Journal of Chemical Ecology, Vol. 23, No. 7, 1997 BIOACTIVE STEROIDS AND TRITERPENES FROM Melilotus messanensis AND THEIR ALLELOPATHIC POTENTIAL1 FRANCISCO A. MACIAS,* ANA M. SIMONET, and JUAN C. G. GALINDO Departamento de Quimica Organica Facultad de Ciencias, Universidad de Cadiz Apdo. 40, 11510 Puerto Real, Cadiz, Spain (Received May 17, 1996; accepted March 10, 1997) Abstract—The aerial parts of Melilotus messanensis (sweet clover) afforded, from moderately and polar bioactive fractions, 11 triterpenes and five steroids. A series of aqueous solutions at 10T^-IO' 9 M of five steroids and nine tri- terpenes was monitored to test their effects on germination and growth of the monocots Hordeum vulgare and Allium cepa, and the dicots Lactuca sativa (var. nigra and var. romana) and Lycopersicon esculentum. An important stimulatory effect on H. vulgare germination (between 40% and 80% for almost all tested compounds) was observed. Some considerations about the ecological role of triterpenes on M. messanensis are made. In addition to known lupane triterpenes (platanic acid and 30,28,30-lup-20(29)-enetriol), oleanane triterpenes (soyasapogenol B, soyasapogenol G, and messagenolide), a gammacerane triterpene (gammacer-16-en-3-one), five new lupane tri- terpenes (messagenic acids A-E: (27-cis-4-hydroxycinnamoyloxy)-betuIinic acid; 27-(trans-4-hydroxycinnamoyloxy)betulinic acid; 20(S)-3/3-hydroxy-29- oxolupan-28-oic acid; 3|8,30-dihydroxylup-20(29)-en-28-oic acid; and 3/3,20- dihydroxylup-18(19)-en-28-oic acid, respectively), and sterols (/3-sitosterol, ergosterol peroxide, 7a-hydroxysitosterol, 7/3-hydroxysitosterol, and 7-oxosi- tosterol) were isolated and chemically characterized. Their structures and ste- reochemistry were elucidated by spectroscopic methods (one- and two-dimen- sional 'H and "C NMR, IR, MS). Key Words—Melitotus messanensis, lupane triterpenes, messagenic acids; messagenolide, soyasapogenol G, gammacer-16-en-3-one, oleanane triter- penes, steroids, stigmasterols, ergosterol peroxide, allelopathy, Lactuca sativa, Lycopersicon esculentum, Allium cepa, Hordeum vulgare. *To whom correspondence should be addressed. ' Part 5 in the series "Natural Products as Allelochemicals"; for Part 4 see Macias et al. (1996). 1781 0098-0331/97/0700-1781$12.50/0 O 1997 Plenum Publishing Corporation