Steam Explosion-Assisted Vacuum Extraction Promotes Enrichment of Bioactive Constituents and Changes in Chemical Composition in Perilla frutescens

Steam explosion-assisted vacuum extraction (SVE), an integrated extraction strategy, was developed to improve the yields of bioactive constituents from Perilla frutescens and to explore the potential mechanisms responsible for the observed performance enhancement. Compared with conventional Reflux extraction (RE), extracts obtained using the integrated SVE process contained higher abundances of major bioactive compounds. The contents of ferulic acid, scutellarin, and rosmarinic acid extracted from P. frutescens leaves rose from 3.126 to 4.025 mg per g of dried leaves (increased 1.29-fold), 0.236 to 0.536 mg/g (increased 2.27-fold), and 0.614 to 2.386 mg/g (increased 3.89-fold), respectively, while the total content of the four quantified bioactive compounds rose from 4.574 to 7.521 mg/g (increased 1.64-fold). Scanning electron microscopy revealed that SVE-treated samples exhibited microstructural alterations characterized by greater surface roughness and visible pore formation, which may enhance solvent accessibility and facilitate mass transfer. Metabolomic profiling further indicated higher levels of hydroxycinnamic acids, flavonoid glycosides, fatty acids, and triterpenoids in SVE-processed samples, reflecting compositional changes in P. frutescens extracts. These favorable changes may be partly attributed to the combined effects of structural modification induced during SVE pretreatment and low-temperature vacuum extraction; such combined effects may facilitate mass transfer and mitigate thermal degradation of heat-sensitive constituents. Overall, this study provides preliminary insights into the possible mechanisms underlying this integrated extraction strategy and may support the development of efficient extraction approaches for P. frutescens.