Tuesday, November 2, 2010

Aktivitas antioksidan, kandungan fenolik total dan kandungan flavonoid total ekstrak etil asetat buah Mengkudu serta fraksi-fraksinya

Aktivitas antioksidan, kandungan fenolik total dan kandungan flavonoid total ekstrak etil
asetat buah Mengkudu serta fraksi-fraksinya 

Antioxidant activities, total phenolic and flavonoid contents of ethyl acetate extract of Mengkudu (Morinda citrifolia, L) fruit and its fractions*
Abdul Rohman, Sugeng Riyanto dan Diah Utari

Fakultas Farmasi , Universitas Gadjah Mada, Yogyakarta, Indonesia.

* A few parts of data in this paper have been presented on Regional Conference on Pharmaceutical and Biomedical
Analysis in ITB Bandung on 16-17 th September 2005.

Abstrak
Penelitian ini dilakukan untuk menguji aktivitas antioksidan, kandungan fenolik total dan kandungan flavonoid total ekstrak etil asetat buah mengkudu serta fraksi-fraksinya. Ekstrak etil asetat difraksinasi dengan kromatografi kolom dan dihasilkan 15 fraksi berdasarkan pada profil
kromatografi lapis tipis (KLT) yang identik. Aktivitas antioksidan dalam ekstak etil asetat dan fraksi-fraksinya ditentukan dengan uji penangkapan radikal 2,2-difenil-1-pikrilhidrazil (DPPH). Kandungan fenolik total dan flavonoid ditentukan dengan metode spektrofotometri. Di antara 15 fraksi ekstrak etil asetat yang diuji, fraksi 8 (IC50 5,49 μg/mL) dan fraksi 7 (IC50 7,90 μg/mL) mempunyai aktivitas antioksidan yang lebih besar daripada vitamin E (IC50 8,27 μg/mL). Kandungan fenolik total berkisar antara 5,94 ± 0,08 sampai 36,52 ± 0,35 g ekivalen asam galat/100 gram sampel, sementara kandungan flavonoid total berkisar antara 1,19 ± 0,02 sampai 17,65 ± 0,17 g ekivalen kuersetin/100 g sampel. Hubungan antara aktivitas antioksidan ekstrak etil asetat dan fraksifraksinya dengan kandungan fenolik total diperoleh persamaan regresi linier y = -1,220x + 44,022; r2 = 0,6682; sementara itu hubungan antara aktivitas antioksidan dan kandungan flavonoid totalnya diperoleh y = -2,202 x + 35,82; r2 = 0,4278

Kata kunci : aktivitas antioksidan, Morinda citrifolia, L, fraksi

Abstract
This present study was carried out to evaluate antioxidant activities, total phenolic and total flavonoid contents of ethyl acetate extract of Mengkudu fruit and its fractions. Ethyl acetate extract was fractionated by column chromatography and yielded 15 fractions based on the identical TLC (thin layer chromatography) profile. Antioxidant activities in ethyl acetate extract and its fractions were determined by radical scavenging assay using DPPH (2,2-diphenyl-1-
picrylhydrazyl) radical. The total phenolic and total flavonoid contents were determined spectrophotometrically. Among 15 fractions of ethyl acetate extract evaluated, fraction 8 (IC50
5,49 μg/mL) and fraction 7 (IC50 7,90 μg/mL) revealed antioxidant activities that higher than that of vitamin E (IC50 8,27 μg/mL). The total phenolic contents ranged from 5.94 ± 0.08 to 36.52 ± 0.35 g of gallic acid equivalent/100 gram dry material whereas the total flavonoid contents ranged from 1.19 ± 0.02 to 17.65 ± 0.17 g of quercetin equivalent/100 gram dry material. A linier positive relationship existed between the antioxidant activities and total phenolic contents of the tested ethyl acetate extract and its fractions y = -1.220x + 44.022; r2 = 0.67, while the correlation between antioxidant activities and total flavonoid contents revealed a linier regression y = -2.202 x + 35.82; r2 = 0.4278.
Key words: antioxidant activity, Morinda citrifolia, L, Fraction

Introduction
Several epidemiological studies have revealed that certain dietary elements play a pivotal role in the prevention of chronic diseases such as heart disease and several types of human cancers. People who consume much plant-derived foods such as fruits, vegetables, and soybeans were found to have lower incidence of cancer (Tsai..et..al.,..2005). Consumption of fruits and vegetables also has been associated with reduced risk of chronic disease (Adom and Liu, 2002).
Natural phenolic phytochemicals in fruits and vegetables have been receiving increased interest from consumers and researcher for the beneficial health effects on coronary heart disease and cancer mainly due to their antioxidant activities (Kim et al., 2002). A number of phenolic compounds mainly flavonoid and phenolic acids are among the antioxidant compounds which present in fruits and vegetables (Madhujith and Shahidi, 2005).

Antioxidant are compounds that can delay, inhibit, or prevent the oxidation of lipids or other molecules by inhibiting the initiation or propagation of oxidative chain reactions (Javanmardi et al., 2003). There are at least four general sources of antioxidant (1) enzymes, for example superoxide dismutase, glutathione peroxidase, and catalase; (2) large molecules (albumin, ceruloplasmin, ferritin); (3) small molecules (ascorbic acid, glutathione, uric acid, tocopherol, carotenoids, (poly)phenols); and (4) some hormones such as estrogen, angiotensin, melatonin, etc (Prior et al., 2005). Synthetic antioxidant such as tertbutylhydroxy anisole, tert-butylhydroxy toluene, and tert-butyl hydroquinone (TBHQ) have been widely used to retard lipid oxidation, however,such synthetic antioxidants are not preferred due to toxicological concerns. For this reason, there have been increasing interest in the exploration of natural antioxidant especially
from fruits and vegetables (Rababah et al.,2004).

Morinda citrifolia, L has been used in folkremedies by Polynesians for over 2000 years and is reported to have a broad range of therapeutic effects, including antibacterial, antiviral, antifungal, antitumor, analgesic, hypotensive, anti-inflammatory, and immune enhancing effect (Wang et al., 2002). The previous study showed that among three extracts evaluated, ethyl acetate extract
revealed the most effective antioxidant with IC50 46.7 μg/mL, whereas chloroform and methanol extracts have IC50 227.7 and 888.6 μg/mL respectively (Abdul and Sugeng, 2005). Zin et al., (2006) has studied the antioxidant activities of crude extract from root, fruit, and leaf of Mengkudu and their fractions on a Sephadex LH-20 column with ethanol as eluate.

However, the antioxidant activities of ethyl acetate extract and its fractions on a silica column as well as their correlation with total phenolic and total flavonoid contens have not been reported yet. The objectives of this study were (i) to fractionate ethyl acetate extract of Mengkudu fruit (ii) to evaluate antioxidant activities by radical scavenging assay using DPPH (2,2- diphenyl-1-picrylhydrazyl) radical (iii) to determine total phenolic and total flavonoid contents, and (iv) to correlate antioxidant activities with total phenolic and total flavonoid contents of ethyl acetate extract and its fractions.

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