Date of Completion

2023

Document Type

Thesis

Degree Name

Bachelor of Science in Biochemistry

Keywords

Aldehyde Dehydrogenase, Carica papaya Linn, Saccharomyces cerevisiae, Disc diffusion assay

Abstract

ALDH enzymes, which catalyze the conversion of aldehydes to carboxylic acids, are overexpressed in cancer stem cells (CSCs) and have thereby been a subject of continued research over the years, most of which involve its inhibition or lessened induction to increase cancer treatment effectivity. Of particular interest are human cytosolic ALDH1 enzymes that aid in the differentiation of CSCs, resulting to cancer relapse. Few eukaryotic organisms share similarity with the ALDH1 of humans, such as Saccharomyces cerevisiae, also known as baker’s yeast, which are 60% similar in terms of cytosolic ALDH enzymes when compared to humans. To this regard, numerous compounds have been synthesized that are either riddled with adverse effects or are too expensive to manufacture and produce at high quantities. This leads to the focus on natural products research which may provide solutions to the aforementioned challenges, such as the utilization of plant leaves which are easily and commercially available like Carica papaya Linn. The study involved the possible inhibitory effects of C. papaya Linn leaf extracts, particularly the ”Sinta” variety indigenous to the Philippines, on the cytosolic ALDH of S. cerevisiae. Extraction of the leaf extracts was done via ethanolic maceration and subsequent solvent evaporation, after which phytochemical testing was done which confirmed the presence of alkaloids, flavonoids, sugars, phenolic compounds, and sterols. Simultaneously, growth of yeast cells on media containing different concentrations of ethanol was done, with which cellular concentration in each media was measured in accordance with McFarland standards using optical densitometry. The results showed a decreasing tendency for yeast cells to grow on media with a higher concentration of ethanol. The crude extracts were then used for qualitative inhibitory tests which measured for the metabolites present within the ethanol metabolism pathway of the cells. Results showed lessened induction of the ALDH enzymes via the lowered quantity of acetic acid found within each media due to the presence of the extracts. Confirmatory test was done via disc diffusion assay where the area of inhibition was measured ranging from 0.283 cm2 to 1.847 cm2 on ethanol-supplemented media, with no measurable inhibitory area found on sugar-based media. This indicated that the acclimated yeast cells grew on sugar-based media, via switch to sugar metabolism, amidst the presence of the extracts, whilst the opposite occurred on ethanol-supplemented media, wherein cells had pure reliance on ethanol metabolism, which produced an antifungal effect due to enzyme inhibition.

First Advisor

Walter Aljohn T. Espiritu

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