Aktivitas antioksidan rumput laut coklat (Sargassu echinocarpum) sebagai pencegah disfungsi sel endotelium aorta tikus diabetes Melitus

Abstract

Diabetes mellitus may cause oxidative stress. Chronic oxidative stress initiates the dysfunction of endothelium cell. Polyphenols are believed to have ability to prevent the dysfunction of endothelium cell. Marine brown algae contain polyphenol which is probably has good antioxidant activity. The aims of this study were to obtain the antioxidant activity and structure of phlorotannin, the lethal dose, the anti oxidative stress, and the anti endothelium cell dysfunction of Sargassum echinocarpum extract. The Sargassum echinocarpum was collected in April 2008 from the coastline of Talango island in Sumenep District of East Java, Indonesia and authenticated by the botanist, Research Centre of Oceanography, Indonesian Institute of Sciences. The antioxidant activity was assayed with DPPH radicals, the structure elucidation was assessed with spectroscopic methods, the lethal dose was investigated on mice, and the anti oxidative stress and the anti endothelium cell dysfunction were evaluated in diabetic rats. The experimental animals were divided into 5 groups, i.e.: (1) normal, (2) diabetic treated with 0, (3) 150, (4) 300, and (5) 450 mg/kg body weight of Sargassum echinocarpum extract, respectively. Extracts were administered by oral gavages for 12 weeks. Diabetes was induced by single administration of streptozotocin (45 mg/kg, i.p.). Diabetes was confirmed ten days later in streptozotocin induced animals with blood glucose levels > 200 mg/dL. After the treatment period, the blood serum acquired was used for antioxidant enzymes assays while the thoracic aorta was used for vasodilatation assay. The result showed that the phlorotannin content of Sargassum echinocarpum extract was 4.25 - 12.16 equivalent of mg phloroglucinol/g extract. The strongest antioxidant activity obtained from the methanol extract of Sargassum echinocarpum, i.e. 67.77 %. The methanol extract of Sargassum echinocarpum contained phloroglucinol and bifuhalol. The methanol extract of Sargassum echinocarpum was relatively non-toxic. The mice treated with 1250 mg/kg or more methanol extract of Sargassum echinocarpum showed inhibition of body weight and necrosis on hepatocyte and tubules of kidney. It was affected by inhibition activity of gastrointestinal enzymes and initiation lipid peroxidation. The diabetic rats revealed the oxidative stress; meanwhile, the diabetic rats treated with 450 mg/kg extract showed the mild oxidative stress. It was caused by free radical scavenging and induction of antioxidant defense activity by extract. The diabetic rats exhibited the endothelial dysfunction; meanwhile, the diabetic rats treated with 450 mg/kg extract showed the mild endothelial dysfunction. It appeared that Sargassum echinocarpum extract has the capability to preserve bioavailability of nitric oxide and protect the muscarinic receptor and endothelium cell against free radical damage.

Petanda awal terjadinya penyulit pada diabetes adalah didapatnya disfungsi sel endotelium. Tingginya kadar radikal bebas pada diabetes dapat mengakibatkan sel endotelium pembuluh darah menjadi lebih permeabel, adesif dan kontraktif. Pencegahan disfungsi sel endotelium pada diabetes dapat dilakukan dengan mengonsumsi antioksidan seperti vitamin C, E, dan polifenol. Antioksidan ini dapat mencegah disfungsi sel endotelium karena berkemampuan menurunkan radikal bebas dalam tubuh. Florotanin adalah polifenol yang terkandung dalam rumput laut coklat. Tujuan penelitian ini adalah mendapatkan aktivitas antioksidan, struktur florotanin, dosis kematian, anti stres oksidatif, dan anti disfungsi sel endotelium aorta tikus diabetes melitus ekstrak rumput laut coklat (Sargassum echinocarpum). Sargassum echinocarpum diperoleh April 2008 dari perairan pulau Talango, kabupaten Sumenep, Jawa Timur. Rumput laut coklat telah diidentifikasi oleh botanis Pusat Penelitian Oseanografi, Lembaga Ilmu Pengetahuan Indonesia. Rumput laut selanjutnya dikeringkan, ditepungkan, dimaserasi, dipekatkan dan dikering bekukan untuk mendapatkan ekstrak. Tepung rumput laut dimaserasi etanol p.a., metanol p.a., aseton 70%, etanol 80%, metanol 80% dan akuades. Kadar florotanin ekstrak ditentukan dengan spektrofotometer dan menggunakan floroglusinol sebagai standar. Uji aktivitas antioksidan ekstrak dilakukan dengan metode diphenyl picrylhydracyl (DPPH). Identifikasi struktur senyawa aktif dalam ekstrak beraktivitas antioksidan terkuat dilakukan secara spektroskopik yaitu ultra ungu, infra merah, dan spektra massa.