Study on the photostability of guaiazulene by high-performance liquid chromatography/mass spectrometry and gas chromatography/mass spectrometry

Photochemical and Oxidative Degradation of Chamazulene Contained in Artemisia, Matricaria and Achillea Essential Oils and Setup of Protection Strategies

Chamazulene (CA) is an intensely blue molecule with a wealth of biological properties. In cosmetics, chamazulene is exploited as a natural coloring and soothing agent. CA is unstable and tends to spontaneously degrade, accelerated by light. We studied the photodegradation of CA upon controlled exposure to UVB-UVA irradiation by multiple techniques, including GC-MS, UHPLC-PDA-ESI-MS/MS and by direct infusion in ESI-MSn, which were matched to in silico mass spectral simulations to identify degradation products. Seven byproducts formed upon UVA exposure for 3 h at 70 mW/cm2 (blue-to-green color change) were identified, including CA dimers and CA benzenoid, which were not found on extended 6 h irradiation (green-to-yellow fading). Photostability tests with reduced irradiance conducted in various solvents in the presence/absence of air indicated highest degradation in acetonitrile in the presence of oxygen, suggesting a photo-oxidative mechanism. Testing in the presence of antioxidants (tocopherol, ascorbyl palmitate, hydroxytyrosol, bakuchiol, γ-terpinene, TEMPO and their combinations) indicated the highest protection by tocopherol and TEMPO. Sunscreens ethylhexyl methoxycinnamate and particularly Tinosorb® S (but not octocrylene) showed good CA photoprotection. Thermal stability tests indicated no degradation of CA in acetonitrile at 50 °C in the dark for 50 days; however, accelerated degradation occurred in the presence of ascorbyl palmitate.

UV filters in everyday cosmetic products, a comparative study

Today, UV filters are found as contaminants in a variety of biological fluids and environment, e.g. in vegetable crops and surface water. This is because UV filters are widely used in everyday products. In this context, we focused this study on cosmetic products, in order to assess the importance of this source of contamination. The study of 742 cosmetic products, excluding actual sunscreen products, but including hygiene, personal care and make-up products and perfumes revealed that the most common UV filters present are butyl methoxydibenzoylmethane (90 products or 12.1% of products tested), octyl methoxycinnamate (75 products or 10.1% of products tested), octocrylene (62 products or 8.3% of products tested), octyl salicylate (43 products or 5.8% of products tested) and titanium dioxide (33 products or 4.4% of products tested). Very few UV filters are found in the hygiene products (only in 12 shampoos/conditioners and in 2 shower gels) and deodorants and toothpastes are completely free of them. Conversely, make-up and perfumes are frequently formulated with at least one UV filter. Seventy-five of the two hundred and forty-four (or 30.7%) skincare products studied contained at least one UV filter. 49.1 of the makeup products studied and 74.3% of perfumes contained it.

Effect of Different Irradiation Modes of Azulene-mediated Photodynamic Therapy on Singlet Oxygen and PGE2 Formation

Azulene samples in ethanol/distilled water (1, 10 and 100 µm) were irradiated with a 638 nm red laser (0.5 watts, light-to-target distance 2 cm, energy density 4 or 40 J cm^-2 ) by either continuous, fractionation or pulse mode. Singlet oxygen in the samples was measured using 10 µm 9,10-dimethyl anthracene (positive control 10 μm erythrosine) and relative fluorescence intensities were measured at 375/436 nm excitation/emission. Peripheral blood mononuclear cells (PBMCs, 1 × 10⁵ cells/well) preincubated with 0.01 μg mL^-1 rhTNF-α for 6 h were cultured with irradiated azulene samples in RPMI-1640 under standard conditions. PGE₂ was quantified by rhPGE₂ ELISA kit using a Varioscan® microplate reader at an excitation wavelength of 420 nm. Kruskal Wallis with Dunn`s test was performed at a significance level of P < 0.05. The highest singlet oxygen amount was found in 10 µm azulene samples irradiated at 40 J cm^-2 under continuous mode (P = 0.001 when compared with 10 µm erythrosine). PGE₂ expression in rhTNF-α-induced PBMCs was reduced to 45% of control by 1 µm azulene irradiated at 40 J cm^-2 under fractionation mode. Fractionation mode with intermediate laser energy density in the presence of low concentration of azulene could increase singlet oxygen and tend to reduce PGE₂ .

Anti-inflammatory effect of photodynamic therapy using guaiazulene and red lasers on peripheral blood mononuclear cells

INTRODUCTION

Photodynamic therapy improves oral mucositis treatment. The reactive oxygen species (ROS) generated from this reaction could contribute to an anti-inflammatory effect by suppressing inflammatory cells.

OBJECTIVE

To evaluate the anti-inflammatory effect of photodynamic therapy using guaiazulene and a red laser in peripheral blood mononuclear cells (PBMCs).

METHODS

Guaiazulene solutions (1, 2, 5, 25, 35, and 100 μM in 99.8 % methanol) were irradiated with red laser light (625 nm, 146.2 mW/cm²) in continuous mode at 0, 4, and 8 J/cm² in black 96-well plates. ROS were measured using spin trapping technique with electron spin resonance (ESR) spectroscopy and fluorescence. The two highest concentrations were tested using cell viability (PrestoBlue®) and anti-inflammation (RANTES and PGE₂ ELISA) assay kits. Kruskal-Wallis and Dunn Bonferroni tests were used for statistical analyses with significant differences at p-value < 0.05.

RESULTS

Guaiazulene solutions between 2 and 5 μM exposed to red laser light at 4-8 J/cm² generated significantly more singlet oxygen compared to the no guaiazulene group (p < 0.01) and reduced RANTES and PGE₂ levels in TNF-α-inflamed peripheral blood mononuclear cells without affecting cell viability.

CONCLUSION

Photodynamic activation of guaiazulene generated singlet oxygen and suppressed inflammatory markers in PBMCs.

Phototoxicity of traditional chinese medicine (TCM)

Phototoxicity can cause toxic responses such as edemas and lesions, and is one of the severe adverse effects that largely limit the use of these phototoxic drugs. Some traditional Chinese medicines (TCMs) and their constituents have been reported to be phototoxic. However, to date, their phototoxicity information is still very limited, and lacks systemic investigation. This article presents the phototoxicity potential of various types of TCMs and their active components in an effort to provide valuable information for drug research and discovery to mitigate phototoxicity concerns. Some potential mechanisms of action (MoAs) of phototoxicity are discussed. In addition, in vivo and in vitro phototoxicity assays are summarized this review.

Computer aided chemical design: using quantum chemical calculations to predict properties of a series of halochromic guaiazulene derivatives

With the scientific community becoming increasingly aware of the need for greener products and methodologies, the optimization of synthetic design is of greater importance. Building on experimental data collected from a synthesized guaiazulene derivative, a series of analogous structures were investigated with time-dependent density functional theory (TD-DFT) methods in an effort to identify a compound with desirable photophysical properties. This in silico analysis may eliminate the need to synthesize numerous materials that, when investigated, do not possess viable characteristics. The synthesis of several computationally investigated structures revealed discrepancies in the calculation results. Further refined computational study of the molecules yielded results closer to those observed experimentally and helps set the stage for computationally guided design of organic photonic materials. Three novel derivatives were synthesized from guaiazulene, a naturally occurring chromophore, exhibiting distinct halochromic behaviour, which may have potential in a switchable optoelectronic system or combined with a photoacid generator for data storage. The protonated forms were readily excitable via two-photon absorption.

Guaiazulene biochemical activity and cytotoxic and genotoxic effects on rat neuron and N2a neuroblastom cells

AIM

Neuroblastoma (NB)cells are often used in cancer researches such as glioblastoma cells since they have the potential of high mitotic activity, nuclear pleomorphism, and tumor necrosis. Guaiazulene (GYZ 1,4-dimethyl-7-isopropylazulene)is present in several essential oils of medicinal and aromatic plants. Many studies have reported the cytotoxic effect of GYZ; however, there are no studies that compare such effects between cancer cell lines and normal human cells after treatment with GYZ.

MATERIALS AND METHODS

In this study, we aimed to describe in vitro antiproliferative and/or cytotoxic properties (by 3-[4,5 dimetylthiazol -2-yl]-2,5 diphenlytetrazolium bromide [MTT] test), oxidative effects (by total antioxidant capacity [TAC] and total oxidative stress [TOS] analysis)and genotoxic damage potentials (by single cell gel electrophoresis)of GYZ.

RESULT

The results indicated that GYZ have anti-proliferative activity suppressing the proliferation of neuron and N2a-NB cells at high doses. In addition, GYZ treatments at higher doses led to decreases of TAC levels and increases of TOS levels in neuron and N2a-NB cells. On the other hand, the mean values of the total scores of cells showing DNA damage were not found different from the control values.

CONCLUSION

From this study, it is observed that GYZ has in vitro cytotoxic activity against neuron and N2a-NB cells.

Phototoxicity of herbal plants and herbal products

Plants are used by humans in daily life in many different ways, including as food, herbal medicines, and cosmetics. Unfortunately, many natural plants and their chemical constituents are photocytotoxic and photogenotoxic, and these phototoxic phytochemicals are widely present in many different plant families. To date, information concerning the phototoxicity and photogenotoxicity of many plants and their chemical constituents is limited. In this review, we discuss phototoxic plants and their major phototoxic constituents; routes of human exposure; phototoxicity of these plants and their constituents; general mechanisms of phototoxicity of plants and phototoxic components; and several representative phototoxic plants and their photoactive chemical constituents.

Persistency assessment and aerobic biodegradation of selected cyclic sesquiterpenes present in essential oils

Sesquiterpenes are ubiquitous in essential oils but an assessment of their environmental behavior is still required for their use as components of natural fragrance ingredients and oral care flavors. Persistency plays a key role in hazard and risk assessment, but the current knowledge on the biodegradation of sesquiterpenes in the aquatic environment is limited. This could have important consequences for the persistent, bioaccumulative and toxic (PBT) assessment of essential oils because most of the sesquiterpene components have a log K(OW) of >4.5 and are identified as potentially bioaccumulating according to REACH screening criteria. In the present study, a persistency screening assessment was conducted on 11 cyclic sesquiterpenes selected from 10 different families of sesquiterpenes characterized by their carbon skeleton. Current biodegradation prediction models (BioWin™, BioHCwin, and Catalogic) were found to be of limited use because most of the sesquiterpenes studied were outside the structural domain of the models. Aerobic biodegradation was measured in a standard or prolonged Organisation for Economic Co-operation and Development (OECD) 301F Manometric Respirometry test for ready biodegradability. α-Bisabolol, α-humulene, β-caryophyllene, α-cedrene, cedrol, longifolene, and δ-cadinene exceeded the pass level of 60% degradation and can be regarded as not persistent. Alpha-gurjunene, himachalenes (α, β, γ), and (-)-thujopsene almost achieved the pass level reaching between 51% and 56% ultimate biodegradation. Although germacrene D only achieved 24% ultimate biodegradation, specific analysis at the end of the test did indicate complete primary degradation. Given that the shape of the biodegradation curves indicates poor bioavailability and ready biodegradability tests are very stringent, it is expected that all the sesquiterpenes tested in the present study would be degraded under environmental conditions.

Cytotoxic activity of guaiazulene on gingival fibroblasts and the influence of light exposure on guaiazulene-induced cell death

Guaiazulene (GA) is widely used as a natural ingredient in many health care products and solutions. Although it has been reported to have interesting biological effects, GA and azulene derivatives have been proven to be cytotoxic against normal human cells and human tumor cells; moreover, guaiazulene has shown photomutagenic properties on bacterial strains. Therefore, we evaluated and compared the cytotoxicity of GA at different concentrations on human gingival fibroblast (HGF) cell cultures under normal conditions and under UV irradiation (UV-A dose: 6.4 J/cm(2)). The compound tested was found to significantly reduce cell viability (dose-dependent trend, IC(50) 72.1 μM), decrease protein procollagen α1 type I synthesis, a marker for HGF protein, and COL1A1 mRNA expression. The cytotoxic effects were accompanied by activation of an intrinsic apoptotic pathway, studied using transmission electron microscopy (TEM) and caspase-3 activation. The light exposure of the cell culture treated decreased GA-induced cell death (IC(50) 128.9 μM), suggesting a photoprotective effect due to the photodegradation of the toxic agent, guaiazulene. Furthermore, the products of the photodegradation reaction of GA proved not to be toxic against HGFs.