Enkleine: An Isoquinolone fromEnkleia siamensis

Abstract

Enkleia siamensis Kurz (Thymelaeaceae) is a climbing shrub commonly found in the northeastern region of Thailand. In a previous communication (1), we have reported on the isolation of three bioactive coumarins, namely, clausarin, daphnoretin, and nordentatin, from a cytotoxic extract of the roots. Further examination of the CHC13 fraction has now led to the isolation of two known compounds, identified as (-)-eudesmin, chamaej asmin(e), and a new isoquinolone alkaloid, enkleine (1), each of which was devoid of significant cytotoxic activity when tested in the KB and P-388 cell culture systems. The first isolate, m.p. 104-106°C, [a]0: 705° was identified as the lignan (-)-eudesmin. Its NMR and mass spectra were consistent with the general structure of eudesmin (2, 3), but the specific optical rotation indicates that it is antipodal to the common (+)-isomer.

Biflavonoids from Stellera chamaejasme

“…Recently, such biflavonoids have also been found in Wikstroemia sikokiana (Baba et al, 1994), W. indica (Hu et al, 2000), and Enkleia siamensis (Boonyaratanakornkit et al, 1991), all of which belong to Thymelaeaceae. The distribution of biflavonoids in these four plants, listed in Table 1, appears to indicate that the chemical relationship between the genera Stellera and Wikstroemia is closer than that between Stellera and Enkleia.…”

Chemical constituents and biological activities from roots ofEnkleia siamensis

“…A water decoction of its root was used traditionally as a laxative and the wood was used for skin disease, expectorate and cough from asthmatic bronchitis (Kesonbua & Chantaranothai 2011, p. 118). Previous phytochemical investigation of E. siamensis demonstrated the presence of (2 )-eudesmin, chamaejasmin, enkleine (Boonyaratanakornkit et al 1991), clausarin, nordentatin and daphnoretin (Luo et al 1986). As a part of our search for bioactive compounds from Thai plants, the crude EtOAc extract of E. siamensis showed a minimum inhibition to acetylcholinesterase (AChE) of 500 ng.…”