Judul: Dugaan Golongan Senyawa Toksik Fraksi Aktif Etil Asetat Karang Lunak Dendronephthya Asal Lampung
Abstrak: Dendronephthya merupakan salah satu karang lunak yang tumbuh subur di wilayah pesisir Indonesia. Penelitian ini bertujuan menentukan fraksi paling toksik serta mengidentifikasi dugaan golongan senyawa aktif yang terkandung dalam ekstrak Dendronephthya. Sampel dimaserasi dengan pelarut metanol, kemudian residunya di maserasi kembali dengan pelarut n-heksana. Ekstrak metanol dipartisi cair-cair dengan pelarut etil asetat. Toksisitas ekstrak diujikan dengan metode uji letalitas larva udang. Ekstrak etil asetat memiliki toksisitas paling tinggi dengan LC50 sebesar 333 g/mL. Ekstrak ini kemudian difraksionasi lebih lanjut dengan kromatografi lapis tipis preparatif dan menghasilkan 3 fraksi. Fraksi 3 memiliki toksisitas paling tinggi dengan LC50 77 g/mL. Hasil uji fitokimia dan spektrum inframerah menunjukkan pada ekstrak etil asetat Dendronephthya diduga mengandung steroid, flavonoid, dan fenolik pada fraksi tersebut.
Keyword: Dendronephthya sp, flavonoids, Phenolic, Steroids, Toxicity, Fraksi paling toksis, Fitokimia eksrak, Toksisitas eksrak, Toksisitas fraksi, Komponen kimia

Judul: Uji Toksisitas Ekstrak Etil Asetat Teraktif Daun Dandang Gendis (Clinacanthus nutans) Menggunakan Uji Letalitas Larva Udang
Abstrak: Dandang gendis (Clinacanthus nutans) is a medical herb commonly used as a traditional medicine as antimalarial and antidiabetic. This study was started with maceration of the dried leaves of dandang gendis with ethanol,and then partitioned using n-hexane. The ethanol extract free of nonpolar compounds was then partitioned with ethyl acetate. The ethanol crude extract, n-hexane fraction, and ethyl acetate fraction were tested by using brine shrimp lethality test to determine the toxicity of each extract. The ethyl acetate fraction showed the highest activity with 50% lethal concentration (LC50) of 32 mg/L. Re-extraction of ethanol extract free of nonpolar compounds by using ethyl acetate in 90 minutes by three times extraction with material:solvent ratio of 1:2 resulted LC50 value of 29.02 mg/L. Phytochemical assay results showed that the ethyl acetate extract of dandang gendis leaves contained saponins, alkaloids, steroids, and flavonoids. Re-extraction of ethyl acetate extract contained higher flavonoids than ethyl acetate extract from the first extraction.
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Judul: A Continuous Vaccination Strategy in the SVIR Epidemic Model
Abstrak: Vaccination is conducted to minimize the spread of a disease. The vaccination is usually done several times within a fixed time interval. In the SVIR model, it is assumed that individuals do not get immediate immunity following a vaccination program. So according to process of vaccination on SVIR model, there are two strategies, i.e. the continuous vaccination strategy (CVS) and the pulse vaccination strategy (PVS). In this study, only the CVS strategy in epidemic model SVIR is considered. Results of the study indicate that dynamics of the CVS system depends on the basic reproductive number. If the basic reproductive number is less than one, then the disease-free fixed point is asymptotically stable. It means that the disease will eventually disappear from the population. Conversely, if the basic reproductive number is greater than one, then the endemic fixed point is asymptotically stable, which means that the disease will remain exist in the population. Simulation result shows that the vaccination would minimize the spread of disease by reducing the basic reproductive number. If the time for the vaccinated recipients to obtain the immunity, as well as a possibility of vaccinated recipients to be infected are neglected, then the disease will be eradicated. This condition is called an over-evaluating effect of vaccination.
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