Judul: Prenilasi Senyawa β-Diketon sebagai Prekursor 3-Prenilflavon
Abstrak: One group of flavonoids that has not been commonly synthesized is 3- prenylflavone. The main objective of this experiment was to synthesize precursor of 3-prenylflavone. Firstly, β-diketone was synthesized via 4 steps from phenol as starting compound with total yield of 24%. Prenylation of β-diketone with prenyl bromide and K2CO3 base produced 4 fractions which were separated by using preparative thin layer chromatography (PTLC) with n-hexane:EtOAc (8:2) as the eluent. Fraction with Rf = 0.80 was further separated by using preparative PTLC with n-hexane:EtOAc (99:1) as the eluent. Two fractions were obtained with Rf = 0.38 and 0.42. The first fraction has been characterized as diprenylated β-diketone with 49% yield. Application of protecting group on the phenolic OH group in β- diketone are needed to obtain monoprenylated β-diketone which can be further cyclized into 3-prenylflavone
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Judul: In silico Study: The Study Between The Relationship of Prenyl and Antioxidant Activity on Some Flavonoids
Abstrak: Flavon dan flavonol merupakan contoh senyawa anggota flavonoid yang memiliki beberapa aktivitas biologis, salah satunya aktivitas antioksidan. Pada penelitian ini, perhitungan energi pemutusan ikatan (BDE) dilakukan terhadap 4 contoh golongan senyawa dari masing-masing golongan flavon dan flavonol terprenilasi. Mekanisme antioksidan yang dikaji adalah pemutusan ikatan antar atom oksigen dan hidrogen pada gugus fenolik, baik secara langsung maupun tidak langsung, sehingga perhitungan BDE dan potensial ionisasi (PI) memenuhi asumsi tersebut. Secara keseluruhan, gugus yang menjadi penyebab meningkatnya nilai BDE secara signifikan adalah cincin piran-7OH dengan tambahan prenil. Sementara, keberadaan cincin piran-5OH disertai prenil tambahan pada posisi 8 merupakan penyebab meningkatnya nilai PI secara tajam. Dari 176 contoh senyawa yang telah dihitung, krisin merupakan golongan senyawa yang pada umumnya mengalami peningkatan aktivitas antioksidan setelah terprenilasi (ΔBDE = -1,708 - -27,728 kcal/mol). Penurunan aktivitas antioksidan paling banyak terjadi pada golongan senyawa kuersetin dan kaemferol terprenilasi. Dari hasil penelitian ini, dapat disimpulkan bahwa penambahan gugus prenil secara umum menurunkan aktivitas antioksidan flavon dan flavonol.
Keyword: Bogor Agricultural University, Institut Pertanian Bogor, IPB, antioxidant, BDE value, prenyl, radical position, Flacon, Nilai BDE, Posisi radikal

Judul: Characteristic of Overshooting Top (OT) Based on  Himawari  8  Satellite  as  a  Convective  Cloud  Feature  that  Generates  Extreme Weather in the Java Island Region
Abstrak: Overshooting Top (OT) is a feature at the top of a convective cloud that is associated with extreme weather. Research on OT in tropical Indonesia is still very limited. The existence of geostationary satellites with wide area coverage and fast frequency observations is useful for observing the fast dynamics of the OT life cycle. Therefore, this study intends to analyze the relationship between OT and extreme weather, updraft and thermodynamic conditions of OT when extreme weather occurs, the best objective method for detecting OT in the day time and night time, and the spatiotemporal distribution of OT in the tropical region of Java Island during the 2018-2021 period. Based on visual analysis using visible channel and Himawari 8 sandwich products, 87% of extreme weather events in Java were accompanied by the appearance of OT. It indicates that the presence of the OT pattern is a convection cloud pattern or feature that is closely related to extreme weather events for the Java Island region. The existence of a time lag between the appearance of OT and extreme weather events on Java Island indicates that the OT of convection cloud can be used as a precursor or nowcasting for the appearance of extreme weather. Most of the convective cloud OT features during extreme weather events on Java Island have altitude that were only able to exceed the altitude of the equilibrium level and few were able to exceed the tropopause level of 9 km – 16 km. The difference in atmospheric conditions during extreme weather events on Java Island, which is in the tropics and subtropics, is a strong and unstable convective energy condition characterized by a larger CAPE, as well as unstable KI, LI, SI and TTI values. It is offset by kinematic factors in the form of a weak vertical wind shear (bulk wind shear 0-6 km) and a higher freezing point height. The difference between extreme weather events in the Java Island region and other tropical regions compared to subtropical regions is the strong updraft speed of convection clouds. The IRW Texture COMB algorithm based on the IRW-Texture Gradient modification and the COMB algorithm shows a significant increase in quality for detecting OT and non-OT pixels in Java. Rainy days with rainfall > 50 mm/day are very common in areas with an altitude of > 500 m. On the other hand, the level of convection activity which is indicated by the presence of OT and lightning is significantly reduced in this area. OT of convective clouds appear more frequently during the DJF season and less frequently during the JJA season. OT often appears during the day time and rarely at night time. Most OTs appear in the central part, away from the south and north coasts of Java Island during the day, while OTs that appear near the south and north coasts of Java Island can appear in the morning or afternoon.
Keyword: convective clouds, extreme weather, Overshooting Tops, Himawari 8 Satellite