~ Pergamon PIh S0031-9422(97)00517-7 Phytochemistry, Vol. 47, No. 1, pp. 117-119, 1998 © 1997 Elsevier Science Ltd. All rights reserved Printed in Great Britain 0031-9422/98 $19.00+0.00 ISOFLAVONOIDS AND A PTEROCARPAN FROM GLIRICIDIA SEPIUM H. M. T. B. HERATH*, R. S. DASSANAYAKE, A. M. A. PRIYADARSHANI, SUSILA DESILVA, G. P. WANNIGAMA~ and JOANNEJAMIE~" Natural Products Programme, Institute of Fundamental Studies, Kandy, Sri Lanka; Department of Chemistry, University of Peradeniya, Peradeniya, Sri Lanka; t Department of Chemistry, University of Wollongong, Wollongong, NSW 2522 Australia (Received 11 March 1997) Key Word Index--Gliricidia sepium; Leguminosae; insecticidal activity; toxicity; isoflavans; isoflavones; isovestitol; formononetin; afrormosin; pterocarpan; medicarpin. Abstract--A new isoflavan, 7,4'-dihydroxy-3'-methoxyisoflavanhas been isolated from the insecticidally active hot dichloromethane extract of the heartwood of Gliricidia sepium, along with the three other isoflavonoids, isovestitol, formononetin and afrormosin, a pterocarpan, medicarpin and 4-hydroxy-3-methoxy- cinnamaldehyde which are new to this species. © 1997 Elsevier Science Ltd INTRODUCTION Gliricidia sepium grows as a shade plant in the tea plantations of Sri Lanka. Previous studies on the insecticidal activity of G. sepium have shown that all parts of this plant have activity against Southern army worm, Cabbage looper, and Yellow woolly bear [1]. Though the main reason for planting G. sepium in a tea field is to cut off direct sunlight to maintain the optimum lighting conditions required by tea plants, it has been found that G. sepium also acts as a good diversionary host plant for Glyptotermes dilatatus, a tea pest responsible for causing great damage in the low country tea plantations of Sri Lanka. Olfac- tometer experiments showed that the attraction of the termite G. dilatatus towards the heartwood and the stem bark of G. sepium, and their organic extracts, is even significantly higher than that to some of the highly susceptible tea clones. Further feeding experi- ments involving different parts of the whole plant, and organic extracts of G. sepium, indicated that the heartwood was highly toxic and that the hexane and dichloromethane extracts were also significantly toxic to Glyptotermes dilatatus. These bioassay results sug- gested that chemical investigation of G. sepium would be of interest in order to isolate the semiochemicals responsible for the attraction, as well as the toxic elements causing the death of termites. Most of the previous chemical investigations of G. sepium have focused on the leaves and this has led to the isolation * Author to whom correspondence should be addressed. of 15 allelopathic compounds [2], including a coumarin. Two new hydrocarbons and another rare hydrocarbon have been found in the petioles of the species [3]. Two flavonoid glycosides [4, 5], an isofla- van, an isoflavene and some other flavonoid constit- uents have also been reported from G. sepium [6, 7]. This paper describes the isolation and structural eluci- dation of a new isoflavan, 7,4'-dihydroxy-3'-methoxy- isoflavan (1) from the heartwood of G. sepium along with another isoflavan, isovestitol (2), two isoflavones, formononetin (3) and afrormosin (4), and a ptero- carpan, medicarpin (5). Afrormosin (4) has been reported as a powerful antitumour promoting agent [8], whilst medicarpin (5) is known to be antifungal [9]. RESULTSAND DISCUSSION HR-MS established the molecular formula C16H1604 for compound 1. The base peak at m/z 150 and another prominent peak at m/z 123 in the mass spectrum of 1 corresponding to the basic fragment ions of the isoflavan ring system, gave evidence for an isoflavan type of structure. Signals for the aliphatic protons H-2, H-3 and H-4 in the ~H NMR spectrum of I indicated the presence of an isoflavan-type C-ring (see Experimental). Decoupling studies on each of the above individual aliphatic proton signals confirmed the assignment of the proton resonances. The aro- matic region of the IH NMR spectrum showed two sets of ABX protons. The base peak m/z 150 in the mass spectrum showed that the single methoxyl group of compound 1 is attached to ring B of the molecule. Irradiation of the protons of this methoxyl group 117