| Summary: | Ginseng root is one of the oldest and most utilized traditional herbal ingredients.
Ginseng has been used to treat many diverse ailments. Compounds in ginseng known as
ginsenosides, which are also known as steroidal saponins, are generally thought to be the most
bioactive component. However, ginseng contains up to 30 different ginsenosides and the type
and proportion of ginsenosides depends on the source of ginseng and portion of the plant
material used. The overall objective was to identify, evaluate and recover sources of bioactive
ginsenosides. In this thesis, the main ginsenosides that showed a propensity to inhibit cultured
cancer cell viability were identified and a LC50 (concentration to inhibit 50% cell viability) was
determined in three distinct cell lines. Generally, ginsenoside aglycones 20(S)-protopanaxadiol
(PD) and 20(S)-protopanaxadiol (PT) and ginsenoside Rh2 were identified to have affected cell
viability in all three cell lines. Specifically, the LC50 values for PD (13 μg/mL), ginsenoside
Rh2 (15 μg/mL), PT (19 μg/mL) and ginsenoside Rhl (210 μg/mL) were established in cultured
leukemia cells (THP-1). In intestinal 407 cells (Int-407), a non malignant embryonic intestinal
cell line established via HeLa cell contamination, the LC50 values were determined for PD (23
μg/mL), PT (26 μg/mL) and ginsenoside Rh2 (53 μg/mL). In comparison, LC50 for PD and PT
were 24 μg/mL and Rh2 was 55 μg/mL in cultured Caco-2 cells, an adenocarcinoma intestinal
cell line. Generally, cell cycle analysis showed that these specific ginsenosides which inhibited
cell viability also resulted in a build up of sub-Gl cells, a characteristic of apoptosis.
Furthermore, treatments that showed the greatest increase (P ≤ 0.05) in sub-Gl cells also had the
largest (P ≤ 0.05) release of lactate dehydrogenase (LDH), a useful bio-marker for membrane
integrity. It was concluded that specific structure-function relationships exist for bioactive ginsenosides. The sources of rare bioactive ginsenosides, such as Rh2 have only been
attributed to Asian red ginseng root. However, ginsenoside Rh2 was found in this study in North
American ginseng leaf, an underutilized resource, as a product of applying thermal energy during
extraction procedure. Furthermore, Rh2 formation was shown to be a function of heating time
and a breakdown product of more abundant ginsenosides (e.g. Rbl and Rd). Specific
mechanistic studies with PD, PT, Rh2 and an enriched Rh2 North American ginseng leaf extract
in THP-1 and Caco-2 cells showed that both ginsenoside concentration and exposure time were
factors causing cytotoxicity. Generally, test ginsenosides increased both the buildup of apoptotic
and necrotic cells while having a varying effect on Caspase-3 activity. In conclusion, the
findings of this thesis indicate that variable bioactive response of ginsenosides may be explained
on the basis of hydrophobic/hydrophilic balance of the compounds. Moreover, the bioactivity
observed was more associated with non-specific changes in cell membrane function than specific
trigger mechanism of programmed cell death. === Land and Food Systems, Faculty of === Graduate
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