Characterization of flavonoids in the extract of Sophora flavescens Ait. by high-performance liquid chromatography coupled with diode-array detector and electrospray ionization mass spectrometry

Prenylated Flavonoids in Sophora flavescens: A Systematic Review of Their Phytochemistry and Pharmacology

Sophora flavescens has been widely used in traditional Chinese medicine for over 1700 years. This plant is known for its heat-clearing, damp-drying, insecticidal, and diuretic properties. Phytochemical research has identified prenylated flavonoids as a unique class of bioactive compounds in S. flavescens. Recent pharmacological studies reveal that the prenylated flavonoids from S. flavescens (PFS) exhibit potent antitumor, anti-inflammatory, and glycolipid metabolism-regulating activities, offering significant therapeutic benefits for various diseases. However, the pharmacokinetics and toxicological profiles of PFS have not been systematically studied. Despite the diverse biological effects of prenylated flavonoid compounds against similar diseases, their structure-activity relationship is not yet fully understood. This review aims to summarize the latest findings regarding the chemical composition, drug metabolism, pharmacological properties, toxicity, and structure-activity relationship of prenylated flavonoids from S. flavescens. It seeks to highlight their potential for clinical use and suggest directions for future related studies.

Osteogenic Activities of Trifolirhizin as a Bioactive Compound for the Differentiation of Osteogenic Cells

Plant extracts are widely used as traditional medicines. Sophora flavescens Aiton-derived natural compounds exert various beneficial effects, such as anti-inflammatory, anticancer, antioxidant, and antiregenerative activities, through their bioactive compounds, including flavonoids and alkaloids. In the present study, we investigated the biological effects of an S. flavescens-derived flavonoid, trifolirhizin (trifol), on the stimulation of osteogenic processes during osteoblast differentiation. Trifol (>98% purity) was successfully isolated from the root of S. flavescens and characterized. Trifol did not exhibit cellular toxicity in osteogenic cells, but promoted alkaline phosphatase (ALP) staining and activity, with enhanced expression of the osteoblast differentiation markers, including Alp, ColI, and Bsp. Trifol induced nuclear runt-related transcription factor 2 (RUNX2) expression during the differentiation of osteogenic cells, and concomitantly stimulated the major osteogenic signaling proteins, including GSK3β, β-catenin, and Smad1/5/8. Among the mitogen-activated protein kinases (MAPKs), Trifol activated JNK, but not ERK1/2 and p38. Trifol also increased the osteoblast-mediated bone-forming phenotypes, including transmigration, F-actin polymerization, and mineral apposition, during osteoblast differentiation. Overall, trifol exhibits bioactive activities related to osteogenic processes via differentiation, migration, and mineralization. Collectively, these results suggest that trifol may serve as an effective phytomedicine for bone diseases such as osteoporosis.

Rationalising the retro-Diels-Alder fragmentation pattern of viscutins using electrospray interface-tandem mass spectrometry coupled to theoretical modelling

RATIONALE

Although mass spectrometry (MS) is a powerful tool in structural elucidation of unknown flavonoids based on their unique fragmentation patterns, proposing the correct fragmentation mechanism is still a challenge from tandem mass spectrometry data only. In recent years, computational tools such as molecular networking and MS2LDA have played a major role in the identification of structurally related compounds through an in-depth survey of their fragmentation patterns.

METHODS

Therefore, in this study, three viscutin molecules in Viscum combreticola Engl. crude extracts were characterised using ultra-high-performance liquid chromatography-quadrupole-time-of-flight tandem mass spectrometry and MS2LDA, a computational tool. Ion-trap mass spectrometry and density functional theoretical modelling were used as confirmatory tools to rationalise the unique fragmentation patterns observed for these molecules.

RESULTS

Here, MS2LDA revealed the presence of a unique Mass2Motif in all the three viscutin molecules at m/z 137, which was confirmed to be a ^1,3 A^- RDA (retro-Diels-Alder) fragmentation product using liquid chromatography-ion-trap mass spectrometry and density functional theoretical modelling. Moreover, MS2LDA proved to be useful in differentiating this spectral feature that was specific to viscutin molecules in the presence of other isobaric ions at m/z 137 occurring in compounds in other molecular families.

CONCLUSION

Therefore, the results of the current study showed that computational tools such as MS2LDA are essential in uncovering some gas-phase fragmentation reactions of molecules in MS and that theoretical modelling is a powerful tool in rationalising these reactions in metabolite identification.

A Novel Method for Identifying Parkin Binding Agents in Complex Preparations of Herbal Medicines

Parkin is a crucial E3 ubiquitin ligase for initiating mitophagy through the PINK1/Parkin pathway. Regulating the expression and activity of parkin can remedy mitophagy and human disease. We developed an efficient method to isolate natural parkin ligands from herbal medicines by combining centrifugal ultrafiltration and liquid chromatography/mass spectrometry. The heterologous expression technology identified functionally active and pure parkin proteins. After evaluating the reliability of the method using DL-selenomethionine and DL-dithiothreitol as positive controls, this method was successfully applied to capture parkin ligands from Polygoni Cuspidati Rhizoma et Radix and Sophorae Flavescentis Radix. LC/MS identified seven novel parkin-targeting compounds, namely, 7,4′-dihydroxy-5-methoxy-8-(γ, γ-dimethylallyl)-flavanone, kushenol I, kurarinone, sophoraflavanone G, torachrysone-8-O-glucoside, apigenin, and emodin, supported by the molecular docking analysis. Five of the seven novel compounds (kushenol I, kurarinone, sophoraflavanone G, apigenin, and emodin) can activate parkin in in vitro autoubiquitination assays. Meanwhile, kushenol I and kurarinone had antisteatosis activity in fat emulsion-damaged human hepatocytes. These results confirmed the effectiveness of the method for identifying parkin ligands from complex preparations, useful to advance drug discovery from medicinal herbs.

Five-Decade Update on Chemopreventive and Other Pharmacological Potential of Kurarinone: a Natural Flavanone

In the present article we present an update on the role of chemoprevention and other pharmacological activities reported on kurarinone, a natural flavanone (from 1970 to 2021). To the best of our knowledge this is the first and exhaustive review of kurarinone. The literature was obtained from different search engine platforms including PubMed. Kurarinone possesses anticancer potential against cervical, lung (non-small and small), hepatic, esophageal, breast, gastric, cervical, and prostate cancer cells. In vivo anticancer potential of kurarinone has been extensively studied in lungs (non-small and small) using experimental xenograft models. In in vitro anticancer studies, kurarinone showed IC₅₀ in the range of 2–62 µM while in vivo efficacy was studied in the range of 20–500 mg/kg body weight of the experimental organism. The phytochemical showed higher selectivity toward cancer cells in comparison to respective normal cells. kurarinone inhibits cell cycle progression in G2/M and Sub-G1 phase in a cancer-specific context. It induces apoptosis in cancer cells by modulating molecular players involved in apoptosis/anti-apoptotic processes such as NF-κB, caspase 3/8/9/12, Bcl2, Bcl-XL, etc. The phytochemical inhibits metastasis in cancer cells by modulating the protein expression of Vimentin, N-cadherin, E-cadherin, MMP2, MMP3, and MMP9. It produces a cytostatic effect by modulating p21, p27, Cyclin D1, and Cyclin A proteins in cancer cells. Kurarinone possesses stress-mediated anticancer activity and modulates STAT3 and Akt pathways. Besides, the literature showed that kurarinone possesses anti-inflammatory, anti-drug resistance, anti-microbial (fungal, yeast, bacteria, and Coronavirus), channel and transporter modulation, neuroprotection, and estrogenic activities as well as tyrosinase/diacylglycerol acyltransferase/glucosidase/aldose reductase/human carboxylesterases 2 inhibitory potential. Kurarinone also showed therapeutic potential in the clinical study. Further, we also discussed the isolation, bioavailability, metabolism, and toxicity of Kurarinone in experimental models.

Inhibitory effects of Coptidis Rhizoma on the intestinal absorption and metabolism of Scutellariae Radix

ETHNOPHARMACOLOGICAL RELEVANCE

The Scutellariae Radix (SR) and Coptidis Rhizoma (CR) herb couple is widely used in traditional Chinese medicine prescriptions for the treatment of diabetes mellitus due to its interaction and synergistic effect compared to either herb alone, but the underlying mechanism of interaction between these herbs is unclear. This study aimed to investigate the effects of CR on the metabolism and absorption of SR.

MATERIALS AND METHODS

After rats were treated with normal saline (NS group) or the CR extract (CR-treated group) for seven consecutive days, the intestinal flora was extracted from rat faeces for a co-incubation with the SR extract to investigate the metabolism of SR flavonoids, and a non-everted gut sac was prepared in vitro to evaluate the intestinal absorption of the SR extract. The components of the SR extract, the metabolites of the SR extract that was co-incubated with intestinal flora, and the dialysate acquired from non-everted gut sacs were identified and determined by an HPLC-MS/MS method. The absorption rate constant (Ka) and the apparent permeability (Papp) of each compound were calculated, and the effects of CR on the metabolism and absorption of flavonoids in SR were evaluated, by comparison the Ka and Papp between two groups using Student's t-test.

RESULTS

Twenty-nine flavonoids were detected and identified in the SR extract, including 16 glycosides and 13 aglycones. In the co-incubation with the intestinal flora, differences in metabolite classes were not observed between the NS group and CR-treated group; however, the metabolic rates of 17 flavonoids in the CR-treated group were significantly higher than the NS group. The Papp of 11 compounds (4 glycosides and 7 aglycones) across the gut sac were greater than 2 × 10-5 cm/s in both groups, while the Papp values of 7 compounds including wogonoside (WG) and other aglycones were significantly decreased in the CR-treated group.

CONCLUSION

Based on these results, CR decreased the metabolism and absorption of SR flavonoids, and exerted much greater inhibitory effects on aglycones than glycosides, which may be one of the potential mechanisms underlying the therapeutic effects of the combination of SR and CR on diabetes mellitus.

Determination of Alkaloids and Flavonoids in Sophora flavescens by UHPLC-Q-TOF/MS

This study is based on UHPLC-Q-TOF/MS and fragment ions to achieve classification and identification of alkaloids and flavonoids in Sophora flavescens. By reviewing the available and relevant literature, the mass fragmentation rules of alkaloids and flavonoids were summarized. 0.1% formic acid water (A) and acetonitrile (B) were used as mobile phases. 37 chemical constituents were identified, including 13 alkaloids and 24 flavonoids. This research method offers a complete strategy based on the fragmentation information of characteristic fragment ions and neutral loss obtained by MS/MS to characterize the chemical composition of Sophora flavescens.

Pharmacokinetic and bioavailability study of kurarinone in dog plasma by UHPLC-MS/MS

Kurarinone, a natural prenylated flavonone isolated from Sophora flavescens, has been exhibited various activities. This study aimed to establish a simple and sensitive ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method for determining kurarinone in dog plasma. Acetonitrile-mediated precipitation was applied for sample pretreatment. Chromatographic separation was achieved on a Waters ACQUITY HSS T3 (100 × 2.1 mm, i. d., 1.8 μm) column with gradient elution using water containing 0.1% formic acid and acetonitrile as mobile phase. Quantitation was performed using an electrospray ionization source in negative multiple reaction monitoring mode. The linearity of this method was over the concentration range 0.1-500 ng/mL with the lowest limit of quantification (LLOQ) of 0.1 ng/mL. The intra- and inter-day precision was less than 10.51% and the accuracy ranged from 94.85% to 97.72%, respectively. The extraction recovery of kurarinone in dog plasma was more than 82.37% and no significant matrix effect was observed. The analyte was stable under tested storage conditions. The validated method was further successfully applied to a preclinical pharmacokinetic study of kurarinone in dog after a single intravenous (2 mg/kg) and oral (20 mg/kg) administration. The results revealed that kurarinone was rapidly absorbed into plasma with good bioavailability (38.19%) and low clearance.

Škrbić B, Jigjiddorj EA, Vágvölgyi C, Szekeres A. Characterization of the Plant Growth-Promoting Activities of Endophytic Fungi Isolated from Sophora flavescens

Endophytic fungi in symbiotic association with their host plant are well known to improve plant growth and reduce the adverse effects of both biotic and abiotic stresses. Therefore, fungal endophytes are beginning to receive increased attention in an effort to find growth-promoting strains that could be applied to enhance crop yield and quality. In our study, the plant growth-promoting activities of endophytic fungi isolated from various parts of Sophora flavescens (a medicinally important plant in Mongolia and China) have been revealed and investigated. Fungal isolates were identified using molecular taxonomical methods, while their plant growth-promoting abilities were evaluated in plate assays. Altogether, 15 strains were isolated, representing the genera Alternaria, Didymella, Fusarium and Xylogone. Five of the isolates possessed phosphate solubilization activities and twelve secreted siderophores, while all of them were able to produce indoleacetic acid (IAA) in the presence or absence of tryptophan. The endogenous and exogenous accumulation of IAA were also monitored in liquid cultures using the HPLC-MS/MS technique to refine the plate assay results. Furthermore, for the highest IAA producer fungi, the effects of their extracts were also examined in plant bioassays. In these tests, the primary root lengths of the model Arabidopsis thaliana were increased in several cases, while the biomasses were significantly lower than the control IAA treatment. Significant alterations have also been detected in the photosynthetic pigment (chlorophyll-a, -b and carotenoids) content due to the fungal extract treatments, but these changes did not show any specific trends.

Involvement of mTOR-related signaling in antidepressant effects of Sophoraflavanone G on chronically stressed mice

SophoraflavanoneG (SG), an important prenylated flavonoid isolated from Sophoraalopecuroides.L, is effective for many illnesses. The present study was designed to investigate whether the compound could reverse depressive-like symptoms and investigate its possible mechanisms. Chronic Unpredictable Mild Stress (CUMS) mice were treated with fluoxetine and SG. The immobility time in forced swimming test (FST) and tail suspension test (TST) were recorded. The levels of pro-inflammatory cytokines and neurotransmitters in the hippocampus were evaluated. Furthermore, the protein expressions of PI3K, AKT, mTOR, p70S6K, BDNF, and Trkb in hippocampus were detected. Rapamycin, the selective mTOR inhibitor, was used to estimate the potential mechanism. As a result, after 7 days of SG treatment, the immobility time in FST and TST was declined obviously. The levels of IL-6, IL-1β, and TNF-α in the hippocampus were significantly reduced, and the quantity of 5-HT and NE was raised considerably in SG-treated group compared with the CUMS-exposed group. Additionally, SG could up-regulate the expressions of PI3K, AKT, mTOR, 70S6K, BDNF, and Trkb. The blockade of mammalian target of rapamycin signaling blunted the antidepressant effect and reversed the up-regulation of BDNF expression caused by SG. These findings suggested that SG treatment alleviated depressive-like symptoms via mTOR-mediated BDNF/Trkb signaling.

Phytochemistry and biological properties of isoprenoid flavonoids from Sophora flavescens Ait

Sophora flavescens Ait (Ku-Shen in Chinese) is a popular traditional Chinese herbal medicine in China for a long history. It shows significant pharmacological activities in the treatment of dysentery, eczema, fever, jaundice, vulvar swelling, gastrointestinal hemorrhage and inflammatory disorders. Alkaloids and flavonoids have been identified as virtual components, especially isoprenoid flavanonols are a class of characteristic compounds for S. flavescens. However, few studies have focused on isoprenoid flavonoids analyses and no comprehensive review has yet been published. In the current review, we systematically summarized the isoprenoid flavonoids, a total of 55 compounds have been isolated from S. flavescens, particularly an isoprenyl and a lavandulyl group in backbone structures. Further pharmacological activities, qualitative and quantitative chemical analyses research will contribute to the development of natural isoprenoid flavonoid products in S. flavescens.

A target-group-change couple with mass defect filtering strategy to identify the metabolites of "Dogel ebs" in rats plasma, urine and bile

"Dogel ebs" was known as Sophora flavescens Ait., a classical traditional Chinese Mongolian herbal medicine, which had the effects on damp-heat dysentery, scrofula, and syndrome of accumulated dampness toxicity. Although the chemical constituents have been clarified by our previous studies, the metabolic transformation of "Dogel ebs" in vivo was still unclear. To explore the mechanism of "Dogel ebs," the metabolites in plasma, bile, and urine samples were investigated. A fast positive and negative ion switching technology was used for the simultaneous determination of flavonoids and alkaloids in "Dogel ebs" in a single run. And a target-group-change coupled with mass defect filtering strategy was utilized to analyze the collected data. 89 parent compounds and 82 metabolites were characterized by high-performance liquid chromatography with quadrupole exactive Orbitrap mass spectrometry. Both phase I and phase II metabolites were observed and the metabolic pathways involved in oxidation, demethylation, acetylation, and glucuronidation. 69 metabolites of "Dogel ebs," including three hydroxyls bonding xanthohumol, formononetin-7-O-glucuronide, 2'-hydroxyl-isoxanthohumol decarboxylation metabolite, oxysophocarpine dehydrogen, 9α-hydroxysophoramine-O-glucuronide, etc. were reported for the first time.

Inhibitory effects of flavonoids isolated from Sophora flavescens on indoleamine 2,3-dioxygenase 1 activity

Indoleamine 2,3-dioxygenase 1 (IDO1), a tryptophan catabolising enzyme, is known as a tumour cell survival factor that causes immune escape in several types of cancer. Flavonoids of Sophora flavescens have a variety of biological benefits for humans; however, cancer immunotherapy effect has not been fully investigated. The flavonoids (1-6) isolated from S. flavescens showed IDO1 inhibitory activities (IC₅₀ 4.3-31.4 µM). The representative flavonoids (4-6) of S. flavescens were determined to be non-competitive inhibitors of IDO1 by kinetic analyses. Their binding affinity to IDO1 was confirmed using thermal stability and surface plasmon resonance (SPR) assays. The molecular docking analysis and mutagenesis assay revealed the structural details of the interactions between the flavonoids (1-6) and IDO1. These results suggest that the flavonoids (1-6) of S. flavescens, especially kushenol E (6), as IDO1 inhibitors might be useful in the development of immunotherapeutic agents against cancers.

New strategy for identifying potential natural HIV-1 non-nucleoside reverse transcriptase inhibitors against drug-resistance: an in silico study

Non-nucleosides reverse transcriptase inhibitors (NNRTIs), specifically targeting the HIV-1 reverse transcriptase (RT), play a unique role in anti-AIDS agents due to their high antiviral potency, structural diversity, and low toxicity in antiretroviral combination therapies used to treat HIV. However, due to the emergence of new drug-resistant strains, the development of novel NNRTIs with adequate potency, improved resistance profiles and less toxicity is highly required. In this work, a novel virtual screening strategy combined with structure-based drug design was proposed to discover the potential inhibitors against drug-resistant HIV strains. Seven structure-variant RTs, ranging from the wild type to a hypothetical multi-mutant were regarded as target proteins to perform structure-based virtual screening. Totally 23 small molecules with good binding affinity were identified from the Traditional Chinese Medicine database (TCM) as potential NNRTIs candidates. Among these hits, (+)-Hinokinin has confirmed anti-HIV activity, and some hits are structurally identical with anti-HIV compounds. Almost all these hits are consistent with external experimental results. Molecular simulations analysis revealed that top 2 hits (Pallidisetin A and Pallidisetin B) bind stably and in high affinity to HIV-RT, which are ready to be experimental confirmed. These results suggested that the strategy we proposed is feasible, trustworthy and effective. Our finding might be helpful in the identification of novel NNRTIs against drug-resistant, and also provide a new clue for the discovery of HIV drugs in natural products.Communicated by Ramaswamy H. Sarma.

Flavonoids rather than alkaloids as the diagnostic constituents to distinguish Sophorae Flavescentis Radix from Sophorae Tonkinensis Radix et Rhizoma: an HPLC fingerprint study

Sophorae Flavescentis Radix (Sophora flavescens Ait., SFR) and Sophorae Tonkinensis Radix et Rhizoma (S. tonkinensis Gapnep., STR) are two commonly used traditional Chinese medicines from Sophora (Leguminosae) plants, which are believed to possess similar bioactive components with entirely different clinical applications. In order to find out the characteristic chemical constituents potentially leading to the unique medicinal properties claimed for each of the two closely related TCMs, an HPLC fingerprint method was developed for analyses of the alkaloid and flavonoid constituents of SFR and STR, respectively, which were further evaluated and compared through similarity calculation and hierarchical clustering analysis (HCA). The results from the present study showed that the alkaloid fingerprints of the two herbs were similar, with many components co-existing in both drugs and various batches of samples from different species being mixed together in the HCA dendrogram. However, their flavonoid constituents were totally different with specific fingerprints being yielded for each herb, and further HCA analysis showed that the tested samples could almost be clearly divided into two groups based on their origins of species. The results from the present study indicated that the flavonoid constituents could serve as the differentially diagnostic constituents of SFR and STR and might potentially attributed to their distinct therapeutic effects.

Inhibition of Cytochrome P450 Activities by Sophora flavescens Extract and Its Prenylated Flavonoids in Human Liver Microsomes

Sophora flavescens possesses several pharmacological properties and has been widely used for the treatment of diarrhea, inflammation, abscess, dysentery, and fever in East Asian countries. S. flavescens is a major source of prenylated flavonoids, such as sophoraflavone and kushenol. In this study, we examined the effects of S. flavescens extract and its prenylated flavonoids on cytochrome P450 (CYP) isoform activity in human liver microsomes. The extract inhibited CYP2C8, CYP2C9, CYP2C19, and CYP3A activities, with IC₅₀ values of 1.42, 13.6, 19.1, and 50 µg/mL, respectively. CYP2B6 was only inhibited in human liver microsomes preincubated with the extract. CYP3A4 was more strongly inhibited by the extract in the presence of NADPH, suggesting that the extract may inhibit CYP2B6 and CYP3A4 via mechanism-based inactivation. Prenylated flavonoids also inhibited CYP isoforms with different selectivity and modes of action. Kushenol I, leachianone A, and sophoraflavone G inhibited CYP2B6, whereas kushenol C, kushenol I, kushenol M, leachianone A, and sophoraflavone G inhibited CYP3A4 via mechanism-based inhibition. Our results suggest that S. flavescens may contribute to herb–drug interactions when coadministered with drugs metabolized by CYP2B6, CYP2C8, CYP2C9, and CYP3A4.

Simultaneous Optimization for Ultrasound-Assisted Extraction and Antioxidant Activity of Flavonoids from Sophora flavescens Using Response Surface Methodology

The ultrasonic-assisted extraction process and antioxidant activity of flavonoids from Sophora flavescens were investigated in this study. In order to optimize the extraction of flavonoids from Sophora flavescens, the influence of extraction time, methanol concentration, ultrasonic temperature, and solvent-to-material ratio was analyzed. Results showed that the extraction yields reached a maximum with the extraction time of 30 min, methanol concentration of 80%, temperature of 80 °C, and solvent-to-material ratio of 26 mL/g. The flavonoids were determined by HPLC, and the mean yields of trifolirhizin, formononetin, isoxanthohumol, maackiain, and kurarinone under the optimal conditions were 2.570, 0.213, 0.534, 0.797, and 3.091 mg/g, respectively. The evaluation of vitro antioxidant activity exhibited Sophora flavescens flavonoids had a strong 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydroxyl radical-scavenging ability with IC50 of 0.984 and 1.084 mg/g, respectively. These results indicate that ultrasonic-assisted extraction is an efficient approach for the selective extraction of flavonoids, and response surface methodology further optimized the extraction.

Analysis of Active Metabolites of Sophora flavescens for Indoleamine 2,3-dioxygenase and Monoamine Oxidases using Ultra-Performance Liquid Chromatography-Quadrupole time-of-Flight Mass Spectrometry

As part of ongoing research on natural products derived from medicinal plants for enzyme inhibition, known dibenzoyl derivatives (1–3, 11 and 20), pterocarpans (4, 15 and 19), flavanones (5, 7, 10, 12–14, 18, 21–24, 26, 27, 29, 31–33, 35, 36, and 38–46), flavones (6, 16, 28, 30 and 37), isoflavones (8 and 17), furocoumarins (9), and chalcones (25 and 34) have been tentatively identified within fractions of Sophora flavescens roots (SFR) using the ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-QTof-MS) technique. The extract and column fractions inhibited indoleamine 2,3-dioxygenase (IDO) and monoamine oxidases (MAOs) differently depending on the metabolite groups. The majority of rich fractions were shown to have residual activities of 49–59% at 10 μg/mL (IDO) and 11.7–34.9% at 50 μg/mL (MAOs) or below. In the total ion current (TIC) chromatogram, significant markers for the metabolites of the bioactive-guided fractions were identified; pterocarpans (4, 15 and 19), flavanones (5, 10, 12–14, 18, 21–23, 26, 29 31–33, 35, 36, and 38–46), isoflavones (8 and 17), furocoumarins (9), dibenzoyl derivatives (11 and 20), flavones (16, 28, 30 and 37), and chalcones (25 and 34) were evaluated among forty-six analyzed metabolites. Possible bioactive markers could be deduced using a data library and previous references, and information regarding spectroscopic characterization and optimal target metabolites was obtained.

Comparative analysis of sixteen flavonoids from different parts of Sophora flavescens Ait. by ultra high-performance liquid chromatography-tandem mass spectrometry

The root of Sophora flavescens Ait. has long been used as a crude drug in China and other Asian countries for thousands of years. The quinolizidine alkaloids and flavonoids are considered as the main bioactive components in this plant. To determine the distribution and content of the flavonoids in different organs of this plant, a rapid, sensitive and reproducible method was established using ultra-high-performance liquid chromatography coupled with a triple quadrupole electrospray tandem mass spectrometry. A total of sixteen flavonoids including five different types (isoflavones, pterocarpans, flavones, flavonols and prenylflavonoids) were simultaneously determined in 10 min. The established method was fully validated in terms of linearity, sensitivity, precision, repeatability as well as recovery and successfully applied in the methanolic extracts of S. flavescens parts (root, stem, leaf, pod and seed). The analysis results indicated that the distribution and contents of different type of flavonoids showed remarkable differences among the five organs of S. flavescens. This study might be useful for the rational utilization of S. flavescens resource.

Profiling of the Major Phenolic Compounds and Their Biosynthesis Genes in Sophora flavescens Aiton

Sophorae Radix (Sophora flavescens Aiton) has long been used in traditional medicine in East Asia due to the various biological activities of its secondary metabolites. Endogenous contents of phenolic compounds (phenolic acid, flavonol, and isoflavone) and the main bioactive compounds of Sophorae Radix were analyzed based on the qualitative HPLC analysis and evaluated in different organs and at different developmental stages. In total, 11 compounds were detected, and the composition of the roots and aerial parts (leaves, stems, and flowers) was significantly different. trans-Cinnamic acid and p-coumaric acid were observed only in the aerial parts. Large amounts of rutin and maackiain were detected in the roots. Four phenolic acid compounds (benzoic acid, caffeic acid, ferulic acid, and chlorogenic acid) and four flavonol compounds (kaempferol, catechin hydrate, epicatechin, and rutin) were higher in aerial parts than in roots. To identify putative genes involved in phenolic compounds biosynthesis, a total of 41 transcripts were investigated. Expression patterns of these selected genes, as well as the multiple isoforms for the genes, varied by organ and developmental stage, implying that they are involved in the biosynthesis of various phenolic compounds both spatially and temporally.

Determination of sophoraflavanone G and kurarinone in rat plasma by UHPLC-MS/MS and its application to a pharmacokinetic study

This study aimed to develop and validate a simple and sensitive ultra high performance liquid chromatography tandem mass spectrometry method for the simultaneous determination of sophoraflavanone G and kurarinone in rat plasma by using rutin as the internal standard. Then, the developed method was applied to investigate the pharmacokinetics of sophoraflavanone G and kurarinone in rats after dosing the flavonoid extract from Sophora flavescens. Plasma samples were processed using a liquid-liquid extraction procedure with ethyl acetate. The analysis was performed on a triple quadrupole tandem mass spectrometer by multiple reaction monitoring with an electrospray ionization source in negative ionization mode. Quantitative ion transitions of m/z 423.2→161.2, 437.2→161.1, and 609.3→300.3 were monitored for sophoraflavanone G, kurarinone, and rutin, respectively. The calibration curves of the two analytes exhibited good linearity (r² >0.9923) over the range of 0.1-200 ng/mL for sophoraflavanone G and 0.1-1000 ng/mL for kurarinone. Relative standard deviations were less than 13.2% for the intra- and inter-day precisions and no more than 12.6% for the recovery, showing good precision and satisfactory accuracy of the developed method. The validated method was successfully applied to the pharmacokinetic study of sophoraflavanone G and kurarinone after a single intravenous (25 mg/kg) and oral (500 mg/kg) administration of the flavonoid extract from S. flavescens, and the absolute bioavailability for sophoraflavanone G and kurarinone was about 36 and 17%, respectively.

Potent selective monoamine oxidase B inhibition by maackiain, a pterocarpan from the roots of Sophora flavescens

Monoamine oxidase (MAO) catalyzes the oxidation of monoamines and its two isoforms, MAO-A and MAO-B, break down neurotransmitter amines. Of the compounds isolated from the roots of Sophora flavescens, (-)-maackiain (4), a pterocarpan, was found to potently and selectively inhibit human MAO-B, with an IC50 of 0.68μM, and to have a selectivity index of 126.2 for MAO-B. As compared with other herbal natural products, the IC50 value of 4 for MAO-B is one of the lowest reported to date. Genistein (1) highly, effectively and non-selectively inhibited MAO-A and MAO-B with IC50 values of 3.9μM and 4.1μM, respectively. (-)-4-Hydroxy-3-methoxy-8,9-methylenedioxypterocarpan (2) effectively and non-selectively inhibited MAO-A and MAO-B with IC50 values of 20.3μM and 10.3μM, respectively. In addition, compound 4 reversibly and competitively inhibited MAO-B with a Ki value of 0.054μM. Molecular docking simulation revealed that the binding affinity of 4 for MAO-B (-26.6kcal/mol) was greater than its affinity for MAO-A (-8.3kcal/mol), which was in-line with our inhibitory activity findings. Furthermore, Cys172 of MAO-B was found to be a key residue for hydrogen bonding with compound 4. The findings of this study suggest compound 4 be viewed as a new potent, selective, and reversible MAO-B inhibitor, and that compounds 1 and 2 be considered useful lead compounds for the developments of nonselective and reversible MAO inhibitors for the treatment of disorders like Parkinson's disease, Alzheimer disease, and depression.

Selective Extraction of Flavonoids from Sophora flavescens Ait. by Mechanochemistry

Flavonoids from Sophora flavescens were selectively extracted by mechanochemical-promoted extraction technology (MPET) after using response surface methodology to determine the optimal extraction parameters. The highest yield of 35.17 mg/g was achieved by grinding the roots with Na₂CO₃ (15%) at 440 rpm/min for 17.0 min and water was used as the sole solvent with a ratio of solvent to solid material of 25 mL/g. Flavonoids prepared by MPET demonstrated relatively higher antioxidant activities in subsequent DPPH and hydroxyl radical scavenging assays. Main constituents in the extracts, including kurarinol, kushenol I/N and kurarinone, were characterized by HPLC-MS/MS, indicating good selective extraction by MPET. Physicochemical property changes of powder during mechanochemical milling were identified by scanning electron microscopy, X-ray powder diffraction, and UV-Vis diffuse-reflectance spectroscopy. Compared with traditional extraction methods, MPET possesses notable advantages of higher selectivity, lower extraction temperature, shorter extraction time, and organic solvent free properties.

Sophoraflavanone G prevents Streptococcus mutans surface antigen I/II-induced production of NO and PGE2 by inhibiting MAPK-mediated pathways in RAW 264.7 macrophages

BACKGROUND

Sophora flavescens AITON (Leguminosae) is a typical traditional Korean medical herb considered to exhibit antibacterial, anti-inflammatory, and antipyretic effects, and is also used for the treatment of skin and mucosal ulcers, sores, diarrhea, gastrointestinal hemorrhage, arrhythmia, and eczema.

OBJECTIVE AND DESIGN

This study examined the inhibitory effects of sophoraflavanone G (SF) of S. flavescens on the bacterial fibrillar protein, Antigen I/II (AgI/II)-N recombinant protein isolated from Streptococcus mutans(rAg I/II)-induced production of nitric oxide (NO) and prostaglandin E2 (PGE2). The investigation was focused on whether SF could inhibit the production of proinflammatory mediators such as nitric oxide (NO) and prostaglandin (PG) E2 as well as the expression of inducible nitric oxide synthase (iNOS), cyclooxygenase (COX)-2, tumor necrosis factor (TNF)-a, interleukin (IL)-6, nuclear factor (NF)-κB and mitogen-activated protein kinases (MAPKs) in rAgI/II-stimulated RAW 264.7 cells using Griess reagent, Enzyme linked immunosorbent assay (ELISA), and Western blotting analysis.

RESULTS

SG significantly inhibited the production of NO and PGE2 and pro-inflammatory cytokines, such as interleukin (IL)-1β, IL-6, and tumor necrosis factor α in Ag I/II-N-stimulated RAW264.7 cells, which were mediated by the down-regulation of inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2) expression. The SF inhibited the phosphorylation of IκB-α, nuclear translocation of p65, and subsequent activation of NF- κB in the rAgI/II-stimulated cells. In addition, the SF suppressed the rAgI/II-stimulated activation of ERK MAPK as well as the MAPK inhibitor significantly reduced the rAgI/II-induced production of NO and PGE2.

CONCLUSION

Collectively, we suggest that the SF inhibits the expression and production of inflammatory mediators by blocking the ERK MAPK mediated pathway and inhibiting the activation of NF-κB.

Negative ion electrospray high-resolution tandem mass spectrometry of polyphenols

Representative compounds with a 1,3-dihydroxybenzene substructure belonging to different important polyphenol classes (stilbenes, flavones, isoflavones, flavonols, flavanones, flavanols, phloroglucinols, anthraquinones and bisanthraquinones) were investigated based on detailed high-resolution tandem mass spectrometry measurements with an Orbitrap system under negative ion electrospray conditions. The mass spectral behaviour of these compound classes was compared among each other not only with respect to previously described losses of CO, CH2 CO and C3 O2 but also concerning the loss of CO2 and successive specific fragmentations. Furthermore, some unusual fragmentations such as the loss of a methyl radical during mass spectral decomposition are discussed. The obtained results demonstrate both similarities and differences in their mass spectral fragmentation under MS(n) conditions, allowing a characterization of the corresponding compound type. Copyright © 2015 John Wiley & Sons, Ltd.

Fragmentation reactions using electrospray ionization mass spectrometry: an important tool for the structural elucidation and characterization of synthetic and natural products

Over the last decade, the number of studies reporting the use of electrospray ionization mass spectrometry (ESI-MS) in combination with collision cells (or other activation methods) to promote fragmentation of synthetic and natural products for structural elucidation purposes has considerably increased. However, the lack of a systematic compilation of the gas-phase fragmentation reactions subjected to ESI-MS/MS conditions still represents a challenge and has led to many misunderstood results in the literature. This review article exploits the most common fragmentation reactions for ions generated by ESI in positive and negative modes using collision cells in an effort to stimulate the use of this technique by non-specialists, undergraduate students and researchers in related areas.

Sophora flavescens Ait.: Traditional usage, phytochemistry and pharmacology of an important traditional Chinese medicine

ETHNOPHARMACOLOGICAL RELEVANCE

Sophora flavescens (Fabaceae), also known as Kushen (Chinese: ), has been an important species in Chinese medicine since the Qin and Han dynasties. The root of Sophora flavescens has a long history in the traditional medicine of many countries, including China, Japan, Korea, India and some countries in Europe. In traditional Chinese medicine (TCM), Sophora flavescens has been used extensively, mainly in combination with other medicinal plants in prescriptions to treat fever, dysentery, hematochezia, jaundice, oliguria, vulvar swelling, asthma, eczema, inflammatory disorders, ulcers and diseases associated with skin burns. The aim of this review is to provide updated and comprehensive information regarding the botany, ethnopharmacology, phytochemistry, biological activities and toxicology of Sophora flavescens and to discuss possible trends and opportunities for further research on Sophora flavescens.

MATERIALS AND METHODS

We systematically searched major scientific databases (PubMed, Elsevier, SpringerLink, Google Scholar, Medline Plus, ACS, "Da Yi Yi Xue Sou Suo (http://www.dayi100.com/login.jsp)", China Knowledge Resource Integrated (CNKI) and Web of Science) for information published between 1958 and 2015 on Sophora flavescens. Information was also acquired from local classic herbal literature, conference papers, government reports, and PhD and MSc dissertations.

RESULTS

The broad spectrum of biological activities associated with Sophora flavescens has been considered a valuable resource in both traditional and modern medicine. Extracts are taken either orally or by injection. More than 200 compounds have been isolated from Sophora flavescens, and the major components have been identified as flavonoids and alkaloids. Recent in vitro and in vivo studies indicate that at least 50 pure compounds and crude extracts from Sophora flavescens possess wide-ranging antitumor, antimicrobial, antipyretic, antinociceptive, and anti-inflammatory pharmacological abilities. The anticancer and anti-infection abilities of these components are especially attractive areas for research.

CONCLUSIONS

Sophora flavescens is a promising traditional medicine, but there is a need for more precise studies to test the safety and clinical value of its main active crude extracts and pure compounds and to clarify their mechanisms of action. Moreover, some existing studies have lacked systematic methods and integration with the existing literature, and some of the experiments were isolated, used small sample sizes and were unreliable. More validated data are therefore required.

The Sophora flavescens flavonoid compound trifolirhizin inhibits acetylcholine induced airway smooth muscle contraction

Asthma is a serious health problem worldwide, particularly in industrialized countries. Despite a better understanding of the pathophysiology of asthma, there are still considerable gaps in knowledge as well as a need for classes of drugs. ASHMI™ (Anti-asthma Herbal Medicine Intervention) is an aqueous extract of Ganoderma lucidum (Fr.) P. Karst (Ling Zhi), Sophora flavescens Aiton (Ku Shen) and Glycyrrhiza uralensis Fisch. ex DC (Gan Cao). It prevents allergic asthma airway hyper-reactivity in mice and inhibits acetylcholine (ACh) induced airway smooth muscle (ASM) contraction in tracheal rings from allergic asthmatic mice. The purpose of this research was to identify individual herb(s) and their active compound(s) that inhibit ASM contraction. It was found that S. flavescens, but not G. lucidum or G. uralensis aqueous extracts, inhibited ASM contraction in tracheal rings from asthmatic mice. Bioassay-guided isolation and identification of flavonoid fractions/compound(s) via methylene chloride extraction, preparative HPLC fractionation, and LC-MS and NMR spectroscopic analyses showed that trifolirhizin is an active constituent that inhibits acetylcholine mediated ASM contraction or directly relaxes pre-contracted ASM independent of β2-adrenoceptors.

Study on Subcritical Water Extraction of Flavonoids from Scutellaria baicalenses

The extraction of baicalin, baicalein, wogonin and wogonoside from Scutellaria Baicalenses was performed using subcritical water. The effects of key operation conditions by varying the temperature (110-160 °C), extraction time (10-90 min), water loadings (2.0-4.0 mL)and particle sizes (>20- <100 mesh) were evaluated. The highest extraction yields of baicalin and wogonoside were obtained at extraction temperature of 160 °C, extraction time of 60 min, water loadings of 4.0 mL and 60-100 mesh. The highest extraction yields of baicalein and wogonin were obtained at extraction temperature of 110 °C, extraction time of 10 min, water loadings of 4.0 mL and 60-100 mesh. The subcritical water extraction was compared with the conventional extraction method. The total extraction yield by SCWE was higher than those obtained using ethanol as the solvent.

Impact of the herbal medicine Sophora flavescens on the oral pharmacokinetics of indinavir in rats: the involvement of CYP3A and P-glycoprotein

Sophora flavescens is a Chinese medicinal herb used for the treatment of gastrointestinal hemorrhage, skin diseases, pyretic stranguria and viral hepatitis. In this study the herb-drug interactions between S. flavescens and indinavir, a protease inhibitor for HIV treatment, were evaluated in rats. Concomitant oral administration of Sophora extract (0.158 g/kg or 0.63 g/kg, p.o.) and indinavir (40 mg/kg, p.o.) in rats twice a day for 7 days resulted in a dose-dependent decrease of plasma indinavir concentrations, with 55%-83% decrease in AUC(0-∞) and 38%-78% reduction in C(max). The CL (Clearance)/F (fraction of dose available in the systemic circulation) increased up to 7.4-fold in Sophora-treated rats. Oxymatrine treatment (45 mg/kg, p.o.) also decreased indinavir concentrations, while the ethyl acetate fraction of Sophora extract had no effect. Urinary indinavir (24-h) was reduced, while the fraction of indinavir in faeces was increased after Sophora treatment. Compared to the controls, multiple dosing of Sophora extract elevated both mRNA and protein levels of P-gp in the small intestine and liver. In addition, Sophora treatment increased intestinal and hepatic mRNA expression of CYP3A1, but had less effect on CYP3A2 expression. Although protein levels of CYP3A1 and CYP3A2 were not altered by Sophora treatment, hepatic CYP3A activity increased in the Sophora-treated rats. All available data demonstrated that Sophora flavescens reduced plasma indinavir concentration after multiple concomitant doses, possibly through hepatic CYP3A activity and induction of intestinal and hepatic P-gp. The animal study would be useful for predicting potential interactions between natural products and oral pharmaceutics and understanding the mechanisms prior to human studies. Results in the current study suggest that patients using indinavir might be cautioned in the use of S. flavescens extract or Sophora-derived products.

Characterization of flavonoids in Millettia nitida var. hirsutissima by HPLC/DAD/ESI-MS n

Millettia nitida var. hirsutissima is a Chinese herbal medicine used for the treatment of gynecological diseases. An HPLC/DAD/ESI-MSⁿ method was established for the rapid separation and characterization of bioactive flavonoids in M. nitida var. hirsutissima. A total of 32 flavonoids were detected, of which 14 compounds were unambiguously characterized by comparing their retention time, UV, and MS spectra with those of the reference standards, and the others were tentatively identified based on their tandem mass spectrometry fragmentation data obtained in the negative ionization mode on line. Nineteen of these compounds characterized were reported from this plant for the first time.

Subcritical water extraction of alkaloids in Sophora flavescens Ait. and determination by capillary electrophoresis with field-amplified sample stacking

The extraction and determination of cytisine, sophocarpine, matrine, sophoridine and oxymatrine in Sophora flavescens Ait. were performed using subcritical water extraction and capillary electrophoresis with field-amplified sample stacking. The effects of extraction temperature, pressure, time and cycle number on the extraction yields were investigated systematically for accelerated solvent extraction with ethanol (ASE) and accelerated solvent extraction with water (subcritical water extraction, SWE). The extraction yields obtained using SWE, ASE, water ultrasonic extraction and chloroform soaking extraction methods were compared. The electrophoresis separation buffer was monosodium phosphate (pH 3.0; 110 mM)-isopropanol (85:15, v/v). The effect of phosphoric acid added to the sample matrix on the reproducibility of the peak heights of the analytes was also examined. Cytisine, sophoridine and oxymatrine showed good linearity (R(2)>0.999) within 0.125-4.0 μg/mL, and sophocarpine and matrine exhibited good linearity (R(2)>0.998) within 0.0625-2.0 μg/mL, with the detection limits in the range of 0.004-0.0013 μg/mL. The five alkaloid contents in medicinal plants from different sources and Sophora instant granule were determined and compared.

Microwave-assisted extraction of oxymatrine from Sophora flavescens

In this paper, microwave-assisted extraction (MAE) of oxymatrine from Sophora flavescens were studied by HPLC-photodiode array detection. Effects of several experimental parameters, such as concentration of extraction solvent, ratio of liquid to material, microwave power, extraction temperature, and extraction time on the extraction efficiencies of oxymatrine were evaluated. The optimal extraction conditions were 60% ethanol, a 20:1 (v/v) ratio of liquid to material and extraction for 10 min at 50 °C under 500 W microwave irradiation. Under the optimum conditions, the yield of oxymatrine was 14.37 mg/g. The crude extract obtained could be used as either a component of some complex traditional medicines or for further isolation and purification of bioactive compounds. The results, which indicated that MAE is a very useful tool for the extraction of important phytochemicals from plant materials, should prove helpful for the full utilization of Sophora flavescens.

8-Prenylkaempferol Suppresses Influenza A Virus-Induced RANTES Production in A549 Cells via Blocking PI3K-Mediated Transcriptional Activation of NF-κB and IRF3

8-Prenylkaempferol (8-PK) is a prenylflavonoid isolated from Sophora flavescens, a Chinese herb with antiviral and anti-inflammatory properties. In this study, we investigated its effect on regulated activation, normal T cell expressed and secreted (RANTES) secretion by influenza A virus (H1N1)-infected A549 alveolar epithelial cells. Cell inoculation with H1N1 evoked a significant induction in RANTES accumulation accompanied with time-related increase in nuclear translocation of nuclear factor-κB (NF-κB) and interferon regulatory factor 3 (IRF-3), but showed no effect on c-Jun phosphorylation. 8-PK could significantly inhibit not only RANTES production but also NF-κB and IRF-3 nuclear translocation. We had proved that both NF-κB and IRF-3 participated in H1N1-induced RANTES production since NF-κB inhibitor pyrrolidinedithio carbamate (PDTC) and IRF-3 siRNA attenuated significantly RANTES accumulation. H1N1 inoculation also increased PI3K activity as well as Akt phosphorylation and such responsiveness were attenuated by 8-PK. In the presence of wortmannin, nuclear translocation of NF-κB and IRF3 as well as RANTES production by H1N1 infection were all reversed, demonstrating that PI3K-Akt pathway is essential for NF-κB- and IRF-3-mediated RANTES production in A549 cells. Furthermore, 8-PK but not wortmannin, prevented effectively H1N1-evoked IκB degradation. In conclusion, 8-PK might be an anti-inflammatory agent for suppressing influenza A virus-induced RANTES production acts by blocking PI3K-mediated transcriptional activation of NF-κB and IRF-3 and in part by interfering with IκB degradation which subsequently decreases NF-κB translocation.

Characterization of alkaloids in Sophora flavescens Ait. by high-performance liquid chromatography-electrospray ionization tandem mass spectrometry

Sophora flavescens Ait., a well-known Chinese herbal medicine, is widely used in clinical practice for the treatment of viral hepatitis, cancer, gastrointestinal hemorrhage, and skin diseases. This paper is the first report on a method based on the combined use of high-performance liquid chromatography, photodiode array detection, and electrospray ionization tandem mass spectrometry for the comprehensive and systematic separation and characterization of bioactive alkaloids in Sophora flavescens Ait. A total of 22 constituents were identified on the basis of the extracted ion chromatograms for different [M+H](+) ions of the alkaloids present in S. flavescens Ait. Among these, 5 constituents were unambiguously identified by comparing the experimental data on their retention times and MS(n) spectra with those of the authentic compounds, and 17 other constituents were tentatively identified on the basis of their MS(n) fragmentation behaviors and/or molecular weight information from literatures. Furthermore, some characteristic fragmentation pathways of the alkaloids in S. flavescens Ait. were detected and examined. This information may be useful for characterizing the bioactive alkaloids present in S. flavescens Ait. and for possible applications in formulations.

Inhibitory activities of prenylated flavonoids from Sophora flavescens against aldose reductase and generation of advanced glycation endproducts

Important targets for the prevention and treatment of diabetic complications include aldose reductase (AR) inhibitors (ARIs) and inhibitors of advanced glycation endproduct (AGE) formation. Here we evaluate the inhibitory activities of prenylated flavonoids isolated from Sophora flavescens, a traditional herbal medicine, on rat lens AR (RLAR), human recombinant AR (HRAR) and AGE formation. Among the tested compounds, two prenylated chalcones — desmethylanhydroicaritin (1) and 8-lavandulylkaempferol (2) — along with five prenylated flavanones — kurarinol (8), kurarinone (9), (2S)-2′-methoxykurarinone (10), (2S)-3β,7,4′-trihydroxy-5-methoxy-8-(γ,γ-dimethylally)-flavanone (11), and kushenol E (13) were potent inhibitors of RLAR, with IC50 values of 0.95, 3.80, 2.13, 2.99, 3.77, 3.63 and 7.74 μM, respectively, compared with quercetin (IC50 7.73 μM). In the HRAR assay, most of the prenylated flavonoids tested showed marked inhibitory activity compared with quercetin (IC50 2.54 μM). In particular, all tested prenylated flavonols, such as desmethylanhydroicaritin (1, IC50 0.45 μM), 8-lavandulylkaempferol (2, IC50 0.79 μM) and kushenol C (3, IC50 0.85 μM), as well as a prenylated chalcone, kuraridin (5, IC50 0.27 μM), and a prenylated flavanone, (2S)-7,4′-dihydroxy-5-methoxy-8-(γ,γ-dimethylally)-flavanone (12, IC50 0.37 μM), showed significant inhibitory activities compared with the potent AR inhibitor epalrestat (IC50 0.28 μM). Interestingly, prenylated flavonoids 1 (IC50 104.3 μgmL−1), 2 (IC50 132.1 μgmL−1), 3 (IC50 84.6 μgmL−1) and 11 (IC50 261.0 μgmL−1), which harbour a 3-hydroxyl group, also possessed good inhibitory activity toward AGE formation compared with the positive control aminoguanidine (IC50 115.7 μgmL−1). Thus, S. flavescens and its prenylated flavonoids inhibit the processes that underlie diabetic complications and related diseases and may therefore have therapeutic benefit.

Diastereomeric differentiation of norbornene amino acid peptides by electrospray ionization tandem mass spectrometry

A new class of diastereomeric pairs of non-natural amino acid peptides derived from butyloxycarbonyl (Boc-)protected cis-(2S,3R)- and trans-(2S,3S)-beta-norbornene amino acids including a monomeric pair have been investigated by electrospray ionization (ESI) tandem mass spectrometry using quadrupole time-of-flight (Q-TOF) and ion-trap mass spectrometers. The protonated cis-BocN-beta-nbaa (2S,3R) (1) (betanbaa = beta-norbornene amino acid) eliminates the Boc group to form [M+H-Boc+H](+), whereas an additional ion [M+H-C(4)H(8)](+) is formed from trans-BocN-beta-nbaa (2S,3S) (2). Similarly, it is observed that the peptide diastereomers (di-, tri- and tetra-), with cis-BocN-beta-nbaa (2S,3R)- at the N-terminus, initially eliminate the Boc group to form [M+H-Boc+H](+) which undergo further fragmentation to give a set of product ions that are different for the peptides with trans-BocN-beta-nbaa (2S,3S)- at the N-terminus. Thus the Boc group fragments differently depending on the configuration of the amino acid present at the N-terminus. It is also observed that the peptide bond cleavage in these peptides is less favoured and most of the product ions are formed due to retro-Diels-Alder fragmentation. Interestingly, sodium-cationized peptide diastereomers mainly yield a series of retro-Diels-Alder fragment ions which are different for each diastereomer as they are formed starting from [M+Na-Boc+H](+) in peptides with cis-BocN-beta-nbaa (2S,3R)- at the N-terminus, and [M+Na-C(4)H(8)](+) in peptides with trans-BocN-beta-nbaa (2S,3S)- at the N-terminus. All these results clearly indicate that these diastereomeric pairs of peptides yield characteristic product ions which help distinguish the isomers.