BIOACTIVE STEROIDS AND TRITERPENES FROM MELILOTUS-MESSANENSIS AND THEIR ALLELOPATHIC POTENTIAL

The aerial parts of Melilotus messanensis (sweet clover) afforded, fro m moderately and polar bioactive fractions, 11 triterpenes and five st eroids. A series of aqueous solutions at 10(-4)-10(-9) M of five stero ids and nine triterpenes was monitored to test their effects on germin ation and growth of the monocots Hordeum vulgare and Allium cepa, and the dicots Lactuca sativa (var. nigra and var. romana) and Lycopersico n esculentum. An important stimulatory effect on H. vulgare germinatio n (between 40% and 80% for almost all tested compounds) was observed. Some considerations about the ecological role of triterpenes on M. mes sanensis are made. In addition to known lupane triterpenes (platanic a cid and 3 beta,28,30-lup-20(29)-enetriol), oleanane triterpenes (soyas apogenol B, soyasapogenol G, and messagenolide), a gammacerane triterp ene (gammacer-16-en-3-one), five new lupane triterpenes (messagenic ac ids A-E: (27-cis-4-hydroxycinnamoyloxy)-betulinic acid; 27-(trans-4-hy droxycinnamoyloxy)betulinic acid; 20(S)-3 beta-hydroxy-29-oxolupan-28- oic acid; 3 beta,30-dihydroxylup-20(29)-en-28-oic acid; and 3 beta,20- dihydroxylup-18(19)-en-28-oic acid, respectively), and sterols (beta-s itosterol, ergosterol peroxide, 7 alpha-hydroxysitosterol, 7 beta-hydr oxysitosterol, and 7-oxositosterol) were isolated and chemically chara cterized. Their structures and stereochemistry were elucidated by spec troscopic methods (one- and two-dimensional H-1 and C-13 NMR, IR, MS).