Phenolic compounds from selected Namibian leafy vegetables: Extraction and characterization

Smujo Editors, AUGUSTU A.M. DOLLY, AHMAD CHEIKHYOUSSEF, MARTHA KANDAWA-SCHULZ
2019 Biofarmasi Journal of Natural Product Biochemistry  
Abstract. Dolly AAM, Cheikhyoussef A, Kandawa-Schulz M. 2018. Phenolic compounds from selected Namibia leafy vegetables: Extraction and characterization. Biofarmasi J Nat Prod Biochem 16: 1-16. The objective of this project was to study the antioxidant potential of selected Namibian Leafy Vegetables (NLV). We measured Total Phenolic Content (TPC), Total Flavonoid contents (TFC), antioxidant activity against Diphenyl-1-picrylhydrazyl (DPPH), 2,2-azino- bis (3-ethylbenzothiazoline-6-sulfonic
more » ... (ABTS), as well as Reducing Power (RP) assays. The study further detects and characterize eight phenolic acids (4- hydroxybenzoic, trans-ferulic, gallic, vanillic, sinapic, syringic, and para-coumaric acids) using Gas Chromatography-Mass Spectrometry (GC-MS). Thirteen leafy vegetables taken from Kavango East Region were known as Hibiscus sabdariffa, Hibiscus cannabinus, Aeschynomene nambalensis, Oxygonum delagoense, Amaranthus hypochondriacus, Amaranthus thunbergii, Vigna unguiculata, Cucurbita maxima, Cleome gynandra, Lagenaria siceraria, Aeschynomene fluitans, Citrullus lanatus, and Corchorus tridens. The leaves were extracted using aqueous methanol, ethanol and acetone solvents. Acid and Base hydrolyzes for extraction of bound phenolic acids which were analyzed by GC-MS. The best results for each assay were as follows: TPC in methanol: 333.8±2.7µgGAE/g in H. sabdariffa. TFC in methanol: 166.0±0.6µgQE/g in A. nambalensis. DPPH assay in methanol: 79.3±0.6% in H. cannabinus. ABTS assay in ethanol: 98.8±0.2% in H. sabdariffa. RP assay in ethanol: 1227.5±106.2% of L. siceraria. The GC-MS detected phenolic acids in twenty extracts of Base Hydrolysed Samples (BHS), seven extracts of Acid Hydrolysed Samples (AHS) and thirteen extracts of Non-Hydrolysed Samples (NHS). BHS yielded the most significant amount of phenolic acids among the three extraction methods, with highest yields of p-coumaric acid in A. nambalensis (53.1µg/g). Results obtained from the TPC, TFC, and antioxidant assays demonstrated that the selected NLVs are potential sources of phenolic compounds and antioxidants. GC-MS analysis suggests that this tool is useful for characterizing phenolic acids. These findings have contributed to our understanding of the phytochemical contents of the selected NLVs, and further studies are necessary for the possible industrial application of the identified phenolic acids.
doi:10.13057/biofar/f170101 fatcat:npfgkhwc6bhyxa2ixuuqerdeja