Judul: Fractionation of Antimicrobial Peptide Candidates from Gandarusa  (Justicia gendarussa) Leaves
Abstrak: Peptida antimikroba adalah senyawa yang ditemukan pada organisme hidup dan berfungsi sebagai komponen penting dalam sistem pertahanan tubuh. Keunggulan peptida antimikroba adalah memiliki sprektum luas membunuh bakteri patogen dan bakteri yang resistan. Daun gandarusa (Justicia gendarussa Burm. F.) memiliki aktivitas antibakteri namun kajian terkait peptida antimikroba pada tanaman tersebut masih terbatas. Penelitian ini bertujuan untuk memfraksinasi peptida antimikroba dari daun gandarusa serta menguji aktivitas antimikrobanya. Ekstraksi peptida daun gandarusa menggunakan pelarut asam asetat 10% dan waktu ekstraksi 2 jam. Kadar total protein diukur dengan metode Bradford, identifikasi kandidat peptida antimikroba dilakukan dengan metode SDS-PAGE, dan pengujian aktivitas antibakteri dilakukan dengan metode difusi sumuran. Hasil penelitian menunjukkan sampel optimum ekstraksi terhadap bobot molekul dan kadar protein daun gandarusa adalah sampel 100 mesh dengan sonikasi. Identifikasidengan SDS-PAGE menunjukkan peptida antimikroba dari daun gandarusa memiliki berat molekul berkisar 10-12 kDa. Uji aktivitas antibakteri Fraksi peptida daun gandarusa terhadap Escherichia coli dan Propionibacterium acnes tidak menunjukkan adanya daya hambat., Antimicrobial peptides are compounds found in living organisms that function as crucial components of the body's defense system. The advantage of antimicrobial peptides lies in their broad spectrum of activity, capable of killing pathogenic bacteria and antibiotic-resistant bacteria. Justicia gendarussa Burm. F. leaves are known to have antibacterial activity; however, research on antimicrobial peptides from this plant is still limited. This study aims to isolate and fractionate antimicrobial peptides from Justicia gendarussa leaves and evaluate their antimicrobial activity. The extraction of peptides from Justicia gendarussa leaves was performed using 10% acetic acid solvent with an extraction time of 2 hours. The total protein content was measured using the Bradford method, antimicrobial peptide candidates were identified using SDS-PAGE, and antibacterial activity was tested using the well diffusion method. The results showed that the optimal sample for extraction, in terms of molecular weight and protein content, was 100 mesh with sonication. Identification with SDS-PAGE indicated that the antimicrobial peptides from Justicia gendarussa leaves have a molecular weight ranging from 10-12 kDa. However, the antibacterial activity test of the peptites fraction of Justicia gendarussa leaves against Escherichia coli and Propionibacterium acnes did not show any inhibitory effect.
Keyword: antibakteri, Justicia gendarussa, peptida antimikroba, dialisis, SDS-PAGE

Judul: Purification of Gendarusa Antioxidant  Compound (Justicia gendarussa Burm. f.) by Column Chromatography Method
Abstrak: Gandarusa (Justicia gendarussa Burm. f.) merupakan salah satu tanaman yang berpotensi sebagai sumber antioksidan karena kandungan metabolit sekundernya. Gandarusa termasuk ke dalam tanaman liar dan sudah lama dimanfaatkan sebagai tanaman obat. Penelitian ini bertujuan menentukan aktivitas antioksidan dengan metode DPPH hasil purifikasi ekstrak gandarusa menggunakan kromatografi kolom. Metode penelitian ini terdiri atas ekstraksi dengan maserasi bertingkat, optimasi pelarut dengan Kromatografi Lapis Tipis (KLT), purifikasi dengan kromatografi kolom, dan analisis antioksidan kualitatif dengan metode KLT bioautografi dan kuantitatif dengan metode DPPH. Pelarut n-heksana:etil asetat (6:4) dapat memisahkan ekstrak gandarusa dengan baik. Hasil purifikasi dengan kromatografi kolom menghasilkan 8 fraksi. Fraksi 3.2 memiliki aktivitas antioksidan tertinggi dengan nilai IC50 sebesar 617,34 µg/mL, sedangkan ekstrak kasarnya sebesar 2551,30 µg/mL. Purifikasi gandarusa dengan kromatografi kolom menghasilkan fraksi dengan aktivitas antioksidan lebih kuat dibandingkan dengan kondisi campurannya (ekstrak kasar)., Gandarusa (Justicia gendarussa Burm. f.) is a plant with potential as an antioxidant source due to its secondary metabolite content. Gandarusa is considered a wild plant and has long been used as a medicinal plant. This research aimed to determine the antioxidant activity using the DPPH method of purified gandarusa extract obtained through column chromatography. The research methods include extraction through stepwise maceration, solvent optimization using Thin Layer Chromatography (TLC), purification with column chromatography, and qualitative antioxidant analysis using TLC bioautography and quantitative analysis using the DPPH method. The n-hexane:acetate (6:4) solvent can effectively separate gandarusa extract. The purification results from column chromatography produced 8 fractions. Fraction 3.2 exhibited the highest antioxidant activity with an IC50 value of 617.34 µg/mL, while the crude extract had an IC50 value of 2551.30 µg/mL. Purification of gandarusa using column chromatography yielded fractions with stronger antioxidant activity compared to the mixed state (crude extract).
Keyword: antioxidant, column chromatography, gendarussa, purification, TLC

Judul: Bifurkasi Hopf pada Model Siklus Bisnis Kaldor Kalecki tanpa dan dengan Waktu Tunda
Abstrak: Business cycle model is one of dynamical system models in economic. One of the business cycles model is Kaldor-Kalecki model. Kaldor-Kalecki business cycle model that is written in delayed defferential equations, is a business cycle model that involves gross product and capital stock of a company. In this paper Kaldor-Kalecki business cycle model is analyzed using both nondelay and delay in time of capital stock. By Taylor expansion for the time delayed model, an analysis of stability around the fixed points has been done. Furthermore, by using Hopf bifurcation theorem, it can be shown that there exists periodic orbits and limit cycle. In the nondelayed model, changing the parameter of goods market could lead to the occurrence of Hopf bifurcation and the existence of limit cycle. Similarly, for the delayed model, it has been shown that changing the time delay parameter may result in the occurrence of Hopf bifurcation and limit cycle.
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