P-Nitrophenol (pNP) is a widely used compound for analytical determinations of several esterases (EC. 3.1.1.X), including lipases (E.C. 3.1.1.3). Most enzymatic measurements employ pNP derivatives such as esters, which are broken down by enzymatic hydrolysis, releasing pNP that is quantified by its absorbance at 410 nm. Although this type of methods was developed a few decades ago, the spectrophotometric analysis of pNP requires analytical measurements of pH and temperature to achieve reliable determinations. The aim of this paper is to offer a graphical update of how pH and temperature affect the p-nitrophenol absorbance at different wavelengths in lipase emulsified media, due to its relevance for the quantitative determination of lipase activity using spectrophotometric methods. To highlight the importance of each variable involved in this analysis, we dissolved pNP in emulsified media (for lipase activity quantification) at several pH values from 4.00 to 11.00, and measured its absorbance in a range of 270 nm – 500 nm and at several temperatures from 25°C to 50°C. The absorption patterns of pNP under the established conditions were graphed in 3D plots. The constructed 3D plots showed that, regardless of the temperature, below pH 6.00, pNP predominantly absorbs at 317 nm, due to the greater abundance of its protonated form, which is completely predominant at pH 3.50 and below. On the other hand, at pH 10.0 and above, the major absorption occurs at about 401 nm, confirming that the equilibrium is completely shifted to the pNP anionic form. These results also indicate that close to neutral pH value pNP, it displays a temperature dependence effect, increasing absorbance to 410 nm at higher temperatures. Due to many analytical determinations of enzymatic activities, the release of pNP is carried around pH 7.00. It is necessary to consider the determinant role of both pH and temperature over these measurements, how these variables must be strictly controlled, and how the calibration curves and blanks should take the reaction media pH and temperature into account.

The cultivation of native corn has decreased in favor of the cultivation of improved commercial corn varieties. This study seeks to evaluate the antioxidant and antibacterial potential of 36 samples of native corn germplasm from the Brunca (BR) and Chorotega (CR) regions of Costa Rica. The main parameters of comparison were the composition of antioxidant compounds, antiradical activity, and microbicidal effect. The total amount of polyphenols in the germplasm (120 mg GAE/100 g d.w.) was not related to the regions from which the samples were obtained. The overall average for antioxidant capacity was 21.20 μmol TE/g d.w. Accessions from the CR region had higher antioxidant capacity. Anthocyanin content was higher in purple accessions and undetectable in white germplasm. Antioxidant capacity was statistically related to polyphenols content (, ). The most promising corn accessions in terms of nutraceutical value came from the CR region.

This study evaluated the antioxidant and antibacterial potential of Passiflora edulis (passion fruit) at three ripening stages—intermediate, ripe, and overripe—to determine the optimal consumption time based on the presence of secondary metabolites (polyphenols, alkaloids, and anthocyanins). Fruits from Costa Rica, including pulp and peel, were analyzed. Qualitative assays (Dragendorff, Mayer, Lieberman Burchard, Ferric Chloride, and Shinoda) and quantitative analyses using Folin–Ciocalteu (total polyphenols), ORAC (antioxidant activity), and Kirby–Bauer (antibacterial activity) methods were conducted. Acetone–water (7:3) was the most effective solvent, with three extractions yielding optimal results. Peels contained significantly higher polyphenols (7.2 ± 0.1 mg GAE/g d.w.) and antioxidant activity (2403 ± 519 µmol TE/g d.w.) than pulps. Anthocyanins were abundant in both, while antibacterial activity was more effective in peels, inhibiting Gram-positive bacteria with 25% relative inhibition, but showing no activity against Gram-negative strains. These findings highlight passion fruit peel as a rich source of bioactive compounds with strong antioxidant and antibacterial properties, particularly in intermediate and overripe stages, supporting its potential use in the development of functional ingredients for nutraceutical applications and promoting sustainable waste management.

Coffee wastes have large amounts of by-products rich in phenolic compounds such as chlorogenic and caffeic acid, with potential applications for developing fine chemicals such as caffeic acid phenethyl ester (CAPE). A screening for microorganisms was undertaken in a coffee plantation environment to isolate native tropical species able to modify secondary metabolites present in this kind of biomass enzymatically. From the screening, 130 fungal strains could grow in lipase inducer media. Fungal strains were identified via ITS-based sequencing. Classification based on BLAST assigned 51 isolates to 12 different genera, including Absidia, Aspergillus, Cunninghamella, Fusarium, Metarhizium, Meyerozyma, Mucor, Neocosmospora, Papiliotrema, Penicillium, Rhizopus, and Trichoderma. DNA sequencing identified 14 putative extracellular lipases. According to the extracellular lipase activity, the most promising strain was identified as Fusarium sp. by DNA barcoding. Extracellular lipases from this strain exhibited maximal hydrolytic activity at a temperature of 45 °C, a pH of 7.00, and 200 ppm of NaCl, with an affinity towards substrates having carbon chain lengths of 8 or longer. Under these conditions, lipase instead of esterase activity is the main feature. The Km and Vmax values calculated using p-nitrophenyl palmitate (pNPP) as hydrolysis substrate were 0.003 mM and 299.8 μmol min⁻¹ mg⁻¹, respectively. Fusarium sp. lipases presented high stability during freeze–thawing, allowing the storage of enzyme solutions at −20 °C, but not as a lyophilized powder. According to our kinetic study, these lipases catalyzed CAPE hydrolysis, showing a progressive decrease in the concentration of the CAPE and a correspondent increase in the caffeic acid concentration as a product of this hydrolysis. Being able to carry out this type of reaction under mild conditions shows that Fusarium sp. lipases recognize CAPE as substrate and suggest CAPE synthesis (reverse reaction) and transformation can be engineered, using caffeic acid from coffee biomass, as a potential industrial application for these lipases.

[Objective] From 1988 to 2018, high school students in Costa Rica had to pass a final exam to graduate from high school and be eligible for public university education. In this context, students had to choose a national science test from the areas of physics, chemistry, and biology. Historically, chemistry was the least chosen (4-6 %) of those sciences. On the other hand, there is a need -at the national level- to increase interest in careers related to STEM (Sciences, technology, engineering, and mathematics). [Methodology] Under both premises, in 2016, the first national camp (called Quimi Camp) to promote scientific vocations was held to encourage high school students in Costa Rica to choose chemistry. Quimi Camp is an event supported by the OLCOQUIM National Chemistry Olympiad and the OLCOCI National Science Olympiad, which are in turn organized by the five Costa Rican State universities and the LANOTEC CENAT National Nanotechnology Laboratory at the National Center of High Technology, with the consent of the Ministry of Education (MEP) and the Ministry of Science, Innovation, Technology and Telecommunication (MICITT). The participating students made the final evaluation of this event. [Results] The results showed an excellent perception of the event regarding its organization and content. [Conclusions] Quimi Camp promoted students' vocation for science and engineering and positively influenced the selection of a University Career in STEM.

[Objective] This study aimed to determine whether there is an optimal harvest time for cephaeline, emetine, and total alkaloids in Ipecac (Carapichea ipecacuanha [Brot.] L. Andersson) production. In addition, the relationship between antibiotic activity and harvest time was tested. Ipeca is an herb with medicinal properties that is grown in northern Costa Rica. The root of this plant is valued based on its alkaloid concentration, which underlies its numerous biological activities. [Methodology] Two Ipecac fields from northern Costa Rican producers were sampled every ~2 months for one year. Samples were dried (via sun and oven), ground, extracted, and analyzed using HPLC and titration to evaluate the alkaloid concentration. Antimicrobial activity was also determined using the Kirby-Bauer test. [Results] Main findings revealed that there is no significant difference between oven-dried and sun-dried samples. In addition, there is an increase in total alkaloid production in roots during the first 16 months, as well as a variation in alkaloid composition: the cephaeline/emetine ratio increases after 16 months. [Conclusions] The highest alkaloid concentration occurs when plants are harvested between 16 and 19 months old. Additionally, the antibiotic activity reaches its maximum at 16 months, and the cephaeline/emetine ratio is two at the same harvest time.