A new minor alkaloid from the flowers of Ecbinops arbinatus has been identified as 7-hydroxy-3-(2-hydroxyethyl)-(3H)quinazolin-4-one and named 7-hydroxyechinozolinone Ill. Earlier work on Ecbinops ecbinatus Roxb. (Compositae) resulted in the isolation of several compounds, viz., a flavone glycoside (l), alkaloids (2), triterpenoids, the antifeedant compound ethyl palmitate (3), and flavonoids (4). So far there have been no chemical investigations reported on alkaloids from the flowers of this plant. The basic fraction of the flowers led to the characterization of a new minor alkaloid, 7-hydroxy-3- (2 -hydroxyethyl)-( 3H)-quinazolin-4-one El], as its hydrochloride.The flowers of E. echinatus were extracted with MeOH, and the CHCI, part of a pH gradient extraction, on chromatographic separation, afforded compound 1, EM]+ mlz 206, as an amorphous base. Compound 1 was found to be homogeneous on tlc and by ms. Its it (KBr) absorption bands at 1658 and 1605 cm-'and theuvspectral data at A max 232, 266, and 340 nm were similar to those of (3H)-quinazolin-4-one (5). The ir spectrum of 1 showed the presence of an OH group (3300 cm-' br), and the uv spectrum on addition of NaOMe was shifted to A max 248, 292, and 384 nm, suggesting the presence of a phenolic hydroxyl group. The 'H-nmr spectrum of 1 (CD,OD, 100 MHz) clearly showed the presence of a P-hydroxyethylrnoiety(64.15,2H, t, 1 $$J = 5$$ Hz; δ 3.58, 2H, t, J = 5 Hz). The presence of a 7-hydroxy group was demonstrated by the appearance of a double at δ 7.82 ( $J = 8.5$ Hz) due to the H-5 and a double doublet at δ 7.54 ( $J_{5,6} = 8.5$ Hz and $J_{6,8} = 2.65$ Hz) due to H-6. The H-8 appeared as a doublet ( $J = 2.65$ Hz) at δ 7.50 due to meta coupling with the H-6. The H-2 appeared as a sharp singlet at δ 8.86.During the literature survey, it was found that the H-2 signal of febrifugine, a 3-substituted (3H)-quinazolin-4-one derivative having antimalarial activity, appeared at 6 8.91 in its hydrochloride (6). This was further confirmed by the 'H-nmr study of synthetic echinozolinone hydrochloride, in which H-2 appeared as a singlet at 6 8.90 (unpublished results). This fact was well corroborated wth the H-2 chemical shift value of compound 1 as its hydrochloride.The eims ion peaks at mlz 135 and 107, due to retro-Diels-Alder fragmentations (2), are consistent with structure 1. The other fragment ion peaks of compound 1 at m/z 189, 188, 162, and 161 were derived in the pathways similar to those of echinozolinone (2). Compound 1 is, therefore, 7-hydroxy-3-(2-hydroxyethyl)-(3H)-quinazolin-4-one hydrochloride, and is a new alkaloid to which the trivial name of 7-hydroxyechinozolinone has been given.