A simple method based on matrix solid-phase dispersion (MSPD) extraction and gas chromatography with electron-capture detection (GC-ECD) is employed to determine pesticide residues in the following tropical fruits: banana, mango, melon, papaya and pineapple. In the MSPD proposed method, C18, silica gel and ethyl acetate presented the best results in the extraction, clean-up and elution steps, respectively. Spiked blank samples were used to minimize the matrix effect in the chromatographic determination. The validation process was conducted at three different concentration levels of spiked samples (0.50-2.50 µg g-1) in within-a-day and in among days assays. The limits of detection for the pesticides ranged from 4.0 to 23 µg kg-1. The method showed acceptable selectivity, coefficients of correlation higher than 0.997, and recovery between 76-105%. The within-a-day precision was assessed through the relative standard deviation (2.8-19%) for the different levels of spiked samples tested.

The study of the Typha species has gained attention in tropical areas due to their rapid growth, nutrient release, and contribution to detritus in lakes. Analysis of the degradation of Typha angustifolia has shown that the first stage of decomposition is marked primarily by the release of soluble compounds, indicating that microorganisms have a minor influence at this stage. In subsequent stages, microorganisms act by degrading and consuming phenolic compounds and phosphorus. The remaining compounds form humic substances and are retained in the detritus. Thus, microorganisms significantly degrade organic matter, resulting in a two-fold increase in decomposition. Different forms of phosphorus could be detected in the remaining mass by 31P NMR (nuclear magnetic resonance). By comparing the 31P NMR data between the samples with and without the antibiotic, we can better understand the slow decomposition process of Typha angustifolia.

Astilbin (5,7,3’,4’-tetrahydroxy-2,3-dihydroflavonol-3-ß-o-rhamnoside), a flavonoid with a large range of biological activities, was isolated from Dimorphandra mollis, a shrub common to the Brazilian Cerrado. The purpose of this study is to verify the effects of astilbin on myeloperoxidase (MPO) and horseradish peroxidase (HRP), and its antioxidant activity against hypochlorous acid (HOCl) and total antioxidant activity (TAC) by the 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS•+). Astilbin inhibited MPO and HRP activities in a concentration-dependent relationship and effectively scavenged HOCl. The TAC by ABTS•+ of astilbin (IC50 ~ 20 mM) was higher than that of uric acid, which was used as a positive control. These data demonstrate that astilbin is a potent antioxidant and that it inhibits MPO and HRP activities efficiently.