Amna Abdurrahim | ALES Graduate Seminar

A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES PhD Final Exam Seminar by Amna Abdurrahim. This seminar is open to the general public to attend.

Thesis Topic: Anthocyanins and Gingerols Exhibit a Synergism in their Anticancer and Antioxidant Effects in vitro

PhD with Dr. Lingyun Chen.

Seminar Abstract:

Anthocyanins and gingerols are naturally occurring phenolic compounds abundant in berries and ginger, respectively. They have been reported to induce antioxidant effects, inhibit the growth of different cancer cell lines, and stimulate apoptosis by modulating different cellular signal pathways. However, low bioavailability limits the health benefits of anthocyanins. Meanwhile, gingerols potentially enhance bioavailability through regulating intestinal function and promoting absorption. This work is predicated on identifying a synergistic effect between these two compounds to increase their bioactive effects, the combined effect of which has not been reported. Evidence-based scientific evaluations are needed to explore their combined efficacy. This thesis aims to demonstrate and characterize the possible synergistic interaction between anthocyanins and gingerols (Ac-G). The Ac-G combinations were tested in cellular models in vitro for their anticancer and antioxidant effects at different effective doses and combination ratios.

In the first study, the growth inhibitory effects and selectivity of Ac-G combination and individual extracts were evaluated by measuring the cell viability of treated Caco-2, Hep G2, and HT-29 cancer cells compared to normal cells CCD33Co. Strong synergism was observed between anthocyanins and gingerols, at Ac/G ratios of 16:1, 8:1, and 4:1, against the growth of Caco-2 and Hep G2 cells, at inhibition levels of ≥80%, as reflected by the low combination index (CI) values of 0.3−0.7, and dose reduction index (DRI) values up to 3-fold for anthocyanin and up to 103-fold for gingerol extracts. Moreover, Ac-G combinations did not show toxicity on normal cells CCD-33Co. These results support the potential synergism of the anthocyanins and gingerols combination for an anticancer effect.

To explore the underlying mechanisms involved in the Ac-G synergistic interaction in inhibiting the growth of cancer cells, cell cycle and apoptotic pathways were explored. Significantly higher levels of cell cycle arrest at the S phase and more apoptotic cells were observed for Caco-2 cells treated with Ac-G combinations (50+3.125)- (50+25) µg/mL, and for Hep G2 cells treated with Ac-G combinations (100+25) and (100+50) µg/mL. The synergism in the growth inhibitory effects of Ac-G combinations on Caco-2 cancer cells was mediated by p53-dependent and p53-independent pathways. Ac-G combinations induced apparent increases in the expression of p21 and reduced expression of the cyclin-CDK complex components, CDK2, cdc25A, CHK1, and cyclin A. The apoptotic response was mediated by increased expression of Caspas3, Caspas8, Bid, and Bax. Thus, the substantial increase in the expression of the cellular CDK inhibitor p21 induced by the Ac-G combination represents remarkable anti-tumor efficacy and selectivity.

Ac-G combinations were subsequently tested for their immediate cellular antioxidant activity (CAA) and cytoprotective effects against oxidative stress on Caco-2 cells. Synergism was observed for all Ac-G combined dosages of (1+0.06) – (1+1) µg/mL in the CAA and the cytoprotective effects with synergistic effect indicator (SE) values of up to 1.6. These results might provide evidence for potential usage of the Ac-G combinations to support the endogenous antioxidant system protecting the normal physiological redox status. An evaluation of the cellular antioxidant defense mechanisms involved in the Ac-G synergistic interaction indicates that Ac-G combinations efficiently boosted the cellular antioxidant defense mechanisms by reducing cellular ROS generation, lipid peroxidation, and oxidant-induced activity of GPx enzyme and simulating cellular production of natural antioxidant compounds such as glutathione. The higher effects of Ac-G combined extracts on these exogenous and endogenous antioxidant biomarkers represent a high potential for synergistic antioxidant activities by combining anthocyanins and gingerols.

Overall, the present research demonstrates synergism between anthocyanins and gingerols in their anticancer and antioxidant activities in cell models. Furthermore, this study reported some molecular mechanisms related to cell cycle arrest and apoptosis and activation of antioxidant defense mechanisms involved in the Ac-G synergistic effects. Identifying effective ratios and doses and understanding these mechanisms could help better guide the use of combination strategies in novel supplements or food products. This gives justification for further in vivo studies. Positive results validated through animal models could enable Ac-G combination usage as natural health products and potential concurrent supplements for cancer patients.