Propylene glycol-based green extraction of polyphenols from industrial hemp stems: process optimization and bioactivity assessment

Industrial hemp (Cannabis sativa L. subsp. sativa) is a multipurpose crop widely cultivated for its fibers, seeds, and oils. Despite the common use of hemp stems for fiber production in textiles and construction, they are frequently discarded as agricultural waste. This study aimed to enhance the utilization of hemp stems through the optimization of ultrasound-assisted extraction (UAE) employing aqueous propylene glycol solvent system as the extraction solvent, guided by Box–Behnken design (BBD). The optimal extraction parameters—an extraction duration of 30 min, a solvent–solute ratio of 28.25 mL/g, and a PG concentration of 32.72%—resulted in a hemp stem extract (HUPG) enriched with bioactive constituents exhibiting significant antioxidant activity. Following analysis by LC–QTOF–MS/MS, a total of 18 phytochemicals were detected, including isofeuric acid, m-coumaric acid, and chelidonic acid. HUPG exhibited antibacterial activity against Staphylococcus aureus, Streptococcus epidermidis, Escherichia coli, and Pseudomonas aeruginosa, and anti-inflammatory effects through 5-lipoxygenase inhibition and NO radical scavenging (1.41 ± 0.38 mg GAE/g). In LPS-induced RAW 264.7 macrophages, HUPG demonstrated inhibitory effect on NO production. Moreover, it enhanced wound closure in HaCaT cells (51.92 ± 6.05% at 10 mg/mL). These findings highlight the promise of HUPG as a sustainable source of bioactive compounds with potential applications in cosmetic and pharmaceutical formulations.