Mn₃O₄ nanoparticles have been synthesized using alcoholic extracts, at pH = 7 and low temperature (60 °C), from different masses (1.00, 3.00, 5.00, and 7.00 g) of fresh leaves from Nerium oleander and Bixa orellana, without additional heat treatment. Appropriate techniques were used to identify the secondary metabolites of the extracts and evaluate the structural, optical, and chemical properties of the nanoparticles. The XRD results confirmed the formation of Mn₃O₄ nanoparticles with crystallite size in the 5−8 nm range, with more notable effects on the crystallinity of the nanoparticles obtained with B. orellana extracts. The greatest effect on the bandgap was observed in nanoparticles synthesized with N. oleander extracts. Raman spectra confirmed phonon confinement, and in the PL spectra, emission bands associated with structural defects, such as oxygen vacancies, were observed. In FTIR spectra, the main bands of Mn₃O₄ were identified, whose intensity decreased as the concentration of extract and other bands associated with functional groups of the extract increased. TEM images showed nanoparticles were spherical with 7.81 nm (N1) and 7.94 nm (B1) average diameters. The extract from N. oleander leaves was more appropriate than that from B. orellana for the synthesis of Mn₃O₄ nanoparticles under the conditions used.

This research was carried out in order to obtain gallic acid by the action of the hydrolytic enzymesof Aspergillus niger that degrade the tannins presents in Caesalpinia spinosa (Fabaceae) “tara”, usinga solid state bioreactor. The fermentations were carried out for 2, 4 and 6 days at room temperature,with an initial pH of 7.0 and a microbial inoculum of 109 espores/ml. The maximum productionwas obtained 4 days after the fermentation process with a purity of 28.71% gallic acid, according tothe readings provided by the UV-Vis spectrophotometer with microplate reader. According to thestatistical analysis, the different exposure times present significant differences. It was determinedthat there is a direct relationship between fermentation time and absorbance.