabolites are major sources of bioproducts. In arid areas of Morocco, medicinal and aromatic plants are abundant and potentially contain rich and unique metabolites, but they have not been widely assessed for their chemical composition as well as biostimulant and bioprotectant potential. In this work, phytochemical profiling of nine medicinal and aromatic plants from Morocco was undertaken. The first report on the chemical profile of Vachellia gummifera including the distribution of metabolites between its leaves and stems is presented. Additionally, this work presents arguably the most comprehensive report on the chemical profile of polar extracts from Ammodaucus leucotrichus that includes five previously undescribed compounds comprising two terpenoids and three lignans, in addition to 39 compounds that are reported from the plant for the first time. The novel compound, 8-(1H-indol-3-yl-methyl)rutin, which is a methylene bridged 1H-indole- flavonoid glycoside conjugate is also reported from the polar leaf extract of Capparis spinosa. Biostimulant assessments using a seed soaking treatment revealed only minor positive effects as most polar extracts showed no significant stimulation of wheat growth. Significant phytotoxicity was however shown with extracts of Peganum harmala and C. spinosa. These inhibited the emergence and growth of wheat seedlings, with more potent activity being observed with C. spinosa. This phytotoxicity could be beneficially exploited in the development of bioherbicides. Bioprotectant assessments through antifungal tests on pathogens relevant to major African crops did not produce any significant results for extracts of all the plant species. The link between chemical profiling and bioactivity, the beneficial exploitation of phytotoxicity, and the key challenges for implementing bioactive extracts on a large scale are discussed.PhD in Environment and Agrifoo