In addition to the known 3-oxoplatanic acid, melilotigenin and soyasapogenol E, two new lupane (messagenic acids F, G), two nor-lupane triterpenic acids (messagenic acids H, I), and three new oleanane triterpenes (melilotigenins B-D) were isolated and characterized from the polar bioactive fractions of Melilotus messanensis. The synthesis of messagenic acids D, F, G, betulonic acid and 3,29-dioxolup-20(30)-en-28-oic acid has been carried out from betulinic acid. These compounds exhibited clear selectivity (parameters and species) over germination and growth of monocotyledon species with average of inhibition of -50% on the germination of Hordeum vulgare, and average of stimulation of 30% on the germination of Allium cepa.