Circular Dichroism of the Photoreceptor Pigment Oxyblepharismin

The blue palette of life: A comprehensive review of natural bluish colorants with potential commercial applications

Considering the growing interest for safer, environmentally friendly and healthier products, the search for natural colorants to replace their synthetic has been raised. This is particularly challenging for the rare and usually unstable bluish coloring substances. This comprehensive review describes several bluish pigments which can be obtained from natural sources (plants and mostly microorganisms), covering less known molecules to well established compounds (although no focus is given for anthocyanins). Key information about each compound, including sources, extraction procedures, properties, and potential applications, are presented. Despite many studies on these molecules, toxicological and stability studies are still lacking for many of them. Therefore, this text also discusses the regulatory requirements for approving new coloring substances. Given the increasing robustness of scientific data supporting the biological activities attributed to many of these pigments, it is possible to envisage that some of them may be commercially available for industrial applications in different fields, not only in traditional food or cosmetic uses but in pharmaceutical formulations as well.

A Review of the Chemistry and Biological Activities of Natural Colorants, Dyes, and Pigments: Challenges, and Opportunities for Food, Cosmetics, and Pharmaceutical Application

Natural pigments are important sources for the screening of bioactive lead compounds. This article reviewed the chemistry and therapeutic potentials of over 570 colored molecules from plants, fungi, bacteria, insects, algae, and marine sources. Moreover, related biological activities, advanced extraction, and identification approaches were reviewed. A variety of biological activities, including cytotoxicity against cancer cells, antioxidant, anti-inflammatory, wound healing, anti-microbial, antiviral, and anti-protozoal activities, have been reported for different pigments. Considering their structural backbone, they were classified as naphthoquinones, carotenoids, flavonoids, xanthones, anthocyanins, benzotropolones, alkaloids, terpenoids, isoprenoids, and non-isoprenoids. Alkaloid pigments were mostly isolated from bacteria and marine sources, while flavonoids were mostly found in plants and mushrooms. Colored quinones and xanthones were mostly extracted from plants and fungi, while colored polyketides and terpenoids are often found in marine sources and fungi. Carotenoids are mostly distributed among bacteria, followed by fungi and plants. The pigments isolated from insects have different structures, but among them, carotenoids and quinone/xanthone are the most important. Considering good manufacturing practices, the current permitted natural colorants are: Carotenoids (canthaxanthin, β-carotene, β-apo-8'-carotenal, annatto, astaxanthin) and their sources, lycopene, anthocyanins, betanin, chlorophyllins, spirulina extract, carmine and cochineal extract, henna, riboflavin, pyrogallol, logwood extract, guaiazulene, turmeric, and soy leghemoglobin.

TD-DFT and structural investigation of natural photosensitive phenanthroperylene quinone derivatives

Structural modification of the phenanthroperylene quinone core affects the electronic structure of a series of natural product photosensitizers.

Target Analysis of Primary Photoprocesses Involved in the Oxyblepharismin-Binding Protein

Target analysis is performed on previously published transient absorption spectra of the 200-kDa oxyblepharismin-binding protein (OBIP) thought to trigger the photophobic response of the ciliate Blepharisma japonicum. The OBIP sample is considered as heterogeneous and made of two distinct classes of chromophore-protein complexes. A so-called nonreactive class is seen to be comparable to free oxyblepharismin in organic solution. Another, reactive, class is shown to undergo a fast picosecond photocycle involving the formation in 4 ps of an intermediate state noted Y1. The spectrum associated to Y1 bears striking similarities with that of the oxyblepharismin radical cation. This element favors the hypothesis that an excited-state intermolecular electron-transfer could be the primary step of the sensory transduction chain of B. japonicum. Proton release is also considered as a possible secondary step. These possibilities support the idea that reactive OBIP functions like an electron or proton pump. We alternatively propose a new hypothesis stating that the fast photocycle of reactive OBIP actually does not generate any photoproduct or protein change of conformation but is involved in another biological function. It would act as a kind of solar screen, providing additional protection to the light-adapted form of B. japonicum in case of excessive illumination.