Oleorresina de copaíba apresenta atividade antinociceptiva tópica em um modelo de queimadura de pele induzido por radiação UVB em camundongos

Abstract

Burn injuries are common worldwide, representing a major public health problem responsible for more than 180,000 deaths annually. These injuries can be caused by several factors, including ultraviolet (UV) radiation. Ultraviolet B (UVB) radiation exposure can result in sunburn, and consequently, in an inflammatory response that contributes to the development of pain, edema and erythema. Pharmacological treatments aim for pain and inflammation relief, however, they are not specific to treat burns and are associated with adverse effects that limit their use. Therefore, the search for therapeutic alternatives for the treatment of sunburn is needed, and natural origin products have attracted the attention of researchers. Copaiba oleoresin is widely used in folk medicine as healing, analgesic, antimicrobial, and mainly as an anti-inflammatory. Thus, we aim to evaluate the antinociceptive and anti-inflammatory potential of the cutaneous application of a formulation containing Copaiba oleoresin in a skin-burn model induced by UVB radiation in male Swiss mice (25-30g). Firstly, the chemical composition of Copaiba's oleoresin was analyzed by gas chromatography (GC-MS). For the skin-burn model, the mice were anesthetized, and the right hind paw was exposed only once to UVB radiation for 21 minutes (0.75 mJ/cm2). The treatments were applied topically (15 mg/paw) once a day, for six days, with Copaiba oleoresin cream (3%), silver sulfadiazine cream (1%; positive control), or base cream (vehicle). The formulations' antinociceptive effect was evaluated by measurement of the mechanical allodynia and thermal hyperalgesia, using von Frey filaments and Hargreaves apparatus, respectively. The anti-inflammatory activity was determined by measuring the dermal thickness and inflammatory cells' infiltration through histological analysis. The formulation characterization was also carried. The formulations presented pH values, spreadability factor, macroscopic and rheological characteristics appropriate for cutaneous application. The Copaiba oleoresin cream reduced UVB radiation-induced mechanical allodynia on the 2nd, 3rd, and 4th day after UVB radiation exposure with a maximum inhibition (Imax) of 64.6 ± 7% observed on the 2nd day. The cutaneous application of Copaiba oleoresin cream also reduced the thermal hyperalgesia on the 1st and 2nd days post UVB radiation, with an Imax of 100% observed on the 2nd day. Moreover, the cutaneous application of Copaiba oleoresin cream inhibited the inflammatory cell infiltration but did not reduce the increase in the dermal thickness UVB-radiation induced. Such effects can be attributed, at least in part, to the presence of biological components, such as β-caryophyllene (60.17%) and other sesquiterpenes identified by GC-MS. Our results demonstrate that the formulation containing Copaiba oleoresin presented antinociceptives and anti-inflammatory effects in mice subjected to UVB radiation and that the cream formulation showed adequate characteristics, ensuring its quality and therapeutic effect. Thus, the cutaneous application of Copaiba oleoresin containing cream may be a promising strategy for treatment and adjuvant therapy for inflammatory pain associated with sunburn.