Effect of the Benzylic Structure of Lignan on Antioxidant Activity

Knotwood and Branchwood Polyphenolic Extractives of Silver Fir, Spruce and Douglas Fir and Their Antioxidant, Antifungal and Antibacterial Properties

The extractive contents of three softwood species largely used in the wood industry, namely Abies alba (Silver fir), Picea abies (spruce) and Pseudotsuga menziesii (Douglas fir), have been determined quantitatively for knots and at different points chosen along their branches, before analysis using high-performance liquid chromatography coupled with Mass Spectrometry (HPLC-MS). The results indicated that branchwood samples located in close proximity to the stem present high contents of extractives similar to those recorded for the knots. HPLC analysis showed quite similar chemical compositions, indicating that first cm of the branches could be considered as an additional source of knotwood. The antibacterial, antifungal and antioxidant activities of knot's extractives have been investigated with the dual objective of better understanding the role of high levels of secondary metabolites present in the knot and evaluating their potential for biorefinery applications. The antioxidant activity study showed that crude extracts of Douglas fir knotwood presented higher radical scavenging activity levels than the extracts of Silver fir and spruce, which presented more or less the same activities. Silver fir and spruce knotwood extracts presented higher antibacterial activity levels than the Douglas fir knotwood extracts did, while Douglas fir knotwood extracts presented more fungal growth inhibition than the spruce and fir knotwood extracts did. The structure-activity relationships indicate that radical scavenging and antifungal activities are associated with a higher relative quantity of flavonoids in the crude extracts, while higher relative quantities of lignans are associated with antibacterial activity.

Antichilblain Components in Eggplant Based on Network Pharmacology and Biological Evaluation

Eggplant, the fruit of Solanum melongena L. (Solanaceae), is applied externally to relieve the symptoms of chilblains in the folk in East Asia. However, the mechanisms and biological ingredients are not clear. A network pharmacology approach was used to shed light on the mechanisms of eggplant against chilblains, which illustrated that anti-inflammation and antioxidation are mainly involved in the curative effects. Bioassay-guided assays led to the isolation of 44 ingredients (1-44), including two new natural compounds (1-2) and 42 known compounds. Thirteen compounds (3-15) were first reported from the Solanum genus. The anti-inflammatory and antioxidative effects of all isolates were evaluated, and the results showed that 11 compounds have anti-inflammatory activity and 27 have antioxidant activity. Fatty acids, flavonoids, alkaloids, phenolic acids, saponins, and lignans from eggplant have certain anti-inflammatory and antioxidant effects. These results provide a scientific basis for eggplant to treat chilblains.

Structural Features of Small Molecule Antioxidants and Strategic Modifications to Improve Potential Bioactivity

This review surveys the major structural features in various groups of small molecules that are considered to be antioxidants, including natural and synthetic compounds alike. Recent advances in the strategic modification of known small molecule antioxidants are also described. The highlight is placed on changing major physicochemical parameters, including log p, bond dissociation energy, ionization potential, and others which result in improved antioxidant activity.

In Vitro Antidiabetic, Antioxidant, and Prebiotic Activities of the Chemical Compounds Isolated from Guizotia abyssinica

India and Ethiopia employ Guizotia abyssinica (niger plant) as a source of edible vegetable oil. Previous studies have documented the niger plant's antioxidant properties and dietary benefits. Here, G. abyssinica extract was obtained and ten known bioactive components (1-10) were isolated. The antioxidant, antidiabetic, and prebiotic properties of whole extract and isolated components of niger and the plant's ability to cooperate symbiotically with probiotic strains were examined. Compound 10, myricetin-3-O-L-rhamnoside, had the highest antioxidant capacity measured in the 2,2-diphenylpicrylhydrazyl (DPPH, 4629.76 ± 6.02 µmol Trolox equivalent/g compound) and ferric-reducing antioxidant power (FRAP, 2667.62 ± 7.5 mol Trolox equivalent/g compound) assays. The lowest α-amylase and glycogen phosphorylase activities and glucose diffusion were obtained with whole G. abyssinica extracts, whereas compounds 8-10 had moderate inhibitory effects. G. abyssinica extract also induced the highest glucose absorption by yeast cells in the presence of 5 mM of glucose. Moreover, Lactobacillus plantarum and L. rhamnosus incubated with β-sitosterol 3-O-D-glucoside (compound 7) showed the highest prebiotic activity score. The levels of L-(+)-lactic acid isomer in the probiotic strains were the highest in presence of the whole extract and decreased progressively in the presence of flavonoid glycosides (compounds 8-10) and β-sitosterol 3-O-D-glucoside. The enzymatic profile of the probiotic strains was unaffected by the niger extract and compounds 7-10. The findings revealed that the biological activities of G. abyssinica extract are mediated by the compounds 1-10, and it may be considered as a promising plant for the treatment of diabetes mellitus.

Effect of flaxseed polyphenols on physical stability and oxidative stability of flaxseed oil-in-water nanoemulsions

Recent studies have shown that the high susceptibility of flaxseed oil nanoemulsions to lipid oxidation limits their incorporation into functional foods and beverages. For this reason, the impact of various flaxseed phenolic extracts on the physical and oxidative stability of flaxseed oil nanoemulsions was investigated. Flaxseed lignan extract (FLE) and secoisolariciresinol (SECO) exhibited antioxidant activity whereas secoisolariciresinol diglucoside (SDG) and p-coumaric acid (CouA) exhibited prooxidant activity in the flaxseed oil nanoemulsions. The antioxidant potential of flaxseed phenolics in the nanoemulsions was as follows: SECO < CouA < SDG ≈ FLE. Moreover, the antioxidant/prooxidant activity of the phenolics was also related to their free radical scavenging activity and partitioning in the nanoemulsions. Our results suggested that both SECO and FLE were good plant-based antioxidants for improving the stability of flaxseed oil nanoemulsions.

The mechanism(s) of action of antioxidants: From scavenging reactive oxygen/nitrogen species to redox signaling and the generation of bioactive secondary metabolites

Small molecule, dietary antioxidants exert a remarkably broad range of bioactivities, and many of these can be explained by the influence of antioxidants on the redox homeostasis. Such compounds help to modulate the levels of harmful reactive oxygen/nitrogen species, and therefore participate in the regulation of various redox signaling pathways. However, upon ingestion, antioxidants usually undergo extensive metabolism that can generate a wide range of bioactive metabolites. This makes it difficult, but otherwise a need, to identify the ones responsible for the different activities of antioxidants. By better understanding their ways of action, the use of antioxidants in therapy can be improved. This review provides a summary on the role of the in vivo metabolic changes and the oxidized metabolites on the mechanisms behind the bioactivity of antioxidants. A special attention is given to metabolites described as products of biomimetic oxidative chemical reactions, which can be considered as models of free radical scavenging. During such reactions a wide variety of metabolites are formed, and they can exert completely different specific bioactivities as compared to their parent antioxidants. This implies that exploring the free radical scavenging-related metabolite fingerprint of each antioxidant molecule, collectively defined here as the scavengome, will lead to a deeper understanding of the bioactivity of these compounds. Furthermore, this paper aims to be a working tool for systematic studies on oxidized metabolic fingerprints of antioxidants, which will certainly reveal an often-neglected segment of chemical space that is a treasury of bioactive compounds.

Effect of the structure of dietary epoxylignan on its cytotoxic activity: relationship between the structure and the activity of 7,7′-epoxylignan and the introduction of apoptosis by caspase 3/7

We compared the cytotoxic activities of dietary epoxylignans and their stereoisomers and found (−)-verrucosin, which is (7S,7′R,8R,8′R)-7,7′-epoxylignan, to be the most cytotoxic epoxylignan against HeLa cells (IC50 = 6.6 μM). On the other hand, the activity was about a factor of 10 less against HL-60. In this research on the relationship between the structure and cytotoxic activity of (−)-verrucosin 13, the 7-(4-methoxyphenyl)-7′-(3,4-dimethoxyphenyl) derivative 60, for which the activity (IC50 = 2.4 μM) is three times greater than (−)-verrucosin 13, was discovered. The induction of apoptosis by caspase 3/7 was observed upon treatment with the (−)-verrucosin derivative.

Evaluation of plant growth regulatory activity of furofuran lignan bearing a 7,9':7',9-diepoxy structure using optically pure (+)- and (-)-enantiomers

The plant growth regulatory activity of furofuran lignan (7,9':7',9-diepoxylignan) was evaluated by employing optically pure synthesized (+)- and (-)-enantiomers. (+)-Sesamin possessing a 3,4-methylenedioxy group on the aromatic rings and 7-aryl structure showed growth promotion activity against lettuce roots (EC50 = 0.50 mM); on the other hand, growth inhibitory activity was observed against lettuce shoots (EC50 = 0.38 mM). Against ryegrass shoots, (-)-sesamolin, which has 3,4-methylenedioxy groups on the aromatic rings and a 7-acetal structure, was effective in showing growth inhibitory activity (EC50 = 0.23 mM). Different activity levels were observed between (+)- and (-)-enantiomers. It was assumed that the 3,4-methylenedioxy group on the aromatic ring was more potent for the plant growth regulatory activity.

Cytotoxic activity of dietary lignan and its derivatives: structure-cytotoxic activity relationship of dihydroguaiaretic acid

Cytotoxic activities of synthesized lignan derivatives were estimated by WST-8 reduction assay against HL-60 and HeLa cells to show the structure-activity relationship. The activities of some effective compounds were examined against Colon 26 and Vero cells. Dietary secoisolariciresinol (SECO, 1) and its metabolite, 9,9'-anhydrosecoisolariciresinol (2), did not show the cytotoxic activity. On the other hand, all stereoisomers of dihydroguaiaretic acid (DGA, 9,9'-dehydroxysecoisolariciresinol, 3-5) exhibited the activity (IC50: around 30 μM). The IC50 value of (8R,8'R)-9-butyl DGA derivative 13 was around 6 μM. This fact means that the hydrophobic group was advantageous for higher activity at 9- and 9'-positions. By the evaluation of the effect of 7and 7'-aryl group on the activity, we discovered the highest activity of (8R,8'R)-7-(3-hydroxy-4-methoxyphenyl)-7'-(2-ethoxyphenyl) DGA derivative 47 showing around 1 μM of IC50 value, which is about 24-fold higher activity than that of natural (8R,8'R)-DGA. The derivative of dietary lignan showed the high cytotoxic activity.

Lignans from the stems of Clematis armandii ("Chuan-Mu-Tong") and their anti-neuroinflammatory activities

ETHNOPHARMACOLOGICAL RELEVANCE

The dried stems of Clematis armandii (Caulis clematidis armandii), named "Chuan-Mu-Tong" in Chinese Pharmacopoeia, have been traditionally used as an herbal remedy mainly for inflammation-associated diseases. The Aim of the study is to identify the potential anti-neuroinflammatory components from Clematis armandii.

MATERIALS AND METHODS

The ethanol extract of "Chuan-Mu-Tong" was suspended in H₂O and exhaustively extracted with CH₂Cl₂. The CH₂Cl₂ fraction was successively subjected to column chromatography (CC) over silica gel, Sephadex LH-20, and semi-preparative HPLC. The structures of the isolated compounds were identified by spectroscopic methods and by comparison with those reported in the literature. Their anti-neuroinflammatory activities were evaluated by inhibitory effects on pro-inflammatory mediators [e.g. nitric oxide (NO) and tumor necrosis factor-alpha (TNF-α)] in lipopolysaccharide (LPS)-activated BV-2 cells.

RESULTS

One new and sixteen known lignans were isolated and characterized. The absolute configuration of the new lignan, (7R,8S)-9-acetyl-dehydrodiconiferyl alcohol (1), was elucidated by a combination of 1D/2D NMR techniques and the Electronic Circular Dichroism (ECD) spectroscopy based on the empirical helicity rules. The anti-neuroinflammatory bioassay showed that compounds 1, (7R,8S)-dehydrodiconiferyl alcohol (2), erythro-guaiacylglycerol-β-coniferyl ether (5), and threo-guaiacylglycerol-β-coniferyl ether (6) displayed significant inhibitory effects on NO production. Among them, neolignans 1 and 2 exhibited more potent activities than the positive control (N(G)-monomethyl-L-arginine, L-NMMA), with an IC₅₀ value of 9.3 and 3.9 μM, respectively. Moreover, both 1 and 2 were also found to concentration-dependently suppress the TNF-α release in LPS-stimulated BV-2 cells.

CONCLUSION

The results revealed that lignans are the major components of "Chuan-Mu-Tong", and their anti-neuroinflammatory activities strongly support the traditional application of this herb medicine on inflammation. Moreover, the dihydrobenzo[b]furan neolignans 1 and 2 as well as Caulis clematidis armandii could be further exploited as new therapeutic agents to treat inflammation-mediated neurodegenerative and aging-associated diseases.

Structure-plant growth inhibitory activity relationship of lariciresinol

The syntheses of 55 lariciresinol derivatives containing derivatives on the 9-position and an aryl group at both 7- and 7'-positions were successful to examine the effect of structure of (-)-lariciresinol (1) on plant growth regulatory activity. (-)-(7R,8R,8'S)-9-Dehydroxylariciresinol 9 showed activity 2-fold more potent than that of natural (-)-lariciresinol (1) and -95% growth inhibitory activity to negative control against rye grass root at 1 mM. The derivatives bearing hydrophobic and smaller groups at the 9-position showed higher activity. The importance of 4- and 4'-hydroxy groups and 3- and 3'-small hydrophobic groups on 7- and 7'-phenyl groups for higher activity was also suggested.

Synthesis and antioxidant evaluation of (S,S)- and (R,R)-secoisolariciresinol diglucosides (SDGs)

Secoisolariciresinol diglucosides (SDGs) (S,S)-SDG-1 (major isomer in flaxseed) and (R,R)-SDG-2 (minor isomer in flaxseed) were synthesized from vanillin via secoisolariciresinol (6) and glucosyl donor 7 through a concise route that involved chromatographic separation of diastereomeric diglucoside derivatives (S,S)-8 and (R,R)-9. Synthetic (S,S)-SDG-1 and (R,R)-SDG-2 exhibited potent antioxidant properties (EC50=292.17±27.71 μM and 331.94±21.21 μM, respectively), which compared well with that of natural (S,S)-SDG-1 (EC50=275.24±13.15 μM). These values are significantly lower than those of ascorbic acid (EC50=1129.32±88.79 μM) and α-tocopherol (EC50=944.62±148.00 μM). Compounds (S,S)-SDG-1 and (R,R)-SDG-2 also demonstrated powerful scavenging activities against hydroxyl [natural (S,S)-SDG-1: 3.68±0.27; synthetic (S,S)-SDG-1: 2.09±0.16; synthetic (R,R)-SDG-2: 1.96±0.27], peroxyl [natural (S,S)-SDG-1: 2.55±0.11; synthetic (S,S)-SDG-1: 2.20±0.10; synthetic (R,R)-SDG-2: 3.03±0.04] and DPPH [natural (S,S)-SDG-1: EC50=83.94±2.80 μM; synthetic (S,S)-SDG-1: EC50=157.54±21.30 μM; synthetic (R,R)-SDG-2: EC50=123.63±8.67 μM] radicals. These results confirm previous studies with naturally occurring (S,S)-SDG-1 and establish both (S,S)-SDG-1 and (R,R)-SDG-2 as potent antioxidants and free radical scavengers for potential in vivo use.

Stereoselective syntheses of all stereoisomers of lariciresinol and their plant growth inhibitory activities

All stereoisomers of lariciresinol were synthesized to examine the effect of stereochemistry on plant growth. Configuration of benzylic 7-positions was constructed through S(N)1 or S(N)2 intramolecular etherification. 8- and 8'-position configurations were established from the starting material except for all cis stereoisomers, the 8-position configurations of which were achieved by employing stereoselective hydroboration. (-)-Lariciresinol and its 7S,8S,8'R stereoisomer inhibited the root growth of Italian ryegrass to 51-55% relative to the negative control, whereas other stereoisomers had less effect. These results demonstrate that the stereochemistry of lignans is one of the important factors influencing their inhibitory activity.

Syntheses of secocyclolignanes and comparative antioxidative activity between secocyclolignane and the dibenzyl type of lignan

The antioxidative activity of secocyclolignanes was compared with that of the corresponding dibenzyl lignans for the first time. The radical scavenging activity of the secocyclolignanes was weaker than that of the corresponding dibenzyl lignans, the butane diol type showing the highest activity. The butane type of secocyclolignane exhibited the highest antioxidant activity of the unsaturated fatty acid.

Isochaihulactone protects PC12 cell against H(2)O(2) induced oxidative stress and exerts the potent anti-aging effects in D-galactose aging mouse model

AIM

to investigate the effect of isochaihulactone (also known as K8), a lignan compound of Bupleurum scorzonerifolium, on H(2)O(2)-induced cytotoxicity in neuronally differentiated PC12 cells (nPC12).

METHODS

viability of neuronal PC12 cells was measured using MTT assay. Protein expression was determined by Western blot. Apoptotic cells was determined using TUNEL assay. D-galactose aging mice were used as a model system to study the anti-oxidant effects of isochaihulactone in vivo.

RESULTS

pretreatment with isochaihulactone (5-10 micromol/L) increased cell viability and decreased membrane damage, generation of reactive oxygen species and degradation of poly (ADP-ribose) polymerase in H(2)O(2)-treated nPC12 cells and also decreased the expression of cyclooxygenase-2, via downregulation of NF-kappaB, resulting in a decrease in lipid peroxidation. The results suggest that isochaihulactone is a potential antioxidant agent. In a murine aging model, in which chronic systemic exposure to D-galactose (D-gal) causes the acceleration of senescence, administration of isochaihulactone (10 mgxkg(-1)xd(-1), sc) for 7 weeks concomitant with D-gal injection significantly increased superoxide dismutase and glutathione peroxidase activities and decreased the MDA level in plasma. Furthermore, H&E staining to quantify cell death within hippocampus showed that percentage of pyknotic nuclei in the D-gal-treated mice were much higher than in control.

CONCLUSION

the results suggest that isochaihulactone exerts potent anti-aging effects against D-gal in mice possibly via antioxidative mechanisms.