Judul: Pengaruh Fraksionasi pada Aktivitas Antioksidan Ekstrak Kulit Buah Langsat (Lansium domesticum)
Abstrak: Langsat (Lansium domesticum) fruit’s peel has been reported to have antioxidant activity but the active compound has yet to be verified. The study objectives were to evaluate antioxidant activities from the crude extract of langsat fruit’s peel and its fractions. The crude extract was obtained through maceration method in 70% ethanol and ethyl acetate. The antioxidant activity was tested by 2,2-diphenyl-1-picrilhydrazil method. The extract with the best activity was further fractionated with the best eluent obtained. The best antioxidant activity was showed by crude 70% ethanol extract with 50% inhibition concentration (IC50) value of 372.90 ppm. The phytochemical compounds in the extract were tannins, flavonoids, alkaloids, and saponins. The fractionation was done by using column chromatography via step gradient elution with at combination of n-hexana and ethyl acetate with increasing polarity giving. 12 fractions which were further tested for their antioxidant activities. However, all fractions did not have antioxidant activities as the inhibition percentage were below 50%.
Keyword: Lansium domesticum, phytochemicals, fractionation, antioxidant

Judul: Potensi Kulit Buah Langsat (Lansium domesticum) sebagai Antibakteri
Abstrak: The fruit peels of langsat (Lansium domesticum) have antibacterial activities. However, the active compounds responsible for the activities have not been studied. Therefore, this research was aimed to determine the metabolite compounds with antibacterial activity in the fruit peel of langsat. Some samples was macerated using ethanol 70% and further fractionated using column chromatography with gradient elution from non-polar to polar solvent. Antibacterial activity was tested to Staphylococcus aureus using dilution method. Antibacterial test results showed that the most active extracts was ethanol 70% extract with minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of 1.00 mg/mL. Fractionation using hexane:ethyl acetate gave 12 fractions and 9 fractions for ethyl acetate:methanol. The most active fraction was F29 with MIC and MBC of 0.5 mg/mL and 2.00 mg/mL, respectively. Based on identification using Fourier transform infrared spectrophotometers, the predicted active compound was flavonoids.
Keyword: fruit peels langsat, fraction, flavonoid, antibacterial

Judul: Mempelajari Model Rancangan Hidrolika Sub Unit Irigasi Curah dengan Tekanan Rendah
Abstrak: Faktor penting dalam keberhasilan penerapan sistem irigasi curah adalah perancangan yang tepat dan efisiensi operasional dari sistem yang dirancang. Desain irigasi curah dilakukan dengan beberapa tahapan. Perhitungan rancangan hidrolika sub unit merupakan tahapan kunci dalam proses desain irigasi curah. Persyaratan hidrolika jaringan perpipaan harus dipenuhi untuk mendapatkan penyiraman yang seragam. Jumlah dan spesifikasi sprinkler (pencurah) maupun jenis dan diameter pipa yang beredar di pasaran sangat beragam. Tahapan rancangan hidrolika sub unit biasa dilakukan dengan metoda coba-ralat (trial-error method). Hal ini cukup rumit dan membutuhkan waktu yang tidak sedikit. Maka dibutuhkan suatu metoda perhitungan rancangan hidrolika sub unit yang sederhana sehingga memudahkan dan meminimalkan kesalahan dalam perancangan irigasi curah.
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