Changes in antinutrients, phenolics, antioxidant activities and in vitro α-glucosidase inhibitory activity in pumpkin leaves (Cucurbita moschata) during different domestic cooking methods

Abstract

Pumpkin leaves (Cucurbita moschata) were subjected to different household cooking methods (boiling, microwaving, steaming, and stir-frying) to evaluate their effect on antinutrients, phenolic compounds, antioxidant properties (ABTS, and DPPH) and in vitro a-glucosidase activity. All cooking methods studied significantly reduced the antinutrients and antioxidant activities, whilst phenolic compounds p-coumaric and ferulic acids significantly increased. The cooking methods reduced the oxalates by more than 50%, tannins by 47% and phytates by 79.22%. Steaming and boiling resulted in highest concentrations of p-coumaric (195.40 mg kg -1 ) and ferulic acids (103.90 mg kg -1 ) compared to other methods. Overall, boiled leaves retained the highest total phenolic compounds, whilst steamed leaves retained the highest antioxidant capacity. Raw pumpkin leaf extracts showed higher in vitro a-glucosidase inhibitory effects than the cooked leaves. Thus, cooking affected the inhibitory effect of in vitro a-glucosidase activity.

Cooking African Pumpkin Leaves (Momordica balsamina L.) by Stir-Frying Improved Bioactivity and Bioaccessibility of Metabolites—Metabolomic and Chemometric Approaches

“…This could also be due to certain compounds concentrated in this fraction that may have higher antioxidant activities. The antioxidant activity of pumpkin leaves was reported to be correlated to the concentration of phenolic compounds [31].…”

“…Trans-4-feruloylquinic acid separated the raw leaves from the cooked African pumpkin leaves. The basis for the ranking of metabolites was on their VIP scores, with only top-ranking metabolites with the highest VIP scores considered [31]. Among the top eight metabolites with VIP scores greater than 1 were trans-4-feruloylquinic acid, rhamnetin-3-O-glucoside, cis-4-feruloylquinic acid, trans-4-coumaroylquinic acid, β-D-glucosyl-2-coumarate (Melilotoside), quercetin 3-galactoside and pseudolaroside A (Figure 1E).…”

“…It is a statistical procedure to analyse the correlation of two quantitative variables. In their simplest form, correlation coefficients illustrate the relationship between two variables, while low correlation coefficients reveal the absence of a relationship [31]. Data were transformed according to Cahvallo et al [31], and a correlation threshold of 0.5 was used for the correlation to be considered significant [36].…”

A Comparison of Bioactive Metabolites, Antinutrients, and Bioactivities of African Pumpkin Leaves (Momordica balsamina L.) Cooked by Different Culinary Techniques

“…These two methods estimate the free radical scavenging activities of antioxidants [ 45 ]. The IC 50 value is the concentration needed for 50% inhibition and determines the strength of the inhibitor [ 19 , 46 ]. The antioxidant activities of African pumpkin leaves cooked by adopting four different house hols cooking methods are given in Table 3 .…”

“…Following the destruction of the cell walls of the leaves by microwave and boiling, it is likely the antinutritive compounds leached out into the boiling water. After boiling pumpkin leaves, Mashitoa et al [ 46 ] reported reduced tannin concentrations (46.24%). Due to contact of the boiling water with the plant material, boiling has the highest leaching compared to the other cooking methods and thus leads to a higher reduction of tannins and alkaloids than other cooking methods [ 17 , 46 ].…”