HPLC method development for the online-coupling of chromatographic Perilla frutescens extract separation with xanthine oxidase enzymatic assay

A novel multi-hyphenated approach to screen and character the xanthine oxidase inhibitors from saffron floral bio-residues

Recently, the incidence of hyperuricemia increased with patient rejuvenation, searching for new xanthine oxidase (XOD) inhibitors from natural products becomes important. In our previous work, a flavonoid extract of saffron floral bio-residues (SFB) was found to alleviate hyperuricemia via inhibiting XOD. In this study, an integrated approach combining two-dimensional liquid chromatography, surface plasmon resonance (SPR) and isothermal titration calorimetry (ITC) was developed to online screen and character the potential XOD inhibitors from SFB. The two-dimensional liquid chromatography consisted of affinity chromatography and reverse phase chromatography (2D-AR), in which an XOD column, an inactive XOD column, and a control column were used in the first dimensional liquid chromatography to avoid phenomena of "false positive" and "missing screen of compounds with weak affinity to XOD" that often occur in the screening process, and a C18 column was used in the second dimensional liquid chromatography to separate the mixed XOD binders. Four flavonoid glycosides, i.e., quercetin-3-O-sophoroside (QS), kaempferol-3-O-sophoroside (KS), kaempferol-3-O-rutinoside (KR), and kaempferol-3-O-glucoside (KG), were thus successfully screened and identified from SFB extract by the 2D-AR method. The affinity of QS, KS, KR, KG, kaempferol (aglycone of KS, KR and KG), and quercetin (aglycone of QS) binding to XOD was investigated using SPR method, with KD ranged from 4.8 μM to 47.6 μM. The inhibitor constant (KI) of KS, KR, KG, quercetin and kaempferol were 4.92 mM, 1.11 mM, 0.294 mM, 4.93 μM and 3.27 μM, respectively, determined using ITC method. Finally, the anti-XOD activities of KS, the most abundant flavonoid in SFB extract, and kaempferol in hyperuricemia mice were verified, which suggested that the multi-hyphenated approach established herein can be applied for screen and character the XOD inhibitors in natural products.

Metabolomic profiling of developing perilla leaves reveals the best harvest time

Ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS) and gas chromatography-mass spectrometry (GC-MS) were applied to analyze metabolites in perilla leaves (PLs) during its developmental process. In total, 118 metabolites were identified, including volatile and non-volatile compounds, such as terpenoids, sugars, amino acids, organic acids, fatty acids, phenolic acids, flavonoids, and others. Principal component analysis (PCA) indicated great variations of metabolites during PLs development. Clustering analysis (CA) clarified the dynamic patterns of the metabolites. The heatmap of CA showed that most of the detected metabolites were significantly accumulated at stage 4 which is the pre anthesis period, and declined afterwards. The results of the present study provide a comprehensive overview of the metabolic dynamics of developing PLs which suggested that pre anthesis period is the best harvest time for PLs.

Lemna minor studies under various storage periods using extended-polarity extraction and metabolite non-target screening analysis

Plant metabolomic studies cover a broad band of compounds, including various functional groups with different polarities and other physiochemical properties. For this reason, specific optimized methods are needed in order to enable efficient and non-destructive extraction of molecules over a large range of LogD values. This study presents a simple and efficient extraction procedure for Lemna minor samples demonstrating polarity extension of the molecular range. The Lemna samples chosen were kept under the following storage conditions: 1) fresh, 2) stored for a few days at -80 °C, and 3) stored for 6 months at -80 °C. The samples were extracted using five specifically chosen solvents: 100 % ethanol, 100 % methanol (MeOH), acidic 90 % MeOH (MeOH-water-formic acid (FAC) (90:9.5:0.5, v/v/v), MeOH-water (50:50, v/v), and 100 % water. The final extraction procedure was conducted subject to three solvent conditions, and the subsequent polarity-extended analysis was applied for Lemna minor samples using RPLC-HILIC-ESI-TOF-MS. The extraction yield is in descending order (acidic 90 % MeOH), 50 % MeOH, 100 % water and 100 % MeOH. The results displayed significant molecular differences, both in the extracts investigated and in the fresh Lemna samples, compared to stored samples, in terms of the extraction yield and reducing contents as well as the number of features. The storage of Lemna minor resulted in changes to the fingerprint of its metabolites as the reducing contents increased. The comparisons enable a direct view of molecule characterizations, in terms of their polarity, molecular mass, and signal intensity. This parametric information would appear ideal for further statistical data analysis. Consequently, the extraction procedure and the analysis/data evaluation are highly suitable for the so-called extended-polarity non-target screening procedure.

A chemically characterized ethanolic extract of Thai Perilla frutescens (L.) Britton fruits (nutlets) reduces oxidative stress and lipid peroxidation in human hepatoma (HuH7) cells

Perilla frutescens is cultivated in East Asian countries including Thailand, and the nutlets (single-seeded fruits) are used as traditional and medicinal food. Perilla nutlets extracted by ethyl acetate (EA), 80% ethanol (Eth), and hot water (HW) sequentially were chemically characterized using high-resolution accurate liquid chromatography-mass spectrometry with the main compounds detected assigned as rosmarinic acid and derivatives of the flavones apigenin and luteolin, with the more diverse chemical composition observed with the Eth extract. All extracts showed dose-dependent free-radical scavenging activity, with the Eth extract the most potent (IC₅₀  = 3.43 mg/ml for ABTS^• scavenging and 0.27 mg/ml for DPPH^• scavenging). The Eth extract also inhibited AAPH-induced hemolysis (IC₅₀  = 0.07 mg/ml) more potently than did the HW (IC₅₀  = 0.38 mg/ml) and EA extracts (IC₅₀  = 1.63 mg/ml). An MTT test revealed all the extracts were noncytotoxic at concentrations up to 200 μg/ml. Only the Eth and EA extracts showed protective effects against the generation of reactive oxygen species and lipid peroxidation in FeCl₃ -induced HuH7 cells in a dose-dependent manner. Our findings suggest the Eth extract of Thai perilla nutlets, containing rosmarinic acid and flavones and their derivatives, may have potential to provide protection against oxidative stress in hepatic disorders.

Characterization of metabolite profiles from the leaves of green perilla ( Perilla frutescens ) by ultra high performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight mass spectrometry and screening for their antioxidant properties

The objective of this research was to access the determination of metabolite profiles and antioxidant properties in the leaves of green perilla (Perilla frutescens), where these are considered functional and nutraceutical substances in Korea. A total of 25 compositions were confirmed as six phenolic acids, two triterpenoids, eight flavonoids, seven fatty acids, and two glucosides using an ultra high performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight mass spectrometry (UPLC-ESI-Q-TOF-MS/MS) technique from the methanol extract of this species. The individual and total compositions exhibited significant differences, especially rosmarinic acid (10), and linolenic acids (22 and 23) were detected as the predominant metabolites. Interestingly, rosmarinic acid (10) was observed to have considerable differences with various concentrations in three samples (Doryong, 6.38 μg/g; Sinseong, 317.60 μg/g; Bongmyeong, 903.53 μg/g) by UPLC analysis at 330 nm. The scavenging properties against 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radicals also showed potent effects with remarkable differences at a concentration of 100 μg/mL, and their abilities were as follows: Sinseong (DPPH, 86%; ABTS, 90%) > Bongmyeong (71% and 84%, respectively) > Doryong (63% and 73%, respectively). Our results suggest that the antioxidant activities of green perilla leaves are correlated with metabolite contents, especially the five major compositions 10 and 22–25. Moreover, this study may be useful in evaluating the relationship between metabolite composition and antioxidant activity.

Effect of Perilla frutescens Extracts on Porcine Jejunal Epithelial Cells

Green-leaved Perilla frutescens extracts were investigated on their effect on cell proliferation of the porcine jejunal epithelial cell line, IPEC-J2, as well as on the gene expression of cell cycle or cancer-related genes. Some extracted compounds were, however, susceptible to degradation in cell culture medium, whereas others were found to be stable during the entire experimental time. Control experiments also included the assessment of H₂ O₂ generation in cell culture medium caused by oxidation of natural extract compounds, which was proved to be absent at low extract concentrations. A fast and significant inhibition of cell growth at low physiological extract concentrations could be observed. This finding, along with an immediate downregulation of 67 kDa laminin receptor and cyclin D1 expression, can be accounted to the presence of Perilla frutescens extract. Copyright © 2016 John Wiley & Sons, Ltd.