Response Surface Methodology for Optimizing the Bovine Serum Albumin Fibrillation

Antiproliferative Activities of the Lipophilic Fraction of Eucalyptus camaldulensis against MCF-7 Breast Cancer Cells, UPLC-ESI-QTOF-MS Metabolite Profile, and Antioxidative Functions

Although a number of pharmacological properties have been linked to Eucalyptus camaldulensis leaf essential oil and extracts, the biological attributes of the lipophilic fraction remain unknown. Moreover, only a limited number of active compounds have so far been identified. This work aimed to investigate the anti-oxidative, anti-aggregation, and cytotoxic properties as well as profile the secondary metabolites in the lipophilic fraction of E. camaldulensis leaf extract (Lipo-Eucam) using UHPLC-ESI-QTOF-MS and gas chromatography-mass spectrometry (GC-MS). It was found that Lipo-Eucam possessed potent antioxidant properties against DPPH, ABTS, and FRAP with IC₅₀ values of 31.46, 32.78, and 10.12 μg/mL, respectively. The fraction was able to attenuate metal-catalyzed oxidation of bovine serum albumin (BSA) in a dose-dependent manner (p < 0.05) and abrogated the aggregation of amyloidogenic BSA as revealed by the Congo red assay and transmission electron microscopy. Furthermore, Lipo-Eucam demonstrated potent cytotoxic effects against MCF-7 (IC₅₀ 7.34 μg/mL) but was noncytotoxic at used concentrations against HEK-293 cells (IC₅₀ > 80 μg/mL), suggestive of its selective anticancer properties. Spectrophotometric, UHPLC-MS, and GC-MS analysis revealed that Lipo-Eucam is rich in phenolics, flavonoids, terpenoids, volatile constituents, and a plethora of active metabolites, probably responsible for the observed activities. These findings indicate that Lipo-Eucam is endowed with pharmacologically relevant active principles with strong potential for use in the amelioration of disease conditions related to oxidative stress, protein aggregation, and breast cancer and therefore worthy of further investigations.

Evaluation of antioxidant and inhibitory properties of Citrus aurantium L. on the acetylcholinesterase activity and the production of amyloid nano-bio fibrils

The blossoms of Citrus aurantium are considered for the treatment of Alzheimer's disease because of their fragrant essential oils. The aim of this study was to investigate the antioxidant and inhibitory effects of Citrus aurantium extract on the acetylcholinesterase and production of amyloid nanobiofibrils from bovine serum albumin (BSA). The Citrus aurantium petals were harvested from Rasht city in northern IRAN. Chemical composition was investigated by GC-MS. The anti-Alzheimer's effects were evaluated by determining the antioxidant percentage by DPPH method and determining acetylcholinesterase activity. Congored spectroscopy was used for investigation of the inhibitory properties of the extract on the production of amyloid nanobiofibrils, and amyloid fibers was confirmed by electron microscopy. The most abundant ingredients were D-Glucuronic acid (9.53%), D-Limonene (5.54%), Linalool (2.06%), Daphnetin (3.73%), Phthalic acid (0.72%), Octadecenoic acid (3.98%), Hexadecanoic acid (2.13%), Pyrrolidinone (1.17%) and the highest antioxidant capacity was at 8 mg/ml (EC₅₀: 2.36 mg/ml). The extract reduced the Acetylcholinesterase activity less than 47.04% (IC₅₀: 42.8 mg/ml) and amyloid production less than 22% (EC₅₀: 3.135). Citrus aurantium petals with inhibitory properties for the production of amyloid nanobiofibrils, can be used as a beneficial drugs for reducing side effects of Alzheimer's disease.

Disulfide-bond scrambling promotes amorphous aggregates in lysozyme and bovine serum albumin

Disulfide bonds are naturally formed in more than 50% of amyloidogenic proteins, but the exact role of disulfide bonds in protein aggregation is still not well-understood. The intracellular reducing agents and/or improper use of antioxidants in extracellular environment can break proteins disulfide bonds, making them unstable and prone to misfolding and aggregation. In this study, we report the effect of disulfide-reducing agent dithiothreitol (DTT) on hen egg white lysozyme (lysozyme) and bovine serum albumin (BSA) aggregation at pH 7.2 and 37 °C. BSA and lysozyme proteins treated with disulfide-reducing agents form very distinct amorphous aggregates as observed by scanning electron microscope. However, proteins with intact disulfide bonds were stable and did not aggregate over time. BSA and lysozyme aggregates show unique but measurable differences in 8-anilino-1-naphthalenesulfonic acid (ANS) and 4,4'-dianilino-1,1'-binaphthyl-5,5'-disulfonic acid (bis-ANS) fluorescence, suggesting a loose and flexible aggregate structure for lysozyme but a more compact aggregate structure for BSA. Scrambled disulfide-bonded protein aggregates were observed by nonreducing sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) for both proteins. Similar amorphous aggregates were also generated using a nonthiol-based reducing agent, tris(2-carboxyethyl)phosphine (TCEP), at pH 7.2 and 37 °C. In summary, formation of distinct amorphous aggregates by disulfide-reduced BSA and lysozyme suggests an alternate pathway for protein aggregation that may be relevant to several proteins.