Quassinoids from Eurycoma longifolia

Abstract

Three quassinoids, eurycolactone D (1), eurycolactone E (2) and eurycolactone F (3) were isolated from the roots of Eurycoma longifolia Jack. The structures of 1–3 were elucidated by spectroscopic methods, and that of 3 was further confirmed by X-ray crystallography. The known quassinoids, laurycolactone B (4) and eurycomalactone (5) were also identified.

Introduction

Eurycoma longifolia Jack, an indigenous plant to Southeast Asia, is a tall slender shrub tree commonly found as an understory in the lowland forests at up to 500 m above sea level (Goh et al., 1995). Over the years, phytochemical studies carried out on the roots of this plant showed that among others, it possesses bitter constituents collectively known as quassinoids (Thoi and Suong, 1970, Suong et al., 1982, Darise et al., 1982, Bates et al., 1984, Chan et al., 1986, Chan et al., 1989, Chan et al., 1991, Chan et al., 1992, Morita et al., 1990, Kardono et al, 1991, Tada et al., 1991, Itokawa et al., 1992, Itokawa et al., 1993, Ang, Chan and Mak, 1995a, Ang, Chan and Mak, 1995b, Darise et al., 1983). The wide spectrum of pharmacological activities viz. antimalarial (Chan et al., 1986, Chan et al., 1989, Kardono et al, 1991, Ang, Chan and Mak, 1995a, Ang, Chan and Mak, 1995b), antiulcer (Tada et al., 1991), antipyretic (Chan et al., 1995) and cytotoxic to cancer cells (Morita et al., 1990, Kardono et al, 1991, Itokawa et al., 1992) associated with these quassinoids has further prompted us to continue on with our investigation for new quassinoids from this plant (Ang et al., 2000).

Hence, we wish to report on the isolation and characterisation of the C₁₈-quassinoid, eurycolactone D (1) and the two C₁₉-quassinoids, eurycolactone E (2) and eurycolactone F (3) along with the two known quassinoids, laurycolactone B (4) (Suong et al., 1982) and eurycomalactone (5) (Suong et al., 1982). The structures of these quassinoids were elucidated based on analysis of spectral evidence.