Abrus cantoniensis Hance (AC) is a common and popular vegetative food that
consumed as beverage, soup and folk medicine in Asia. However, there is scant
scientific data on the phytochemical profile and biological activities of this
functional herb. The phytochemical profile of AC was determined by UPLC. The
antioxidative and anti-proliferative activities of AC were evaluated by means of
biochemical assays.
Abrus mollis Hance (AM) is an alike species that used as an alternative in the
manufacture of beverage. For quality control and species authentication, ten batches
of each AC and AM were collected from different origins and used for fingerprinting.
Five major phytochemicals, namely, abrine, catechin hydrate, emodin, chrysophanol
and ursolic acid were simultaneously identified and quantified. Results showed that,
AC and AM shared similar chromatogram profile but varied in phytochemicals
content. It was revealed by AVNON and PCA analyses that, confusing species AC
and AM can be identified from each other based on the level of the three leading
phytochemicals: emodin, chrysophanol and ursolic acid.
Methanol extracts AC and AM were further comprehensively compared for their
antioxidant activities by various assays, including FRAP, radicals scavenging,
reducing power and inhibition of linoleic acid peroxidation. The methanol extracts
(ME) of both AC and AM had high level of total phenolic content (TPC) and total
flavonoid content (TFC). The IC50 values of radical scavenging activities of AC
extracts were lower than those of AM, indicating that AC had stronger radical
scavenging activities than AM (p < 0.05). Pearson’s coefficients revealed that, the
TPC showed a high positive correlation with FRAP, DPPH and ABTS cation
scavenging activities (r = 0.919, 0.957 and 0.948, respectively) (p < 0.01). The
component plot of PCA implied two clusters of the AC and AM parameters,
meaning that the two species can be distinguished from each other according to their
TPC, TFC and antioxidative activities.
The ME of AC was subjected to serial extraction with solvents of different
polarity, and then yielded four fractions. The antioxidant activities of AC fractions
and phytochemicals were evaluated. The ethyl acetate fraction (EF) exhibited the
strongest radical scavenging activities, reducing power and inhibition of linoleic acid
peroxidation, showing comparable antioxidant activities with that of the synthetic
antioxidants trolox and BHT. The EF also revealed robust cellular antioxidant
activities in the cell-based model with EC50 value at 99.29 ± 4.22 μg/mL. Statistical
analysis indicated the high correlation between the TPC, TFC and the antioxidant
activities of the four fractions, as all Pearson’s coefficient indexes were over 0.954
(p < 0.05). The abrine showed potent ABTS cation scavenging activity with IC50
value at 37.50 ± 0.40 μg/mL, while soyasaponin I exhibited strong superoxide anion
radical clearing capacity with IC50 value at 78.25 ± 2.46 μg/mL. In comparison with
trolox and BHT, abrine, soyasaponin I, 18β-glycyrrhetinic acid (18GA) and ursolic
acid (UA) had a potent non-site-specific hydroxyl radical decreasing activity, all of
which had relative low IC50 values around 30 to 48 μg/mL.
When the anti-proliferative activities of AC fractions were evaluated, the EF
showed selective growth inhibitory effects on the Hela, DU145, MCF-7 and Hep3B
cancer cell lines in a dose-dependent manner. Cell cycle analysis by flow cytometry
demonstrated that, all tested cancer cells were arrested at G2/M phase. Moreover,
early apoptosis was induced in Hela, MCF-7 and Hep3B but not DU145 cells.
Proteomics studies revealed that, six proteins with a score over 70 and the expression
decreased over 1.4 fold were successfully identified. The EF affected Hela cell cycle
at mitosis phase via down-regulation of Myt1 and phospho-cdc2 (Tyr15), as well as
up-regulation of phospho-Wee1, Cyclin B1 and phospho-His H3 (Ser 10). It also
induced DNA damage pathway via up-regulation of phospho-53, p21Waf1/Cip1,
phospho-Chk1 and phospho-Chk2. Results revealed that, the EF also triggered Hela
cell apoptosis via an intrinsic pathway by down-regulation of PARP, caspase 9,
caspase 3, caspase 7, caspase 8, Bcl-2, Bcl-xL, BID, Bim, Bik, and up-regulation of
the corresponding cleaved proteins and pro-apoptosis protein Bad, Bax and Bak.
To obtain synergetic anti-proliferative effects, four phytochemicals in AC,
including abrine, soyasaponin I, 18GA and UA, were combined with 5-fluorouracil
(5-FU) or sorafenib (SF) at various ratios, respectively. Results revealed that SF
combined with UA at 1:7.5 ratio showed synergism, with CI value at 0.7 and DRI
value at 4.79 (SF) and 1.69 (UA), respectively. After drug combination of SF and
UA at 1:7.5, both HepG2 and Hep3B were arrested at G0/G1 phased and induced
early apoptosis.
The whole study indicated that, AC is an antioxidant-rich herb material showing
potent antioxidative and anti-proliferative properties. This study suggests AC could
be served as a potential and promising functional food for health beneficial effects
| Date of Award | 15 Jul 2015 |
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| Original language | English |
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| Awarding Institution | - City University of Hong Kong
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| Supervisor | Hon Yeung CHEUNG (Supervisor) |
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