In vitro antioxidant and photoprotective activity of five native Brazilian bamboo species

Abstract

Nature provides an abundant source of antioxidant substances as well as potential compounds for sunscreen products. Asian bamboos, well known and widely cultivated, are already used in cosmetic and pharmaceutical industries thanks to their rich phenolic contents which is related to their antioxidant activity. This study aimed to evaluate the photoprotective and antioxidant activities of five native Brazilian bamboo species. Firstly, hydroalcoholic extracts from culms and leaves of Aulonemia aristulata (Döll) McClure., Chusquea bambusoides Rupr. ex Döll, Chusquea capituliflora Trin. var. pubescens McClure, Chusquea meyeriana Rupr., Merostachys pluriflora Munro ex E.G. Camus were evaluated for their DPPH scavenging activity and total contents of flavonoids and phenolic compounds. Secondly, cosmetic formulations containing the extracts in a combination with three different synthetic ultraviolet (UV) filters (avobenzone, octyldimethyl PABA, and octyl methoxycinnamate) were developed to evaluate their Sun Protection Factor (SPF), critical wavelength (cλ) and photostability by diffuse transmittance analysis to determine the interactions involving the extracts and the anti-UV active ingredients. The bamboos’ antioxidant potential, expressed in IC50, varied between 137.55 and 260 μg/mL. Phenolic contents ranged from 43.64 to 87.81 mg of gallic acid equivalents (GAE) per g of plant material. The extract richest in flavonoids was that from C. bambusoides leaves with 6.44 mg of equivalents of quercetin (EQ) per g of dried leaves. The SPF of the formulations with bamboo extracts varied between 34 and 86 before the irradiation, and the obtained UV absorption profile allowed to classify them as broad spectrum. After irradiation, the SPF values diminished to 14–44, whereas, the area of the absorbed wavelengths remained equal. This study showed that the addition of bamboo extracts to commercial UV filters increased significantly their SPF and photostability.