Parameter Optimization and Potential Bioactivity Evaluation of a Betulin Extract from White Birch Bark

Owing to its pharmacological potential, betulin has attracted substantial attention in the past two decades. The present work attempts to extract betulin from Betula platyphylla Suk. bark by the ultrasonic-assisted ethanol method and to evaluate its potential bioactivities. The critical process variables affecting the yield were optimized by a four-factor, three-level, central composite response surface methodology (RSM). A betulin yield of 92.67% was achieved under the optimum conditions: 65% ethanol concentration, 1:25 ratio of white birch bark to solvent, an extraction temperature of 30 °C, and an extraction time of 30 min. The ratio of solid to solvent is the most significant parameter in terms of yield. The optimal conditions were validated through experiments, and the observed value (92.67 ± 2.3%) was interrelated with the predicted value (92.86 ± 1.5%). The betulin extract was analyzed quantitatively by HPLC and quantitatively by LC/MS, before its potential biological activities were evaluated. Bioactivity surveys confirmed that the betulin extract showed not only no embryo deformity through zebrafish administration experiments, but also no cytotoxicity through MTT assays. Furthermore, the betulin extract had strong antioxidant activities in vitro by scavenging ferric reducing power (FRAP), 1, 1-diphenyl-2-picryl hydrazyl(DPPH), 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and chelating metal ions. This study demonstrates that ultrasonic-assisted ethanol extraction may be a green, efficient method for the extraction of betulin from white birch bark, and that betulin extracts are potentially useful in cosmetics, food supplements, or pharmaceutical applications.