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Phenolics and Carotenoids Contents and Radical Scavenging Capacity of Some Selected Solanaceous Medicinal Plants

Rumana Islam
Department of Crop Botany, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

Md. Nesar Uddin
Department of Crop Botany, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

Md. Ashrafuzzaman
Department of Crop Botany, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

Md. Injamum-Ul-Hoque
Department of Crop Botany, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

Abstract/ Executive Summary:

Plants being an important source of medicine play significant role in human health. The aim of the present study was to evaluate the total phenolics and carotenoids contents, and free radical scavenging capacity of leaves and fruits of selected five solanaceous medicinal plants, namely Solanum melongena (brinjal), Solanum torvum (tit begun), Solanum virginianum (kantikari), Solanum sisymbrifolium (sada kantikari) and Solanum nigrum (futi begun). Carotenoids content in the leaves and fruits of solanaceous plants varied significantly among the species. Leaf phenolics content ranged between 147.40 (S. melongena) and 585.15 (S. virginianum) mg gallic acid equivalent (GAE)/100 g fresh weight, while fruit phenolics content varied from 50.52 (S. nigrum) to 105.02 (S. virginianum) mg GAE/100 g fresh weight. IC50 values for scavenging 2, 2-diphenyl-1-picrylhydrazyl radical (DPPH) radical ranged between 31.52 (S. nigrum) and 33.55 (S. melongena) mg mL⁻¹ in leaf, while in fruit it ranged between 27.90 (S. virginianum) and 33.11 (S. melongena) mg mL⁻¹. The highest carotenoids content (0.370 mg g⁻¹ fresh weight) was measured from Solanum nigrum leaf. S. virginianum leaf contained about 4−fold high phenolics content than that in S. melongena. S. nigrum leaf had about 15−fold high carotenoids content (0.370 mg g⁻¹ fresh weight). compared to S. torvum and S. virginianum fruits (0.024 mg g⁻¹ FW in each). Because of the highest fruit phenolics and carotenoids content along with the lowest IC50 values for scavenging DPPH, S. virginianum fruit can be considered as superior for its health beneficial biochemical constituents.

Keywords: Solanum, Antioxidant, DPPH, Carotene

Location: Bangladesh Agricultural University, Mymensingh

Start Date:

End Date:

Program Area: Development of Host and Medicinal Plants

Commodity: Medicinal Plants

Objectives:

To assess and compare total phenolics content in different medicinal plants; to determine radical scavenging ability of plant extracts as an index of antioxidative power of these plants against oxidative stress; and to quantify carotenoids content in these plant samples.

Methodology:

Plant materials and experimental sample collection Cultivated eggplant (Solanum melongena L.) and its four wild relatives, namely tit begun (Solanum torvum Sw.), kantikari (Solanum virginianum L.), sada kantikari (Solanum sisymbrifolium L.) and futi begun (Solanum nigrum L.) were studied in this research. They were collected from the Botanical Garden, Bangladesh Agricultural University, Mymensingh. For each plant genotype studied, three different healthy plants from three different colonies were considered as three replicates. At morning time, part of the shoot with leaves were dissected from each colony and immediately placed in a zip lock bag to check moisture loss. Soon after collection samples were brought to the laboratory for chemical analyses. As tender leaves and mature fruits are often been used for consumption, both tender leaves and relatively mature fruits of each species from each replication were separated and chopped separately to produce working samples for leaves and fruits. Phytochemical and biochemical characterization Total phenolics content assay Total phenolics compound assayed with the method modified after Albano and Miguel (2011). Exactly 5 g of working samples for leaf or fruit were taken to a 250 mL beaker and 100 mL ice cooled methanol were added to it and then the samples were homogenized for 2 minutes using OV-5 Homogenizer, VELP, Italy. The mixture was kept for 30 minutes in the dark condition and centrifuged for 5 minutes at 1500 rpm and then its supernatant was treated as working sample extract. An aliquot amount of extract was used for determining total phenolics content or DPPH scavenging activity. Gallic acid was used here as standard. Exactly, 330 µL different concentrations of gallic acid solutions or suitable amount of plant extracts were taken into a 50 mL test tube. Then 0.16 mL of Folin-Ciocalteu reagent and 3 mL of Na_²CO_³ (10%) solution was added to 1 mL of gallic acid solution. The mixture was kept in dark condition for half an hour at room temperature (25⁰C). Then absorbance was measured at 760 nm. The absorbance value is the reflection of the total phenolic content of the compound. After plotting the absorbance in ordinate against the concentration a linear relationship was obtained which was used as a standard curve for the determination of the total phenolics content of the test samples. DPPH radical scavenging assay Free radical scavenging activity of the medicinal plant extracts were determined by using a stable 2,2-diphenyl1-picrylhydrazyl radical (DPPH) (Brand-Williams et al., 1995). DPPH is a free radical of violet colour. The antioxidants in the sample scavenge the free radicals and turn it into yellow colour. The change of colour from violet to yellow is proportional to the radical scavenging activity. Briefly, the assay contained 2.7 mL of 0.1 mM DPPH in methanol and made up to 3 mL with 300 µL plant extracts (working sample). The contents were mixed well immediately and then incubated for 30 min at room temperature (25°C). The degree of reduction of absorbance was recorded at 517 nm using DR 6000 UVSpectrophotometer. The percentage of scavenging activity was calculated as: (Ac – As)/ Ac × 100, where ‘Ac’ is the absorbance of control (without extract) and ‘As’ is the absorbance of sample with plant extract. Percentage of radical scavenging activity was plotted against the corresponding concentration of the extract to obtain IC50 value. IC50 is defined as the amount of antioxidant material required to scavenge 50% of free radical in the assay system. The IC50 values are inversely proportional to the antioxidant activity (Nisha et al., 2009). Pigments determination This protocol describes how the contents of chlorophylla, b and total carotenoids can be determined in a whole pigment extract of green plant tissue by spectrophotometer (Lichtenthaler, 1987). From the fresh composite leaf or fruit samples, 50 mg were taken in glass bottles and 200 µL distilled water were added to it. Then 16 mL ethanol were added and shaken properly and finally the content was kept in dark condition for 24 h. Absorbance reading was taken in the following day in a spectrophotometer (DR 6000, Hach, USA) at 470, 649, 664 and 750 nm wave lengths. Afterward, amount of total carotenoids (sum of carotene and xanthophyll) were calculated using the following formulae:
Carotenoids (Cx+c)=(4.785 A470+3.657 A664−12.76 A649)×16.2/FW Where, A649 = Absorbance at 649 nm A664 = Absorbance at 664 nm A470 = Absorbance at 470 nm FW = Fresh weight of plant tissue (mg).
Statistical analyses Mean values of each parameter studied for each group of medicinal plants were subjected to one way ANOVA analysis using Minitab 17.3 to determine whether significant differences in the group existed or not. In case of having significant F-ratio, means were subjected to Tukey's post-hoc test to observe the significant differences among the mean values.

Source of Information: J Bangladesh Agril Univ 16(1): 56–61, 2018 ISSN 1810-3030 (Print) 2408-8684 (Online)

Article Link (Online Journal): doi: 10.3329/jbau.v16i1.36481

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The leaf of S. virginianum acts as a good source of phenolics as it has the highest amount of phenolics than that in the fruits. S. virginianum, S. sisymbrifolium and S. nigrum leaf and fruit extracts showed the lowest IC50 values, and thus had the highest radical scavenging capacity while S. torvum and S. melongena fruit extracts had the lowest radical scavenging capacity. Coarotenoids contents were maximum in S. nigrum leaf extracts as well as in S. torvum and S. virginianum fruit extracts. Thus, S. virginianum leaves and fruits appear to be superior for their health beneficial biochemical constituents.

Knowledge Management: Journal