HPLC analysis of Phenolic Substances and Anti-Alzheimer's Activity of Korean Quercus Species

This study aimed to establish the quantitative method to analyze the content of peroxynitrite-scavengers belonging to polyphenols in six Korean Quercus species (Quercus mongolica, Q. dentata, Q. acutissima, Q. alienta, Q. serrata, and Q. variabilis) by HPLC. The twelve peroxynitrite-scavengers, flavanols (catechins: (+)-catechin, (−)-epicatechin, and (−)-epigallocatechin), flavonols (kaempferol and quercetin), flavonol glycosides (astragalin, quercitrin, and isoquercitrin), flavonol acylated glycosides (astragalin 6″-gallate and isoquercitrin 6″-gallate), gallic acid and its dimer (ellagic acid) were analyzed by HPLC. Further, anti-Alzheimer's activity was assayed in a passive avoidance testusing mice by measuring the retention latency (sec), the concentration of acetylcholine (ACh), and acetylcholinesterase (AChE) activity. Simultaneous analysis of the extracts of the six Quercus leaves was achieved on a Capcell C18 column (5 µm, 250 mm × 4.6 mm i.d.) with a gradient elution of 0.05% HAc and 0.05% HAc in CH₃CN. In the extract of Q. mongolica leaves, the content of gallic acid (32.53 mg/g), (+)-catechin (28.78 mg/g), (−)-epicatehin (22.03 mg/g), astragalin 6″-gallate (20.94 mg/g), and isoquercitrin 6″-gallate (44.11 mg/g) and peroxynitrite-scavenging activity (IC₅₀, 0.831 µg/ml) were high. This extract delayed the retention latency and inhibited acetylcholinesterase activity in scopolamine-induced memory impairment of mice, suggesting that it has anti-Alzheimer's activity.

The Effect of Raffaelea quercus-mongolicae Inoculations on the Formation of Non-conductive Sapwood of Quercus mongolica

In Korea, mass mortality of Quercus mongolica trees has become obvious since 2004. Raffaelea quercus-mongolicae is believed to be a causal fungus contributing the mortality. To evaluate the pathogenicity of the fungus to the trees, the fungus was multiple- and single-inoculated to the seedlings and twigs of the mature trees, respectively. In both the inoculations, the fungus was reisolated from more than 50% of inoculated twigs and seedlings. In the single inoculations, proportions of the transverse area of non-conductive sapwood at inoculation points and vertical lengths of discoloration expanded from the points were significantly different between the inoculation treatment and the control. In the multiple inoculations, no mortality was confirmed among the seedlings examined. These results showed that R. quercus-mongolicae can colonize sapwood, contribute to sapwood discoloration and disrupt sap flows around inoculation sites of Q. mongolica, although the pathogenicity of the fungus was not proven.

Chemical constituents from barks of Quercus mongolica / 中草药

Objective: To study the chemical constituents from the barks of Quercus mongolica. Methods: The chemical constituents were isolated and purified on the base of silica gel column chromatography and HPLC method. The structural elucidation was performed according to the physicochemical properties and spectral analysis. Results: Twenty compounds were isolated and identified as taraxerone (1), taraxerol (2), 20β-hydroxydammara-23-en-3-one (3), 20 (S), 24 (S)-dihydroxydammara-26-en-3-one (4), ursotic acid acetate (5), lupeol (6), β-sitosterone (7), isofouquierol (8), gallic acid (9), 5, 6, 7, 4'-tetrahydroxyflavanone (10), taxifolin (11), scopoletin (12), kaempferol (13), β-sitosterol (14), secoisolariciresinol (15), erythrodiol (16), (-)-epicatechin (17), daucosterol (18), (-)-epipinoresinol (19), and salicylic acid (20). Conclusion: Compounds 1, 2, 5, 6, and 11 are isolated from this plant for the first time, and compounds 4, 7, and 8 are isolated from the plants of Quercus L. for the first time.