Extract of Bletilla formosana callus elevates cellular antioxidative activity via Nrf2/HO-1 signaling pathway and inhibits melanogenesis in zebrafish

BACKGROUND: Bletilla species are endangered terrestrial orchids used in natural skin care formulas in Asia for a long history. In order to explore the bioactivity potential of Bletilla species as a cosmetic ingredient in a sustainable resource manner, the callus of Bletilla formosana (Hayata) Schltr. was established and extracted by an eco-friendly supercritical fluid CO(2) extraction (SFE-CO(2)) method. The intracellular reactive oxygen species (ROS) scavenging activity and antioxidation-related gene expression of the callus extract were evaluated in both Hs68 fibroblast cells and HaCaT keratinocytes. The melanogenesis-inhibitory effect was investigated in B16F10 melanoma cells and in an in vivo zebrafish model. RESULTS: The calli of B. formosana were propagated for 10–15 generations with a consistent yellow friable appearance and then subjected to SFE-CO(2) extraction to obtain a yellow pasty extract. Obvious intracellular ROS scavenging activity of the extract was detected in both Hs68 and HaCaT cells with 64.30 ± 8.27% and 32.50 ± 4.05% reduction at the concentration of 250 μg/mL. Moreover, marked expression levels of heme oxygenase-1 (HO-1) and (NAD(P)H) quinone oxidoreductase-1 (NQO1) genes were detected after 6-h and 24-h treatments. These results indicate the cellular antioxidative activity of B. formosana callus extract was probably activated via the nuclear factor erythroid 2-related factor 2 (Nrf2)/HO-1 signaling pathway. Melanogenesis-inhibitory effect of the extract was observed in α-MSH stimuli-inducing B16F10 cells with 28.46% inhibition of intracellular melanin content at the concentration of 50 μg/ml. The effect was confirmed with in vivo zebrafish embryos that showed a relative pigmentation density of 80.27 ± 7.98% at the concentration of 100 μg/mL without toxicity. CONCLUSION: Our results shed light on a sustainable utilization of Bletilla species as a potential ingredient for skin.