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Phytochemical study and biological activities of the chemical constituents of Helichrysum pandurifolium Schrank
Author(s)
Moser, Justin John
Date Issued
2021
Type
Thesis
Publisher
Cape Peninsula University of Technology
Abstract
The Cape Floral Kingdom in South Africa is one of six recognised floral kingdoms in the world
containing one of the largest concentrates of high density endemic plant species. Over 40 %
of the world`s Helichrysum species are found in Southern Africa, many of which have not yet
been chemically categorised, and offers a potential resource for new bioactive phytochemicals.
Helichrysum plays an important role within many of the South African traditions, historically
used as medicine by the native amaXhosa and isiZulu communities.
Chemical investigation of Helichrysum pandurifolium Schrank resulted in the isolation of four
flavonoids (C1-C4). Chemical structures were elucidated based on their spectroscopic data,
the compounds were identified as 5-hydroxy-3,7-dimethoxyflavone (C1), 3,5-dihydroxy-6,7,8-
trimethoxyflavone (C2), 3`,4`,7-trihydroxy-3-methoxyflavone (C3) and 5,7-dihydroxy-3-
methoxyflavone (C4).
In vitro assays used to determine the antioxidant activities for the isolated compounds as well
as the total extract include the Ferric ion reducing antioxidant power (FRAP) and Trolox
equivalent absorbance capacity (TEAC) assays. The total phenolic content (TPC) of the total
extract was also quantified. Anti-diabetic activities were determined via the in vitro inhibition of
key digestive enzymes a-glucosidase and a-amylase.
Compounds C2-C4 revealed FRAP total antioxidant capacities of IC50 equal to 272.8 ± 7.1;
1183.6 ± 69.7 and 17.6 ± 2.8 μmol AAE/g respectively. Compounds C1-C4 measured TEAC
antioxidant activities as 246.8 ± 2.9; 799.8 ± 8.6; 952.9 ± 1.5 and 486.6 ± 3.7 μmol TE/g
respectively. Compounds C1-C3 showed a-glucosidase inhibitions of 18.7 ± 2.4; 40.5 ± 11.6
and 3.3 ± 0.4 μg/mL respectively, where compound C3 was found to have and a-amylase
inhibition of 116.2 ± 5.8 μg/mL. The total phenolic content of the total extract was quantified to
be 108.3 ± 18.9 mg GAE/g and resulted in FRAP, TEAC and a-glucosidase inhibition of 248.2
± 0.1 μmol AAE/g; 722.4 ± 16.6 μmol TE/g and 126.5 ± 14.3 μg/mL respectively.
This is the first report on the isolation and identification of methoxyflavanoids from H.
pandurifolium and their biological activities. Results suggest that the isolated phytochemicals
may be used as a natural source of anti-diabetic medication by reducing the risk of
hyperglycaemia and as preventative medication related to various chronic diseases, however
further in-vivo studies will be required.
containing one of the largest concentrates of high density endemic plant species. Over 40 %
of the world`s Helichrysum species are found in Southern Africa, many of which have not yet
been chemically categorised, and offers a potential resource for new bioactive phytochemicals.
Helichrysum plays an important role within many of the South African traditions, historically
used as medicine by the native amaXhosa and isiZulu communities.
Chemical investigation of Helichrysum pandurifolium Schrank resulted in the isolation of four
flavonoids (C1-C4). Chemical structures were elucidated based on their spectroscopic data,
the compounds were identified as 5-hydroxy-3,7-dimethoxyflavone (C1), 3,5-dihydroxy-6,7,8-
trimethoxyflavone (C2), 3`,4`,7-trihydroxy-3-methoxyflavone (C3) and 5,7-dihydroxy-3-
methoxyflavone (C4).
In vitro assays used to determine the antioxidant activities for the isolated compounds as well
as the total extract include the Ferric ion reducing antioxidant power (FRAP) and Trolox
equivalent absorbance capacity (TEAC) assays. The total phenolic content (TPC) of the total
extract was also quantified. Anti-diabetic activities were determined via the in vitro inhibition of
key digestive enzymes a-glucosidase and a-amylase.
Compounds C2-C4 revealed FRAP total antioxidant capacities of IC50 equal to 272.8 ± 7.1;
1183.6 ± 69.7 and 17.6 ± 2.8 μmol AAE/g respectively. Compounds C1-C4 measured TEAC
antioxidant activities as 246.8 ± 2.9; 799.8 ± 8.6; 952.9 ± 1.5 and 486.6 ± 3.7 μmol TE/g
respectively. Compounds C1-C3 showed a-glucosidase inhibitions of 18.7 ± 2.4; 40.5 ± 11.6
and 3.3 ± 0.4 μg/mL respectively, where compound C3 was found to have and a-amylase
inhibition of 116.2 ± 5.8 μg/mL. The total phenolic content of the total extract was quantified to
be 108.3 ± 18.9 mg GAE/g and resulted in FRAP, TEAC and a-glucosidase inhibition of 248.2
± 0.1 μmol AAE/g; 722.4 ± 16.6 μmol TE/g and 126.5 ± 14.3 μg/mL respectively.
This is the first report on the isolation and identification of methoxyflavanoids from H.
pandurifolium and their biological activities. Results suggest that the isolated phytochemicals
may be used as a natural source of anti-diabetic medication by reducing the risk of
hyperglycaemia and as preventative medication related to various chronic diseases, however
further in-vivo studies will be required.
Additional information
Thesis (Maser of Applied Science: Chemistry)--Cape Peninsula University of Technology, 2021
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