Theoretical and spectroscopic study of vanillic acid

New phenanthrenequinones from Cymbidium ensifolium roots and their anti-inflammatory activity on lipopolysaccharide-activated BV2 microglial cells

The roots of Cymbidium ensifolium yielded a total of 17 compounds, comprising two new compounds (1-2), one new natural product (3), and 14 known compounds (4-17). The structures of new compounds were determined through the analysis of their spectroscopic data, including NMR, MS, UV, FT-IR, optical rotation, and CD. The anti-inflammatory activity of the isolated pure compounds was assessed using lipopolysaccharide-activated BV2 microglial cells. Compounds 1, 3, 6, 12, 14, and 16 showed the ability to reduce LPS induced NO release in BV2 microglial cells, with IC50 values of 9.95 ± 2.13, 8.77 ± 3.78, 2.39 ± 0.91, 6.69 ± 2.94, 2.96 ± 1.38, 8.42 ± 2.99 μM, respectively and reduced the secretion of proinflammatory mediators (TNF-α, IL-6, MCP-1) in a concentration-dependent manner. Furthermore, the mechanistic role of the compound 3 was determined, which demonstrated its ability to inhibit the nuclear factor-κB (NF-κB) pathway through decreasing phosphorylation of p65 subunits.

A new phenanthrene with a spirolactone ring from Dendrobium ochreatum

Dendroochreatene (1), a new phenanthrene derivative with a spirolactone ring, was isolated from the whole Dendrobium ochreatum plant together with 11 known compounds (2-12). The structure of the new compound was elucidated spectroscopically and phenolic compounds were firstly reported from D. ochreatum. Moscatilin (4), major compound isolated from D. ochreatum, was found to be cytotoxic toward H460 lung-cancer cells, with an IC50 value of 147.3 ± 0.9 µM, while loddigesiinol C (7), C-α-methoxy derivative was inactive.

Phytochemical investigation of Asarum sieboldii var. seoulense and the phenotypic profiles of its constituents against a Parkinson's Disease olfactory cell line

Asarum sieboldii var. seoulense is a plant species under the family Aristolochiaceae and has been used for centuries as an ingredient in a well-known Traditional Chinese medicine (TCM), "Xixin", to treat symptoms of the neurodegenerative condition Parkinson's Disease (PD). Although there have been studies on the neuroprotective effect of this TCM, the phenotypic profiles of its chemical constituents against PD-implicated cellular organelles have not been reported. This research investigated the chemistry of A. sieboldii var. seoulense extract to identify the active small molecules that exhibited perturbation to the cellular compartments related to PD, potentially supporting its traditional application in treating this condition. 1H NMR-guided chemical investigation of this plant yielded twenty secondary metabolites which belong to isobutylamides, lignans and phenolics. The compounds were evaluated against an olfactory cell line derived from a PD patient using phenotypic assay. Several isolates, 2, 3, 7, 11, 13-16 and 18-20, were found to induce moderate perturbation to the staining of mitochondria, autophagosome and α-tubulin of the cells. Considering that PD pathogenesis is closely related to these cellular compartments, the results provided a rationale for the traditional application of Xixin in the treatment of PD.

Efficient strategies for preparative separation of iridoid glycosides and flavonoid glycosides from Hedyotis diffusa

Efficient strategies for the preparative separation of iridoid glycosides and flavonoid glycosides from Hedyotis diffusa using preparative high-performance liquid chromatography combined with appropriate pretreatment technologies were developed. Four fractions (Fr.1-1, Fr.1-2, Fr.1-3, and Fr.2-1) were firstly isolated from the crude extract of Hedyotis diffusa by column chromatography with C18, resin, and silica gel materials, respectively. Then, corresponding separation strategies were developed according to the polarity and chemical constituents. High-polar compounds of Fr.1-1 were purified by hydrophilic reversed-phase liquid chromatography and hydrophilic interaction liquid chromatography mode. The combination of C18 and phenyl columns realized the complementary separation of iridoid glycosides in Fr.1-2. Meanwhile, the improved selectivity caused by the change of organic solvent in the mobile phase was utilized to realize the purification of flavonoid glycosides in Fr.1-3 and Fr. 2-1. Finally, 27 compounds (purity > 95%) mainly involving nine iridoid glycosides and five flavonoid glycosides were obtained. A complete strategy was established for the separation of a complex sample with a wide polarity range, to jointly solve the problems of enrichment of target components and separation of structural analogs.

Biosynthesis of vanillic acid by Ochrobactrum anthropi and its applications

Vanillic acid has always been in high-demand in pharmaceutical, cosmetic, food, flavor, alcohol and polymer industries. Present study achieved highly pure synthesis of vanillic acid from vanillin using whole cells of Ochrobactrum anthropi strain T5_1. The complete biotransformation of vanillin (2 g/L) in to vanillic acid (2.2 g/L) with 95 % yield was achieved in single step in 7 h, whereas 5 g/L vanillin was converted to vanillic acid in 31 h. The vanillic acid thus produced was validated using LC-MS, GC-MS, FTIR and NMR. Further, vanillic acid was evaluated for in vitro anti-tyrosinase and cytotoxic properties on B16F1 skin cell line in dose dependent manner with IC₅₀ values of 15.84 mM and 9.24 mM respectively. The in silico Swiss target study predicted carbonic acid anhydrase IX and XII as key targets of vanillic acid inside the B16F1 skin cell line and revealed the possible mechanism underlying cell toxicity. Molecular docking indicated a strong linkage between vanillic acid and tyrosinase through four hydrogen and several hydrophobic bonds, with ΔG of -3.36 kJ/mol and Ki of 3.46 mM. The bioavailability of vanillic acid was confirmed by the Swiss ADME study with no violation of Lipinski's five rules.

A new prenylated 3-benzoxepin derivative with anti-influenza A virus activity from Elsholtzia penduliflora

A new prenylated 3-benzoxepin derivative, elsholtzioxin (1), together with fifteen known compounds (2-16) were isolated from the whole parts of Elsholtzia penduliflora. Their structures were elucidated on the basis of various spectroscopic techniques and chemical evidences. The antiviral activities of these compounds were evaluated in vitro. The new compound (1) exhibited potential anti-influenza virus activity against strain A/WSN/33/2009 (H1N1) with inhibition rate of 47.19%. Compounds 2, 9 and 12 exhibited significant inhibitory activities with IC₅₀ value of 26.16, 34.66 and 20.81 μM, respectively.

Theoretical investigation on the mechanisms and kinetics of OH/NO3-initiated atmospheric oxidation of vanillin and vanillic acid

Vanillin and vanillic acid are two kinds of lignin pyrolysis products that are generated by biomass combustion. The gas-phase oxidation mechanisms of vanillin and vanillic acid initiated by OH/NO₃ radicals were investigated by using density functional theory (DFT) at M06-2X/6-311+G(3df,2p)//M06-2X/6-311+G(d,p) level. The initial reactions of vanillin and vanillic acid with OH/NO₃ radicals can be divided into two patterns: OH/NO₃ addition and H-atom abstraction. For vanillin reacted with OH radical, the OH addition mainly occurs at C2-position to produce highly chemically activated intermediate (IM2). The oxidation products 3,4-dihydroxy benzaldehyde, malealdehyde, methyl hydrogen oxalate, methylenemalonaldehyde, carbonyl and carbonyl compounds are formed by the subsequent reactions of IM2. H-atom abstracting from aldehyde group occurs more easily than from the other positions. In addition, vanillin reacting with NO₃ radicals principally proceeds via NO₃-addition at C1 sites and H-atom abstracting from OH group (C1) to generate HNO₃. The primary reaction mechanisms of vanillic acid with OH/NO₃ radicals were similar to vanillin. The Rice-Ramsperger-Kassel-Marcus (RRKM) theory was performed to calculate the rate constants of the significant elementary reactions. The total rate constants for OH-initiated oxidation of vanillin and vanillic acid are 5.72 × 10^-12 and 5.40 × 10^-12 cm³ molecule^-1 s^-1 at 298 K and 1 atm. The atmospheric lifetimes were predicted to be 48.56 h and 51.44 h, respectively. As a supplement, the kinetic calculations of NO₃ radicals with two reactants were also discussed. This work investigates the atmospheric oxidation processes of vanillin and vanillic acid, and hopes to provide useful information for further experimental research.

Cocrystallization-driven self-assembly with vanillic acid offers a new opportunity for surmounting fast and excessive absorption issues of antifungal drug 5-fluorocytosine: a combined theoretical and experimental research

The cocrystal of 5-fluorocytosine (FCY) with vanillic acid (VAA) was assembled via a cocrystallization technique, giving a novel understanding for conquering the dose-limited hepatotoxicity caused by the rapid and almost complete absorption of FCY.

Decarboxylation of p-Coumaric Acid during Pyrolysis on the Nanoceria Surface

Temperature-programmed desorption mass spectrometry (TPD MS) was used to study the pyrolysis of p-coumaric acid (pCmA) on the nanoceria surface. The interaction of pCmA with the CeO2 surface was investigated by FT-IR spectroscopy. The obtained data indicated the formation on the nanoceria surface of bidentate carboxylate complexes with chelate (Δν = 62 cm−1) and bridge structure (Δν = 146 cm−1). The thermal decomposition of pCmA over nanoceria occurred in several stages, mainly by decarboxylation. The main decomposition product is 4-vinylphenol (m/z 120). The obtained data can be useful for studying the mechanisms of catalytic thermal transformations of lignin-containing raw materials using catalysts containing cerium oxide and the development of effective technologies for the isolation of pCmA from lignin.

Catalytic Pyrolysis of Lignin Model Compounds (Pyrocatechol, Guaiacol, Vanillic and Ferulic Acids) over Nanoceria Catalyst for Biomass Conversion

Understanding the mechanisms of thermal transformations of model lignin compounds (MLC) over nanoscale catalysts is important for improving the technologic processes occurring in the pyrolytic conversion of lignocellulose biomass into biofuels and value-added chemicals. Herein, we investigate catalytic pyrolysis of MLC (pyrocatechol (P), guaiacol (G), ferulic (FA), and vanillic acids (VA)) over nanoceria using FT-IR spectroscopy, temperature-programmed desorption mass spectrometry (TPD MS), and thermogravimetric analysis (DTG/DTA/TG). FT-IR spectroscopic studies indicate that the active groups of aromatic rings of P, G, VA, and FA as well as carboxylate groups of VA and FA are involved in the interaction with nanoceria surface. We explore the general transformation mechanisms of different surface complexes and identify their decomposition products. We demonstrate that decomposition of carboxylate acid complexes occurs by decarboxylation. When FA is used as a precursor, this reaction generates 4-vinylguaiacol. Complexes of VA and FA formed through both active groups of the aromatic ring and decompose on the CeO2 surface to generate hydroxybenzene. The formation of alkylated products accompanies catalytic pyrolysis of acids due to processes of transalkylation on the surface.

Bioactive tetrahydrofuran lignans from roots, stems, leaves and twigs of Anogeissus rivularis

Four previously undescribed tetrahydrofuran lignans, named anorisols A-D (1-4) and fourteen known compounds (5-18) were isolated from the roots, stems, leaves and twigs of Anogeissus rivularis. The chemical structures were elucidated on the basis of their spectroscopic data and by comparison with the literature data. The absolute configurations of 1-4 were established by comparison of the experimental ECD spectra with the calculated ECD spectra. Some isolated compounds were evaluated for their cytotoxic activity as well as anti-HIV-1 activity employing reverse transcriptase (RT) and syncytium reduction assays using the ^ΔTat/RevMC99 virus in 1A2 cell line systems. Compound 6 displayed the most potent activity in syncytium inhibition assay with effective concentration at 50% (EC₅₀) value of 13.3 μM (SI >3.0). In the reverse transcriptase assay, compound 1 exhibited moderate activity with IC₅₀ value of 213.9 μM.

New Isoflavones with Antioxidant Activity Isolated from Cornulaca monacantha

In the course of phytochemical and chemotaxonomical investigations of Cornulaca monacantha (Amaranthaceae), two new isoflavones, 3-(2-hydroxyphenyl)-5,7-dimethoxy-6-(methoxymethyl)-4H-1-benzopyran-4-one (1) and 7-hydroxy-3-(4-hydroxyphenyl)-5-methoxy-6-(methoxymethyl)-4H-1-benzopyran-4-one (2) were isolated from the fresh aerial parts of C. monacantha among with three known compounds named vanillic acid (3), N-cis-feruloyltyramine (4) and N-trans-feruloyltyramine (5). Their structures were elucidated by means of spectroscopic methods including one- and two-dimensional NMR and HR-ESI-MS techniques. The isolated compounds exhibited interesting antioxidant activity determined by DPPH, ABTS and TAC tests.

Norlignan glucosides from Hypoxis hemerocallidea and their potential in vitro anti-inflammatory activity via inhibition of iNOS and NF-κB

Eleven diarylpentanoid/norlignan glucosides, along with five other specialized metabolites, were isolated and characterized from the hydro-alcoholic extract of Hypoxis hemerocallidea corms. Hypoxhemerolosides A-F were found to be undescribed compounds. Curcapicycloside was isolated and identified for the first time in its original form, previously it was reported as a methylated derivative. In addition, (1S,2R)-1-(3,4-dihydroxyphenyl)-5-(4-β-D-glucopyranoxy-3-hydroxyphenyl)-1-methoxypent-4-yn-2-ol and (1S,2R)-1-(3,4-dihydroxyphenyl)-1-ethoxy-5-(4-β-D-glucopyranoxy-3-hydroxyphenyl)pent-4-yn-2-ol were isolated and characterized as artifacts, generated during extraction/isolation procedures from possible 1-(3,4-dihydroxyphenyl)-5-(4-β-D-glucopyranoxy-3-hydroxyphenyl)pent-4-yne-1,2-diol. Structure elucidation was mainly achieved by the interpretation of 1D and 2D NMR and HRESIMS data. The isolated compounds were screened for anti-inflammatory activity in terms of iNOS and NF-κB inhibition as well as for cytotoxicity. Hypoxhemerolosides C-E and obtuside A moderately inhibited nitric oxide production in LPS-stimulated mouse macrophages (RAW 264.7).

Diploquinones A and B, Two New Phytotoxic Tetrasubstituted 1,4-Naphthoquinones from Diplodia mutila, a Causal Agent of Grapevine Trunk Disease

Two new phytotoxic tetrasubstituted 1,4-naphthoquinones, named diploquinones A and B, were isolated together with vanillic acid from Diplodia mutila (DAR78993), a grapevine pathogen involved in Botryosphaeria dieback in Australia. Diploquinones A and B were characterized as 6,7-dihydroxy-2-methoxy-5-methylnaphthalene-1,4-dione and 3,5,7-trihydroxy-2-methoxynaphthalene-1,4-dione using spectroscopic methods (essentially 1D and 2D ¹H and ¹³C NMR and HR ESIMS). The already known vanillic acid was isolated for the first time as fungal phytotoxin and as metabolite of D. mutila. The three compounds were assayed on detached grapevine leaves ( Vitis vinifera cv. Shiraz) at concentrations of 10^-3 M and 2.5 × 10^-3 M. Vanillic acid showed the highest phytotoxic effect on grapevine leaves irrespective of the tested concentration, while diploquinones A and B showed varying degrees of toxicity.

Characterization of tyrosinase inhibitory constituents from the aerial parts of Humulus japonicus using LC-MS/MS coupled online assay

In the screening of natural products for the development as cosmetic ingredients, the EtOAc-soluble fraction of Humulus japonicus showed tyrosinase inhibitory activity. HPLC-MS/MS coupled online tyrosinase assay of EtOAc-soluble fraction of H. japonicus characterized the twenty-eight constituents including two unknown ones and their tyrosinase inhibitory activity. Fractionation of H. japonicus using various chromatographic techniques yielded thirty-eight compounds. The chemical structures of isolated compounds were identified by spectroscopic analysis. As characterized by HPLC-MS/MS analysis, we isolated twenty-four predicted compounds and further identified two unknown ones, named humulusides A (1) and B (2). Additional ten compounds were also identified by purification. Tyrosinase inhibitory activity of isolated compounds were evaluated, which was closely correlated with the results from HPLC-MS/MS coupled online tyrosinase assay. Consistent with predicted data, two major compounds, trans-N-coumaroyltyramine (14) and cis-N-coumaroyltyramine (15) showed tyrosinase inhibition with IC₅₀ values of 40.6 and 36.4 μM. Taken together, H. japonicus is suggested as whitening ingredient in cosmetic products. In addition, HPLC-MS/MS coupled tyrosinase assay is powerful tool for predicting active compounds with short time and limited amounts, although identification of new compounds and verification of predicted data are also needs to be demonstrated by further experiment.

Sessilifol A and B, Urease Inhibitory Pimarane-type Diterpenes from Hymenocrater sessilifolius

New pimarane type diterpenes named sessilifol A (1) and B (2) have been isolated from the EtOH soluble fraction of Hymenocrater sessilifolius Benth., along with eight known constituents cirsimaritin (3), gardenin C (4), β-sitosterol (5), saringosterol (6), β-sitosterol glucoside (7), ursolic acid (8), sucrose (9) and vanillic acid (10). Their structures were elucidated on the basis of 1H- and 13C-NMR spectra and by 2D-NMR experiments. The structure of 1 was further confirmed by single crystal X-ray diffraction technique. The compound 2 showed potent inhibitory potential against the enzyme urease while 1, 3, 4 and 10 were moderately active.

Chemical Constituents from Walsura pinnata (Meliaceae)

A phytochemical study on the bark of Walsura pinnata has led to the isolation of a new oleanane triterpene acid, 3-oxo-olean-9(11),12-dien-28-oic acid (1), together with nine known compounds (2–10). Their structures were established on the basis of the detailed spectroscopic analysis, including one- and two-dimensional NMR, ESI-MS and HR-ESI-MS techniques. Compounds 2, 3, 5, 6 and 8 were isolated from W. pinnata for the first time. Compounds 3 and 4 showed in vitro growth inhibitory activity against two human cancer cell lines MCF-7 and SK-OV-3 with IC50 values within the range of 8.85 - 18.28 μg/mL. To the best of our knowledge, this is the first report on the cytotoxic activity of compound 3 towards both cancer cell lines.

Inositol Derivatives and Phenolic Compounds from the Roots of Taraxacum coreanum

In this study, the characterization of chemical constituents and biological activity of the roots of Taraxacum coreanum (Asteraceae) was attempted. Phytochemical investigation of the roots of T. coreanum led to the isolation of two new inositol derivatives, taraxinositols A (1) and B (2), and a new phenolic compound, taraxinol (16), together with twenty known compounds including four inositol derivatives, neo-inositol-1,4-bis (4-hydroxybenzeneacetate) (3), chiro-inositol-1,5-bis(4- hydroxybenzeneacetate) (4), chiro-inositol-2,3-bis (4-hydroxybenzeneacetate) (5) and chiro-inositol- 1,2,3-tris (4-hydroxybenzeneacetate) (6), nine phenolic compounds: p-hydroxybenzaldehyde (7), vanillin (8), syringaldehyde (9), vanillic acid (10), 4-methoxyphenylacetic acid (11), 4-hydroxy- phenylacetic acid methyl ester (12), optivanin (13), isoferulic acid (14) and dihydroconiferyl alcohol (15), four coumarins: nodakenetin (17), decursinol (18), prangol (19) and isobyakangelicin (20), and three lignans: syringaresinol-4′-O-β-d-glucoside (21), syringaresinol (22), and pinoresinol (23). The structures of isolated compounds were determined on the basis of spectroscopic analysis. Among the isolated compounds, vanillic acid, isoferulic acid and syringaresinol showed radical scavenging activity with IC₅₀ values ranging from 30.4 to 75.2 μM.

Isolation and characterization of an α-glucosidase inhibitor from Musa spp. (Baxijiao) flowers

The use of α-glucosidase inhibitors is considered to be an effective strategy in the treatment of diabetes. Using a bioassay-guided fractionation technique, five Bacillus stearothermophilus α-glucosidase inhibitors were isolated from the flowers of Musa spp. (Baxijiao). Using NMR spectroscopy analysis they were identified as vanillic acid (1), ferulic acid (2), β-sitosterol (3), daucosterol (4) and 9-(4′-hydroxyphenyl)-2-methoxyphenalen-1-one (5). The half maximal inhibitory concentration (IC₅₀) values of compounds 1–5 were 2004.58, 1258.35, 283.67, 247.35 and 3.86 mg/L, respectively. Compared to a known α-glucosidase inhibitor (acarbose, IC₅₀ = 999.31 mg/L), compounds 3, 4 and 5 showed a strong α-glucosidase inhibitory effect. A Lineweaver-Burk plot indicated that compound 5 is a mixed-competitive inhibitor, while compounds 3 and 4 are competitive inhibitors. The inhibition constants (K_i) of compounds 3, 4 and 5 were 20.09, 2.34 and 4.40 mg/L, respectively. Taken together, these data show that the compounds 3, 4 and 5 are potent α-glucosidase inhibitors.

Chemical composition of the bark of Tetrapterys mucronata and identification of acetylcholinesterase inhibitory constituents

The secondary metabolite content of Tetrapterys mucronata, a poorly studied plant that is used occasionally in Brazil for the preparation of a psychotropic plant decoction called "Ayahuasca", was determined to establish its chemical composition and to search for acetylcholinesterase (AChE) inhibitors. The ethanolic extract of the bark of T. mucronata exhibited in vitro AChE inhibition in a TLC bioautography assay. To localize the active compounds, biological profiling for AChE inhibition was performed using at-line HPLC-microfractionation in 96-well plates and subsequent AChE inhibition bioautography. The analytical HPLC-PDA conditions were transferred geometrically to a preparative medium-pressure liquid chromatography column using chromatographic calculations for the efficient isolation of the active compounds at the milligram scale. Twenty-two compounds were isolated, of which six are new natural products. The structures of the new compounds (9, 10, 16-18, and 20) were elucidated by spectroscopic data interpretation. Compounds 1, 5, 6, 9, and 10 inhibited AChE with IC50 values below 15 μM.

Molecular structure and spectroscopic analysis of homovanillic acid and its sodium salt--NMR, FT-IR and DFT studies

The estimation of the electronic charge distribution in metal complex or salt allows to predict what kind of deformation of the electronic system of ligand would undergo during complexation. It also permits to make more precise interpretation of mechanism by which metals affect the biochemical properties of ligands. Theinfluence ofsodium cation on the electronic system of homovanillic acid was studied in this paper. Optimized geometrical structures of studied compounds were calculated by B3LYP/6-311++G(**) method. Mulliken, MK and ChelpG atomic charges were analyzed. The theoretical NMR and IR spectra were obtained. (1)H and (13)C NMR as well as FT-IR and FT-Raman spectra of studied compounds were also recorded and analyzed. The calculated parameters are compared with experimental characteristics of these molecules.

cis-Aconitic Anhydride Ethyl Ester and Phenolic Compounds from the Seeds of Alisma orientale

From the seeds of Alisma orientale, cis-aconitic anhydride ethyl ester and cis-2,4,5-trihydroxycinnamic acid were isolated, together with nine known phenolic compounds and a megastigmane sesquiterpene. All compounds are reported for the first time from Alisma species.

Canthin-6-one Alkaloids and a Tirucallanoid from Eurycoma longifolia and Their Cytotoxic Activity against a Human HT-1080 Fibrosarcoma Cell Line

Phytochemical investigation of the stems of Eurycoma longifolia Jack led to the isolation of two new canthin-6-one alkaloids, 4,9-dimethoxycanthin-6-one (1) and 10-hydroxy-11-methoxycanthin-6-one (2), and a new tirucallane-type triterpenoid, 23,24,25-trihydroxytirucall-7-en-3,6-dione (3), along with 37 known compounds. Among these, an oxasqualenoid (4) was isolated as a natural product for the first time. The structures of the isolates were elucidated by spectroscopic and mass spectrometric means. All the isolates were evaluated for their cytotoxic activity against a HT-1080 human fibrosarcoma cell line. Among them, 9,10-dimethoxycanthin-6-one (14, IC50 = 5.0 μM), 10-hydroxy-9-methoxycanthin-6-one (15, IC50 = 7.2 μM), dihydroniloticin (18, IC50 = 8.2 μM), and 14-deacetyleurylene (34, IC50 = 3.2 μM) displayed stronger activity than the positive control 5-FU (IC50 = 9.2 μM).