Valorisation of phytochemical from Sitka spruce (Picea sitchensis) needles: Impact of ultrasound/microwave-assisted extraction

Sitka spruce (Picea sitchensis) needles contain a variety of bioactive compounds including phenolic compounds and flavonoids, many of which have been used in the cosmetic, pharmaceutical, and food industries. This study aimed to investigate the effects of novel extraction techniques, including ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE) and simultaneous ultrasound–microwave-assisted extraction (UMAE) on the recovery of phenolic, flavonoids and associated antioxidant and anti-cancer properties from Sitka spruce (Picea sitchensis) needles. The ferric reducing antioxidant power (FRAP) assay was used to evaluate the antioxidant capacity, and the Alamar Blue assay using the human brain glioblastoma cancer cell line (U-251 MG) was used to evaluate the cytotoxicity activity. Results showed that US-probe accomplished the highest recovery of phenolic and flavonoids at 38 W cm⁻² for 10 min (106.3 ± 2.5 mg GAE g⁻¹ DW and 63.2 ± 3.8 mg QE g⁻¹ DW, respectively). Hence, the highest cytotoxicity activity of IC₅₀ (0.0114% w/v) was achieved by US-probe at 19 W cm⁻² for 10 min. However, the antioxidant capacity of (2591.3 ± 92.5 mM TE g⁻¹ DW) was achieved under UMAE at ultrasound intensity of 38 W cm⁻², microwave power of 302.4 W for 10 min. This study emphasised the potential application of UAE and MAE in the extraction of bioactive as an environmentally friendly method to be used in the valorisation of by-products in food and agro-industries.