Isolamento e caratterizzazione chimico-strutturale di metaboliti secondari dal genere Ononis e Seseli

In a continuation of our research on bioactive natural products form Seseli praecox we now focused on a population growing on the island of San Pietro (Sardinia). With respect to the population growing on limestone from Ogliastra (Sardinia) studied previously this population grows on weathered volcanic substrate and shows different morphological characteristics. Seseli sp. is a classical medicinal plant taxon and mentioned by Dioscorides as well as Galenos amongst other indications against orthopnea, chronic cough, uterine spasms and epilepsy. Orthopnea, a form of breathlessness caused by increased central and pulmonary blood volume has been associated with chronic heart failure. The phytochemical investigation of the extract obtained from the stems of S. praecox afforded five known khellactones, five furocumarines, two coumarins, two chromone, as well as falcarinol and falarindiol and a new natural compound 5-hydroxy-6-[3-(hydroxymethyl)-4-methyl-2-pentenyl]-7-methoxy-2-methyl-4-H-cromen-4-one. Khellactones are dihydroseselin type angular pyranocumarins and have been obtained from different Apiaceae species used in local medicine as well as food. Similar to the medicinal indications of Seseli sp., Ammi visnaga (L.) Lam. is used against cardio-vascular and urological problems. Visnadine, a khellactone obtained from A. visnaga fruits was shown to inhibit Ca2+ channels ex vivo. According on these data, 5 khellactones are tested as potential inhibitors to the Ca2+ channel. Only Hyuganin D was active. Different papers suggest that pyranocoumarins could be a potential MDR reversing agent. In this thesis we remark that Hyuganin D showed ability to induces calcium transients reproducible and in the same time are able to inhibit P-gp in Rhodamine123 efflux assay in Pgp transfected MDCK cells with an effect similar to vinblastine. We are currently developing the cytotoxicity test. We have also investigated the secondary metabolites of Ononis natrix, a small shrub belongs to the family Legumynose (tribe Trifoleae). The infusion of its roots and flowers has been used for the treatment of some disturbances of the urinary tract, in fact have been reported to have diuretic and antirheumatic proprieties. Members of this genus has been also used in folk medicine for the treatment of jaundice, kidney stones and skins diseases. Compounds isolated from the genus Ononis have also show antibiotic, molluscicidal, antiviral activities. In this thesis we describe the isolation and determination of the structure of three new natural product: two dihydroisocoumarins(1-1[(6,8-dihydroxy-1-oxo-3,4-dihydro-1H-isochromen-3-yl)methyl]heptyl acetate 1-[(6,8-dihydroxy-1-oxo-3,4-dihydro-1H-isochromen3 yl)methyl]-5-oxoheptyl acetate) and 4-methoxyphenyl 3-(4-methoxyphenyl)propanoate. Additionally we have isolated 12 know compounds (two flavones, four flavanones, a chalcone and six dihydrochalcones). All compounds were evaluated for their activity against Staphylococcus aureus and Candidaalbicans. The most active compound against S.aureus is 2’,6’-dihydroxy-4’-methoxydihydrochalcone (2 μg). 2’,4’-dihydroxy-6’-methoxydihydrochalcone, 1-[(6,8- dihydroxy-1-oxo-3,4-dihydro-1H-isochromen-3-yl)methyl]heptyl acetate and 4-methoxyphenyl 3-(4-methoxyphenyl)propanoate show a good activity against S. aureus(16 μg). Other compounds are less active than these. The most active compound against C. albicans is 7-hydroxy-8-methoxyflavone (8 μg) and 2’,4’-dihydroxy-6’-methoxy-dihydrochalcone show a good activity against C. albicans (16 μg).