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Endophytic microorganisms show great potential for biotechnological exploitation because they are able to produce a wide range of secondary compounds involved in endophyte–plant adaptation, and their interactions with other living organisms that share the same microhabitat. Techniques used to chemically extract these compounds often neglect the intrinsic chemical characteristics of the molecules involved, such as the ability to form conjugate acids or bases and how they influence the solubilities of these molecules in organic solvents. Therefore, in this study, we aimed to evaluate how the pH of the fermented broth affects the process used to extract the secondary metabolites of the Diaporthe citri strain G-01 endophyte with ethyl acetate as the organic solvent. The analyzed samples, conducted by direct-infusion electrospray-ionization mass spectrometry, were grouped according to the pH of the fermented broth (i.e., m/z were observed mainly at acidic pH, while 226.5, 298.3, and 430.1 m/z ions were observed at pH ≥ 7. Extraction at a pH between 4 and 9 may be of interest for exploring the differential secondary metabolites produced by endophytes. Furthermore, pH influences the chemical phenotype of the fungal metabolic extract.

This work propose the development of an experiment that may be used for the teaching of chemistry for undergraduate students in general, using the analysis of olive oil and soybean oil toward the direct injection electrospray ionization Mass Spectrometry - DI-MS/MS with 18-crown-6 as organic modifier. Firstly, olive oil was analyzed from two different brands, one of reputed brand and the other of popular brand and lower price. Soybean oil of popular brand was also analyzed in order to search possible similarities in the components of these oils and to search adulterations of olive oil with soybean oil. The mass spectra were obtained in positive ion mode of analysis, and allowed us to observe characteristic ions of soybean oil, olive oil, and identify the adulterated olive oil. This simple experiment of easy development may be applied in any institution which has a mass spectrometer with electrospray ionization. In addition, with the use of the experiment, the teacher can illustrate general chemistry concepts such as: molecular mass, preparation of solutions, oxidation, and acid-base reactions.