Moringa oleifera Lam. has been used as a traditional medicine for the treatment of several diseases. In this study, the antioxidant activity and simultaneous HPLC profiling of polyphenolic compounds in 80% ethanol and water extracts of M. oleifera tender and mature leaves available in Bangladesh were investigated. The 80% ethanol extract of M. oleifera tender leaves contained high concentration and more amount of 3,4- dihydroxybenzoic acid, (-) epicatechin and rosmarinic acid (201.32±1.94, 213.08±1.96 and 133.84±1.42 mg/100 g of dry extract, respectively) than that of mature leaves (82.55±1.09, 141.86±1.10 and 16.23±0.76 mg/100 g of dry extract, respectively). On the other hand, the water extract of M. oleifera tender leaves contained a high concentration of catechin hydrate, trans-ferulic acid and quercetin (530.05±1.91, 166.38±0.90 and 771.74±1.34 mg/100 g of dry extract, respectively) than that of mature leaves (207.21±0.90, 62.42±0.45 and 483.25±1.04 mg/100 g of dry extract, respectively). It was also found that 3,4-dihydroxybenzoic acid, catechol, p-coumaric acid and trans-cinnamic acid were detected only in 80% ethanol extract of M. oleifera leaves but syringic acid was identified in the water extract. In DPPH free radical scavenging activity test, IC50 values of 80% ethanol extract of tender leaves (EETL), 80% ethanol extract of mature leaves (EEML), water extract of tender leaves (WETL) and water extract of mature leaves (WEML) were found to be moderately significant (105.50±1.05, 115.00±1.14, 216.00±1.34 and 269.50±1.56 μg/mL, respectively) when compared to the IC50 value of ascorbic acid, 3.32±0.07 μg/mL. The polyphenolic compounds are responsible for antioxidant activity. On the basis of the present study, it can be suggested that the leaves show antioxidant activity and it’s contained a significant amount and different types of polyphenolic compounds. Standardized polyphenolic compounds from M. oleifera leaves could be used as a better source of natural antioxidant supplement.

People in Bangladesh are traditionally used to consume mainly black tea. However, some tea manufacturing companies are now producing green tea, though in a small scale. To create new knowledge as well as awareness about the consumption of green tea, the present study was carried out to compare the black and green tea available in Bangladesh based on their bioactive compounds and antioxidant activity. A total of eight brands of black tea and two brands of green tea were bought from the supermarkets. Total phenolics, total tannin, total flavonoids, and caffeine content were measured as bioactive compounds, and antioxidant activity was evaluated by using two different methods such as DPPH (1,1- diphenyl-2-picrylhydrazyl) radical-scavenging activity and ABTS+ radical scavenging activity of methanol extracts of black and green tea. Every bioactive compound in black and green tea was found to be significantly different (P < 0.05). The total phenolic content, on average, was measured at 242.46 mg GAE/g dry extract and 763.41 mg GAE/ g dry extract in black and green tea, respectively. Black tea contained 6.47 mg TAE/g dry extract tannin, whereas green tea had much more tannin content, 14.51 mg TAE/g dry extract, which is more than double in amount. On the other hand, the total flavonoid content was almost double in black tea (61.82 mg QE/g dry extract) compared to green tea (31.85 mg QE/g dry extract). Antioxidant activities were determined at different concentrations of tea samples. At every concentration, green tea presented higher ABTS+ and DPPH radical scavenging activity than black tea. The highest percentage of inhibition was observed at 20 ppm both in black and green tea, finding 98.50 % and 99.07 % inhibition, respectively. Overall, significantly (P < 0.05) higher amount of phenolic compounds as well as antioxidant activity were observed in green tea.

Jute leaves (Corchorus spp.) have been used as a medicinal plant for the treatment of various diseases. The study was investigated on the antioxidant activities and HPLC profiling of polyphenolic compounds in ethanol extract of Corchorus olitorius (C. olitorius) and Corchorus capsularis (C. capsularis) leaves. The total antioxidant capacity was evaluated by phosphomolybdenum method and Identification and quantification of polyphenolic compounds were performed using HPLC-DAD system. The results indicated that eight polyphenolic compounds were found in the C. capsularis leaves but C. olitorius leaves contain six polyphenolic compounds. In fact, major identified polyphenolic compounds of C. capsularis leaves were caffeic acid (CA), 55.93±0.13; trans-ferulic acid (FA), 58.02±0.18; rutin hydrate (RH), 32.16±0.08; ellagic acid (EA), 53.65±0.11 and quercetin hydrate (QU), 46.17±0.09 mg/100 g of dry extract respectively. Whereas in C. olitorius leaves which were rutin hydrate (RH), 152.17±0.51; ellagic acid (EA), 143.27±0.58 and quercetin hydrate (QU), 292.83±0.73 mg/100 g of dry extract respectively. The results showed that C. capsularis leaves contained high level of total antioxidant capacity (214.32±1.95 mg of ascorbic acid/g of dry extract) than that of C. olitorius (165.66±1.30 mg of ascorbic acid/g of dry extract) leaves. The overall data suggested that C. olitorius and C. capsularis leaves contain a significant amount of several polyphenolic compounds that could be used as a natural antioxidant for functional foods.