This study was designed to evaluate antimicrobial and antioxidant activities of the essential oil and methanol extract from Mentha longifolia L. hudson. Antioxidant activity was evaluated through 2,2-diphenyl-l-picryl...This study was designed to evaluate antimicrobial and antioxidant activities of the essential oil and methanol extract from Mentha longifolia L. hudson. Antioxidant activity was evaluated through 2,2-diphenyl-l-picrylhydrazyl （DPPH） assay and β-carotene/linoleic acid assay. The essential oil and methanol extract were individually tested [disc-diffusion assay and evaluating minimum inhibition concentration （MIC）] against a number of bacteria. The essential oil showed strong antimicrobial activity against bacteria tested whereas the methanol extract almost remained inactive. In contrast, the extract showed much better activity than the essential oil in antioxidant activity assays employed, e.g. in the inhibition of free radical DPPH and β-carotene/linolcic acid systems. In the former, the extract was able to reduce the stable free radical DPPH with an IC50 of 55.3μg/mL while that of the oils were 10,630μg/mL. When compared to BHT （butylated hydroxytoluene）, a synthetic antioxidant, both showed weaker antioxidative potential. Similarly, in β-carotene/linoleic acid assay, these samples were not effectively able to inhibit the linoleic acid oxidation; exhibiting only 24% and 36% inhibitions at 2 mg/mL, respectively; both were far below than that of BHT. Total phenolic constituent of the extract was approximately 4.5 g/100 g as gallic acid equivalent. Gas chromatography-mass spectroscopy （GC-MS） analysis of the oil resulted in the identification of 45 constituents, ei^-piperitone epoxide, pulegone and piperitenone oxide being the main components. The results indicate that essential oil and extract ofM. longifolia L. hudson may be used as natural preservative in food against the agents of foodborne diseases and food spoilage.展开更多
Homogeneous and heterogeneous types of catalysis are frequently considered as separate disciplines or even opposed to each other.In the present work,a new type of mixed het-ero-/homogeneous catalysis was demonstrated ...Homogeneous and heterogeneous types of catalysis are frequently considered as separate disciplines or even opposed to each other.In the present work,a new type of mixed het-ero-/homogeneous catalysis was demonstrated for the case of selective alkylarene oxidation by molecular oxygen.The proposed catalytic system consists of two widely available components:N-hydroxyphthalimide(NHPI,a homogeneous organocatalyst for free-radical chain reactions)and nanosized TiO_(2)(heterogeneous UV-active photoredox catalyst).The interaction of NHPI with TiO_(2) allows for a shift from UV to visible light photoredox activity and generation of phthalimide-N-oxyl(PINO)radicals that diffuse into the solution where NHPI/PINO-catalyzed free-radical chain reaction can proceed without the additional light input providing a fundamental increase in energy efficiency.The NHPI/TiO_(2) ratio controls the selectivity of oxidation affording preferential formation of hydroperoxide or ketone from alkylarene.展开更多
文摘This study was designed to evaluate antimicrobial and antioxidant activities of the essential oil and methanol extract from Mentha longifolia L. hudson. Antioxidant activity was evaluated through 2,2-diphenyl-l-picrylhydrazyl （DPPH） assay and β-carotene/linoleic acid assay. The essential oil and methanol extract were individually tested [disc-diffusion assay and evaluating minimum inhibition concentration （MIC）] against a number of bacteria. The essential oil showed strong antimicrobial activity against bacteria tested whereas the methanol extract almost remained inactive. In contrast, the extract showed much better activity than the essential oil in antioxidant activity assays employed, e.g. in the inhibition of free radical DPPH and β-carotene/linolcic acid systems. In the former, the extract was able to reduce the stable free radical DPPH with an IC50 of 55.3μg/mL while that of the oils were 10,630μg/mL. When compared to BHT （butylated hydroxytoluene）, a synthetic antioxidant, both showed weaker antioxidative potential. Similarly, in β-carotene/linoleic acid assay, these samples were not effectively able to inhibit the linoleic acid oxidation; exhibiting only 24% and 36% inhibitions at 2 mg/mL, respectively; both were far below than that of BHT. Total phenolic constituent of the extract was approximately 4.5 g/100 g as gallic acid equivalent. Gas chromatography-mass spectroscopy （GC-MS） analysis of the oil resulted in the identification of 45 constituents, ei^-piperitone epoxide, pulegone and piperitenone oxide being the main components. The results indicate that essential oil and extract ofM. longifolia L. hudson may be used as natural preservative in food against the agents of foodborne diseases and food spoilage.
文摘Homogeneous and heterogeneous types of catalysis are frequently considered as separate disciplines or even opposed to each other.In the present work,a new type of mixed het-ero-/homogeneous catalysis was demonstrated for the case of selective alkylarene oxidation by molecular oxygen.The proposed catalytic system consists of two widely available components:N-hydroxyphthalimide(NHPI,a homogeneous organocatalyst for free-radical chain reactions)and nanosized TiO_(2)(heterogeneous UV-active photoredox catalyst).The interaction of NHPI with TiO_(2) allows for a shift from UV to visible light photoredox activity and generation of phthalimide-N-oxyl(PINO)radicals that diffuse into the solution where NHPI/PINO-catalyzed free-radical chain reaction can proceed without the additional light input providing a fundamental increase in energy efficiency.The NHPI/TiO_(2) ratio controls the selectivity of oxidation affording preferential formation of hydroperoxide or ketone from alkylarene.
