ABSTRACT
Natural or synthetic graphite as precursors for the preparation of graphene oxide (GO) have constraints due to their limited availability, high reaction temperature for processing of synthetic graphite and higher generation cost. The use of oxidants, long reaction duration, the generation of toxic gases and residues of inorganic salts, the degree of hazard and low yield are some of the disadvantages of the oxidative-exfoliation methods. Under these circumstances, biomass waste usage as a precursor is a viable alternative. The conversion of biomass into GO by the pyrolysis method is ecofriendly with diverse applications, which partially overcomes the waste disposal problem encountered by the existing methods. In this study, graphene oxide (GO) is prepared from dry leaves of sugarcane plant through a two-step pyrolysis method using ferric (III) citrate as a catalyst, followed by treatment with conc. H2SO4. The synthesized GO is analyzed by UV-Vis., FTIR, XRD, SEM, TEM, EDS and Raman spectroscopy. The synthesized GO has many oxygen-containing functional groups (-OH, C-OH, COOH, C-O). It shows a sheet-like structure with a crystalline size of 10.08 nm. The GO has a graphitic structure due to the Raman shift of G (1339 cm-1) and D (1591 cm-1) bands. The prepared GO has multilayers due to the ratio of 0.92 between ID and IG. The weight ratios between carbon and oxygen are examined by SEM-EDS and TEM-EDS and found to be 3.35 and 38.11. This study reveals that the conversion of sugarcane dry leaves into the high-value-added material GO becomes realistic and feasible and thus reduces the production cost of GO.
ABSTRACT
Spontaneous fermentation during black tea production involves several reactions, including the oxidation of phenolic compounds. This process has usually been studied without considering the potential involvement of indigenous tea microorganisms. This work utilised a metagenomic technique targeting bacterial 16S rRNA genes and evaluated the profile of phenolic compounds generated during the production of black tea. The resulting data were used to develop correlational and predictive functional analyses related to bacterial dynamics and the syntheses of various phenolic compounds. In particular, the genera Methylobacterium and Devosia were correlated with gallic acid and quercetin. Concurrently, the genera Sphingomonas, Chryseobacterium and Aureimonas were correlated with kaempferol, theaflavins, thearubigins and theabrownins. These results, supported by predicted functional analysis based on 16S rRNA genes associated with phenolic compounds, indicated that yfiH (polyphenol oxidase) and katG (catalase-peroxidase) are likely the dominant genes of the bacterial community involved in the black tea production process. This research suggests that bacteria could potentially contribute to the production process of black tea.
ABSTRACT
Objective: To study the chemical constituents from the ethyl acetate extract of the leaves of Adinandra nitida. Methods: Several column chromatography including silica gel, Sephadex LH-20 gel, and ODS were applied in isolation and purification. The structures were elucidated on the basis of physicochemical properties and spectral data from 1H-NMR, 13C-NMR, ESI-MS and so on. Results: Nine flavonoids, three phenolic acids, and two other compounds were isolated and determined as apigenin (1), naringenin (2), luteolin (3), chrysoeriol (4), (-)-epicatechin (5), quercetin (6), quercitrin (7), camellianin A (8), camellianin B (9), p-methoxyphenol (10), protocatechuic acid (11), 3,3',4,4'-tetrahydroxybiphenyl (12), scopoletin (13), and palmitic acid (14). Conclusion: Compounds 3, 10-14 are firstly isolated from the plant of A. nitida and compounds 3, 10, 12, and 13 are obtained from Theaceae for the first time.
ABSTRACT
In Brazil, Ocimum species are commonly known as aromatic and restorative herbs. The present research aimed to study the chemical composition of the essential oils of fresh and dry basil (Ocimum sp) leaves obtained by hydrodistillation and analyzed by GC-FID and GC-MS. The obtained yield was 0.70% for dry leaves and 0.26% for fresh leaves. The major compounds were: linalool (29.50-32.26%) and methyl chavicol (36.81-41.62%). Eucalyptol could also be detected (9.99-7.68%). The oil from dry leaves presented a more complex chemical composition. This study serves to contribute to the knowledge of medicinal plants occurring in Brazil.
No Brasil, as espécies de Ocimum são conhecidas como ervas aromáticas e restaurativas. Nesse trabalho foi estudado a composição química dos óleos essenciais das folhas frescas e secas de manjericão (Ocimum sp) obtido por hidrodestilação e analisados por CG-FID e CG-EM. Os teores encontrados foram de 0,70% para as folhas secas e 0,26% para as folhas frescas. Os componentes majoritários foram: Linalol (29,50-32,26%) e metil-chavicol (36,81-41,62%). Eucaliptol também foi detectado (9,99-7,68%). O óleo das folhas secas apresentou composição química mais complexa. Esse trabalho contribui para o conhecimento das plantas medicinais de ocorrência no Brasil.
