Two new azulene pigments, 7-(1-hydroxy-1-methylethyl)-4-methylazulene-1-carbaldehyde (1) and 4methyl-7-(1-methylethyl)azulene-1-carboxylic acid (2), were isolated from the fruiting bodies of the basidiomycete Lactarius hatsudake, together with one known azulene pigment (3). Their structures were determined by spectroscopic means (including 2D-NMR) and by HR-TOF-MS experiments.
Introduction. -The mushrooms belonging to the genus Lactarius (family Russulaceae, Basidiomycotina) form a milky juice when their fruiting bodies are injured. In the great majority of Lactarius species, different kinds of sesquiterpenes play important biological roles, being responsible for the pungency and bitterness of the milky juice, and for changes in latex color when exposed to air.
Lactarius hatsudake is an edible, slightly bitter mushroom widely distributed in China, Japan, Europe, and North America. Similar to L. deliciosus, the latex of the fruiting bodies is at the beginning orange-colored, but then slowly darkens (within minutes), and eventually turns blue-green when the fruiting bodies are cut or broken [1]. These colors in L. deliciosus have previously been shown to be due to guaiane sesquiterpenes. Lactaroviolin [2], the free dihydroazulene alcohol and its stearic acid ester [3], lactarazulene [4], and lactarofulvene [5] have been isolated from specimens of L. deliciosus in different areas of the world.
During our search of bioactive metabolites of Lactarius and Russula species from Yunnan Province, China [6 -10], we recently isolated two new azulene pigments from the fruiting bodies of L. deliciosus [11]. Herein, we report the isolation and structure elucidation of two the new azulene pigments 1 and 2 from the fruiting bodies of L. hatsudake.
Results and Discussion. -The fresh fruiting bodies of L. hatsudake (4.65 kg) were extracted with acetone, and the combined extracts were evaporated to give a deepbrown syrup, which was partitioned between H 2 O and AcOEt. The organic layer was concentrated in vacuo to afford a residue (40 g), which was subjected to repeated column chromatography to afford compounds 1 -3.
Compound 1 was obtained as a red-purple solid. Its molecular formula was determined as C 15 H 16 O 2 on the basis of HR-TOF-MS data ([M + H] + at m/z 229.1229;