Changes in Phenolic Metabolites and Biological Activities of Pumpkin Leaves (Cucurbita moschata Duchesne ex Poir.) During Blanching

Abstract

Pumpkin leaves (Cucurbita moschata Duchesne ex Poir.) are popularly consumed in Sub-Saharan Africa and Asia. Blanching the leaves before drying is a method of preservation during off-season. In this study, different blanching treatments and media are used to test the changes in non-targeted phenolic compounds, antioxidant capacity (FRAP and ABTS activity), in vitro α-glucosidase activity and cell cytotoxicity of pumpkin leaves. Steam blanching in plain water led to the highest retention of total phenolic content and reduced the loss of quercetin 3-glucoside 7-rhamnoside (Rutin), kaempferol 7-neohesperidoside, isoorientin 2″-O-rhamnoside, isorhamnetin-3-O-rutinoside, quercetin 3-galactoside, coumaroyl glucaric acid, isorhamnetin-3-galactoside-6″-rhamnoside, 2-caffeoylisocitric acid, quercetin 3-galactoside 7-rhamnoside by (3.04%), (7.37%), (10.65%), (10.97%), (14.88%), (16.1%), (16.73%), (18.88%), and (23.15%), respectively, and coumaroyl isocitrate increased by 14.92%. Candidate markers, 2-O-caffeoylglucaric acid, 2-(E)-O-feruloyl-D-galactaric acid, quercetin 3-galactoside 7-rhamnoside (rutin) and unidentified compounds ([(M-H) 677.28 and at RT 21.78] were responsible for the separation of the steam blanched samples in plain water from the other blanching treatments. Steam blanching in plain water increased the antioxidant capacity (FRAP and ABTS activity). There were no cytotoxic effect or inhibitory effect of α-glucosidase activity detected in the raw or blanched pumpkin leaves. Thus, this study recommends steam blanching in plain water for African cuisine, and confirms it is safe to consume pumpkin leaves frequently.

Effect of Freeze Drying and Simulated Gastrointestinal Digestion on Phenolic Metabolites and Antioxidant Property of the Natal Plum (Carissa macrocarpa)

“…In its MSE spectrum, peak 7 had a base peak ion at m / z 300 [M-H-147-162] as a result of the successive loss of rhamnose and the galactose moiety. The fragment ion at m / z 300 indicated that the compound is a quercetin derivative [ 26 ]. Peak 7 was tentatively identified as quercetin-3-galactoside 7-rhamnoside.…”

“…A secondary peak was observed at m / z 463 [M-H-146] as a result of the loss of the rhamnose moiety from the parent ion. Another secondary fragment observed at m / z 179 was due to retrocyclisation following fission of the C ring of quercetin [ 26 ]. As such, peak 7 was tentatively identified as quercetin-3-glucoside 7-rhamnoside (rutin).…”

“…Similar to peak 7, the MSE spectrum of peak 8 had a base peak ion at m / z 300[M-H-146] due to the cleavage of a galactosyl residue from the parent ion. Observation of the peak at m / z 300 revealed that peak 8 was a quercetin derivative [ 26 ]. A secondary fragment observed at m / z 153 was due to the cleavage of the quercetin moiety.…”

Influence of Different Types of Drying Methods on Color Properties, Phenolic Metabolites and Bioactivities of Pumpkin Leaves of var. Butternut squash (Cucurbita moschata Duchesne ex Poir)

“…Predominant polyphenolic metabolites present in leaves of var. Butternut squash ( C. moschata) were extracted and quantified using a Waters Synapt G2 Quadrupole time-of-flight (QTOF) mass spectrometer (MS), hyphenated to a Waters Aquity ultra-performance liquid chromatograph (UPLC) (Waters, Milford, MA, USA), as described earlier by Mashitoa et al ( 3 ). Briefly, the instrument was used in the negative mode electrospray ionization with a cone voltage of 15 V, a desolvation temperature of 275°C, and desolvation gas of 650 L/h, and the rest of the MS settings were optimized for best resolution and sensitivity.…”

“…The FAO/WHO ( 2 ) recommends a serving size of 80–100-g green leafy vegetables in four to five servings for adults. The nutritional information present in the leaves of pumpkin species C. moschata is given in detail in the study of Mashitoa et al ( 3 ). The leaves of pumpkin species ( C. moschata ) are functional vegetables due to their higher phenolics, flavonoid content, and antioxidant scavenging activity ( 4 – 6 ).…”