Judul: (In Vitro) Inhibition of α-Amylase, α-Glucosidase and Lipase by Roselle (Hibiscus Sabdariffa) Extracts by In Vitro Method
Abstrak: Obesity is caused as the result of an imbalance between energy intake and expenditure. Moreover, obesity is a strong risk factor for various diseases, such as hypertension, arteriosclerosis, diabetes mellitus. The aim of the present study is to evaluate the ability of roselle aqueous extract (RAE) to inhibit porcine pancreas lipase, S. Cerevisiae α-glucosidase, Bacillus. sp α-amylase and porcine pancreas α-amylase activity in vitro. Fresh roselle flower was extracted by aquadest at 70, 85 and 100o C for 15 and 30 minutes. We also analyzed total soluble phenolic content of the extract by the Folin-Ciocalteu reagent and total acidity by titratable acidity methods. The results indicated that RAE without pH treatment had more than 80% inhibitory activity for lipase, α-glucosidase and both α-amylase. Next we treated the pH of RAE similiar to intestinal digestion condition as follow : the pH was reduced to pH 2 for 30 minutes and than increased to pH 6,8. The pH treated RAE had no effect on α-glucosidase and low inhibition on lipase activity but it showed the highest inhibition activity against α-amylase. Kinetic studies revealed uncompetitive inhibition of RAE on α-amylase porcine pancreas. Based on its strong α-amylase inhibitory RAE seems promising to be an anty obesity agent, although needs further study to proof in vivo efficacy.
Keyword: 

Judul: In Vitro Assay of Water and Ethanol Extracts of Asam Gelugur Fruits, Lengkuas, and Kencur Rhizomes as Inhibitor of Pancreatic Lipase Activity.
Abstrak: Asam gelugur fruits of Garcinia oftenly used to reduce body weight. Lengkuas and kencur are traditional herbal that potential as inexpensive and available antiobesity because they had been studied could reduce the level of phospholipids, triglycerides, and cholesterol. This research evaluated the potencies of these herbal as antiobesity by their water and ethanol extracts capabilities in inhibiting pancreatic lipase activity in vitro at pH 8,0, incubation time 45 minutes, and temperature 40°C. This research used human pancreatic lipase (1,4 × 10-5 μg/μL) and sesame oil (16,2 μg/μL) as substrate. The water and ethanol extracts of asam gelugur fruits contained saponins and alkaliods, respectively. The water extract of lengkuas rhizomes contained alkaloids, flavonoids, saponins, dan quinones, while the ethanol extract contained alkaloids, flavonoids, saponins, and steroids. The water extract of kencur rhizomes contained saponins and quinones, while the ethanol extract contained alkaloids, flavonoids, steroids, and quinones. These plants have potencies as antiobesity based on in vitro assay in inhibiting pancreatic lipase activity. The highest inhibitory effect of all extracs was obtained from the ethanol extract of asam gelugur fruits with value of 86,3% at 150 ppm. The highest inhibitory effect of lengkuas extracts was from the ethanol extract at 200 ppm, which was about 56,2%. The highest inhibitory effect of kencur was showed by the ethanol extract with the value 37,6% at 300 ppm. These values were higher than the inhibitory effect of the positive control (Xenical®) at 100 ppm, about 10,6%.
Keyword: 

Judul: Desain Sistem Transfer Energi Nirkabel Berbasiskan Tesla Coil
Abstrak: Tesla coil merupakan alat yang ditemukan oleh Nikola Tesla yang dapat mentransmisikan daya tanpa kabel dengan memanfaatkan prinsip induksi elektromagnetik. Pada penelitian ini dibuat sebuah prototype Tesla Coil dengan menggunakan transistor C1970 dan receiver menggunakan rangkaian LC. Identifikasi alat meliputi pengaruh daya input transmitter terhadap receiver, bentuk signal yang dipancarkan transmitter, pengaruh jarak transmitter dan receiver, nilai efisiensi serta efek alat terhadap perangkat lain. Hasil pengamatan menunjukkan bahwa semakin besar daya input maka semakin besar daya yang dipancarkan oleh transmitter. Bentuk sinyal yang dipancarkan oleh transmitter berupa gelombang listrik AC sinusoidal dengan frekuensi ~2.9 MHz. Semakin jauh jarak receiver terhadap transmitter maka semakin kecil amplitudo gelombang AC yang diterima oleh receiver, menyebabkan semakin kecil daya yang diterima oleh receiver. Adapun nilai efisiensi terbesar penangkapan daya oleh receiver yaitu sebesar 0.00516 % serta terdapat gangguan pada alat-alat tertentu seperti monitor komputer dan radio.
Keyword: rangkaian LC, receiver, tesla coil, transistor C1970, transmitter