Studies on biological activities of Scottish plants.

This thesis describes the investigation of 48 species from 26 different plant families for their bioactive properties as antioxidants, antibacterial and general toxicity. There are 45 species indigenous or naturalised to Scotland. Three Centaurea species from Turkey were also investigated to compare the differences in activity between Scottish species and the Turkish species. It also describes the phytochemical investigation of 18 of these species which yielded 45 compounds. The structures of the isolated compounds were elucidated using UV, IR, MS, and NMR data and where possible tested in the above bioassays. There were 8 alkaloids, 5 coumarins, 13 flavonoids, 6 lignans, 5 secoiridoids, 3 cyanogenic glycosides, 2 diaryl heptanoids, 1 phytoecdysteroid, a cinnamic acid derivative and an acetophenone derivative isolated in this study. These included the novel compounds hederacine A, hederacine B, two tropane alkaloids isolated from Glechoma hederacea, centcyamine and cis-centcyamine, two indole alkaloids from Centuarea cyanus. The other alkaloids isolated were moschamine, cis-moschamine and N-(p-coumaroyl)-serotonin were isolated from Centaurea species. The five furanocoumarins bergapten, imperatorin, isoimperatorin, phellopterin and xanthotoxin were isolated from Angelica species. The 13 flavonoids isolated were luteolin and its derivatives luteolin 3'-Beta-D-glucopyranoside, luteolin 4'-Beta-D-glucopyranoside, swertish, swertiajaponin, isoscoparin-2-Beta-D-glucopyranoside, genkawanin, naringenin, kaempferol and its derivatives astragalin and tiliroside. There were 6 lignans, arctiin, arctigenin, matairesinoside, matairesinol, Lappaol and thujaplicatin methyl ether isolated from Centaurea species. Three secoiridoids sweroside, swertiamarin and gentiopicroside were isolated from Centaurium erythrae. The cyanogenic glycosides amygdalin, prunasin and sambunigrin were isolated from Prunus spinosa. The diaryl hepatanoids hisutanonol and oregonin were isolated from Alnus glutinosa. An acetophenone derivative paeonol from Alliaria petiolata, 3, 4-dihydroxycinnamic acid and 20-hydroxyecdysone were isolated from Centaurea amercana. The extracts of 48 species were tested in antimicrobial, antioxidant and general toxicity assays. In the antimicrobial assay 25 of the MeOH extracts were shown to possess antibacterial activity against one or more bacterial species. The MIC values showed that 12 species Achillea millefolium, Alnus glutinosa, Ceutaurea huber-morathii, Ceutaurium erythrae, Euonymus europaeus, Fraxinus excelsior, Glechoma hederacea, Hippophae rhamnoides, Malva moschata, Prunus padus, Prunus spinosa and Reseda lutea had activity against three or more bacterial species. The methanol extract of Glechoma hederacea had activity against 11 of the 20 bacterial species tested whilst Achillea millefolium had activity against 7 bacterial species. Of note was the activity against penicillin resistant strain of Staphylococcus aureus (MRSA) by the MeOH extracts of 4 species, namely Achillea millefolium (6.3 x l0-1 mg/mL), Centaurium erythrae (1.0 mg/mL), Malva moschata (1 x 10-1 mg/mL), and Prunus padus (1 x 10-1 mg/mL). Amongst the alkaloids isolated in this study the highest level of antibacterial activity was seen with moschamine and cis-moschamine. Four of the furanocoumarins bergapten, imperatorin, isoimperatorin, and xanthotoxin had some degree of antimicrobial activity, however most significant antibacterial activity was seen with isoimperatorin which had an MIC of 18.5 x 10-5 mM against Escherichia coli. Amongst the flavonoids the most significant antibacterial activity was seen with tiliroside which had an MIC of 0.017 x 10-5 mM against Proteus mirabilis, followed by the activity of genkwanin against Bacillus cereus (MIC = 0.018 x lO-5 mM). Of the isolated lignans only thujaplicatin methyl ether had any activity. The secoiridoids sweroside, swertiamarin and gentiopicroside exhibited antimicrobial activity against some of the bacterial species. In the DPPH assay MeOH extracts of 39 species had antioxidant activity. The most significant antioxidant activity was obserxed with the methanol extract of Agrimonia eupatoria with an RC50 value of 4.7 x 10-4 mg/mL. There was antioxidant activity recorded in 20 of the DCM extracts and 20 of the n-hexane extracts. The highest antioxidant activity amongst the DCM extracts was by Prunus padus (RC50 = 2.52 x 10-4 mg/mL). Among the compounds isolated in this study, all the lignans had antioxidant activity ranging from RC50 = 4.66 x 10-4 - 4.04 x 10-6 mM. Among the flavonoids, luteolin, and its derivatives, had moderate antioxidant activity having the RC50 values within the range of 3.68 x 10-3 - 8.55 x 10-6 mM. In this study 29 of the species demonstrated some degree of generalised toxicity in the BSLA. The most toxic extract was the methanol extract of Malva moschata (LD50 2.25 X 10-3 mg/mL). The most toxic compound in the BSLA was moschamindole (LD50 = 9.14 X 10-6 muM) followed by hederacine A (LD50 = 1.09 x 10- muM), matairesinol (LD50 = 1.18 x 10-6 muM) when compared to the control podophyllotoxin (LD50 = 6.5 x 10-6 muM). The two lignans, arctiin and malairesinol and the control podophyllotoxin were tested in in both hypoxic and normoxic conditions, using 3 cell lines CaCo2, MCF -7, and MDA 468 and it was observed that they had higher acitivty in hypoxic conditions compared to normoxic conditions, an interesting finding as often larger tumours have hypoxic states in the peripheral regions. The two tropane alkaloids hederacine A and hederacine B were tested in normoxic conditions and had a IC50 value of 86.6 and 301.0 muM in CaCo2 cell lines, the control podophyllotoxin had an IC50 of 6.7 X 10-2 muM.

Grantor dc:publisher.institution

Robert Gordon University

Year dc:date.issued

2006

Author dc:creator

• Kumarasamy, Yashodharan

Advisor dc:contributor.advisor

• S.D. Sarker, P. Cox and M. Jaspars

• Bioactive properties
• Indigenous flora
• Scotland
• Phytochemical investigation
• Antioxidant activity

Language dc:language

en

Identifier

oai:rgu-repository.worktribe.com:2807439
https://doi.org/10.48526/rgu-wt-2807439

OAI identifier oai:identifier

oai:rgu-repository.worktribe.com:2807439