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    In vitro antibacterial activity of Hibiscus rosa sinensis leaf extracts against some pathogens associated with urinary tract infections
    Cabayao, Coney B. (Department of Chemistry, College of Arts and Sciences, University of the Philippines Visayas, 2011-04)
    The in vitro antibacterial activity of Hibiscus rosa sinensis leaf ( methanolic, dichloromethane, ethyl acetate, n-hexane, and aqueous ) extracts were studied against Gram-negative (Escherichia coli and Pseudomonas aeruginosa ) and Gram-positive ( Streptococcus faecalis) bacteria. The methanolic extract was subjected to sequential liquid-liquid extraction using solvents of varying polarity and concentrations. Out of the 5 extracts, methanolic and dichloromethane extracts exhibited the highest antibacterial activity as measured using the zone of inhibition. This was followed by ethyl acetate and n-hexane extracts. At 200 mg/ml concentration, all extracts were considered active when tested with E. coli and S. faecalis, and were partially active against P. aeruginosa. The aqueous extract was inactive towards the three bacteria. The 200 mg/ml concentration showed no significant difference when compared with the positive control, amoxicillin (12.51μg/ml). This shows that Hibiscus rosa sinensis exhibits a promising antibacterial activity. Phytochemical analysis of the active fraction- the methanolic extract- showed the presence of alkaloids, tannins, glycosides, saponins, steroids, flavonoids, terpenoids, and anthraquinones. These bioactive components could be responsible for the antibacterial activity of Hibiscus rosa sinensis leaf extracts.
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    Development of a high-performance thin layer chromatography (HPTLC)-densitometric method for the estimation of quercetin and kaempferol in Euphorbia hirta (Tawa-tawa) extract
    Baladjay, Diane Monique S. (Department of Chemistry, College of Arts and Sciences, University of the Philippines Visayas, 2017-06)
    A sensitive, fast, efficient, and repeatable high-performance thin-layer chromatographic (HPTLC) method has been developed for simultaneous analysis of quercetin and kaempferol from the extracts of the aerial parts of Euphorbia hirta. In the development of the HPTLC method, different extraction parameters were evaluated and quantification of quercetin and kaempferol in the extract of E.hirta was performed using a densitometric software, Quantiscan™. Among the different combinations of mobile phases used, best separation was achieved in toluene: ethyl acetate: formic acid: methanol (5: 6: 2: 1) solvent system. E.hirta was extracted using the developed extraction method which involves the use of 80% ethanol, 8 minutes of sonication and serial extraction until 3rd extraction. This determined method provides a maximum yield of the compounds at minimum time and cost. The method was also validated for linearity and precision specifically repeatability. The results show that the produced calibration is linear, as supported by the obtained correlation coefficient (r) of > 0.999 and coefficient of determination (R2) of > 0.997. Moreover, the obtained slopes of the calibration curves show that the method is most sensitive towards quercetin and least sensitive to gallic acid. The method was also found out to be repeatable and precise as the %RSD for both the inter-day and intra-day trials obtained a value less than <2%. The present method is being reported for the first time and can be used for routine quality control and quantification of quercetin and kaempferol in various plant samples, extracts, and market formulations.