Analysis of phytochemical in a Malaysian medicinal plant and the bioavailability of dietary hydroxycinnamates

Omar, Maizatul Hasyima (2013) Analysis of phytochemical in a Malaysian medicinal plant and the bioavailability of dietary hydroxycinnamates. PhD thesis, University of Glasgow.

Abstract

The first study was looking into the phytochemical analysis of herbal medicinal plant from Malaysia. Phenolic compounds in an aqueous infusion from leaves of Ficus deltoidea (Moraceae), a well-known herbal tea in Malaysia, were analysed by HPLC coupled to photodiode-array and fluorescence detectors and an electrospray ionization tandem mass spectrometer. Following chromatography of extracts on a reverse phase C12 column 25 flavonoids were characterized and/or tentatively identified, with the main constituents being flavan-3-ol monomers, proanthocyanidins and C-linked flavone glycosides. The proanthocyanidins were dimers and trimers comprising (epi)catechin and (epi)afzelechin units. No higher molecular weight proanthocyanidin polymers were detected. The antioxidant activity of F. deltoidea extract was analysed using HPLC with on-line antioxidant detection. This revealed that 85% of the total antioxidant activity of the aqueous F. deltoidea infusion was attributable to the flavan-3-ol monomers and the proanthocyanidins

In terms of the bioavailability of hydroxycinnamates with the high occurrence of p-coumaroylquinic acid in F. deltoidea extract, further study was carried out using radiolabeled caffeic acid. In the study, male Sprague-Dawley rats ingested 140 x 106 dpm of [3-14C]trans-caffeic acid and over the ensuing 72 h period body tissues, plasma, urine and faeces were collected and the overall levels of radioactivity determined. Where sufficient radioactivity had accumulated samples were analysed by HPLC with on-line radioactivity and tandem mass spectrometric detection. Nine labeled compounds were identified, the substrate and its cis isomer, 3-O- and 4-O-sulphates and glucuronides of caffeic acid, 4-O-sulphates and glucuronides of ferulic acid and isoferulic acid-4-O-sulphate. Four unidentified metabolites were also detected. After passing down the gastrointestinal tract the majority of the radiolabeled metabolites were excreted in urine with minimal accumulation in plasma. Only relatively small amounts of unidentified 14C-labeled metabolites were expelled in faeces. There was little or no accumulation of radioactivity in body tissues, including the brain. The overall recovery of radioactivity 72 h after ingestion of [3-14C]caffeic acid was ~80% of intake.
The role of colonic microflora in the metabolism of caffeic acid was carried using an in vitro model of the human colonic microflora. Caffeic acid (55 µmoles) was incubated with human faecal materials obtained from five Asian donors, and caffeic acid degradation was monitored from 0-8 h. Faecal samples were analysed by GC-MS, where major phenolic acids identified were dihydrocaffeic acid, 3-(3-hydroxyphenyl)propionic acid and phenylacetic acid. Caffeic acid was quickly degraded by the colonic microflora, as it disappeared after 4 h of incubation in two of the faecal samples. The degree of degradation of caffeic acid was significantly influenced by the addition of glucose as well as individual variations in the density and the composition of microflora. These findings support extensive metabolism of caffeic acid in the colon, depending on the substrate concentration and the supplement of glucose which resulting the formation of simple phenolics.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Ficus deltoidea, medicinal plant, LCMS,caffeic acid, in vitro fermentation
• Subjects: Q Science > QD Chemistry
• Colleges/Schools: College of Medical Veterinary and Life Sciences
• Supervisor's Name: Crozier, Prof. Alan and Mullen, Dr. William
• Date of Award: 2013
• Depositing User: Mrs Maizatul Hasyima Omar
• Unique ID: glathesis:2013-4439
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 16 Aug 2013 07:10
• Last Modified: 16 Aug 2013 07:12
• URI: https://theses.gla.ac.uk/id/eprint/4439