Hydrophilic antioxidant activity, vitamin C and total phenol content of selected varieties of commonly consumed fruits and vegetables of Bangladesh

Abstract

Fruits and vegetables contain a wide variety of phytochemicals including thousands of bioactive compounds, many of which are implicated with health effects like protective action against heart disease, hypertension, diabetes and some form of cancer. The present study involved to estimate the content of vitamin C and total phenol and assessing the antioxidant activity in the hydrophilic extracts from edible portions of five different fruits and five vegetables commonly consumed by Bangladeshi people. The fruits analyzed included a total of 11 varieties from Banana, Guava, Lemon, Mango and Pineapple, and the vegetables covering a total of 17 varieties included Bottle Gourd, Brinjal, Pumpkin, Radish and Tomato – all the varieties of a particular fruit or vegetable followed a standard cultivation system in the research field of Bangladesh Agricultural Research Institute (BARI). After collection, samples were prepared by washing (under running tap water followed by distilled water), air-drying, dressing and weighting of refusal. A portion of the edible parts of fresh sample was used for the analysis of Vitamin C content employing the principles and techniques of High-Performance Liquid Chromatography (HPLC). The remaining portion was freeze-dried at -180°C, weighed, ground and stored in air tight package at -20°C until sequential extraction by Hexane: Dichloromethane (1:1) followed by acetone: water: acetic acid (70:29.5:0.5) to get the hydrophilic extracts for the estimation of Total Phenol Content (TPC) and Antioxidant Activity (AA) according to the Folin-Ciocalteu method and 2, 2-diphenyl-1-1-picrylhydrazyl radical scavenging assay (DPPH-RSA) respectively. Vitamin C content (mean±SD), expressed as mg L-Ascorbic Acid (L-AA)/100 g fresh weight (FW), of different varieties of fruits and vegetables respectively varied from 1.03±0.15 in Banana (BARI Kola-2) to 71.57±2.83 in Guava (BARI Peara-2) and 0.33±0.05 in Brinjal (BARI Hybrid Begun-3) to 14.43±0.21 in Radish (BARI Mula-2: Pinky). For vegetables, TPC (mean±SD), expressed as μg Galic Acid Equivalent (GAE)/100g FW, ranged from 0.07×104±0.00 in Radish (BARI Mula-3: Druti) to 3.23×104±0.24 in Brinjal (BARI Begun-1: Uttara). For fruits, TPC varied from 0.14×104±0.01 in Pineapple (Justice) to 11.31×104±0.11 in Guava (BARI Kazi Peara). Among the fruits, the highest AA (mean ± SD), 428.40±4.50 μM Trolox Equivalent (TE)/100g FW was observed in Guava (BARI Peara-2) and the lowest in Lemon (BARI Lebu-3) at a level of 6.41±0.0 μM TE/100g FW. In vegetables, AA (mean±SD) ranged from 3.00±1.20 μM TE/100g FW in Bottle Gourd (BARI Lau-3) to 107.00±24.78 μM TE/100g FW in Brinjal (BARI Begun-8). In two varieties of Guava (BARI Kazi Peara and BARI Peara-2), AA, TPC and Vitamin C were high of all the values. The Vitamin C content of Lemon (BARI Lebu-3) was high although its AA was negligible with TPC being below the detection level. BARI Aam-3, a variety of Mango demonstrated high AA and Vitamin C while TPC was low. TPC was high in two varieties of Banana (BARI Kola-1: BARI Sagar Kola, BARI Kola-2). Three varieties of Brinjal as BARI Begun-1: Uttara, BARI Begun-4: Kajla and BARI Begun-8 showed AA and TPC, and two varieties of Radish like BARI Mula-2: Druti and BARI Mula-3: Pinky demonstrated Vitamin C in highest position among all studied vegetables. The findings of the present study indicates that some of the selected varieties of fruits and vegetables cultivated by BARI contain considerable amount of Vitamin C and Phenolic compounds that may serve as a potential source of dietary antioxidants in order to help the balance of body’s antioxidant defense system against oxidative stress.