Obtenção de extrato de lignina kraft como ingrediente para protetores solares

Abstract

Lignin is a complex organic polymer found in the supporting tissues of most plants. It is considered the second most abundant biopolymer in nature, second only to cellulose. Despite its wide availability, it is still treated as waste or a low-value material. However, its physicochemical properties - such as resistance to ultraviolet (UV) light, thermal stability, biodegradability, and low toxicity - make it a promising candidate for high-value applications, especially in the cosmetics industry. In recent years, lignin has gained attention as a potential UV-blocking material and natural antioxidant agent. This study aimed to evaluate the potential of a lignin sample as an ingredient for sunscreen by assessing its antioxidant properties and in vitro sun protection factor (SPF). The lignin sample was provided by a paper manufacturing company from the state of Paraná, Brazil; it was kraft-type and in powder form. The selection of the best extraction parameters was based on the total phenolic compound content, determined by the Folin-Ciocalteu method. For this preliminary evaluation, the solvents used were methanol, bidistilled glycerin, and ethylene glycol; in solute-to-solvent ratios of 1:10 and 1:50; at temperatures of 40 and 55 ºC; and extraction times of 60 and 120 minutes. Methanol and ethylene glycol yielded the best results, both at 40 ºC. Regarding extraction time, methanol showed better results at 60 minutes, while ethylene glycol performed best at 120 minutes. After evaluating preliminary results, the study proceeded using ethylene glycol while replacing methanol with ethanol due to its lower toxicity. The total antioxidant activity of lignin was assessed using the DPPH and ABTS methods. The IC50 results obtained by the ABTS method (281.89 to 336 mg/L) and the DPPH method (1180.53 to 1531.25 mg/L) indicate that the prepared extracts may serve as alternatives to the commercial antioxidants BHA and BHT currently in use. For SPF evaluation of the extracts, an in vitro spectrophotometry method was employed. The final sample, prepared with ethylene glycol at a 1% concentration, yielded the best results, with an SPF of 54.28 and a critical wavelength of 371.58 nm.