Phytochemical Screening of Quaking Aspen (Populus tremuloides) Extracts by UPLC-QTOF-MS and Evaluation of their Antimicrobial Activity.

The continual emergence of pathogen resistance is a recurring challenge and pushes for the development of antimicrobial compounds. Here, we investigated compounds from quaking aspen trees (Populus tremuloides) as potential antimicrobial agents. Several extractions using different solvents were realized, and corresponding antimicrobial activity was tested against eight microorganisms. Results revealed that polar extraction solvents including water, ethanol and methanol gave the best extraction yields (>15.07%). Minimal inhibition concentration (MIC) and minimal bactericidal/fungicidal concentration (MBC/MFC) demonstrated that water extracts had the best antimicrobial activity by a weak to moderate inhibition of growth of all eight tested microorganisms in addition to having a bactericidal effect on three of them. The quaking aspen methanol extract also displayed antimicrobial activity but to a lower level than the water extract. Ultra-performance liquid chromatography quadrupole time-of flight mass spectrometry (UPLC-QTOF-MS) analysis led to the identification of 92 compounds, mainly polyphenols in both extracts, with 22 molecules previously known for their antimicrobial properties. According to the relative abundance, 4-hydroxybenzaldehyde (5.44% in methanol extract) and kaempferol (5.03% in water extract) were the most abundant antimicrobial compounds. Among antimicrobial molecules identified, nine were from the flavonoid family. The results of our study demonstrate the interest of using quaking aspen as source of antimicrobial compounds.

Antimicrobial activity and chemical composition of white birch (Betula papyrifera Marshall) bark extracts.

Extracts from white birch have been reported to possess antimicrobial properties, but no study has linked the chemical composition of bark extract with antimicrobial activity. This study aimed to identify white birch (Betula papyrifera Marshall) bark extracts with antimicrobial activity and elucidate its composition. In order to obtain the highest extraction yield, bark residues >3 mm were retained for extraction. A total of 10 extraction solvents were used to determine the extraction yield of each of them. Methanol and ethanol solvents extracted a greater proportion of molecules. When tested on eight microorganism species, the water extract proved to have the best antimicrobial potential followed by the methanol extract. The water extract inhibited all microorganisms at low concentration with minimal inhibitory concentration between 0.83 and 1.67 mg/ml. Using ultraperformance liquid chromatography coupled to a time-of-flight quadrupole mass spectrometer, several molecules that have already been studied for their antimicrobial properties were identified in water and methanol extracts. Catechol was identified as one of the dominant components in white birch bark water extract, and its antimicrobial activity has already been demonstrated, suggesting that catechol could be one of the main components contributing to the antimicrobial activity of this extract. Thus, extractives from forestry wastes have potential for new applications to valorize these residues.

Study of antioxidant properties of thylakoids and application in UV protection and repair of UV-induced damage.

BACKGROUND: Skin is affected by environmental stress such as ultraviolet exposure. Topically applied antioxidants confer protection against this stress. Spinach thylakoid extracts are plant samples known as photosynthetic membranes containing antioxidant molecules able to dissipate excess of energy and oxidative stress. METHODS: Antioxidant contents and activities were tested in thylakoid extracts stored for different periods at 4°C to compare their efficacities. Cytotoxicity of thylakoids was tested on human THP-1 cells along with the capacity to protect from oxidative stress using flow cytometry. Protection of thylakoids against ultraviolet was tested on engineered human skin using two formulations and evaluated by electronic microscopy. RESULTS: Results indicate that thylakoid extracts possess antioxidant molecules that were not significantly affected by storage at 4°C whereas photosynthetic activity was storage-dependent. Thylakoid extracts were not cytotoxic to human THP-1 cells, and three extracts protected cells against reactive oxygen species. Moreover, formulation comprising 0.1% or 0.01% of thylakoids and sunscreen provided a synergetic protection against UV exposure. Thylakoid extracts mixed with a neutral cream were also able to repair UV damages on engineered human skin. CONCLUSIONS: Thylakoid extracts contained various antioxidant molecules, and their properties were maintained in over storage at 4°C for more than 72 months. Molecules and enzymes present in thylakoid extracts are involved in protecting and restoring the harmful effects of UV exposure. The involvement of antioxidant molecules such as carotenoids, SOD, and Fe-S clusters in cellular and regulatory metabolic reactions may explain the observed protective effects.