Research Output
Profiling of Bioactive Compounds and Bioactivity of the Kenaf (Hibiscus Cannabinus L.) Leaf Extract
Quantitation of Protein Cysteine-Phenol Adducts in Minced Beef Containing 4-Methyl Catechol
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Publication
The current research examines the impact of different solvents and maturity stages of the kenaf leaf (Hibiscus Cannabinus L. var. Everglade 51) on the bioactive compound and bioactivity, which specifically focused on antioxidant and antimicrobial properties. The kenaf’s leaf powder was extracted sequentially using hexane, acetone, and methanol. The total phenolic compound (TPC), flavonoid content (TFC), and free-radical scavenging activity using DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging assay were measured using UV–Vis spectrometry. The antibacterial activity of the extract was determined using the disc diffusion method on both Gram-positive and -negative bacteria. Results show that the methanol extracts had a significant (p < 0.05) quantity of TPC and TFC compared to other extracts. Results showed that the antioxidant compound amount measured as TPC and TFC in extract increased from shoot stages into mature leaves by 11% and 24%, respectively. As expected, methanolic extract of mature leaf exerts the highest TPC and TFC value compared to that of other solvents. This also reflects the antioxidant activity among the different extract where methanolic extract showed the highest antioxidant activity with value 60.48 ± 0.24% of radical scavenging activity. Meanwhile, only the methanolic and acetone extracts demonstrated a significant (p < 0.05) inhibitory zone against Gram-negative microorganisms. Overall, mature kenaf leaf extracted with methanol and acetone solvents showed a particularly high in terms of antioxidant capacity and antimicrobial characteristics. Mature kenaf leaf was recommended for food product development due to their strong antioxidant activity and ability to inhibit Gram-negative bacteria.
Publication
Thiol groups of cysteine (Cys) residues in proteins react with quinones, oxidation products of polyphenols, to form protein-polyphenol adducts. The aim of the present work was to quantify the amount of adduct formed between Cys residues and 4-methylcatechol (4MC) in minced beef. A Cys-4MC adduct standard was electrochemically synthesized and characterized by liquid chromatography-mass spectrometry (LC-MS) as well as NMR spectroscopy. Cys-4MC adducts were quantified after acidic hydrolysis of myofibrillar protein isolates (MPIs) and LC-MS/MS analysis of meat containing either 500 or 1500 ppm 4MC and stored at 4 °C for 7 days under a nitrogen or oxygen atmosphere. The concentrations of Cys-4MC were found to be 2.2 ± 0.3 nmol/mg MPI and 8.1 ± 0.9 nmol/mg MPI in meat containing 500 and 1500 ppm 4MC, respectively, and stored for 7 days under oxygen. The formation of the Cys-4MC adduct resulted in protein thiol loss, and ca. 62% of the thiol loss was estimated to account for the formation of the Cys-4MC adduct for meat containing 1500 ppm 4MC. Furthermore, protein polymerization increased in samples containing 4MC as evaluated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and the polymerization was found to originate from protein-polyphenol interactions as evaluated by a blotting assay with staining by nitroblue tetrazolium.