Judul: Daun Ki Pahit (Tithonia diversifolia) sebagai Sumber Antibakteri dan Antioksidan
Abstrak: Antibacterial and antioxidant analysis have been assayed on extracts and essential oil of ki pahit leaves (Tithonia diversifolia). The antibacterial activity was tested toward Staphylococcus aureus and S. epidermidis, and the antioxidant activity was assayed toward 1,1-diphenyl-2-picryl hydrazyl (DPPH). The most active extract was the residual methanol extract with minimum inhibitory concentration (MIC) values against S. aureus and S. epidermidis were 1.00 and 2.00 mg/mL, respectively, the minimum bactericidal concentration (MBC) value >2.00 mg/mL, and the inhibition of 50% DPPH, IC50 was 27.88 μg/mL. The residual methanol extract was fractionated using column chromatography to obtain 13 fractions. F1 was the most active fraction with MIC values against S. aureus and S. epidermidis with 0.25 and 1.00 mg/L and MBC values were 0.50 and 2.00 mg/mL, respectively. The IC50 of the antioxidant was 22.88 μg/mL. The F1 fraction was further fractionated by thin layer chromatography to obtain 11 fractions. The F1.2 fraction was the most active fraction as indicated by inhibition the growth of S. aureus and S. epidermidis that of 0.25 and 0.50 mg/mL and indicated by killing the bacteria that of 0.50 and 2.00 mg/ml, respectively, and 50% DPPH that could inhibit was 30.94 μg/mL. Based on identification using ultraviolet-visible and fourier transform infrared spectrophotometers, the active compound was indicated to be in auron group.
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Judul: Kajian Aktivitas Antibakteri Daun Gatel (Laportea decumana (Roxb.) Wedd.) dan Daun Benalu Cengkeh
Abstrak: Many researches showed that several plants have a good antibacterial activity. The leaves of gatel and clove mistletoe are empirically used to cure several diseases. The aims of this research were: (1) to study the potential of antibacterial activity of gatel and clove mistletoe hexane, ethyl acetate and methanol extracts against Bacillus cereus, Staphylococcus aureus, Escherichia coli, Salmonella typhimurium and Pseudomonas aeruginosa by the well diffusion method; (2) to calculate the minimum inhibitory concentration (MIC) value of the potential extracts; and (3) to study the effect of various pH to antibacterial activity of the extracts. The results showed ethyl acetate and methanol extracts of the studied plants have low antibacterial activity against B. cereus and E. coli. Based on the MIC values, the ethyl acetate extract of gatel leaves showed over 99% percent inhibition against E. coli at a concentration of 3.5%, 4.0%, 4.5% and 5.0%. The same result was obtained by modifying the pH (4, 5 and 6) at the extracts concentration of 5% and 10%. The methanol extract of gatel leaves showed below 60% inhibition of B. cereus at a concentration of extract 4.0%, 4.5%, 5.0%, 5.5% and 6.0%, and more than 90% inhibition at the pH. The ethyl acetate extract of clove mistletoe showed more than 98% inhibition againts E. coli at a concentration of 3.5%, 4.0%, 4.5% and 5.0% and at pH 4, 5 and 6. Percent of inhibition less than 50% occured in the methanol extract of clove mistletoe at 4.0%, 4.5%, 5.0%, 5.5% and 6.0% concentration against B. cereus. For the methanol extract of clove mistletoe, the effect of pH variation (4, 5, 6 and 7) resulted in 92%-97% inhibition. The result may increase the utilization of research plant not only for health purposes but also as a natural food preservative and open new possibilities for the development of natural functional foods.
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Judul: Selang kepercayaan untuk koefisien B1 dari garis regresi apabila ragam galat tidak homogen dengan metode ols, wls dan bootstrap
Abstrak: Slope estimation of a regression line and its confidence interval can be constructed by OLS (Ordinary Least Squares) and WLS (Weighted Least Squares) method. Confidence interval being found by both method must satisfy assumption about normality of error term with zero mean and common variance for OLS method and heteroscedasticity for WLS method and independency of error term. NC (Nanayakkara and Cressie) method is a method aimed to reduce variance of estimate resulted from OLS method when error term has non- constant variance.
Keyword: Percentite-bootstrap, Ordinary Least Squares, Weighted Least Squares