Thermal Ageing of Black Garlic Enhances Cellular Antioxidant Potential Through the Activation of the Nrf2-Mediated Pathway.

Abstract

Research background: Oxidative stress plays a crucial role in different diseases, including chronic hepatitis, cirrhosis and liver cancer, which are a major cause of mortality worldwide. Liver cell injury resulting from oxidative stress contributes to the development of these diseases. Garlic is known for its diverse physiological activities, and black garlic, produced by thermal ageing of raw garlic, has attracted attention due to its biological properties.

Experimental approach: This study investigates the hepatoprotective potential of black garlic prepared in an electric cooker. The study includes mass loss, browning index, free amino acids, free-reducing sugar content, total phenolic compounds and DPPH radical scavenging activity. Additionally, the sensory evaluation shows a preference for the black garlic sample over raw garlic. The study also investigates the activation of Nrf2-ARE pathway in HepG2-C8 cells and evaluates the protective effect against H₂O₂-induced damage.

Results and conclusions: The results indicate that black garlic lost mass, possibly due to water loss and the Maillard reaction, which led to an increase in the browning index and a decrease in free amino acids. However, the content of free reducing sugars increased. After 14 and 21 days, the total phenolic content of black garlic increased and its ability to scavenge DPPH radicals improved. Significant activation of the Nrf2-ARE pathway was observed in HepG2-C8 cells. Sensory evaluation showed a preference for the 14-day aged black garlic. The Nrf2 pathway can be effectively activated in HepG2 cells by a 14-day aged black garlic extract, resulting in protection against H₂O₂-induced damage.

Novelty and scientific contribution: Our research shows the significant effect of thermal ageing on black garlic and highlights its enhanced antioxidant properties. A simple approach has been developed to prepare black garlic that is more effective, healthier and can potentially be used to protect the liver and treat diseases related to oxidative stress.