Antioxidant, antimicrobial, and α-glucosidase inhibitory activities of saponin extracts from walnut (Juglans regia L.) leaves
Youssef Elouafy1, Adil El Yadini1, Salma Mortada2, Mohamed Hnini3, Hicham Harhar1, Asaad Khalid4, Ashraf N Abdalla5, Abdelhakim Bouyahya6, Khang Wen Goh7, Long Chiau Ming8, My El Abbes Faouzi2, Mohamed Tabyaoui1
1 Laboratory of Materials, Nanotechnology and Environment, Faculty of Sciences, Mohammed V University in Rabat, Rabat, Morocco
2 Laboratories of Pharmacology and Toxicology, Pharmaceutical and Toxicological Analysis Research Team, Faculty of Medicine and Pharmacy, Mohammed V University in Rabat, Rabat, Morocco
3 Center of Plant and Microbial Biotechnology, Biodiversity and Environment, Microbiology and Molecular Biology Team, Faculty of Sciences, Mohammed V University in Rabat, Rabat, Morocco
4 Substance Abuse and Toxicology Research Center, Jazan University, Jazan 45142, Saudi Arabia; Medicinal and Aromatic Plants and Traditional Medicine Research Institute, National Center for Research, Khartoum, Sudan
5 Department of Pharmacology and Toxicology, College of Pharmacy, Umm Al-Qura University, Makkah, Saudi Arabia
6 Laboratory of Human Pathologies Biology, Faculty of Sciences, Mohammed V University in Rabat, Morocco
7 Faculty of Data Science and Information Technology, INTI International University, Nilai, Malaysia
8 School of Medical and Life Sciences, Sunway University, Sunway City, Malaysia
Laboratory of Human Pathologies Biology, Faculty of Sciences, Mohammed V University in Rabat
Long Chiau Ming
School of Medical and Life Sciences, Sunway University, Sunway City
Source of Support: The study was supported by the Deanship of Scientific Research at Umm Al-Qura University (Grant code: 22UQU4331128DSR77), Conflict of Interest: None
Objective: To investigate the relationship between triterpenoid saponin content and antioxidant, antimicrobial, and α-glucosidase inhibitory activities of 70% ethanolic, butanolic, aqueous, supernate and precipitate extracts of Juglans regia leaves.
Methods: Triterpenoid saponins of different Juglans regia leaf extracts were measured by the vanillin method. Antioxidant activity was evaluated against DPPH and ABTS free radicals. We also assessed α-glucosidase inhibitory and antimicrobial activities of the leaf extracts. Pearson's correlation coefficient was evaluated to determine the correlation between the saponin content and biological activities.
Results: The butanolic extract was most effective against DPPH with an IC50 of 6.63 μg/mL, while the aqueous extract showed the highest scavenging activity against ABTS free radical with an IC50 of 42.27 μg/mL. Pearson's correlation analysis indicated a strong negative correlation (r = -0.956) between DPPH radical scavenging activity (IC50) and the saponin content in the samples examined. In addition, the aqueous extract showed the best α-glucosidase inhibitory activity compared with other extracts. All the extracts had fair antibacterial activity against Bacillus subtilis, Escherichia coli, and Klebsiella pneumoniae except for the aqueous extract.
Conclusions: Juglans regia extracts show potent antioxidant, antimicrobial, and α-glucosidase inhibitory activities. There is a correlation between saponin levels in Juglans regia leaf extracts and the studied activities. However, additional research is required to establish these relationships by identifying the specific saponin molecules responsible for these activities and elucidating their mechanisms of action.