Antioxidants from Lespedeza homoloba. (I)

Molecular Docking and Dynamics Simulation Studies Predict Potential Anti-ADAR2 Inhibitors: Implications for the Treatment of Cancer, Neurological, Immunological and Infectious Diseases

Altered RNA editing has been linked to several neurodevelopmental disorders, including autism spectrum disorder (ASD) and intellectual disability, in addition to depression, schizophrenia, some cancers, viral infections and autoimmune disorders. The human ADAR2 is a potential therapeutic target for managing these various disorders due to its crucial role in adenosine to inosine editing. This study applied consensus scoring to rank potential ADAR2 inhibitors after performing molecular docking with AutoDock Vina and Glide (Maestro), using a library of 35,161 compounds obtained from traditional Chinese medicine. A total of 47 compounds were predicted to be good binders of the human ADAR2 and had insignificant toxicity concerns. Molecular dynamics (MD) simulations, including the molecular mechanics Poisson–Boltzmann surface area (MM/PBSA) procedure, also emphasized the binding of the shortlisted compounds. The potential compounds had plausible binding free energies ranging from −81.304 to −1068.26 kJ/mol from the MM/PBSA calculations. ZINC000085511995, a naphthoquinone had more negative binding free energy (−1068.26 kJ/mol) than inositol hexakisphosphate (IHP) [−873.873 kJ/mol], an agonist and a strong binder of ADAR2. The potential displacement of IHP by ZINC000085511995 in the IHP binding site of ADAR2 could be explored for possible deactivation of ADAR2. Bayesian-based biological activity prediction corroborates the neuropharmacological, antineoplastic and antiviral activity of the potential lead compounds. All the potential lead compounds, except ZINC000014612330 and ZINC000013462928, were predicted to be inhibitors of various deaminases. The potential lead compounds also had probability of activity (Pa) > 0.442 and probability of inactivity (Pi) < 0.116 values for treating acute neurologic disorders, except for ZINC000085996580 and ZINC000013462928. Pursuing these compounds for their anti-ADAR2 activities holds a promising future, especially against neurological disorders, some cancers and viral infections caused by RNA viruses. Molecular interaction, hydrogen bond and per-residue decomposition analyses predicted Arg400, Arg401, Lys519, Trp687, Glu689, and Lys690 as hot-spot residues in the ADAR2 IHP binding site. Most of the top compounds were observed to have naphthoquinone, indole, furanocoumarin or benzofuran moieties. Serotonin and tryptophan, which are beneficial in digestive regulation, improving sleep cycle and mood, are indole derivatives. These chemical series may have the potential to treat neurological disorders, prion diseases, some cancers, specific viral infections, metabolic disorders and eating disorders through the disruption of ADAR2 pathways. A total of nine potential lead compounds were shortlisted as plausible modulators of ADAR2.

4-Dimethylaminopyridine (DMAP), A Superior Mediator for Morita-Balylis-Hillman Reaction-Triggered Annulative Condensation of Salicylaldehydes and Acrylonitrile to Form 3-Cyano-2H-chromenes

We unveiled superior base mediators for the annulative condensation of salicylaldehydes and acrylonitrile to give 3-cyano-2H-chromenes, which has been mediated only by 1,4-diazabicyclo[2.2.2]octane (DABCO) over the past two decades. The reactions were most efficiently mediated by 4-dimethylaminopyridine (DMAP), which yielded 3-cyano-2H-chromenes in higher yields than DABCO in most cases. We also confirmed that the reaction remained high yielding in a decagram-scale experiment with a catalytic amount of DMAP. The utility of this reaction was also exemplified by derivatization of an obtained 3-cyano-2H-chromene into a known 2H-chromene-3-carboxylic acid, which was previously synthesized with a non-readily available reagent.

LSD1 inhibitors from the roots of Pueraria lobata

One new 6a,11a-dehydropterocarpan derivative, 6-O-methyl-anhydrotuberosin (1), one new 6a-hydroxypterocarpan, (6aR,11aR,11bR)-hydroxytuberosone (7), and seven known compounds including two 6a,11a-dehydropterocarpans (2 and 4), two coumestans (3 and 5), one isoflavonoid (6) and two other phenolic compounds (8 and 9) were isolated from the roots of Pueraria lobata. The structures of the isolated compounds were elucidated with spectroscopic and spectrometric methods (1 D and 2DNMR, HRESIMS). Compounds 1, 2, 4-5 showed potent LSD1 inhibitory activities with IC₅₀ values ranging from 1.73 to 4.99 μM. Furthermore, compound 2 showed potent cytotoxicity against gastric cancer cell lines MGC-803 and BGC-823, and lung cancer cell lines H1299 and H460.

Polyphenolic Compounds from Lespedeza bicolor Protect Neuronal Cells from Oxidative Stress

Pterocarpans and related polyphenolics are known as promising neuroprotective agents. We used models of rotenone-, paraquat-, and 6-hydroxydopamine-induced neurotoxicity to study the neuroprotective activity of polyphenolic compounds from Lespedeza bicolor and their effects on mitochondrial membrane potential. We isolated 11 polyphenolic compounds: a novel coumestan lespebicoumestan A (10) and a novel stilbenoid 5’-isoprenylbicoloketon (11) as well as three previously known pterocarpans, two pterocarpens, one coumestan, one stilbenoid, and a dimeric flavonoid. Pterocarpans 3 and 6, stilbenoid 5, and dimeric flavonoid 8 significantly increased the percentage of living cells after treatment with paraquat (PQ), but only pterocarpan 6 slightly decreased the ROS level in PQ-treated cells. Pterocarpan 3 and stilbenoid 5 were shown to effectively increase mitochondrial membrane potential in PQ-treated cells. We showed that pterocarpans 2 and 3, containing a 3’-methyl-3’-isohexenylpyran ring; pterocarpens 4 and 9, with a double bond between C-6a and C-11a; and coumestan 10 significantly increased the percentage of living cells by decreasing ROS levels in 6-OHDA-treated cells, which is in accordance with their rather high activity in DPPH^• and FRAP tests. Compounds 9 and 10 effectively increased the percentage of living cells after treatment with rotenone but did not significantly decrease ROS levels.

Determination of Afzelin and Astragalin from Lespedeza cuneata on Aldose Reductase Inhibition

The bioactive chemicals in L. cuneata were investigated by repeated column chromatography and their effect on aldose reductase (AR), obtained from rat lenses, was examined. Results showed that the ethyl acetate and n-butanol fractions of L. cuneata exhibited potential inhibitory effect against AR with IC50 values of 0.57 and 0.49 μg/mL, respectively. Phytochemical analysis of these two fractions resulted in the isolation of five flavonoids namely, acacetin (1), afzelin (2), astragalin (3), kaempferol (4) and scutellarein 7-O-glucoside (5). The AR inhibitory effect of compounds 1-5 was explored; compounds 2, 3 and 5 showed potential AR-inhibitory effects with IC50 values of 2.20, 1.91 and 12.87 μM, respectively. Quantitative analysis of afzelin (2) and astragalin (3) in L. cuneata by high performance liquid chromatography with ultraviolet detection revealed its content to be 0.722-11.828 and 2.054-7.006 mg/g, respectively. Overall, this study showed that L. cuneata is rich in flavonoids with promising AR-inhibitory activities, which can be utilized for the development of natural therapies for treating and managing diabetic complications.

Lespedeza bicolor Extract Ameliorated Renal Inflammation by Regulation of NLRP3 Inflammasome-Associated Hyperinflammation in Type 2 Diabetic Mice

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder characterized by hyperglycemia. The chronic hyperglycemic condition causes hyperinflammation via activation of nucleotide-binding oligomerization domain-like pyrin domain containing receptor 3 (NLRP3) inflammasome and abnormally leads to morphological and functional changes in kidney. A previous study showed a protective effect of Lespedeza bicolor extract (LBE) on endothelial dysfunction induced by methylglyoxal glucotoxicity. We aimed to investigate whether LBE ameliorated renal damage through regulation of NLRP3 inflammasome-dependent hyper-inflammation in T2DM mice. After T2DM induction by a high fat diet and low dose of streptozotocin (30 mg/kg), the mice were administered with different dosages of LBE (100 or 250 mg/kg/day) by gavage for 12 weeks. LBE supplementation ameliorated kidney dysfunction demonstrated by urine albumin-creatinine at a low dose and plasma creatinine, blood urea nitrogen (BUN), and glomerular hypertrophy at a high dose. Furthermore, a high dose of LBE supplementation significantly attenuated renal hyper-inflammation associated with NLRP3 inflammasome and oxidative stress related to nuclear factor erythroid 2-related factor 2 (Nrf-2) in T2DM mice. Meanwhile, a low dose of LBE supplementation up-regulated energy metabolism demonstrated by phosphorylation of adenosine monophosphate kinase (AMPK) and Sirtuin (SIRT)-1 in T2DM mice. In conclusion, the current study suggested that LBE, in particular, at a high dose could be used as a beneficial therapeutic for hyperglycemia-induced renal damage in T2DM.

Flavonoids from the stems of Millettia pachyloba Drake mediate cytotoxic activity through apoptosis and autophagy in cancer cells

In this study, systematic separation and subsequent pharmacological activity studies were carried out to identify cytotoxic natural products from the dried stems of Millettia pachyloba Drake. Five previously undescribed isoflavones, pachyvones A-E; one previously undescribed xanthone, pachythone A; and twenty-two known compounds were obtained. The structures of these compounds were assigned on the basis of 1D/2D NMR data and high-resolution electrospray ionization mass spectroscopy analysis. Preliminary activity screening with HeLa and MCF-7 cells showed that ten compounds (3-5, 9, 12, 17-19, 24, and 25) had potential cytotoxicity. Further in-depth activity studies with five cancer cell lines (HeLa, HepG2, MCF-7, Hct116, and MDA-MB-231) and one normal cell line (HUVEC) revealed that these ten compounds showed specific cytotoxicity in cancer cells, with IC50 values ranging from 5 to 40 μM, while they had no effect on normal cell lines. To investigate whether the cytotoxicity of these ten compounds was associated with autophagy, their autophagic effects were evaluated in GFP-LC3-HeLa cells. The results demonstrated that compound 9 (durmillone) significantly induced autophagy in a concentration-dependent manner and had the best activity as an autophagy inducer among all of the compounds. Therefore, compound 9 was selected for further study. The PI/Annexin V double staining assay and Western blotting results revealed that compound 9 also induced obvious apoptosis in HeLa and MCF-7 cells, which suggests that it mediates cytotoxic activity through activation of both apoptosis and autophagy. Taken together, this study identified ten natural cytotoxic products from the dried stems of Millettia pachyloba Drake, of which compound 9 induced apoptosis and autophagy and could be an anticancer drug candidate.

Cytotoxic polyphenolic compounds from Lespedeza bicolor stem bark

Four new pterocarpans (6aR,11aR)-6a,11a-dihydrolespedezol A₂ (2), (6aR,11aR)-2-isoprenyl-6a,11a-dihydrolespedezol A₂ (3), (6aR,11aR,3'R)-6a,11a-dihydrolespedezol A₃ (4), (6aR,11aR,3'S)-6a,11a-dihydrolespedezol A₃ (5) and one new stilbenoid with 1,2-diketone fragment named bicoloketone (6) along with one previously known pterocarpen lespedezol A₂ (1) have been isolated from Lespedeza bicolor stem bark using multistage column chromatography on polyamide and silica gel. The structures of the isolated polyphenolic compounds were determined by spectroscopic methods. The absolute configurations of 4 and 5 were determined by comparison of their electronic circular dichroism (ECD) spectra obtained experimentally and the spectra calculated using time-dependent density functional theory (TDDFT). The isolated compounds exhibited a moderate DPPH scavenging effect and ferric reducing power compared to the reference antioxidant quercetin. The cytotoxicity of compounds against three human cancer cell lines, HTB-19, Kyse-30, and HEPG-2, and two normal cell lines, RPE-1 and HEK-293, was tested using the MTT assay. Compound 3 showed the strongest cytotoxic activity against all cell lines (IC₅₀ 6.0-19.1 μM) compared with the positive control cisplatin. The other tested compounds possessed moderate cytotoxic activity against cancer cells.

Preventive effects of a novel herbal mixture on atopic dermatitis-like skin lesions in BALB/C mice

BACKGROUND

A combination of parts of Cornus officinalis, Rosa multiflora, Lespedeza bicolor, Platycladus orientalis, and Castanea crenata is commonly used for alleviating inflammatory skin disorders. Therefore, this study was carried out to evaluate the in vitro and in vivo preventive effects of a novel herbal formula made from the five plants (C2RLP) against atopic dermatitis in BALB/C mice.

METHODS

Mice were allocated into five groups (n = 8) including, control (Normal, petrolatum, and betamethasone treated) and treatment groups (treated with 2.5 and 5% C2RLP ointment). Atopic lesion was induced by applying 1-Chloro-2, 4-dinitrobenzene to the dorsal thoracic area of mice. Macroscopical and histological evaluations were performed to determine the effects of treatment on the progress of the skin lesions. The effects of treatment on the production and release of interleukins, interferon -ϒ, nitrite, prostaglandin E2, thymus and activation-receptor chemokine, and β-hexosaminidase were evaluated and comparisons were made between groups. In addition, the chemical compounds present in C2RLP were identified by Liquid Chromatography-Mass Spectrometry.

RESULTS

Topical application of C2RLP reduced the dermatitis score and suppressed histopathological changes in mice. Treatment significantly reduced (P < 0.05) plasma IL-4 level, the production of nitrite, prostaglandin E2, and thymus and activation-receptor chemokine production. The lipopolysaccharide-induced iNOS-mRNA expression in RAW 264.7 cells was also suppressed by high concentrations of C2RLP. In addition, C2RLP showed an inhibitory effect against DPPH free radical (IC50 = 147.5 μg/ml) and β-hexosaminidase release (IC50 = 179.5 μg/ml). Liquid Chromatography-Mass Spectrometry analysis revealed the presence of various compounds, including loganin, ellagic acid, and kaempferol 3-glucoside.

CONCLUSION

Down-regulation of T- helper 2 cellular responses and suppression of inflammatory mediators contributed to the protective effects of C2RLP from atopic dermatitis in BALB/C mice.

Collective Syntheses of 2-(3-Methylbenzofuran-2-yl)phenol-Derived Natural Products by a Cascade [3,3]-Sigmatropic Rearrangement/Aromatization Strategy

A cascade [3,3]-sigmatropic rearrangement/aromatization strategy to the synthesis of 2-(3-methylbenzofuran-2-yl)phenol derivatives was developed and applied to the collective syntheses of seven 2-arylbenzofuran-containing natural products, namely glycybenzofuran, glycyuralin E, lespedezol A₁, puerariafuran, 7,2',4'-trihydroxy-3-benzofurancarboxylic acid, coumestrol, and 4'-O-methylcoumestrol. Among them, the total syntheses of glycybenzofuran, glycyuralin E, puerariafuran, 7,2',4'-trihydroxy-3-benzofurancarboxylic acid, and 4'-O-methylcoumestrol were reported for the first time. The practicality of this novel strategy in preparation of the key intermediates was demonstrated by performing the reaction on gram scale and by synthesizing a series of natural products with 2-(3-methylbenzofuran-2-yl)phenol scaffolds in a common strategy.

A new exploration of licorice metabolome

The roots and rhizomes of licorice plants (genus Glycyrrhiza L.) are commercially employed, after processing, in confectionery production or as sweetening and flavouring agents in the food, tobacco and beer industries. G. glabra, G. inflata and G. uralensis are the most significant licorice species, often indistinctly used for different productions. Licorice properties are directly related to its chemical composition, which determines the commercial values and the quality of the derived products. In order to better understand the characteristics and properties of each species, a chemical characterization of three species of licorice (G. glabra, G. inflata, G. uralensis) is proposed, through an untargeted metabolomic approach and using high-resolution mass spectrometry. The statistical analysis reveals new possible markers for the analyzed species, and provides a reliable identification of a high number of metabolites, contributing to the characterization of Glycyrrhiza metabolome.

Seasonal Variations of Metabolome and Tyrosinase Inhibitory Activity of Lespedeza maximowiczii during Growth Periods

Lespedeza species are useful for pasture and energy crops as well as medical plants. We determined the metabolites discriminated from the each growth period (3, 4, 6, 8, 15, and 18 months) after germination in leaves and stems of Lespedeza maximowizii by a metabolomics technique. Specifically, levels of sugars and luteolin-dominated derivatives were significantly elevated in samples harvested in November. This may be related to the cold tolerance mechanism against the low temperatures of the winter season. The concentrations of secondary metabolites, isoflavones and flavanones, as well as tyrosinase inhibitory activity were the highest in the 6 month samples, which were harvested in September, during the fall season. The tyrosinase inhibitory activity in leaves was higher than that in stems irrespective of the growth period. This study suggests that mass spectrometry-based metabolite profiling could be used as a tool to examine quantitative or qualitative metabolite changes related to seasonal variations and to understand the correlation between activity and metabolites.

A potential anti-inflammation activity and depigmentation effect of Lespedeza bicolor extract and its fractions

Postinflammatory hyperpigmentation (PIH) is an acquire hypermelanosis after cutaneous inflammation and injury. The aim of the present study was to investigate a natural ingredient with the anti-inflammatory and depigmentation activities into possible applications of postinflammatory hyperpigmentation. Methanol extracts of Lespedeza bicolor and its various fractions inhibited LPS-induced NO production in RAW 264.7 macrophages in a concentration-dependent manner. In particular, the ethyl acetate fraction was shown to be inhibition of NO production (89%) and down-regulation of iNOS mRNA without causing cytotoxicity. In addition, ethyl acetate fraction significantly attenuated LPS-induced NF-κB activation (P < 0.05), indicating the anti-inflammatory activity due to NF-κB inhibition. Moreover, extracts, mainly ethyl acetate fraction, exhibited not only DPPH free radical scavenging activity (IC₅₀, 112.45 μg/mL) with 4 times lower activity than ascorbic acid, but also anti-tyrosinase activity (IC₅₀, 1 μg/mL) with a similar activity to arbutin showing a competitive inhibitor. Furthermore, vitexin and haginins A, B and C were identified through LC–MS analysis as potential compounds responsible for these effects. These results suggest that L. bicolor extract have anti-inflammatory, antioxidant activities and tyrosinase inhibitory effect and it might be used in the management of postinflammatory pigmentation through inhibition of pathogenic process involved in hyperpigmentation.

Desmodianone H and uncinanone B, potential tyrosinase inhibitors obtained from Lespedeza maximowiczii by using bioactivity-guided isolation

A new bioactive compound, namely desmodianone H(1), and another known compound uncinanone B(2) were first isolated using bioactivity-guided isolation from the leaves of Lespedeza maximowiczii and structures were elucidated by comprehensive analysis of their nuclear magnetic resonance and mass spectrometry data. Compounds 1 and 2 exhibited strong inhibitory effects on mushroom tyrosinase activity.

Palladium-catalyzed tandem reaction of 2-hydroxyarylacetonitriles with sodium sulfinates: one-pot synthesis of 2-arylbenzofurans

Palladium-catalyzed desulfinative addition and intramolecular annulation tandem reactions of 2-hydroxyarylacetonitriles with sodium sulfinates for one-pot synthesis of 2-arylbenzofurans.

Stereospecific microbial production of isoflavanones from isoflavones and isoflavone glucosides

A Gram-negative anaerobic microorganism, MRG-1, isolated from human intestine showed high activities of deglycosylation and reduction of daidzin, based on rapid TLC analysis. A rod-shaped strain MRG-1 was identified as a new species showing 91.0% homology to Coprobacillus species, based on 16S rRNA sequence analysis. The strain MRG-1 showed β-glucosidase activity toward daidzin and genistin, and daidzein and genistein were produced, respectively. However, the strain MRG-1 did not react with flavone glycosides, flavanone glycosides, and isoflavone C-glucoside. Besides, MRG-1 showed stereoselective reductase activity to isoflavone, daidzein, genistein, 7-hydroxyisoflavone, and formononetin, resulting in the formation of corresponding R-isoflavanone enantiomers. The new isoflavanones of 7-hydroxyisoflavanone and dihydroformononetin were characterized by NMR, and the absolute configurations of the enantiomers were determined with CD spectroscopy. The kinetic study of the anaerobic biotransformation showed both activities were exceptionally fast compared to the reported conversion by other anaerobic bacteria.

Pterocarpenes elicited by Aspergillus caelatus in peanut (Arachis hypogaea) seeds

The substituted pterocarpenes named aracarpene-1 (1) and aracarpene-2 (2) were isolated from wounded peanut seeds challenged by a strain of Aspergillus caelatus. The structures of these putative phytoalexins were determined by interpretation of NMR and MS data. The aracarpenes were investigated for their antifungal and antibacterial activities as well as antioxidant, anti-inflammatory, and cytotoxic activities in mammalian cells. Aracarpene-2 demonstrated high antibacterial properties against tested gram-positive and gram-negative bacteria, whereas aracarpene-1 displayed low antibacterial properties against the same bacteria. Both compounds had no antifungal activity against Aspergillus flavus. Together with peanut stilbenoids that are also produced in the challenged seeds, these compounds may represent a class of low-molecular weight peanut metabolites with a defensive role(s) against pathogenic microorganisms.

Two new dihydrofuranoisoflavanones from the leaves of Lespedeza maximowiczi and their inhibitory effect on the formation of advanced glycation end products

Two new dihydrofuranoisoflavanones, 2',4',5-trihydroxy-[5''-(1,2-dihydroxy-1-methylethyl)-dihydrofurano(2'',3'':7,8)]-(3S)-isoflavanone (1) and 2', 4', 5-trihydroxy-[5''-(1,2-dihydroxy-1-methylethyl)-dihydrofurano(2'',3'':7,8)]-(3R)-isoflavanone (2) as well as one already-known compound, (+)-catechin (3), were isolated from an n-BuOH soluble fraction from the leaves of Lespedeza maximowiczi. Spectroscopic data was used to elucidate the structures of compounds 1 and 2. All of the isolates were evaluated in vitro for their inhibitory activity on the formation of advanced glycation end products (AGEs). Among these, compounds 1, 2, and 3 exhibited inhibitory activity against AGEs formation with IC(50) values of 20.6, 18.4, and 5.6 microM, respectively.

Conversion of (3S,4R)-tetrahydrodaidzein to (3S)-equol by THD reductase: proposed mechanism involving a radical intermediate

To elucidate the mechanism of (3S)-equol biosynthesis, (2,3,4-d(3))-trans-THD was synthesized and converted to (3S)-equol by THD reductase in Eggerthella strain Julong 732. The position of the deuterium atoms in (3S)-equol was determined by (1)H NMR and (2)H NMR spectroscopy, and the product was identified as (2,3,4(alpha)-d(3))-(3S)-equol. All the deuterium atoms were retained, while the OH group at C-4 was replaced by a hydrogen atom with retention of configuration. To explain the deuterium retention in this stereospecific reduction, we propose a mechanism involving radical intermediates.

Stereospecific biotransformation of dihydrodaidzein into (3S)-equol by the human intestinal bacterium Eggerthella strain Julong 732

Stereochemical course of isoflavanone dihydrodaidzein (DHD) reduction into the isoflavan (3S)-equol via tetrahydrodaidzein (THD) by the human intestinal anaerobic bacterium Eggerthella strain Julong 732 was studied. THD was synthesized by catalytic hydrogenation, and each stereoisomer was separated by chiral high-performance liquid chromatography. Circular dichroism spectroscopy was used to elucidate the absolute configurations of four synthetic THD stereoisomers. Rapid racemization of DHD catalyzed by Julong 732 prevented the substrate stereospecificity in the conversion of DHD into THD from being confirmed. The absolute configuration of THD, prepared by reduction of DHD in the cell-free incubation, was assigned as (3R,4S) via comparison of the retention time to that of the authentic THD by chiral chromatography. Dehydroequol (DE) was unable to produce the (3S)-equol both in the cell-free reaction and in the bacterial transformation, negating the possible intermediacy of DE. Finally, the intermediate (3R,4S)-THD was reduced into (3S)-equol by the whole cell, indicating the inversion of stereochemistry at C-3 during the reduction. A possible mechanism accounting for the racemization of DHD and the inversion of configuration of THD during reduction into (3S)-equol is proposed.

Melanin synthesis inhibitors from Lespedeza floribunda

In the course of our search for new melanin synthesis inhibitors from plants, 40 new flavonoids and 11 known flavonoids were isolated from the roots of Lespedeza floribunda Bunge. The structures of the new compounds were determined by MS and NMR analyses, and the absolute configurations by CD spectra. Many of the compounds inhibited melanin synthesis in normal human epidermal melanocytes (NHEM), and compounds 3, 7, 8, 11, 16, 24, 27, 29, 33, 43, 45, and 51 were particularly inhibitory. Their activities were stronger than that of hydroquinone, which is known as a major skin-lightening drug.

Melanin synthesis inhibitors from Lespedeza cyrtobotrya

From the roots of Lespedeza cyrtobotrya, 45 flavonoids were isolated along with 20 new and 25 known compounds. Lipophilic flavonoids 2, 3, 7, 9, 11, 28, 30, and 39 exhibited strong inhibitory activities on melanin synthesis in normal human epidermal melanocytes.

Antioxidant 2-phenylbenzofurans and a coumestan from Lespedeza virgata

Two 2-phenylbenzofurans, lespedezavirgatol (1) and lespedezavirgatal (2), and a coumestan, lespedezacoumestan (3), were isolated from the aerial parts of Lespedeza virgata, together with nine known flavonoids. Their structures were determined on the basis of spectroscopic data. The three new compounds showed strong oxygen radical absorbance capacity and potent inhibition toward lipid peroxidation in both plasma and kidney homogenate of renal failure rats.

Practical synthesis of lespedezol A1

A practical formal synthesis of lespedezol A 1 ( 1) was accomplished in 33% yield for four steps starting from formation of the substituted chalcone. Of particular note is a useful protocol for reduction of the 2-ene bond in the isoflavone intermediate. A significant improvement in the final ring closure when water was scavenged from the reaction is also noteworthy. The ready availability of lespedezol A 1 will provide material for further pharmacological evaluation and for exploration of the pterocarpene nucleus as a potential entry into various 6a-hydroxypterocarpans.

A novel flavonoid from Lespedeza virgata (Thunb.) DC.: Structural elucidation and antioxidative activity

Bioactivity guided fractionation of the ethanolic extract of the whole plants of Lespedeza virgata (Thunb.) DC. resulted in the isolation of a novel flavonoid (1) along with five known compounds 2-6. The molecular and structural formula as well as the stereochemistry of compound 1 were determined using data obtained from (1)H and (13)C NMR spectra, DEPT135 and by 2D HSQC, HMBC, (1)H-(1)H correlated spectroscopy ((1)H-(1)H COSY), and nuclear overhauser effect spectroscopy (NOESY) experiments. The superoxide anion scavenging activities of all isolated compounds were evaluated by the hypoxanthine nitro blue tetrazolium and ESR methods and the new compound 1 showed the strongest antioxidative activity 95.79% (IC(50)=0.14 mg/ml).

Isoflavonoids of the leguminosae

Isoflavonoids are found predominantly in subfamily Papilionoideae of the Leguminosae. This review describes more than 420 new examples of Leguminosae isoflavonoids, giving details of their source, identification, biological activity, synthesis, and ecological or chemosystematic significance. Other topics addressed include the application of hyphenated analytical techniques to the characterisation of legume-derived isoflavonoids, and advances made in biosynthetic studies. A checklist of new compounds by species is given, and 404 references are cited.

Phytochemical medicinal agents. A quinone-based route to pterocarpins

The synthesis of 6,9 di-demethoxy kushecarpin A has been achieved by the coupling of a benzofuran anion with a quinone monoketal followed by a regioselective cyclization and a stereoselective hydrogenation reaction.

Advances in flavonoid research since 1992

Some of the recent advances in flavonoid research are reviewed. The role of anthocyanins and flavones in providing stable blue flower colours in the angiosperms is outlined. The contribution of leaf flavonoids to UV-B protection in plants is critically discussed. Advances in understanding the part played by flavonoids in warding off microbial infection and protecting plants from herbivory are described. The biological properties of flavonoids are considered in an evaluation of the medicinal and nutritional values of these compounds.