Chemical profiling and sustainable valorization of post-distillation residues of Vitex rotundifolia

Abstract

Post-distillation residues (PDR) from Vitex rotundifolia essential-oil production represent an underutilized biomass stream that can retain medium- and high-polarity constituents. Here, PDR and raw fruits were extracted with 30–96% ethanol under matched ultrasound-assisted extraction conditions and evaluated by TPC/TFC and four bioactivity assays (DPPH, ABTS, NO inhibition, and xanthine oxidase). Among residue-derived extracts, R70 showed the best overall performance (DPPH and ABTS IC₅₀ = 24.87 and 24.90 µg mL⁻¹; NO IC₅₀ = 104.99 µg mL⁻¹), comparable to the corresponding raw extract (E70; NO IC₅₀ = 102.86 µg mL⁻¹). Untargeted UHPLC-QTOF-MS/MS enabled curated tentative annotation of 88 metabolites in R70, dominated by flavonoids, phenolic derivatives, terpenoids, and oxylipins, and four representative known constituents (casticin, quercitrin, vitexilactone, and agnuside) were isolated and structurally confirmed. A comparative greenness screening showed improved mass-based metrics for the residue-based route (PMI/E-factor 1409/1407 vs. 1925/1921 for the raw-material route), while per-batch energy-related indicators were higher (climate change 3.63 vs. 2.49 kg CO₂-eq), highlighting a material-energy trade-off. Overall, PDR can serve as a viable secondary feedstock for recovering non-volatile bioactive constituents, and the environmental performance of residue valorization is condition-dependent.