Depolymerization of lignin is an important step to obtain a lignin monomer for the synthesis of functional chemicals. In the context of more lignin produced from biomass and pulp industry, converting real lignin with low purity is still required more studies. In this study, the influence of solvent composition and reaction parameters such as binary solvents ratio, time, and temperature, the solvent-to-lignin ratio on the depolymerization of rice straw lignin was investigated carefully. Essential lignin-degraded products including liquid product (LP), char (solid), and gas were obtained, and their yields were directly influenced by reaction conditions. Results show that the maximum lignin conversion rate of 92% and LP yield of 66% was under the condition of 275°C, 30 min, 75 : 1 (mL solvent/1 g lignin), and ethanol 50%. Gas chromatography-mass spectroscopy (GC-MS) analysis was used for the analysis of the depolymerization products and identified 11 compounds which are mainly phenolic compounds such as 2-ethylphenol, 3-ethylphenol, phenol, methyl 2,4,6-trimethylbenzoate. The structure changes of LP and char in various conditions were analyzed using Fourier-transform infrared (FTIR).
Objectives. The study aimed to test the ethanol extracts of ten medicinal plants for xanthine oxidase inhibitory activity.Methods. The degree of xanthine oxidase inhibitory activity was determined by measuring the absorbance spectrophotometrically at 290 nm, which is associated with uric acid formation. The selected medicinal plants included Piper lolot C.DC. (Piperaceae), Pandanus amaryllifolius R.(Pandanaceae), Brassica juncea L. (Brassicaceae), Piper betle L. (Piperaceae), Perilla frutescens L. (Lamiaceae), Anacardium occidentale L. (Anacardiaceae), Polygonum barbatum L. (Polygonaceae), Artocarpus Altilis P. (Moraceae), Vitex negundo L. (Verbenaceae), Annona squamosal L. (Annonaceae), which were selected based on folk medicine.Results. The results showed that the Piper betle L. has a strong ability to inhibit xanthine oxidase with an IC50 value of up to 1.18 μg/mL, compared to allopurinol 1.57 μg/mL. Different parts of Piper betle L. were compared and the leaves of Piper betle L. showed the best value for xanthine oxidase inhibitory and antioxidant activity.Conclusions. Piper betle L. showed the best potential for inhibition of xanthine oxidase among ten medicinal plants. Piper betle L. leaf extract showed strong xanthine oxidase inhibitory and antioxidant activity, compared to the whole plant, and the stem extract, which promises to be applied in the treatment of gout.
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