Niebla homalea (Ach.) Rundel & Bowler

Zhang, Yan, Tan, Choon Yong, Spjut, Richard W., Fuchs, James R., Kinghorn, A. Douglas & Rakotondraibe, Liva Harinantenaina, 2020, Specialized metabolites of the United States lichen Niebla homalea and their antiproliferative activities, Phytochemistry (112521) 180, pp. 1-7 : 5-7

3.3. Extraction and isolation of secondary metabolites of Niebla homalea

The lichen Niebla homalea (Ach.) Rundel & Bowler (62 g) was macerated for 1 week with 3 L of ethyl acetate. The extract was filtered and concentrated in vacuo to yield 4 g of a brown residue. This ethyl acetate residue was subjected to passage over a silica gel column [SiliaFlash® P60 (230–400 mesh)], and eluted sequentially with hexane containing increasing amounts of ethyl acetate (1:0, 20:1, 10:1, 5:1, 2:1, 1:1, and 0:1), to afford ten major fractions labeled N1 to N10. Fraction N2 (20 mg) yielded compound 6 (5 mg) by precipitation in chloroform (CHCl 3). Fractions N3 (6 mg) and N4 were washed with chloroform to afford compounds 4 (1 mg) and 7 (6 mg), respectively. Fraction N5 (40 mg) was purified using a C 18 column ( CH 3 CN–H 2 O, 7:3) to give 5 (3 mg). Fraction N6 (40 mg) was purified also via a C 18 column ( CH 3 CN–H 2 O, 3:2) to yield compound 9 (3 mg). Fraction N7 (120 mg) was chromatographed over a Sephadex LH-20 column with hexane-CHCl 3 -MeOH (5:5:1) as solvent and washed with hexanes-CHCl 3 -MeOH (5:5:1) to afford 11 (6 mg). Fraction N8 (170 mg) was chromatographed over a Sephadex LH-20 column, eluted with hexanes-CHCl 3 -MeOH (5:5:1), and further purified via silica gel column chromatography (hexanes-EtOAc, 5:1) to yield 12 (4 mg) and 8 (4 mg). Fraction N9 (130 mg) was chromatographed over a Sephadex LH-20 column with hexanes-CHCl 3 - MeOH (5:5:1) and further purified via a C 18 column ( CH 3 CN–H 2 O, 7:3) to yield compounds 2 (2 mg) and 3 (2 mg). Fraction N10 (70 mg) was chromatographed over a Sephadex LH-20 column with hexanes-CHCl 3 - MeOH (5:5:1) and washed with hexanes-CHCl 3 -MeOH (5:5:1) to yield 3 mg of 1 and 4 mg of 10.