Introduction: Olax imbricata, owning antibacterial, antioxidant, and anti-inflammatory activities, has been investigated as one of traditional diabetic plants in Vietnam. In our previous publications on Olax imbricata, the structure analysis of the isolated compounds were reported, including two phenolic compounds, three phenolic glycosidic compounds, a sesquiterpenoid tropolone and 1,2,3,4-tetrahydronaphthalene derivatives. This article described the isolation and structure elucidation of three triterpenoid glycosides isolated from the methanol extract of Olax imbricata growing in Phu Yen province. Additionally, the evaluation of inhibitory activity for α-glucosidase was performed on a pure compound. Method: The methanol extract of this plant applied the chromatographic techniques, including thin-layer chromatography and silica gel column chromatography, led to the isolation of three pure compounds. The structures of three isolated compounds were elucidated by the spectroscopic data, including 1D and 2D NMR spectra in a combination of HRESIMS, and the sugar moieties were elucidated by acid hydrolysis. The α-glucosidase inhibitory assay was applied to a pure compound by the colorimetric method. Results: Three triterpenoid glycosides, namely 3-O-α-L-rhamnopyranosyl-(1→4)-β -D-glucopyranosyl-(1→3)-6 ′ -O-ethyl-β -Dglucuronyl oleanolic acid (1), oleanolic acid 28-O-β -D-glucopyranoside (2) and spergulacin (3) were isolated and elucidated. The compound 2 showed its strong potential α-glucosidase inhibitory activity with the IC 50 value of 56.15 ± 1.31 µM. Conclusion: Among them, compound 1 is a new one, the compounds 2 and 3 were isolated for the first time from the genus Olax. The compound 2 exhibited the potential α-glucosidase inhibition activity, contributing to demonstrating the diabetes treatment ability of Olax imbricata in the folklore.
With increasing energy demands and environmental issues, renewable energy‐related conversion systems have gained significant attention as a potential substitute for traditional fossil fuel‐based energy technologies. First introduced by S.W.Grove in 1838, fuel cells have been extensively developed into many different types, and direct alcohol fuel cells (DAFCs) are of interest as a potential power source because of their large power density, quick start, simplicity, and nearly zero emission. However, the high cost and poor catalytic efficiency of current catalysts are primary barriers to commercializing DAFCs. Designing advanced nanocatalysts for both anode and cathode electrodes is of crucial importance for practical DAFC development; however, a brief evaluation of current progress in electrocatalyst development for the alcohol oxidation reaction (AOR) and oxygen reduction reaction (ORR) is still very little. Herein, recent advances in fuel cell catalysts, mainly focusing on several most active areas (i.e., Pt‐ and Pt‐free‐based catalysts, metal‐free carbon, carbon‐based nonprecious metal composites) are concisely summarized. Also, challenges and prospects for DAFCs are highlighted to supply a comprehensive view for further designing high‐performance DAFC catalysts.
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