Oxygen-doped Carbon Nitride Nanocages with Efficient Photon-to-Electron Conversion for Selective Oxidation of Xylose/Xylan to Yield Xylonic Acid

Highly efficient photon-to-electron conversion is crucial for achieving photocatalytic conversion.In this study,oxygen-doped carbon nitride nanocages(O@CNNCs)were engineered via dual strategies of morphology-controlled heteroatom doping,which was successfully used in the photocatalytic selective oxidation of xylose/xylan to xylonic acid.The nanocage-shaped O@CNNCs had a larger surface area,which was 4.02 times of carbon nitride(CN).Furthermore,with the assistance of morphology regulation and O-doping,O@CNNCs exhibit highly efficient photon-to-electron conversion,enhanced visible-light utilization,high photocurrent,low resistance,and fast separation/migration of electron-hole pairs.Correspondingly,the photocatalytic oxidation of xylose to xylonic acid using O@CNNCs was successfully achieved under mild reaction conditions with a yield of 83.4%.O@CNNCs have excellent recyclability,in which the yield of xylonic acid in the 5th cycle was 98.2%of its initial use.The O@CNNC photocatalytic system was also suitable for macromolecular xylan,and a xylonic acid yield of 77.34 mg was obtained when 100 mg xylan was used.The oxidation-active species captured experiments indicated that holes were crucial for the selective oxidation of xylose to xylonic acid.Overall,this study provides a new strategy for the preparation of photocatalysts with excellent photon-to-electron conversion and selective oxidation of biomass-derived feedstocks to xylonic acid.

Annulohypoxylon stygium,a Pandanus simplex-associated fungal endophyte withα-glucosidase inhibitory activity

Fungal endophytes offer structurally diverse and unique secondary metabolites with interesting biological activities.Several reports have shown the potential of fungal endophytes as sources ofα-glucosidase inhibitors to alleviate diabetes.In this study,the fungal endophyte Annulohypoxylon stygium(Xylariales,Ascomycota)was identified for the first time from the leaves of the endemic tropical plant,Pandanus simplex Merr.Crude extract was obtained by fermenting the fungal endophyte in Potato Dextrose Broth for 30 days at room temperature.The A.stygium crude extract exhibited good inhibition to theα-glucosidase enzyme with an IC_(50) of 31.88±2.86μg/mL.Purification of the crude extract afforded 8-methoxynaphthol with an IC_(50) value of 676.3±1.03μg/mL.The isolation of 8-methoxynaphthol from A.stygium is reported herein for the first time.This study highlights the ability of A.stygium to produce metabolites that may be useful as antidiabetic drugs.