Data Availability StatementNot applicable. kraft lignin. The activity of the hydroxyl radicals will be quenched when it abstract hydrogen atoms from the phenolic hydroxyl groups. strong class=”kwd-title” Keywords: TiO2, Hydroxyl radical, Lignin, Oil palm empty fruit bunch, Lignin/TiO2 composite Introduction Titanium dioxide (TiO2) is used as an inorganic agent in sunscreens due to its ability to reflect, scatter and absorb a wide range of ultraviolet radiation in sunlight [1]. The maximum loading of TiO2 in sunscreens is 25%, and the crystalline form of TiO2 that mostly used for this application is anatase [2]. The TiO2 is also employed as opacifiers and pigments in paints and paper coatings due to the whiteness and opaque characteristics [3]. Moreover, TiO2 possesses excellent photocatalytic capability which makes it suitable for removal of organic compounds in contaminated water [4]. However, this capability of TiO2 is a Rabbit Polyclonal to OR52E5 double-edged sword. The photocatalytic activity of TiO2 can generate superoxide and hydroxyl radicals by the irradiation of sunlight. This is unfavorable for the application in sunscreens. These reactive oxygen species with cytotoxic and genotoxic characteristics can react with biomolecules such as protein and DNA upon formation on the surface of TiO2 [5]. This may result in carcinogenesis, enzyme inactivation and potential damage of biomolecules [5]. The reactive oxygen species will cause the SPD-473 citrate degradation of other organic agents in sunscreen [6]. A variety of methods have adopted by many researchers to reduce the photocatalytic activity of TiO2. The alumina was used to coat TiO2 by Picatonotto et al. [7]. The inorganic surface coating minimizes the photocatalytic activity by reducing holes and electrons generation and enhancing electronChole recombination which leads to quenching of photocatalytic activity. The encapsulation of TiO2 in zeolites reduced its photocatalytic efficiency by increasing the band gap so that excitation can only take place under ultraviolet radiation with the wavelength below 265?nm (ultraviolet C (UVC) region) [8]. The UVC can be absorbed by the ozone layer and will not reach the surface of the earth. Moreover, instead of inhibiting the photocatalytic activity of TiO2, Chen et al. [9] utilized the antioxidant properties of chitosan to capture the free SPD-473 citrate radicals generated by the photocatalytic activity of TiO2. Chemically, lignin is a natural, amorphous and cross-linked phenolic biopolymer with very complex structure [10]. Lignin provides structural rigidity for plants and supports transport of nutrients and water in plants. It can be extracted from the black liquor which is always considered as waste in pulping and paper industries [11]. Lignin is made up of three main phenylpropanoid products that differ in the quantity of methoxyl groups specifically em p /em -hydroxyphenyl (H), guaiacyl (G) and syringyl (S) as demonstrated in Fig.?1 [10]. It could be extracted from different biomass components such as SPD-473 citrate essential oil hand ligocellulosic waste materials, and kenaf through soda pop, kraft, ethanol or additional pulping procedures [10, 12]. The properties and structure of lignin vary for different pulping procedures, types, and elements of vegetation. Open in another home window Fig.?1 The structure of 3 main phenylpropanoid units of lignin The oil hand clear fruit bunch (OPEFB) is among the agriculture wastes generated from the oil hand industry. The essential oil hand agriculture wastes are usually burnt in incinerators and therefore result in environmental pollutions such as for example haze which affect human being health [13]. In the last research, OPEFB lignin continues to be employed in many applications such as for example meals emulsifying agent, rock adsorption for waste materials SPD-473 citrate water treatment, timber adhesive, corrosion chemicals and inhibitor in dirt drilling [14]. The special benefit of OPEFB lignin can be that it could be from agriculture wastes rather than additional vegetation such as for example pine tree and acacia tree which might involve deforestation. The prior study demonstrated that oil hand empty fruit number lignin exhibited antioxidant properties and acted as free of charge radical scavenger because of the existence of phenolic hydroxyl group [15]. The phenolic hydroxyl organizations become a proton donor and may stabilize the.