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: 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: Dampak QBO terhadap Curah Hujan yang Dipengaruhi oleh MJO di Indonesia.
Abstrak: QBO memiliki hubungan yang kuat dengan MJO di wilayah tropis selama musim dingin di belahan bumi utara (BBU). Frekuensi dan jumlah hari MJO lebih tinggi ketika fase timuran QBO (QBOE) dibanding fase baratannya (QBOW). Meskipun, QBO dan MJO terhubung erat, tetapi dampak QBO terhadap curah hujan belum diketahui. Penelitian ini dilakukan untuk menganalisis dampak fase – fase QBO terhadap curah hujan saat MJO aktif di Indonesia. Fase QBO ditentukan menggunakan anomali kecepatan angin zonal 50 hPa sedangkan fase MJO ditentukan menggunakan real-time multivariate index (RMMI ). Curah hujan dari TRMMv7 digunakan untuk menganalisis dampak QBO terhadap curah hujan MJO. Total kolom uap air, suhu 100 hPa, dan angin vertikal digunakan untuk menganalisis hubungan QBO-MJO terhadap variabilitas curah hujan. Untuk mengisolasi sinyal MJO, digunakan band-pass filter. Aktivitas konveksi MJO yang dianalisis menggunakan outgoing longwave radiation (OLR) menunjukkan amplitudo lebih besar saat QBOE dibanding QBOW. Sejalan dengan hal tersebut, anomali curah hujan harian meningkat (menurun) hingga 3,3 mm/hari (1,8 mm/hari) dan adanya propagasi ke timur yang lebih (kurang) jelas saat QBOE (QBOW). Selain itu, saat QBOE (QBOW) perubahan peluang curah hujan ekstrem meningkat (menurun) hingga 100% (70%) dan tersebar lebih tinggi (rendah) selama fase basah MJO. Suhu tropopause lebih dingin (hangat), distribusi luas (sempit) dari total kolom uap air, dan vertikal adveksi ke atas (ke bawah) teramati terjadi saat QBOE (QBOW). Pengamatan tersebut mengarah pada adanya konveksi skala besar yang lebih kuat (lemah) dan peningkatan (penurunan) intensitas curah hujan dan peluang curah hujan ekstrem.
Keyword: curah hujan, fase baratan QBO, fase timuran QBO, Indonesia, MJO.