Mohammad Khairul Alam

Background: Polyphenolic compounds are known to provide health benefits and protect against degenerative chronic diseases. Utilization and identification of foods with a high content of these compounds are gaining greater attention nowadays. Objective: The present study reports the total phenolic content (TPC), polyphenolic composition and antioxidant activity (DPPH, FRAP and TEAC) of 10 commonly consumed leafy vegetables growing in Bangladesh. Materials and Methods: The samples were collected from different locations of Bangladesh and mixed together to ensure sample representativeness. Folin-Ciocalteu method was used for the analysis of TPC, and quantification of polyphenolic components was done by high-performance liquid chromatography (HPLC- DAD). Additionally, antioxidant activities of the selected vegetables were also analysed by utilizing DPPH, FRAP & TEAC. Results and Discussion: TPC ranged from 23.64 ± 1.20 to 45.59 ± 3.04 mg gallic acid equivalent (GAE)/g freeze-dried sample (fds). The polyphenolic spectrum ranged from 0.30 ± 0.02 to 647.42 ± 147.12 mg/100 g fds; quantity and spectrum of which varied in the vegetables. Among the studied vegetables, Centella asiatica contained the highest amount of TPC (45.59 ± 3.04 mg GAE/g fds) and also exhibited high antioxidant capacities, as documented by DPPH, FRAP and TEAC assays. Moreover, Principal component analysis (PCA) of investigated variables clearly separated Centella asiatica from other samples. Conclusion: Phenolic compounds being strong antioxidants reduce the risk of chronic diseases and the finding of this study would aware the people to take vegetables rich in phenolics. It would also fill up the data gap in the existing food composition table of Bangladesh.

The present study was aimed at evaluating mineral contents, B-vitamins (B1, B2, B3, B6), vitamin C, total carotenoids content and carotene composition of unconventional vegetables, comprising 7 leafy and 4 non-leafy, growing in Bangladesh. Investigated unconventional vegetables were found to have varied amount of minerals (0.04 ± 0.01 to 786.41 ± 6.37 mg/100 g), B-vitamins (0.06 ± 0.01 to 1.05 ± 0.13 mg/100 g) and vitamin C (5.23 ± 0.81 to 59.01 ± 2.23 mg/100 g). The study findings also revealed that the selected plant samples exhibited diverse amount of β-carotene ranging from 106.26 ± 5.32 µg/100 g EP in Orhor dal to 994.81 ± 21.01 µg/100 g EP in Orhor Pata whereas lutein content ranged from 7.76 ± 1.02 µg/100 g EP in Pahari Kolar Thor to 566.33 ± 20.63 µg/100 g EP in Kachuripana. It can be suggested that regular intake of these vegetables may contribute to daily minerals and vitamins requirement and can combat micronutrient deficiency. Graphical Abstract

Background: Phenolics and carotenoids are natural antioxidants, which provide health benefit and protect against degenerative chronic diseases. Utilization and identification of foods with high content of these received greater attention nowadays. Objective: The present study reports the total phenolics (TPC) and total carotenoids (TCC) contents of thirty-two selected unconventional vegetables growing in Bangladesh. In addition, they were also analyzed for their antioxidant potentials. Methods: Folin-Ciocalteu and acetone–petroleum ether extraction followed by spectrophotometric measurement were employed for TPC and TCC, respectively. The antioxidant capacities of the selected unconventional leafy vegetables were analyzed using DPPH and Trolox equivalent antioxidant capacity (TEAC) assays. Results: The results revealed that the TPC ranged from 82.41 mg GAE/100 g in Kiokro to 2711.05 mg GAE/100 g in Mrolapiong whereas the TCC values ranged from 43.05 µg/100 g in Fala to 12863.54 µg/100 g in Roktodrone. The study findings also revealed that the selected plant samples exhibited high antioxidant capacities. Mrolapiong demonstrated highest DPPH inhibition (91.31 %) and TEAC (485.55 μmol Trolox/g) value, than others. The antioxidant capacities were attributed to phenolic compounds as there exist a positive correlation between these two variables. Bioactive phytochemicals are widely distributed in these vegetables, although their amounts are varying among the different types of vegetables. Conclusion: The study results suggest that the vegetables analyzed may provide a possible source of dietary antioxidant and serve as material for functional foods. Therefore, their production and consumption must be encouraged in order to preserve biodiversity and prevent their extinction.

Dietary fibres are known to provide health benefit and protect against degenerative chronic diseases. Thus, the present study reports the total dietary fibre (TDF) content of sixty-nine selected ethnic and unconventional vegetables and fruits growing in Bangladesh. The samples were collected from different locations of Bangladesh and mixed together to ensure sample representativeness. Dietary fibre assay kit according to the AOAC method was utilized for the analysis of TDF in selected vegetables and fruits. In the ethnic varieties, the TDF content ranged from 1.02 ± 0.16 to 7.16 ± 0.16 g for leafy (LV), 0.18 ± 0.01 to 6.71 ± 0.49 g for non-leafy vegetables (NLV) and 1.21 ± 0.12 to 5.29 ± 0.20 g for fruits per 100 g edible portion (EP). In the unconventional items, it arrayed from 3.08 ± 0.34 g to 7.75 ± 0.13 g for LV and 1.02 ± 0.06 to 8.82 ± 0.40 g for NLV per 100 g EP. Among the analysed samples, the highest and lowest content of TDF was found in Orohordal and Mairabokong, respectively. The unconventional vegetables contained much higher content of TDF than the ethnics and the commonly consumed similar varieties. Data on TDF content in underutilized vegetables and fruits of Bangladesh is sparse. Thus, the finding of this study would fill up the data gap in the existing food composition table of Bangladesh and also would aware the people to take vegetables and fruits rich in fibres.

Wild plants are considered the richest source of essential nutrients and other beneficial phytochemicals. Hence, the objective of this study was to evaluate the nutritional composition, antioxidant- and α-amylase inhibition activities of leaves and roots of selected Bangladeshi wild plants. These wild plants were found to have high fiber (13.78–22.26 g/100 g), protein (7.08–21.56 g/100 g) and ash (8.21–21.43 g/100 g) contents. The total phenolic and total flavonoid contents were significantly higher in the leaves than the roots. Additionally, antioxidant activity was evaluated using ferric-reducing antioxidant power, 2, 2-diphenyl-1-picrylhydrazyl radical (DPPH) and trolox equivalent antioxidant capacity assays and was strongly correlated with phenolic compounds. The leaf extracts of the selected plants also exhibited potent α-amylase inhibition (~71%) and were significantly higher than their root counterparts. Thus, the study findings concluded that the investigated plants were good sources of fiber, protein, mineral, natural antioxidant compounds and α-amylase inhibitors, and their increased intake could provide health benefits. The principal component analysis (PCA) of analyzed variables divided the samples into three clear groups, and the first two principal components accounted for 86.05% of the total data set variance.

Nowadays, more attention has been paid on wild plants as new source of natural antioxidants. Therefore, methanolic extracts of 10 traditionally consumed wild leafy vegetables of Bangladesh were analyzed for their total phenolic content (TPC) and free radical scavenging activity. Folin-Ciocalteu method followed by spectrophotometric measurement was used to quantify the TPC of the selected wild leafy vegetables. Free radical scavenging activity was examined utilizing 1,1-diphenyl-2-picryl-hydrazyl (DPPH) assay. Different concentrations of the plant extract were applied to ascertain the dose response relationship in inhibiting DPPH free radical. The results revealed that the TPC ranged from 102.20 to 710.42 mg GAE/100g dry weight (DW). The highest TPC was observed in Bauhinia acuminata (Shetokanchan) while Leucas aspera (Shetodhron) exhibited the lowest TPC among the undertaken vegetables. The studied samples proportionately inhibited DPPH with increasing concentrations. At high concentration (500 µg.mL-1), the percentage inhibition of DPPH radical by plant extract ranged from 68.1 ±2.65 % to 93.1 ±1.23 %. The highest DPPH radical inhibition was observed in Bauhinia acuminata (Shetokanchan) (93.10 ±1.23 %), followed by Commelina benghalensis (Bat baittashak) (91.97 ±1.31 %), Hydrocotyle sibthorpiodes L. (Sakumubakla) (91.83 ±2.13 %). The lowest DPPH radical inhibition among the studied samples was observed in Leucas aspera (Shetodhron) (68.1 ±2.65 %). IC50 values measured by DPPH assay in this study ranged from 11.64 to 313.79 µg.mL-1. The study findings indicated that the samples under study possesses strong activity against DPPH, and thus could be used as natural antioxidants in the food and/or pharmaceutical industry.