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DPPH radical scavenging activity of methanol extract of Indonesian Etlingera elatior flower and leave

This research goal was to investigate the antioxidant activity of methanol extract of kecombrang (Etlingera elatior) flowers and leaves. Extraction processes by using maceration technique. Dried samples were extracted by using commercial methanol for 48 h. Antioxidant activity was measured as DPPH radical scavenging activity. The results showed that IC50 of the methanol extract of kecombrang shoot leaves was 14.53 ppm; the methanol extract of kecombrang mature leaves was 28.97 ppm; and the methanol extract of kecombrang flowers was 105.90 ppm. It is indicated that the extracts can be used as an agent to scavenging free radicals.


Introduction
Antioxidant compounds are widely found in some parts of plants [1]. Antioxidant is a substance that, when present concentration much lower than that of an oxidizable substrate, significantly delays or inhibits the substrate oxidation [2]. Many plants have been reported to have strong antioxidant activities [3]. Many parts of plant such as wood, bark, stems, leaves, fruits, roots, flowers, pollen and seeds, are sources of antioxidant and commonly known as polyphenols [4].
Indonesia has around 40,000 endemic plant species and 6,000 medicinal plants. Thus, Indonesia is known as the second largest biodiversity in the world [5]. Family of Zingiberaceae is one of the medicinal plants distributed in tropical and subtropical areas such as Indonesia, Brunei, Malaysia, Papua New Guinea, Philippines, Singapore and South of Thailand. Etlingera elatior is one of species in the family of Zingiberaceae [6].
E. elatior has been known as kecombrang and honje in Indonesia. It is also known as porcelain rose and torch ginger (English) and kantan (Melayu). Many parts of kecombrang such as flowers (buds, receptacle, and petal), fruits, hearth of young leafy pseudostemps, rhizome and seeds can be used as condiments, eaten as salad and pickled, cooked as foods, produced as "manisan" [7]. Researches on some parts of kecombrang have been done including its antioxidant, anticancer, hepatoprotective, and tyrosinase inhibition activities [7][8][9]. Ghasemzadeh and his colleagues reported that aqueous and ethanol extract of kecombrang flowers from different area in Malaysia resulted significantly different on its total phenolic contents, total flavonoid contents and total tannin contents as well as its antioxidant activities [8]. Based on the introduction above, this research was conducted to analysis antioxidant activity of flowers and leaves of Indoneisan kecombrang by using DPPH Radical scavenging method.

Plant materials and chemicals
The flowers and leaves of kecombrang were collected from villager at Lubuk Sawah, Mugirejo, Samarinda, Indonesia. Methanol was a commercial grade and other used chemicals were purchased from Sigma Aldrich GmbH (Germany).

Preparation of the extracts
Both of flowers and leaves of kecombrang were dried under shade for 7 days. The dried samples were crushed into powder by using commercial blender. Then, the powders of samples ca 50 g were extracted with methanol for 48 h. and the mixture was filtered by using filter paper to get extract solution. Afterwards the extract solution was concentrated by using a rotary evaporator at 39ºC.

DPPH antioxidant assay
DPPH (2,2-diphenyl-1-picrylhydra-zyl) radical scavenging assay was done by using a method which described by Sukemi et al with few modifications [10]. Five hundred microliters of each concentration of methanol solution of tested sample was mixed with 500 µL of 30 ppm DPPH methanol solution. Then, the mixture was kept in the dark for 20 minutes and its absorbance was measured at 517 nm using UV-Vis spectrophotometer. Ascorbic acid was used as positive control. The DPPH scavenging activity (%) was calculated using equation 1.

DPPH scavenging activity=
where A0 was the absorbance of control and A1 was the absorbance of tested sample. The value of IC50 was obtained from the line corresponding to the line plotted concentration versus the percentage of scavenging activity.

Result and discussion
Data of IC50 value of the methanol extract of kecombrang flowers and leaves to scavenge DPPH radical are shown in the table 1. The capability of plant extract or compound as donor of hydrogen to DPPH radical can be evaluated by using DPPH radical scavenging assay [10]. As shown in table 1, ascorbic acid showed a good performance to scavenge DPPH radical with an IC50 of 13.06 ppm. It was clear that methanol extract of kecombrang shoot leaves had insignificantly less DPPH radical scavenging activity with an IC50 value of 14.53 ppm than ascorbic acid. However, the IC50 of methanol extract of kecombrang mature leaves and flowers were significantly lower about twice and eight times than that of ascorbic acid, respectively.

Conclusion
The present study suggests that the methanol extract of kecombrang shoot leaves possessed DPPH radical scavenging activity. Thus, the methanol extract of kecombrang shoot leaves can be considered as an agent of potential antioxidants.