Abstract
M.Tech. (Food Technology)
Cleome gynandra is an African green leafy vegetable categorized as an indigenous, underutilized specie that deserves more consideration and research. It has been reported to contain essential phenolic compounds such as flavonoids and phenolic acids that have been found to assist in lowering the incidence of diabetes, cancer, hypertension, obesity and cardiovascular diseases. These compounds could be highly affected by different processing methods such as cooking (boiling, steaming, blanching) and drying that are used prior to consumption of C. gynandra leaves. Therefore C. gynandra was subjected to boiling, steaming, blanching and drying processes and analysed for its Total Phenolic Content (TPC), Total Flavonoid Content (TFC), antioxidant and antimicrobial activity as well as Fourier transform infrared spectroscopy (FTIR). Cooking and drying significantly (p < 0.05) increased the levels of phenolic compounds and antioxidant activity of the vegetable. The boiled sample filtrate exhibited the lowest TPC of 157.23 ± 0.67 mg Gallic Acid Equivalent/100 g (dry weight) followed by the raw sample at 812.01 ± 24.1 mg GAE/100 g (dw) while the steamed sample depicted the highest TPC of 3074.17 mg GAE/100 g (dw). The antioxidant activity was analysed by the DPPH (2, 2-diphenly-1- picrylhydrazyl), ABTS (2, 2- azinobis (3-ethyl-benzothiazoline-6-sulfonic acid) and FRAP (Ferric reducing antioxidant power) assays. There was a significant difference between the processing methods used and the raw sample at p < 0.05 for all the antioxidant assays. The steamed sample showed the highest DPPH, FRAP and ABTS with mean values of 499.38 ± 2.44, 578.68 ± 5.19, and 214.39 ± 12.33 μM Trolox Equivalent/g respectively. Across all assays used the boiled sample filtrate depicted the lowest activity at 32.50 ± 0.31 μM TE/g for DPPH, 38.88 ± 0.033 μM TE/g for FRAP, and 11.09 ± 0.94 μM TE/g for ABTS. Antibacterial activities of the dried sample were tested against Escherichia coli, Pseudomonas aeruginosa, Enterococcus aerogenes and Enterrococcus cloacae using the Minimum Inhibitory Concentration assay (MIC). The sample showed minimum inhibition at 32 mg/mL against all strains except E. cloacae. Although antibacterial activity was generally negatively affected by cooking, an improvement was observed with drying. Further, targeted metabolomics guided approach was used to study the processing induced-perturbation of flavonoid molecules (Apigenin 6,8 C-dihexose, Quercetin -3-rutinoside, Kaempferol -3-rutinoside, Quercetin -3-rutinoside, Quercetin -3-glucoside, Kaempferol – 3-rutinoside). Here, UPLC-QTOF–MS was used to detect and interpret the effect of cooking and drying on the levels of these six flavonoids molecules. An increase in quercetin-3-rutinoside, quercetin-rhamnoside,..