Background: Salix gilgiana is a deciduous tree that grows in northern Japan, the Korean peninsula, eastern Russia along the Ussuri River, and northeast China. The stem of this tree is dried and consumed orally as a folk medicine. Our intensive screening of various plant materials found that the MeOH extract of its dried stem exhibited significant antiproliferative activity against HL-60 leukemic cells with an IC50 of 16 ppm. We systematically investigated the biologically active compounds of the MeOH extract of the dried stem of S. gilgiana.
Methods: The MeOH extract of S. gilgiana dried stem was fractionated by a repeated chromatography monitored by antiproliferative activity against HL-60 leukemic cells. Five active compounds were isolated and the structures were elucidated by MS, 1H- and 13C-NMR spectroscopy, and X-ray analysis.
Results: The active compounds were identified as 7-ketositosterol (I), 7β-hydroxysitosterol (II), 7α- hydroxysitosterol (III), (4-hydroxyphenyl)ethanol (IV), and (4-hydroxyphenyl)propan-1-ol (V). The strongest activity was found for 7α-hydroxysitosterol (III), with an IC50 of 8.4 µM. This is the first report of the isolation of these compounds from S. gilgiana.
Conclusion: Five compounds were isolated by a repeated chromatography under the guidance of antiproliferative bioassay using HL-60. The structures were identified as three β-sitosterol oxides and two phenolic compounds. Since Salix species, namely, willow trees, have beneficial characteristics including rapid growth, easy cloning, and resistance to high humidity and dryness, they may be utilized as a relatively inexpensive tool for the efficient production of useful bioactive materials.
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