Antioxidant, anti-inflammatory, anti-diabetic, and cytotoxic potential of ethanolic leaf extracts from Englerina woodfordiodes M. Gilbert and Oncocalyx fischeri (Ebgl.) M. Gilbert

Introduction: In patients with type-2 diabetes (T2D), oxidative stress is closely associated with chronic inflammation and plays an important patho-physiological role in T2D and its related complications. Therefore, antioxidants may be particularly beneficial in the treatment of diabetic patients, and therapies based on phytochemicals from plants are of great interest as a potential alternative and safer treatment for oxidative stress, chronic inflammation, and T2D. The aim of this study is to investigate the antioxidant, anti-inflammatory, and anti-diabetic potential of ethanolic extracts and subsequent fractions of E. woodfordiodes and O. fischeri.

Materials and methods: The leaves of the plants were extracted with 99% ethanol and subsequently fractionated using n-hexane, chloroform, ethyl acetate, and n-butanol. The antioxidant, anti-inflammatory, and anti-diabetic activities, as well as cytotoxicity, of each extract/fraction were evaluated, respectively, by DPPH^• inhibition and Ferric Reducing Antioxidant Power (FRAP) assays; xanthine oxidase inhibition (XOI); glucose uptake by Caco-2 cells; and cell viability.

Results and Discussion: The n-butanol fraction and the crude extract of E. woodfordiodes exhibited very high DPPH^• inhibitory activities (84.3% and 85.9%, respectively). The crude extract of O. fischeri also showed a significant DPPH^• inhibition activity (50.7%). In the XOI assay, the n-hexane fraction of O. fischeri (82.9%) and the ethyl acetate fraction of E. woodfordiodes (79.1%) demonstrated statistically significant reductions of peroxide formation. Regarding the Bradford assay, none of the fractions from either plant showed a significant reduction in cell viability. In comparison to the respective controls, most of the fractions of E. woodfordiodes and O. fischeri significantly reduced (p<0.05) glucose uptake in Caco-2 cells.

Conclusion: The findings reveal the promising antioxidant, anti-inflammatory, and anti-diabetic potential of E. woodfordiodes and O. fischeri leaves, mainly of their crude extracts. Due to their safety compared to other solvents, these extracts could be applied in several food- and health-related areas.