Judul: Aktivitas antioksidan dan kandungan kimiawi ekstrak daun wungu (Graptophyllum pictum L. Griff.)
Abstrak: Graptophyllum pictum L. Griff., a plant that originated from Papua and Polynesia, is believed to have antioxidant activity. This study aimed to examine of antioxidant activity and chemical content of Graptophyllum pictum L. Griff. leaves. Also, it was designed to determine the best extracting solvent that provides the highest antioxidant activity. This study used four different solvents, which were the solvent water, ethanol 30%, ethanol 70%, and ethanol 96%. Extracts of each solvent were studied to determine the presence or absence of the antioxidant activity and chemical content by using vitamin C as a comparison. The antioxidant activity of water extract, ethanol 30%, ethanol 70%, and ethanol 96% extract were determined using the DPPH (2,2 diphenyl-1-picryl-hydrazyl) with a spectrophotometer at a wavelength of 517 nm. Phytochemical test showed that water extract, ethanol 30%, ethanol 70%, and ethanol 96% Graptophyllum pictum L. Griff. leaves contain alkaloids and flavonoids. Ethanol 30% and ethanol 70% extract were contained saponin. Ethanol 70% and ethanol 96% extract contained tannins and steroids. Antioxidants activity test (IC50) of four types of solvents showed that the antioxidant activity is not active on four types of solvent used, but ethanol 70% extract of Graptophyllum pictum L. Griff. leaves has a weak antioxidant activity with IC50 of 257.79 ppm. It can be concluded that water, ethanol 30%, ethanol 96% extract Graptophyllum pictum L. Griff. leaf have no antioxidant activity as measured using the DPPH method.
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Judul: Aktivitas Inhibisi Enzim α-Glukosidase dan Antioksidan dari Ekstrak Etanol Daun Wungu (Graptophyllum pictum (L.) Griff) dan Partisinya
Abstrak: Wungu leaves (Graptophyllum pictum (L.) Griff) is a plant that is widely used in treating a variety of ailments, including diabetes and known to contain phenolic compounds that have antioxidant activity. The purpose of this study was to determine the inhibition of the enzyme α-glucosidase and antioxidant activities of ethanol extracts and fractions of diethyl ether, ethyl acetate, and butanol from wungu leaves (Graptophyllum pictum (L.) Griff) by in vitro studies. Extraction of wungu leaves was done by maceration and the fractination was done through liquid-liquid extraction. Results showed that ethanol extracts and its fraction have no inhibitory activity toward α-glucosidase, but it was potentially as antioxidant through inhibition of radical DPPH. Ethyl acetate fraction (500 ppm) can capture the DPPH radical 74.105% with IC50 values of 68.11 ppm which is the highest antioxidant activity and is followed by the fraction of butanol, ethanol, and diethyl ether.
Keyword: DPPH, wungu leaves, α-glucosidase, antioxidant, antidiabetic

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