Jae Yeon Lee

Neolignan inhibitors of antigen-induced degranulation in RBL-2H3 cells from the needles of Pinus thunbergii

The ethanolic extract of the needles of Pinus thunbergii was found to suppress antigen mediated degranulation of rat basophilic leukemia (RBL-2H3) cells. A new neolignan glycoside, named pinusthunbergiside A (1), as well as six known neolignan glycosides (2-7) were isolated from the ethanolic extract using bioassay-guided fractionation. Their structures were elucidated by a combination of 1D and 2D NMR, HRESI-MS, and circular dichroism (CD) data. Compounds 2-7 were found for the first time in this plant. The inhibitory effects of isolated constituents on the release of β-hexosaminidase from RBL-2H3 cells were examined, and compounds 2, 3, 5, and 6 were found to show the inhibitory activity with IC₅₀ values ranging between 52.3 and 75.3 μM.

Inhibition of Antigen-Induced Degranulation by Flavonoids Isolated from the Leaves of Quercus Acuta in RBL-2H3 Cells

The genus Quercus has been taxonomically included in the Fagaceae with over 500 species from all corners of the globe. Q. acuta is distributed only in Korea, Japan, China s Guizhou Province, and Guangdong Province and grows in warmtemperate evergreen broadleaf forests [1]. The stems of Q. acuta have been used as a medicinal source for the treatment of various disorders such as diarrhea, dermatitis, arteriosclerosis, and haemorrhagia in Korea [2]. Previous phytochemical studies on this plant have reported the isolation of various types of phenolic compounds such as tannins, proanthocyanidins, lignans, and flavonoids, which possess various pharmacological effects such as anti-inflammatory, antibacterial, and antioxidant activities [2, 3]. In our research program on plant-derived inhibitors of the release of -hexosaminidase, the ethanolic extract of the leaves of Q. acuta was found to suppress antigen-mediated degranulation of rat basophilic leukemia (RBL-2H3) cells. A polyacylated flavonol glucoside (1), three flavone derivatives (2, 5, and 9), and seven flavonol derivatives (3, 4, 6, 7, 8, 10, and 11) were isolated from the ethanol extract using bioassay-guided fractionation. Compounds 1–11 were identified as kaempferol 3-(3 ,4 -diacetyl-2 ,6 -di-E-p-coumaryl)-glucoside (1), luteolin (2), guiajaverin (3), avicularoside (4), cynaroside (5), quercitrin (6), hyperoside (7), isoquercitrin (8), apigenin (9), quercetin (10), and kaempferol (11), by spectroscopic analysis (MS, 1D, and 2D NMR) and comparisons with literature data. This is the first time that the isolation of compounds 1–11 has been reported from Q. acuta species. We tested the antiallergic activity monitored by the enzyme -hexosaminidase: the compounds 1, 2, 9, 10, and 11 showed a good antiallergic potential (Table 1).