Comprehensive identification of potential antioxidant components in the aerial parts of Polygonum chinense L. var. hispidum using ultra high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry

Distribution of polyphenolic and sugar compounds in different buckwheat plant parts

The aim of this study was to provide information on the phenolic and sugar profiles of different parts of the buckwheat plant, which can define that buckwheat is a functional food, with a high nutritional value and very useful for human health. Therefore, the extracts of buckwheat leaf, stem, and flower, as well as buckwheat grain were analysed for the content of polyphenol and antioxidant tests. The identification of a notable number of phenolic compounds and quantification of sugars in different parts of buckwheat indicates that buckwheat is a highly valuable plant. A total of 60 phenolic compounds were identified (18 cinnamic acid derivatives, 14 flavonols, 13 flavan-3-ols (including proanthocyanidins), 10 hydroxybenzoic acid derivatives, and 5 flavones) using ultra-high-performance liquid chromatography (UHPLC), coupled with a hybrid mass spectrometer which combines the Linear Trap Quadrupole (LTQ) and OrbiTrap mass analyzer. The highest number of phenolic compounds was found in the analysed buckwheat flower sample, and then in the leaf, followed by the grain and the stem. In addition, the sugar profile of buckwheat leaf, stem, flower and grain, as well as the buckwheat pollen and the nectar was analysed. Hence, 16 sugars and 5 sugar alcohols were detected by the high-performance anion exchange chromatography (HPAEC) with a pulsed amperometric detector (PAD). Sucrose was found in a significant amount with the highest content in buckwheat leaf. Trisaccharides had similar accumulation in the sample extracts, while disaccharides dominated in buckwheat leaf, followed by nectar and pollen. The sugar alcohols showed the highest content in buckwheat grain, where erythritol was predominant. The obtained results show that buckwheat is very rich in phenolic compounds and sugars. In addition to grain, the other parts of the buckwheat plant can be used as a very good source of different classes of phenolic compounds. This study provides useful information on the distribution of phytochemicals in different parts of the buckwheat plant, which contribute to the maintaining of the status of buckwheat as a functional food.

The aim of this study was to provide information on the phenolic and sugar profiles of different parts of the buckwheat plant, which can define that buckwheat is a functional food, with a high nutritional value and very useful for human health.

Rapid qualitative profiling and quantitative analysis of phenolics in Ribes meyeri leaves and their antioxidant and antidiabetic activities by HPLC-QTOF-MS/MS and UHPLC-MS/MS

Ribes meyeri leaves are used as traditional Kazakh medicine in China. However, no study on the characterization of the phenolic compounds in R. meyeri leaves has been reported, resulting in the lack of quality control measures and poor standardization. This study was conducted to identify the phenolic compounds in R. meyeri leaves and evaluate their antioxidant and antidiabetic activities. A total of 77 phenolics were tentatively identified by liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry. Ultra-high performance liquid chromatography coupled with triple quadrupole mass spectrometry was applied to simultaneously quantify 12 phenolics in R. meyeri leaves. Rutin, epigallocatechin, isoquercitrin, epicatechin, protocatechuic acid, and kaempferol-3-O-rutinoside were abundant in the R. meyeri leaves. The methanol extract and four different extracts enhanced the glucose uptake in 3T3-L1 adipocytes. The ethyl acetate extracts showed a total phenolic content of 966.89 ± 3.59 mg gallic acid equivalents/g, a total flavonoid content of 263.58 ± 17.09 mg catechin equivalents/g, and good protein-tyrosine phosphatase-1B inhibitory activities (IC₅₀ : 0.60 ± 0.03 μg/mL). To our knowledge, this work is the first to identify and quantify the major phenolics in R. meyeri leaves.

Ellagitannins and Oligomeric Proanthocyanidins of Three Polygonaceous Plants

The aim of this study was to characterize hydrolyzable tannins in Polygonaceous plants, as only a few plants have previously been reported to contain ellagitannins. From Persicaria chinensis, a new hydrolyzable tannin called persicarianin was isolated and characterized to be 3-O-galloyl-4,6-(S)-dehydrohexahydroxydiphenoyl-d-glucose. Interestingly, acid hydrolysis of this compound afforded ellagic acid, despite the absence of a hexahydroxydiphenoyl group. From the rhizome of Polygonum runcinatum var. sinense, a large amount of granatin A, along with minor ellagitannins, helioscpoinin A, davicratinic acids B and C, and a new ellagitannin called polygonanin A, were isolated. Based on 2D nuclear magnetic resonance (NMR) spectroscopic examination, the structure of polygonanin A was determined to be 1,6-(S)-hexahydroxydiphenoyl-2,4-hydroxychebuloyl-β-d-glucopyranose. These are the second and third hydrolyzable tannins isolated from Polygonaceous plants. In addition, oligomeric proanthocyanidins of Persicaria capitatum and P. chinensis were characterized by thiol degradation. These results suggested that some Polygonaceous plants are the source of hydrolyzable tannins not only proanthocyanidins.