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Undergraduate Theses

Permanent URI for this collectionhttps://hdl.handle.net/20.500.14583/13

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2018 - 20193

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Committee Chair: search.filters.chair.Ortillo, Danilo O.Committee Member: search.filters.committeemember.Martizano, Jay O.

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    Spontaneous formation of silver nanoparticles in humid acid-rich water of Santa Barbara, Iloilo
    Cadelina, Mary Dored Ann D. (Department of Chemistry, College of Arts and Sciences, University of the Philippines Visayas, 2018-06)
    Humic acid (HA) - rich water of Sta. Barbara, Iloilo is successful in acting as a reducing and capping agent in the synthesis of silver nanoparticles (AgNPs). UV-Visible spectroscopy was used to determine the effect of irradiation time, varying HA and AgNO3 concentration, and electrolyte addition. Furthermore, the bactericidal efficacy of AgNPs was evaluated using broth microdilution method. Measurement of AgNPs was done using transmission electron microscopy (TEM). Lower irradiation time (10- 40 min) shows an increasing absorbance trend. However, absorbance decreased and showed bathochromic shifts when irradiated at longer times (50-60 min). AgNP formulations of 40 ppm HA with 4 mM AgNO3 and 50 ppm HA with 4 mM AgNO3 showed the highest peak intensity for varying AgNO3 and HA concentration, respectively. These results were found in both irradiated and un-irradiated samples. Aggregation occurred upon the addition of 50 mM, 100 mM, and 500 mM NaCl but was more prominent at 500 mM NaCl. Dialyzed and un-dialyzed AgNPs have bactericidal activity. However, un-dialyzed AgNP was a more effective treatment because it showed a bactericidal activity up to 1:16 dilution for both Staphylococcus aureus and Escherichia coli as compared to the dialyzed AgNPs which showed a bactericidal activity up to 1:4 for S. aureus and 1:8 for E. coli. The dialyzed AgNPs are polydispersed but were mostly small with sizes less than 10 nm based on the TEM image.
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    Antifungal activities of lemongrass (Cymbopogon citratus) essential oil -B-cyclodextrin inclusion complex incorporated in commercial fish feeds
    Baure, Jiaren G. (Department of Chemistry, College of Arts and Sciences, University of the Philippines Visayas, 2019-06)
    During the wet season in the Philippines, fish feeds can be contaminated with mycotoxins, affecting fish production. The addition of essential oil (EO) is one of the ways to prevent this, but it is prone to physical and chemical reactions. Thus, this study aims to encapsulate lemongrass essential oil (LGEO) in B-cyclodextrin (B-CD) to produce an inclusion complex (IC) that can be used as an additive in commercial tilapia feeds to prevent or minimize fungal contamination. The inclusion complex was made using the co-precipitation method and was characterized by Fourier Transform Infrared (FTIR) Spectroscopy. The spectrum was similar to that of citral, a major component of lemongrass essential oil that is responsible for inhibiting fungi. The antifungal activities of pure and encapsulated LGEO at varying concentrations against Aspergillus species were carried out by the Agar Well Diffusion assay. Results showed that A. flavus was more susceptible in LGEO and IC compared with A. fumigatus. The tested concentration of EO could inhibit both fungi. However, it would take 50% IC to effectively inhibit the growth of both fungi. The stability of the inclusion complex in commercial fish feeds was also evaluated. The feeds were stored in an area with the appropriate conditions that could promote the growth of molds, such as temperature (>27°C), moisture levels (14%), and relative humidity levels (>70%). The results showed that the encapsulated LGEO was effective in extending the shelf life of the feeds and was best observed at a concentration of 5 g kg-1 IC. The oil remained active for nine days, wherein about 10- 40% of the feeds with 5 g kg-1 IC were covered with molds. On the other hand, about 70-100% of the surface of the feeds with essential oil was contaminated with molds after nine days, which indicated that encapsulation of EO was needed to maintain its effectiveness as an antifungal agent.
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    Determination of the concentration of essential minerals (Ca, Fe, K, Mg, Na, Zn) in honey samples from Negros Occidental
    Arellano, Lory Mae F. (Department of Chemistry, College of Arts and Sciences, University of the Philippines Visayas, 2018-06)
    Honey is a natural, sweet and highly nutritional substance produced by bees through a series of nectar collection and chemical processes. Due to the popularity of the product, certain regions in the Philippines has been producing honey and recently, different apiaries from Negros Occidental has been producing its own share of popular product in the market. The products are well received by the consumers, but the problem is the lack of characterization which gives the product doubtful and unconfirmed nutritional value. This study focuses on the quantification of essential minerals (Ca, Fe, K, Mg, Na, Zn) present in local honey samples from Negros Occidental. Eight honey samples were obtained from the different apiaries including an external sample from Mindoro. Samples were acid digested using HNO3/H2O2 solution at 130 °C. The concentration of each minerals in the honey samples were analyzed using AAS. The data reported high concentration (5.71 to 93.20 ppm) of K on most of the samples. The second most abundant mineral in the local honey is Ca ranging from 13.67 to 45.88 ppm. The Mg concentration ranges from 1.19 to 4.09 ppm while Na is in between 0.82 to 3.14 ppm. The mineral Zn and Fe contained the lowest concentration in most of the samples with Zn at 0.46 to 0.86 ppm and Fe at 0.04 to 0.30 ppm.