Recebido em 11/2/10; aceito em 24/7/10; publicado na web em 26/11/10 PRODUCTION OF SILICA GEL USING RESIDUAL RICE HUSK ASH. This paper presents a study on the production of silica gel in hydrothermal process using residual rice husk ash. Measurements of the chemical composition, X-ray diffraction, infrared spectroscopy, particle size distribution, and pozzolanic activity were carried out in order to characterize the obtained material, and the optimal silica gel was selected for use as a mineral additive in cement pastes. The compressive strengths were determined for cement pastes containing silica gel (0.0, 2.5 or 5% by mass) in different times. The results indicate that the mixtures containing silica gel showed improved mechanical behavior over all time periods evaluated.

(+)-N-formylnorglaucine (1), an aporphine alkaloid containing a formyl group linked to the heterocyclic nitrogen, was isolated from the leaves of Unonopsis stipitata, an Amazon medicinal plant. The chemical structure was characterized based on 1D-and 2D-NMR spectroscopy and HR-ESI-MS. NMR spectra revealed that 1 is composed of two rotamers (1a and 1b) in a ratio of approximately 2:1. In addition, the fragmentation behavior of 1 displayed an unusual fragmentation pattern compared to regular aporphine alkaloids. Thus, this compound is reported for the first time as a natural product in this study.

The essential oils from leaves, twigs and trunk bark of Onychopetalum amazonicum R.E. Fr. (Annonaceae), obtained by hydrodistillation, were analysed by GC and GC-MS, and also were evaluated for in vitro antimicrobial activity. Forty-one compounds, which correspond to 75.0-92.2% of the oil components, were identified. Major compounds were sesquiterpenes, including (E)-caryophyllene, caryophyllene oxide, spathulenol, α-gurjunene, allo-aromadendrene and α-epi-cadinol. The oils were evaluated for antimicrobial activities against four bacteria strains and five pathogenic fungi. The oil of the trunk bark exhibited good activity against Staphylococcus epidermidis ATCC 12228, Escherichia coli ATCC 10538 and Kocuria rhizophila ATCC 9341, with a minimal inhibitory concentration of 62.5 μg/mL. The essential oil composition and the antimicrobial evaluation are reported for the first time for the genus Onychopetalum.

EVALUATION OF AMAZONIAN FUNGI BIOMASS AS A SOURCE OF LIPASES FOR BIOCATALYSIS. We evaluated the biomass of twenty Amazonian fungal isolates as a potential source of mycelium-bound lipases with hydrolytic, synthetic or enantioselective activity for biocatalysis application. We compared the hydrolytic activity of three biomass treatments (delipidated, non-delipidated and cultivated in medium without inducer). Delipidated biomass showed better results in the hydrolysis of p-nitrophenyl palmitate compared to the other two treatments for fifteen isolates. Delipidated biomass of six Aspergillus strains and UEA_115 strain showed a high synthesis activity of ethyl palmitate by transesterification in organic medium. Results were confirmed by spectrophotometry (410 nm) and gas chromatography. In this reaction, the isolate DPUA_1539 A. flavo-furcatis reached a maximum value of 668.5 ± 23.5 mU g-1. Enantioselective activity assays indicated that biomass-bound lipases from UEA_115 isolate (E = 3.58; ee s = 7 ± 0) and in particular from the DPUA_1539 A. flavo-furcatis isolate (E = 24.15; ee s = 91 ± 1) have the ability to discriminate enantiomers of the drug ibuprofen by ester synthesis, preferably with (R)-enantiomer. These results encourage further investigations of these fungi as potential lipase suppliers for biocatalytic processes such as biodiesel production and enantiopure drugs.