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In Vitro Antioxidant Activity of the Methanolic Extract of Leaves of a Hill Tract Plant Begonia Roxburghii

Taslima Akter
Department of pharmacy, Jahangirnagar University, Savar, Dhaka-1342 Bangladesh

Afra Nawar
Department of pharmacy, Jahangirnagar University, Savar, Dhaka-1342 Bangladesh

Md. Nur Alam
Department of pharmacy, Jahangirnagar University, Savar, Dhaka-1342 Bangladesh

Md. Rafiquzzaman
Department of pharmacy, Jahangirnagar University, Savar, Dhaka-1342 Bangladesh

Abstract/ Executive Summary:

The study was designed to investigate the antioxidant activities of the methanolic extract of leaves of Begonia roxburghii by five different in vitro methods namely Folin-Ciocalteu, total flavonoid content, phosphomolybdenum, total reducing power determination, and DPPH scavenging activity. Phenol content ( Gallic acid equivalent) was found as 180.40±0.03 mg/g of the dry sample by the Folin-Ciocalteu method. Flavonoid assay method revealed the content of flavonoids ( Quercetin equivalent) as 60.43±0.27 mg/g of the dry sample. Total antioxidant capacity of the extract was observed 243.43±0.11 mg/g ( ascorbic acid equivalent) by phosphomolybdenum method. Free radical scavenging activity (measured by the DPPH test) of the methanolic extract was found 158.36±0.22 µg/mL whereas ascorbic acid, the standard, showed 19.53±0.04 µg/mL. The methanolic extract of Begonia roxburghii leaves exhibited positive and linear dose dependent reducing power activity and its activity was comparable to the standard ascorbic acid for a given dose. Phytochemical screening of the extract showed positive results for alkaloids, carbohydrates, flavonoids, glycosides, saponins, steroids, and tannins, which demonstrate definite pharmacological actions on human body. The extract showed negative results for the steroids.

Keywords: Begonia roxburghii, Methanolic extract, Antioxidant.

Location: Bangladesh national herbarium

Start Date:

End Date:

Program Area: Conservation and Biodiversity

Commodity: Medicinal Plants

Objectives:

To investigate the antioxidant activities of the methanolic extract of leaves of Begonia roxburghii by five different in vitro methods namely Folin-Ciocalteu, total flavonoid content, phosphomolybdenum, total reducing power determination, and DPPH scavenging activity.

Methodology:

Plant Materials: Leaves of Begonia roxburghii were collected from Chittagong, Bangladesh. The leaves were then sent to the Bangladesh national herbarium (access number 46521) for identification and confirmation and upon their confirmation that the collected leaves were of Begonia roxburghii, those were considered for methanolic extract preparation. Extraction: The collected and identified leaves were washed to remove dirt and then dried in the sun. The dried samples were ground to coarse powder with a mechanical grinder. The grinder was thoroughly cleaned before grinding of the dried leaves, to avoid contamination with any previously ground material or other foreign matter deposited on the grinder. An air-tight glass jar with plastic cover was taken and washed thoroughly, the jar was rinsed with methanol and it was allowed to dry. The prepared coarse powder of the Begonia roxburghii leaves was taken into the jar. A sufficient amount of methanol was added so that the sample was submerged. This jar was kept for 4 days at room temperature and was shaken time to time for better extraction from the powder of the leaves. The soaked material was filtered after four (4) days and the filtrate was dried on an electrical water bath at 70? temperature to remove the solvent methanol completely. The dried extract thus obtained was kept in pre-cleaned glass vials for experiment purposes. Chemicals and Reagents: Ascorbic acid, Folin-Ciocalteu, quercetin, gallic acid, and 1,1- diphenyl-2-picryl-hydrazyl (DPPH) were purchased from Sigma Co. (MO, USA). Other chemicals and reagents were of analytical grade. Phytochemical screening: The methanolic extract of the leaves of Begonia roxburghii was screened by the established methods (Tiwari et al., 2011) for the identification of certain phytochemicals like alkaloids, carbohydrates, flavonoids, glycosides, saponin, steroids, and tannin which are secondary metabolites of plants and are considered to have medicinal properties. Folin-Ciocalteu Method: Folin-Ciocalteu reagent was used to determine total phenols (Folin & Ciocalteu, 1927). A dilute plant extract (0.5 mL of 1:10 g/mL diluted with distilled water) was mixed with Folin-Ciocalteu reagent (5 mL,1:10 diluted with distilled water) and aqueous Na₂CO₃ (4 mL,1M). The mixture was kept for 15 minutes and the total phenol content was estimated by colorimetry at 765 nm. In this experiment gallic acid was used as standard phenolic compound. The standard curve was prepared using 0, 50, 100, 150, 200, 250 mg/l solutions of gallic acid in methanol: water (50:50, v/v). Determination of Flavonoid content: The content of flavonoid was determined using Aluminum Chloride colorimetric method (Chang et al., 2002). The plant extract (0.5 mL of 1:10 g/mL) in methanol was mixed with 1.5 mL of methanol, 0.1 mL of 10% Aluminum Chloride, 0.1 mL of 1 M potassium acetate and 2.8 mL of distilled water. It was allowed to stand for 30 minutes at room temperature. The absorbance of this mixture was measured at 415 nm. ?Determination of Total Reducing power: The reducing power of the sample extract was determined following the method of (Oyaizu M. 1986). 10 mg of extract in 1 mL of distilled water was mixed with phosphate buffer (2.5 mL, 0.2M, pH 6.6) and potassium ferric-cyanide [K₃Fe(CN)₆] (2.5 mL, 1%). It was incubated at 50 ? for 20 minutes. 2.5 mL of tri-chloroacetic acid (10%) was then added to the mixture and centrifuged at 3000 rpm for 10 minutes. The upper layer of the solution (2.5mL) was mixed with distilled water (2.5 mL) and FeCl₃ (0.5 mL, 0.1%). After that the absorbance was measured at 700 nm. Ascorbic acid was used as reference compound in this experiment. All the experiments were done in triplicate and the mean result was calculated.

Source of Information: Jahangirnagar University J. Biol. Sci. 9(1 & 2): 79-89, 2020 (June & December)

Article Link (Online Journal):

Funding Source:

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Achievement/Findings:

The present study revealed that Begonia roxburghii leaves contain active plant metabolites - alkaloids, carbohydrates, flavonoids, glycosides, saponin and Tannin. Based on the findings of the current research work, it can be concluded that the methanolic extract of leaves of Begonia roxburghii is a potential source of antioxidants. This work thus provided the scientific basis for further studies with the various parts, especially the leaves, of the Begonia roxburghii plant to elucidate their nutraceuticals as well as medicinal values or prospective.

Knowledge Management: Journal