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Reduced Porphyrins as Photosensitizers: Synthesis and Biological Effects
Published in Barbara W. Henderson, Thomas J. Dougherty, Photodynamic Therapy, 2020
Cleavage of the isocyclic ring of chlorophylls generates a more water-soluble derivative, known as chlorophyllin. Removal of magnesium results in generation of chlorin e640. This sensitizer has photodynamic activity in vitro and modest activity in vivo [45,46]. However, better results were obtained with amino acid derivatives of chlorin e6, in particular, with the mcwoaspartyl derivative known as MACE or NPe641 [47,48]. As with many water-soluble chlorophyll derivatives, MACE appears to be cleared rapidly from skin, and good tumor responses can be obtained only after irradiation within hours of sensitizer administration [49]. A recent report had also suggested the use of the lysine conjugate of chlorin e6 (i.e., 42) for photodegradation of 9L rat gliomas [50]. Again, photoirradiation was carried out shortly after sensitizer administration (4 hr) and, although no data were presented, it seems likely that this will also fall under the category of short-acting drugs.
Spray Drying for Production of Food Colors from Natural Sources
Published in M. Selvamuthukumaran, Handbook on Spray Drying Applications for Food Industries, 2019
Mehmet Koç, Feyza Elmas, Ulaş Baysan, Hilal Şahin Nadeem, Figen Kaymak Ertekin
Chlorophylls used as natural colorants are stable at neutral pH and temperatures up to 120º C. However, chlorophyll is not a resistant pigment and the green color disappears rapidly during the blanching of the vegetables. The rate of this degradation of chlorophyll pigment is accelerated when the medium pH level is lowered. Furthermore, chlorophylls have limited use due to their poor stability and low color intensity (Downham and Collins 2000). Because of this, chlorophyll extracts obtained from various green plants such as nettle and clover can be standardized with a vegetable oil and converted into a water-dispersible structure mixed with the permissible emulsifiers (Altuğ 2001). Also, chlorophyll stability can be supported with copper complexes. Chlorophyll stability can be enhanced by the chlorophyll de-etherifying through the addition of copper ions, which is more stable compared to the intact equivalent having a permanent green color. Although this reaction is irreversible, strong complexes can be formed when Cu+2 or Zn+2 ions are centralized in this chromophore. This metal coordination not only add stability to the pigment but also cause the acquizition of more desirable green colors. The formation of Cu chlorophyll complexes occurs naturally, in which reactions are also carried out on the extracted chlorophyll for commercial applications (Humphrey 2004). Although Cu-chlorophyllin and associated complexes are approved for broad-range use in foods in the European Union, the use of chlorophyll as a color in foods is limited to Na-Cu chlorophyllin in some beverage mixes in the United States (Martins et al. 2016).
Biomolecules from Microalgae for Commercial Applications
Published in Kalyan Gayen, Tridib Kumar Bhowmick, Sunil K. Maity, Sustainable Downstream Processing of Microalgae for Industrial Application, 2019
Meghna Rajvanshi, Uma Shankar Sagaram, G. Venkata Subhash, G. Raja Krishna Kumar, Chitranshu Kumar, Sridharan Govindachary, Santanu Dasgupta
Chlorophyll a is a green pigment universally present in microalgae, cyanobacteria and green plants. Chlorophyll b is present in Chlorophyta and Euglenophyta, whereas chlorophyll c, d and e are found in diatoms and act as accessory pigments in photosynthesis. Notably, the anti-oxidant properties of chlorophyll are used in health care and as a colorant in the food industry. For example, its therapeutic use reduces the risk of colorectal cancer (Balder et al. 2006). Chlorophyll-related compounds (CRC) are obtained by natural catabolism or are derived chemically or thermally. The major CRC used in many therapeutics are pheophytin (lack of Mg atom), chlorophyllide or chlide (lacking phytol tail) and pheophorbide or pho (lacking both phytol tail and Mg atom) (Hsu et al. 2014). Historically, chlorophyll-rich foods are consumed by humans, yet there is limited literature on the bioavailability of chlorophyll, and it is assumed to be non-absorbable by humans (Ferruzzi and Blakeslee 2007). However, Chao et al. (2018) have reported that upon consumption of spinach, chlorophyll rapidly converted into CRC and was detected in the blood after three hours as pheophytin and pheophorbide and thus can be absorbed by the human body (Chao et al. 2018). Chlorophyllin, another derivative of chlorophyll, acts as a chemo-preventive agent in human colon cancer cells and as a deodorant in personal hygiene. Copper-chlorophyllin (Cu-Chl) and sodium copper chlorophyllin (SCC) are chemically derived by replacing the magnesium ion with copper through acid treatment. The FDA has approved SCC as a food colorant derived from a plant source. SCC is also used in wound healing and for the control of calcium oxalate crystals (Ferruzzi and Blakeslee 2007). In addition, porphyrin-based photosensitizers are used in cancer therapy (Sternberg, Dolphin, and Brückner 1998). Microalgae can potentially be a reliable source of chlorophyll globally because of its year-round availability.
Feasibility study of the use of superheated steam spray drying to produce selected food powders
Published in Drying Technology, 2022
Khamphon Ma, Luxsika Ngamwonglumlert, Sakamon Devahastin, Nathamol Chindapan, Naphaporn Chiewchan
Feasible utilization of superheated steam spray drying to produce instant coffee and natural green color (or sodium copper chlorophyllin) powders was assessed. The results showed that superheated steam spray drying might not be a proper method for producing instant coffee powder. At all test conditions, the feed extract adhered and dried on the wall of the drying chamber when superheated steam was used; coffee powder could not therefore be collected. In the case of natural color powder, type of the drying medium and feed rate only slightly affected the yield, moisture content, water activity, hygroscopicity and color of the powders. Colors of the solutions reconstituted from the air-dried and steam-dried powders were also not significantly different. Drying medium, however, significantly affected bulk density, particle size and solubility of the color powders. The steam-dried powder possessed higher bulk density, smaller particle size and more wrinkle surface than its air-dried counterpart; these led to superior solubility of the former. It could therefore be preliminarily concluded that superheated steam spray drying has the potential to enhance the solubility of a powdery food product.
Effects of gallic acid grafted chitosan on improving light fastness of cotton fabric dyed with gardenia yellow
Published in The Journal of The Textile Institute, 2021
Zhong Zhao, Chris Hurren, Liming Zhou, Lu Sun, Jihong Wu
Photofading of natural colorants is commonplace as the conjugated structures in the dye chromophores are prone to bond breakage or molecular cleavage after their exposure to sunlight irradiation (Dodangeh et al., 2019). In one of our previous studies, reactive oxygen species (ROS) were detected in the photofading of two natural dyes, sodium copper chlorophyllin and gardenia yellow (Zhao et al., 2020b). The result also provides an explanation as to why antioxidants like gallic acid, caffeic acid and ascorbic acid can inhibit the photofading of natural dyes (Cristea & Vilarem, 2006). Besides, our previous work found that reducing agents like sodium citrate, glucose were also effective alternatives to antioxidants to inhibit photofading of natural dyes (Zhao et al., 2020a). Thus, the light fastness of fabrics dyed with natural dyes can be improved by treating the dyed fabrics with aqueous solutions of antioxidants or reducing agents via the dipping and padding method. However, this improvement can be quickly offset by the loss of antioxidants after the laundering of treated fabrics as no stable covalent bonds were formed between the water-soluble antioxidants and the dye molecules or fabric substrates. Besides, to achieve satisfactory light fastness properties of textiles dyed with natural dyes and treated with these antioxidants, these chemicals will be used in large amounts. This means that directly using them as additives to treat fabrics dyed with natural dyes via the dipping and padding method will significantly raise the cost of production as these antioxidants are expensive (Grigonis et al., 2005; Sharma & Murugan, 2017).