This study explored the batch membrane filtration of 40% ethanol extracts from spent lavender, containing valuable compounds like rosmarinic acid, caffeic acid, and luteolin, using a polyamide-urea thin film composite X201 membrane. Conducted at room temperature and 20 bar transmembrane pressure, the process demonstrated high efficiency, with rejection rates exceeding 98% for global antioxidant activity and 93–100% for absolute concentrations of the target components. During concentration, the permeate flux declined from 2.43 to 1.24 L·m⁻²·h⁻¹ as the permeate-to-retentate-volume ratio increased from 0 to 1. The process resistance, driven by osmotic pressure and concentration polarization, followed a power–law relationship with a power value of 1.20, consistent with prior nanofiltration studies of rosmarinic acid solutions. Notably, no membrane fouling occurred, confirming the method’s scalability without compromising biological activity. The antioxidant activity, assessed via the DPPH method, revealed that the retentate exhibited double the activity of the feed. Antibacterial assays using broth microdilution showed that the retentate inhibited Escherichia coli by 73–96% and Bacillus subtilis by 97–98%, making it the most active fraction. These findings validate the effectiveness of the X201 membrane for concentrating natural antioxidants and antibacterial agents from lavender extract under sustainable operating conditions.

The essential oil produced from R. damascena petals is one of the most valuable and important base materials in the flavour and fragrance industry. For each ton of processed rose flowers, less than 0.5 kg of essential oil and about 4 tons of residual water is generated. Due to the presence of polyphenolic compounds in the latter, its uncontrolled disposal has an adverse effect on the ecological balance. Moreover, valuable substances with biological activity are lost. The possibility to recover by nanofiltration a refined polyphenolic fraction, composed primarily of flavonoids, their glycosides and polyphenolic acids, contained in the waste residual water was demonstrated in the present work. The nanofiltrations were carried out with DL (Veolia) and NP030 (Mycrodin Nadir) commercial nanofiltration membranes. The DL membrane was proposed for process design due to its lower susceptibility to fouling by the target solutes. The experimentally determined membrane permeance for the DL membrane ranged from 1.8 to 0.5 LMH bar-1 during batch concentration at an operating pressure of 10 bar and degree of feed volume reduction in the range from 1 to 2. Since the target compounds are well known antioxidants, their concentrations in the studied materials were evaluated in terms of global antioxidant activity. The retentates were up to 2.00 times more potent antioxidants compared to the feed solutions. The experimentally determined membrane rejection coefficients for both membranes with respect to global antioxidant activity were in agreement with theoretically predicted values reported in a previous study, indicating efficient membrane fractionation.

Oxidative stress and metal-driven redox processes are key contributors to the pathogenesis of chronic diseases and cancer, motivating the search for novel antioxidant molecules. In this study, the antioxidant potential of a series of synthetic peptides previously reported to possess antitumor and antibacterial properties was evaluated using two complementary electron-transfer assays: ferric reducing antioxidant power (FRAP) and cupric ion reducing antioxidant capacity (CUPRAC). Both assays were calibrated against caffeic acid, and results were expressed as caffeic acid equivalents (CAE). The FRAP assay revealed substantial differences in reducing activity, with Si8 exhibiting the highest value (0.558 ± 0.132), followed by Si12 (0.478 ± 0.0240), Si10 (0.293 ± 0.0220), and Si15 (0.250 ± 0.0200), whereas Si1 (0.00439 ± 0.00240) and Si11 (0.00260 ± 0.000500) showed negligible responses. A comparable pattern was observed in the CUPRAC assay, where Si8 again displayed the strongest reducing capacity (0.381 ± 0.0948), with Si12 (0.290 ± 0.0225), Si15 (0.262 ± 0.0223), and Si10 (0.224 ± 0.0290) also demonstrating appreciable activity, while Si1 (0.001800 ± 0.000400) and Si11 (0.0132 ± 0.000500) remained inactive. The combined application of FRAP and CUPRAC provided complementary and reproducible measures of peptide antioxidant capacity, establishing a framework for systematic characterization of redox-active peptides in relation to oxidative stress.

The present study explores the possibility of combining membrane concentration, spray drying, and low-temperature precipitation into a single process for the valorization of spent lavender biomass as a source of ingredients rich in antioxidants. Lavender spent plant material was subjected to solid–liquid extraction, and the obtained hydroalcoholic extracts were further concentrated using a dead-end membrane filtration cell (METcell) with a polyamide–urea thin-film composite X201 membrane. The feed and the obtained retentate were subsequently spray dried using a Nano Spray Dryer B-90 (BÜCHI) under different temperature conditions (120 °C and 85 °C). Low-temperature precipitation was further applied for the retentate. An eight-fold concentration of the extracts was achieved, with membrane rejection coefficients of 100% for antioxidant activity and 98.5% for dry solids content. The permeate flux ranged from 2.25 to 0.201 L·m⁻²·h⁻¹. Spray drying at a lower inlet temperature resulted in minimal losses for antioxidant activity (below 6%). The low-temperature storage of the membrane concentrate led to clear phase separation, allowing for the recovery of a precipitated fraction. The obtained results demonstrate that the integrated approach may support the sustainable and scalable valorization of lavender by-products.

Free oxygen radicals released in the body as a result of various metabolic processes could lead to the so-called oxidative stress in cells, which is a precursor to various types of cancer. Protecting cells from oxidative stress is an important step in the prevention of cancer. Nature has a large supply of compounds with powerful antioxidant properties. One of them is caffeic acid. In the present study, caffeic acid was combined to obtain bioconjugates with analogs of the natural peptide with proven antitumor properties (KLAKLAK)₂. Here we report the antioxidant potential of these molecules as it was investigated with the well-known from the literature DPPH method, in search of a synergistic effect between the two pharmacophores of the molecule. The obtained results identify Si18 (Caf-(KnLAKnLAK)2-NH2) as the lead candidate approaching the caffeic acid benchmark under the tested conditions with EC₅₀ = 0.0178 mM.