Characterization and profiling of plant protein extract from ficus deltoidea for vitexin biosynthesis
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Date
2018
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Teknologi Malaysia
Abstract
Ficus deltoidea (F. deltoidea) is a popular medicinal plant, and locally known as Mas Cotek. The decoction of this plant has traditionally used by Malay women as tonic during post-partum to strengthen uterus and treat variety of illnesses. Recent pharmacological studies reported that F. deltoidea extract exhibited strong antioxidant, anti-inflammatory, anti-ulcer and anti-hyperglycemic activities, mainly because of the phytochemicals in the plant extract. It is believed that the biological activities can also be attributed by primary metabolites, particularly plant proteins or peptides. Therefore, the objectives of this study were to compare protein extraction methods from F. deltoidea leaves, to characterize and profile plant proteins based on molecular size and peptide mass fingerprinting, to determine antioxidant and antibacterial capacity of extracted proteins and to propose biochemical pathway of vitexin biosynthesis from the identified proteins. Three extraction techniques such as solvent based extraction, Trichloroacetic acid-acetone precipitation and phenol extraction were used and compared to obtain high quality of proteins based on their high resolution on polyacrylamide gels and peptide mass fingerprinting. Phenol extraction was able to extract proteins with less plant impurities such as polysaccharides and polyphenols. There were 229 proteins identified from the leaves of the plant. 17% of the identified proteins are related to stress and defence mechanism in plants. The extracted proteins were fractionated and examined for their antioxidant capacity using 2,2-diphenyl-1- picryl-hydrazyl-hydrate (DPPH) assay, and anti-bacterial activity using microdilution broth method. The DPPH assay revealed that protein hydrolysate, 3 kDa possessed remarkable antioxidant capacity which was comparable to standard bovine serum albumin. Smaller protein hydrolysates showed to have stronger scavenging activity, probably due to the exploration of more active sites for bioactivity. The protein hydrolysates also displayed anti-bacterial activity with the minimum inhibitory concentration ranged from 1 to 64 µg/L against Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli. This is the first time the antioxidant and anti-bacterial properties of protein hydrolysates from F. deltoidea is reported. From the identified proteins, the biosynthesis pathway of active compounds: vitexin and isovitexin (apigenin-C-glucosides) were successfully predicted. Their biochemical pathway probably requires four major steps of mechanism: condensation by plant polyketide chalcone synthase, isomerization either spontaneous or catalysed by chalcone isomerase, oxidation by cytochrome P450 to convert flavanone to flavone, and transfer of sugar moiety by C-glycosyl transferase followed by dehydration step to produce flavone-6-C-glucosides. This prediction can serve as a platform to understand the biosynthesis of the therapeutically useful C-glycosylated flavones from plant proteins for future study to enhance the content of vitexin and isovitexin production
Description
Thesis (PhD. (Bioprocess Engineering))
Keywords
Plant Extracts—therapeutic use, Medicinal plants—Research, Plant proteins—Synthesis