Exploring the multifaceted effects of Ammi visnaga: subchronic toxicity, antioxidant capacity, immunomodulatory, and anti-inflammatory activities

Ammi visnaga (A. visnaga) is an annual herb that has been used in traditional medicine to treat various ailments attributed to the presence of its bioactive compounds. The purpose of this study was to identify and examine the phytochemical properties of the hydroalcoholic extract of A. visnaga using in vitro and in vivo models. Our findings demonstrated that the extract contained a variety of beneficial components, including phenols, flavonoids, tannins, coumarins, saponins, khellin, and visnagin. The total polyphenolic content and total flavonoid content were 23.26 mg/GAE/g dry weight and 13.26 mg/GAE/g dry weight, respectively. In vitro tests demonstrated that the extract possessed antioxidant properties as evidenced by the ability to scavenge free radicals, including DPPH, ABTS, nitric oxide (NO), phosphomolybdate, and ferric-reducing antioxidant power (FRAP). Further, the extract was found to inhibit hydrogen peroxide (H2O2)-induced hemolysis. In a 90-d in vivo study, female Wistar rats were administered 1 g/kg of A. visnaga extract orally resulting in a significant increase in total white blood cell count. Although morphological changes were observed in the liver, no marked alterations were noted in kidneys and spleen. In a female Swiss albino mice model of acetic acid-induced vascular permeability, A. visnaga significantly inhibited extravasations of Evans blue at doses of 0.5 or 1 g/kg with inhibition percentages of 51 and 65%, respectively, blocking tissue necrosis. The extract also demonstrated potential immunomodulatory properties in mice by enhancing antibody production in response to antigens. In silico molecular docking studies demonstrated a strong affinity between khellin or visnagin and immunomodulatory proteins, NF-κB, p52, and TNF-α. These findings suggest that A. visnaga may be considered a beneficial antioxidant with immunomodulatory properties and might serve as a therapeutic agent to combat certain diseases.

Nanostructured Lipid Carriers Can Enhance Oral Absorption of Khellin, a Natural Pleiotropic Molecule

A novel formulation based on nanostructured lipid carriers (NLCs) was developed to increase solubility and intestinal absorption of khellin. K-NLCs were prepared with stearic acid, hempseed oil, Brij S20, and Labrafil M 1944 CS, using the emulsification-ultrasonication method. Developed nanoparticles were chemically and physically characterized by liquid chromatography, light scattering techniques, and electron microscopy. The size, about 200 nm, was optimal for oral delivery, and the polydispersity index (around 0.26), indicated high sample homogeneity. Additionally, K-NLCs showed a spherical morphology without aggregation by microscopic analysis. The encapsulation efficiency of khellin was about 55%. In vitro release studies were carried out in media with different pH to mimic physiological conditions. K-NLCs were found to be physically stable in the simulated gastric and intestinal fluids, and they preserved about 70% of khellin after 6 h incubation. K-NLCs were also successfully lyophilized testing different lyoprotectants, and obtained freeze-dried K-NLCs demonstrated good shelf life over a month. Lastly, permeability studies on Caco-2 cells were performed to predict khellin passive diffusion across the intestinal epithelium, demonstrating that nanoparticles increased khellin permeability by more than two orders of magnitude. Accordingly, developed NLCs loaded with khellin represent a versatile formulation with good biopharmaceutical properties for oral administration, possibly enhancing khellin's bioavailability and therapeutic effects.

Khellin and Visnagin, Furanochromones from Ammi visnaga (L.) Lam., as Potential Bioherbicides

Plants constitute a source of novel phytotoxic compounds to be explored in searching for effective and environmentally safe herbicides. From a previous screening of plant extracts for their phytotoxicity, a dichloromethane extract of Ammi visnaga (L.) Lam. was selected for further study. Phytotoxicity-guided fractionation of this extract yielded two furanochromones, khellin and visnagin, for which herbicidal activity had not been described before. Khellin and visnagin were phytotoxic to model species lettuce (Lactuca sativa) and duckweed (Lemna paucicostata), with IC₅₀ values ranging from 110 to 175 μM. These compounds also inhibited the growth and germination of a diverse group of weeds at 0.5 and 1 mM. These weeds included five grasses [ryegrass (Lolium multiflorum), barnyardgrass (Echinocloa crus-galli), crabgrass (Digitaria sanguinalis), foxtail (Setaria italica), and millet (Panicum sp.)] and two broadleaf species [morningglory (Ipomea sp.) and velvetleaf (Abutilon theophrasti)]. During greenhouse studies visnagin was the most active and showed significant contact postemergence herbicidal activity on velvetleaf and crabgrass at 2 kg active ingredient (ai) ha^-1. Moreover, its effect at 4 kg ai ha^-1 was comparable to the bioherbicide pelargonic acid at the same rate. The mode of action of khellin and visnagin was not a light-dependent process. Both compounds caused membrane destabilization, photosynthetic efficiency reduction, inhibition of cell division, and cell death. These results support the potential of visnagin and, possibly, khellin as bioherbicides or lead molecules for the development of new herbicides.

Synthesis of new benzofuran-1,3-thiazolidin-4-one derivatives from natural sources and study of their antioxidant activity

Synthesis of benzofuran-1,3-thiazolidinone derivatives is described herein. These compounds were prepared via a concise and short route by condensation reaction of khellinone with aromatic/aliphatic amines followed by cyclization using thioglycolic acid. The newly synthesized compounds were characterized using the well known spectroscopic tools (IR, 1H NMR, and mass spectroscopy), as well as microanalysis. In frames of biological screening of the compounds, antioxidant activity was assessed in vitro.

Antitumor and antimicrobial activities of some hetero aromatic benzofurans derived from naturally occurring visnagin

Bromination of visnaginone (1) yielded the dibromo derivative (2), which upon methylation with methyl iodide gave 1-(2,7-dibromo-4,6-dimethoxybenzofuran-5-yl) ethanone (3). Compound (3) reacted with dimethylformamide dimethylacetal to give (4). The reaction of (3) with aromatic aldehydes namely (vanillin, benzaldehyde and 3-anisaldehyde) in ammonium acetate, malononitrile and/or butyric cyanoanhydride gave the 2-amino substituted nicotinonitriles (5a-c) and the 2-hydroxyl substituted nicotinonitriles (7a-c), respectively, while in piperidine gave (E)-1-(2,7-dibromo-4,6-dimethoxybenzofuran-5-yl)-3-(substituted)prop-2-en-l-one (11a-c). (5a) was hydrolyzed with sulfuric acid on cold to give the nicotinic acid derivative (6a). When compound (3) reacted with hydrazines and aromatic amines, it gave the Schiff bases (8a,b) and (10a,b), respectively. (8b) reacted with thioglycolic acid to give the thiazolidin-4-one (9b). When (11a-c) reacted with thiourea, it gave the pyrimidine derivatives (12a-c). (11a,b) also reacted with butyric cyanoanhydride and hydroxylamine hydrochloride to give (13a,b) and (15a,b), respectively. When the carboxylate (13a) was treated with 2,4-dinitroaniline, it gave the carboxamide (14a). Compounds (11b,c) reacted with hydrazine derivatives (hydrazine hydrate and phenylhydrazine) yielding the substituted pyrazole derivatives (16b,c) and (17b,c), respectively. All the structures of the synthesized compounds were elucidated by elemental analyses and spectral data. The newly synthesized benzofuran compounds showed a strong to moderate cytotoxicity against liver HEPG2 cancer cell line compared to 5-fluorouracil and doxorubicin (the anticancer agents). Compounds (2, 6a, 13a, 14a, 16c and 17b) were the most active compounds in descending order. The synthesized compounds were also tested for their antimicrobial activity. Compound (10b) showed the highest activity against all the tested strains followed by 6, 10a, 5a, 8b and 7a in descending order.

Synthesis of 6- and 9-alkylaminomethyl furoflavones as gastroprotective agents

The synthesis of 9- and 6-alkylaminomethyl furoflavones 5a, b, 9a-c, 13a, b, 15a-g and 18 from the naturally occurring chromones visnagin and khellin. Gastroprotective potency of these compounds in the ethanol damage model was determined. The results indicate that, through appropriate substitution, furoflavones can be obtained that are gastroprotective.

Application of 1D BIRD or X-filtered DEPT long-range C-C relay for detection of proton and carbon via four bonds and measuring long-range 13C-13C coupling constants

We propose the 13C-detecting 1D DEPT long-range C-C relay to detect super long-range H-C connectivity via four bonds (1H-13C-X-X-13C, X represents 12C or heteronuclear). It is derived from the DEPT C-C relay which detects the H-C correlations via two bonds (1H-13C-13C) by setting the delays for J(CC) in the C-C relay sequence to the (LR)J(CC). This sequence gives correlation signals split by small (LR)J(CC), which seriously suffers from residual center signal. The unwanted signal is due to long-range C-H couplings ((LR)J(CH)). The expected relayed magnetization transfer 1J(CH) --> (LR)J(CC) occurs in the 1H-13C-X-(X)-13C isotopomer, whereas the unwanted signal of (LR)J(CH) comes from 1H-12C-(X)-13C isotopomers, whose population is 100 times larger than that of the 1H-13C-X-(X)-13C isotopomer. The large dispersive line of this unwanted center signal would be a fatal problem in the case of detecting small (LR)J(CC) couplings. This central signal could be removed by an insertion of BIRD pulse or X-filter. DEPT spectrum editing solved a signal overlapping problem and enabled accurate determination of particular (LR)J(CC) values. We demonstrate here the examples of structure determination using connectivity between 1H and 13C via four bonds, and the application of long-range C-C coupling constants to discrimination of stereochemical assignments.

Ultraviolet photoionization of the photosensitizers khellin and visnagin in aqueous solution and in micelles: one-photon ionization is a minor process

One-photon ionization, leading to formation of hydrated electrons and radical cations, has been proposed as a possible mechanism of action of some sensitizers in photobiology. In this contribution, we have investigated this proposal for the compounds khellin and visnagin, used in photomedical applications. Nanosecond transient absorption spectroscopy covering a wide range of laser pulse energies was employed to measure the formation of radical cations and hydrated electrons in aqueous solution and in cationic (CTAB) as well as anionic (SDS) micellar solutions. A model allowing for simultaneous one- and two-photon processes and fully accounting for the nonlinearity of the pulse energy dependence was used to simulate the data. The results did not support the hypothesis of a significant role of one-photon ionization, the upper limits of the quantum yields of radical cation formation being phi < 0.01 for visnagin and phi < 0.004 for khellin.

Nanosecond time-resolved infrared studies of visnagin and khellin triplets and radical ions

Time-resolved infrared spectroscopy (TRIR) and density functional theory (DFT) calculations were used to directly observe and assign the vibrational spectra of the triplet states of visnagin and khellin, and to investigate their electron-transfer chemistry. The TRIR spectra of triplet visnagin and triplet khellin, and of their radical cations and anions, were obtained upon 266 nm laser flash photolysis in acetonitrile and in deuterated acetonitrile. The radical cations were observed in the presence of chloranil, and the radical anions were formed in the presence of NaI and KSCN. The TRIR spectra are in good agreement with the calculated vibrational spectra. We did not observe the related neutral radicals by TRIR spectroscopy upon laser flash photolysis (LFP) of khellin in the presence of hydroquinone, but we found evidence for the formation of semiquinone and neutral visnagin radicals upon LFP of visnagin and hydroquinone.

Photosynthesis of furocoumarin- and furochromone-types potential intercalative alkylating and oxidizing agents of DNA through photooxidations using gamma-ray

The photooxygenation of imperatorin (1a) under gamma-ray irradiation afforded the hydroperoxides 2a and 3a. Similarly, the photooxygenation of alloimperatorin (1b) gave the hydroperoxide (2b). Visnagin (1c) was also photooxygenated to give the hydroperoxide (2c) as sole product. On the other hand, the photooxygenation of khellin (1d) gave the endoperoxide (2d) as a sole product. The epoxidation of imperatorin (1a) using hydrogen peroxide under gamma-ray irradiation afforded the epoxide 5a. Similarly visnagin (1c) and khellin (1d) were epoxidized to give the epoxides 5c and 5d.

A new synthesis of oxadiazole, thiazolidinone, N-phthalimidoamino carbonyl and arylidene derivatives with potential antimicrobial activity

Condensation of carbohydrazide derivatives Ia, b with dimethyl acetylenedicarboxylate and acetylenedicarboxylic acid yielded benzofuran derivatives II a-d. Reaction of Ib with aromatic aldehydes formed products III a-d. Treatment of compounds III a-d with mercaptoacetic acid yielded the cyclocondensation products (IVa-d). Phthalic anhydride reacted with compounds (Ia, b)to form products (Va, b). It has been found that both khellin and visnagin (VIa, b)react with aromatic aldehydes to give arylidene derivatives (VIIa-e). Condensation of diphenyl nitrilamine with 2-arylidene furochromones VII derivatives afforded cyclo-adducts (VIII a-i). The antibacterial activities of the selected compounds were tested against Staphylococcus aureus, B. subtilis, E. coli, Pseudomonas, Salmonella and Erwinia with good results.

Furanochromone radical cations: generation, characterization and interaction with DNA

The radical cations of naturally occurring furanochromones visnagin (VI) and khellin (KH) have been generated and identified for the first time by use of laser flash photolysis and pulse radiolysis techniques. The lifetimes of VI(.+) and KH(.+) are determined as approximately 6 and approximately 35 micros under these conditions, respectively. Direct 308-nm excitation of VI in aqueous buffer at physiological pH results in monophotonic photoionization to generate VI(.+), with a quantum yield of 0.075, which is much higher than that of 8-methoxypsoralen and KH under identical conditions. Though VI(.+) is a more powerful oxidant than KH(.+), both of them react with guanosine mononucleotide (k=1.2x10(9) and 3.8x10(7) dm(3) mol(-1) s(-1), respectively) via electron transfer to give the guanine radical cation. Furthermore, selective oxidation of guanine in single and double strand DNA by VI(.+) was also observed. These novel findings suggest that electron transfer reactions involving furanochromone radical cations may be of considerable importance in furanochromone photochemotherapy.

Photophysical properties and photobiological activity of the furanochromones visnagin and khellin

The larger photobiological activity of visnagin (VI) versus khellin (KH) toward several living organisms, including fungi, viruses, yeasts and bacteria, induced a detailed investigation of the photophysical properties of these naturally occurring furanochromones, using laser-flash-photolysis, photoacoustic calorimetry and fluorescence (steady-state and time-resolved) techniques in solvents with different polarity and content of water, including micelles and vesicles. The results have shown that the magnitude of all the three rate constants out of S1 (radiative, kf; internal conversion, kic and intersystem crossing, kisc) for VI and KH strongly depend on the solvent, namely on its hydrogen bonding ability and polarity. The changes of kf and kisc are due to the solvent-assisted mixing and/or inversion of the two first singlet excited states (1n, pi and 1 pi, pi), while kic increases with a decrease of the S0-S1 energy gap. As a consequence, the quantum yield of triplet formation (phi T) strongly decreases from values of approximately 0.8 in dioxane to < 0.05 in water for both compounds. The magnitude of solvent polarity/hydrogen bonding ability required, at which the state order is inverted and phi T starts to decrease, is greater for VI than for KH and consequently phi T (VI) >> phi T (KH) over a broad range of water content including that appropriate to the environment of the compounds in a living system. These facts account for the larger photobiological activity of VI with respect to KH, regarding both the fungus Fusarium culmorum L. and the wild strain of Escherichia coli, studied by us.

Synthesis and anticonvulsant activity of new thiazolidinone and thioxoimidazolidinone derivatives derived from furochromones

Various new thiazolidinone and thioxoimidazolidinone derivatives were synthesized starting from 4,9-dimethoxy-5 H-furo[3,2-g][1]benzopyran-5-on-7-carboxaldehyde. The anticonvulsant activity of the synthesized compounds was evaluated. Most of the compounds showed anticonvulsant activity equal or superior to phenobarbital.

Photosensitized cleavage and cross-linking of pBR322 DNA with khellin and visnagin

The naturally occurring furanochromones khellin and visnagin have received considerable attention, largely because of their vasodilatory properties and of their ability (particularly that of khellin) to induce skin pigmentation upon ultraviolet light treatment of patients suffering from vitiligo. There are conflicting statements in the literature on whether or not they are capable of cross-linking DNA photochemically. Supercoiled and linear pBR322 DNA was used to probe this reaction. The results showed that both khellin and, to a greater extent, visnagin photosensitized DNA cross-linking. In addition, both photosensitizers induced extensive DNA cleavage.

Solvent spin-labelling for investigating the interaction of biological ligands with macromolecules. A 1H paramagnetic relaxation study

The paramagnetic contributions to the spin-lattice relaxation rates of khellin protons, induced by the presence in an aqueous solution of TEMPO nitroxide, have been analyzed in the interaction of the furochromone with DNA. The relaxation data obtained at different temperatures, nitroxide and DNA concentrations indicate that the average solvent exposure of the furanic moiety of khellin is lower than that of the pyranic group. This feature suggests that the former is the main site of approach of khellin to DNA.