Phytochemical investigation of food and medicinal plants from the Saudi Arabia flora

In the context of the efforts for building up a comprehensive inventory of Saudi medicinal plants, my PhD thesis came to contribute in these efforts to ‗unearth' Saudi plants treasure. The Kingdom of Saudi Arabia (KSA) is a giant arid area covering about 2,250,000 km2 of the Arabian Peninsula among which, KSA possesses the richest flora biodiversity. Great advancements in Saudi health care systems experienced in last decades did not substitute the use of plants as folk medicine among Saudi population. A considerable number of these medicinal plants were subjected to phytochemical and biological studies and these studies have revealed astonishing biological activities and have uncovered novel phytochemicals among Saudi flora. In my PhD, two Saudi plants were selected: Cissus rotundifolia (Forssk.) Vahl and Anvillea garcinii subsp. radiata (Coss & Durieu) Anderb, on the basis of their traditional use by Saudi population in folk medicine and/or as food. C. rotundifolia is an edible plant traditionally used as antihyperglycemic agent. The ethanolic extract of this plant was subjected to a bio-guided fractionation which led to the isolation of a new sucrose diester of truxinic acid (cissuxinoside), an unprecedented glycosylated and extensively conjugated dicarboxylic acid (cissoic acid), three flavones C-glycosides (one of which was fully characterized for the first time), and two coumaric acid derivatives. One of these latter compounds (namely, 1-O-p-coumaroyl-β-D-glucopyranose) was found to be the main responsible for the anti-diabetic activity of the extract. The second plant investigated in my project was A. garcinii, which is traditionally used to treat dysentery, gastric ulcers, and pulmonary infections. In this project A. garcinii was subjected to comprehensive phytochemical investigation which revealed the presence of four new sesquiterpenoids, five known germacranolides in addition to flavonoids and polypenolics. The isolated compounds were tested for their antimicrobial activities against pathogenic fungi and bacteria and Anvillea sesquiterpenoids have shown remarkable activity against some of the tested pathogens.